Replacing a Previa head gasket.

[timsrv]

This is a copy/paste of a thread I posted on TVP a few years ago. Enjoy :)>:.

Okay, so you've got a Toyota Previa with a blown head gasket. No big deal, right? Head gaskets aren't that bad, right? Well, that's what I thought too. I used to work as a flat rate mechanic for Toyota and if I can do a 22R head gasket in under 2 hrs, then I could certainly do a 2TZ head gasket in under 6, right? Wrong!
http://i8.photobucket.com/albums/a23/timsrv/01-1.jpg


It wasn't unit I removed this access panel that I realized it's not going to be so easy. As you can see by this picture, it could almost be possible. Yeah, the access hole would need a little enlarging on the back side, but what about the intake manifold? This thing is huge and spans across the entire top of the engine. Just how the heck is this coming off? Plasma cutter? Well, I'm not that brave, so Darn it, I had to settle for option #2 (pulling the engine). My original goal was to do the job in under 6 hrs. Well forget that. After 8 hrs, here's what I was able to do.
http://i8.photobucket.com/albums/a23/timsrv/02.jpg


I got to finally use my Harbor Freight extra large jack stands on the tallest setting!
http://i8.photobucket.com/albums/a23/timsrv/03.jpg


The next few pix are taken after dropping the engine out from the bottom using a floor jack and a makeshift 2x10 wood support. The engine was cleaned with solvent and then pressure washed.
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http://i8.photobucket.com/albums/a23/timsrv/06.jpg


Although a pain to work on, I couldn't help be impressed by the design of this power train. Look at how thin this thing is.
http://i8.photobucket.com/albums/a23/timsrv/07.jpg


I had hoped to keep it simple and leave the cams installed. Unfortunately they block access to the head bolts and must be removed before taking off the head.
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After removing the cams, the valve shim assy's must be removed or they will fall out while handling the head. It is very very important to keep these in order. Unless you plan on re-shimming and replacing, they must be reinstalled in the exact location they were taken from. I used a piece of cardboard to keep them in the correct order.
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Well, looks like the diagnostic was correct. A blown head gasket is definitely the problem here. #1 was unintentionally steam cleaned by vaporizing coolant!
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Here is a close-up of the trouble spot. You can see a definite path between the water jacket and the cylinder.
http://i8.photobucket.com/albums/a23/timsrv/11.jpg


#3 wasn't much better. It hadn't blown completely yet, but was well on it's way. I believe this was a result of #1 blowing and over pressurizing the cooling system. Notice how the gasket material is pushed toward the cylinder instead of away from it.
http://i8.photobucket.com/albums/a23/timsrv/12.jpg


Here's a view of the underside of the head
http://i8.photobucket.com/albums/a23/timsrv/13.jpg


A close-up of the trouble spot
http://i8.photobucket.com/albums/a23/timsrv/14.jpg


Close-ups of the removed gasket
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New gasket has more metal in it. The new design probably wouldn't have helped much against the type of failure I had. It would however protect against blowing of the gasket between the water jacket and the exterior of the engine.
http://i8.photobucket.com/albums/a23/timsrv/17.jpg


For clean-up and prepping of metal surfaces, I use a 2" angled die grinder with scotch brite surface conditioning pads. I prefer this color for head gaskets.
http://i8.photobucket.com/albums/a23/timsrv/18.jpg


Grinding should done carefully in patterns parallel to the outside diameter of the cylinders. This type of conditioning pad will allow controlled removal of gasket material without damaging metal surfaces. It will however leave small microscopic grooves in the metal. This is good and will aid in bonding of the new gasket (gives it something to bite into). The reason for keeping patterns parallel to cylinders is done so we don't leave grooves that may promote future leaks. In other words, each parallel groove is like a road block, where-as perpendicular grooves may serve as a potential path. After all old gasket material is removed, both mating surfaces are wiped down several times with lacquer thinner. I typically use a clean paper towel each time I wipe it down, and continue wiping until the paper towel remains clean. This is to ensure no oil or other contamination will prevent a good bonding of the new gasket.
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Engine is re-assembled and prepped for re-installation.
http://i8.photobucket.com/albums/a23/timsrv/21.jpg


Due to the age and worth of the vehicle, I took a few short cuts. I purchased this Previa for $150 and it has 187k miles on it. If this had been a nicer vehicle, I probably would have had the head shaved, re-shimmed the valves, and checked a variety of other things. Sure, I'm rolling the dice a little bit, but feel confident this will be a lasting repair. With any luck this head gasket should outlast the rest of the vehicle.
If it's not raining tomorrow, I'll stuff it back in and let you know how she runs. Tim

[timsrv]

I got it finished & it runs okay, but something doesn't seem quite right. It idles a little slow and rough, & when I set the timing, I had to rotate the distributor all the way to the stop to get it set. I'm not sure, but judging from this, I think I might have got the exhaust cam one tooth off. I didn't feel like messing with it anymore today, so I hung it up for the night. The motor was too hot anyhow & I'm tired. I'll check it out in the next few days and let you know how it goes. At least I have good access to the cams through the passenger side access hole, so it shouldn't be so bad.

As far as time, I'll definitely make flat rate. I spent about 7 hrs on it today, so that's only about 15 hrs so far. In addition to the head gasket, I also replaced the heater motor, changed oil, serviced the tranny, replaced belts, changed the differential gear oil, flushed the cooling system and performed several other small maintenance items. I didn't put the passenger side panel back on yet, so I should be able to reposition that cam in under an hr.

Here are a couple of pix I took of it going back in. Tim
http://i8.photobucket.com/albums/a23/timsrv/22.jpg


http://i8.photobucket.com/albums/a23/timsrv/23.jpg

[timsrv]

Well, that's what it was. I pulled the valve cover back off after work today and sure enough, I somehow managed to get the exhaust cam 1 tooth off. I repositioned it to the correct location and now she purs like a kitten. I set the timing by ear, then checked it with the timing light (it was dead on :) ). Now all I have left to do is adjust the side sliding door and put the new seat covers on. I can't believe I'm actually starting to run out of things to fix on this van! Tim

[Previa dude]

Do you have to pull the engine to do the gasket. The reason I ask is I have to do it on my 91. I have done headgaskets before but never on a Toyota, let along an mid engine Toyota with twin cams. I guess what I am asking is, is it harder to pull the engine to do the gasket, or just a nightmare to try and do it while the engine is in the van? Also the cams on that van have two alignment marks on them. How do I know witch ones to use when putting it all back together to make sure when I turn it over for the first time that I don't throw a valve threw a piston?

[timsrv]

There's a guy over on the yahoo Previa group that made a nice write-up on doing the job with the engine "sort of installed". I attached a PDF of his procedure to this post. I say "sort of installed" because you nearly need to remove the engine to get the access you need. IMHO, if you go to that much trouble you're almost there. Get the thing out in the open where you can have ample access to do the job without complications. There will likely be other things that need attention and then there's gasket clean-up etc. Of course I'm a bit lazy and would rather be sitting in a chair in my garage working on the engine than bent over hanging through an access hole. Having room to swing tools without restriction is worth mentioning too. When it comes right down to it I believe the time you save by avoiding complete removal will be lost by the limited access.

Of course this is all talk based on assumptions (as I never seriously considered doing the job without complete removal). If you're not sure then start doing it his way (everything he outlines has to be done regardless of which way you choose). When you get to the part of removing the intake re-assess the situation and make your final decision then. Tim

[Previa dude]

Thank you Tim. That was good advise, and I will do just that. One more question though sir. when i reinstall the cam shafts what would be the best way to ensure proper alignment. I am unsure of witch marks to follow to make sure everything will be in time. Just curious as to how you did it. if you knowof another thread on the matter and any futher advise would be greatly apprecated.

[timsrv]

Do you have a factory service manual? If not I would highly recommend getting one before tackling a job like this. There is a procedure for this outlined in the manual. My manual is packed away but here's my best shot from memory. Basically you set the engine at TDC and set the intake cam to the chain (there's a lighter colored chain link that aligns with a mark on the cam sprocket). The exhaust cam gear has a marked tooth that aligns with a mark on the intake cam gear. Tim

[Previa dude]

i ordered one on line and i am just waiting for it to arrive. i know from what i read on the web it sounds like a pain in da butt. i was just woundering of any tricks you may have to tackle it a little bit easier.

[timsrv]

I would wire-tie the sprocket to the chain so there's no chance of it moving from it's original location. Then when you separate the intake cam from the sprocket leave it sitting in the chain guides. On assembly, another thing worth mentioning is the chain tensioner. The tensioner has a lock feature that only allows it to extend. It should only extend when there's oil pressure, so it probably won't move, but just to be safe I would release the lock and push it back to it's retracted position. This can be a bit tricky if you're not removing the timing cover, but it can be done with a screwdriver and a little patience.

If I were to do this job again, due to the access issues & other reasons, I'd probably replace the timing set at the same time. I'd definitely go with a genuine Toyota "valve grind gasket kit", but I might go aftermarket on the timing set (depending on price comparison & "perceived" quality). I purchased a timing set from this guy on eBay a few years ago and it seemed to be all high quality components. Here's a link: http://www.ebay.com/itm/90-95-TOYOTA-PREVIA-TIMING-GEAR-KIT-NEW-/360218785655?pt=Motors_Car_Truck_Parts_Accessories&hash=item53deb67777

[Previa dude]

thank you Tim. good advise like always

[Previa dude]

hey there Tim, i pulled the head out in just under four hours using the link you post. i read you didnt send your head out for service. i have always sent them out for service, and was wondering if i should just clean it myself and put it back in like you did. or should i just send it out like i would normally do. please advise.

[timsrv]

If everything looks fine when you get the head off, and assuming you can see an obvious flaw in the head gasket, then you might take a chance and just simply replace the gasket. Regardless of how far you go, gasket surface clean-up and prep is critical. Take steps to avoid introducing grit or foreign material inside your engine. After you're done scraping the mating surfaces use a strong solvent like lacquer thinner or carb cleaner to wipe these down. Before final assembly it's a good idea to use brake-clean for the final cleaning (as it won't leave any residue). If you decide to "chance it" you should take the time to check a couple of things before proceeding. You can do a poor man's valve seal inspection by turning the head upside down and filling the chambers with carb cleaner or brake clean. If there is a warped valve or one with a damaged seal surface the cleaning liquid will leak out of the chamber. Sometimes you will get cracks (usually next to valve seats) and if bad enough the fluid will leak through there. If you have a crack, IMO the head is toast. If your test fluid leaks through a valve, if it leaks a lot you'll need to take the head in for repairs. If it leaks a little, then you could probably get by with lapping the valves by hand. If you decide to lap by hand you will need a valve spring removal tool. These can be rented at most of the big auto parts stores or you could purchase one for around $50 or so. If you remove the valves, be sure to keep track of where each one goes as you will want to put them back into the original holes. Removing the valves will also allow you to clean them and inspect the valve guides. You will also be able to replace the valve seals (can't be done with the springs installed). You can check the guides by trying to wiggle the valves side to side in the guides. If you find one with excessive side play then the head will need to go in for repairs. Any time a head is off it should also be checked with a straight-edge. Assuming you have one available to you, it should be laid lengthwise on each side then diagonally (both ways) on the gasket surface. Each time it's in position feeler gauges are used to determine if the head is warped.

One final thing to consider is head-bolts. I've always re-used the old head bolts, but I've heard of others having trouble doing so (bolts broke during final torque). Perhaps they over-torqued or just weren't smart enough to know how to use a torque wrench, but this is a commonly debated subject. Its something each mechanic should consider and many choose to purchase all new head bolts. Always lube the threads and contact areas of the head bolts (under the heads) with engine oil and follow correct torque values/tightening sequences outlined in the service manual. Tim

[Previa dude]

Hey there Tim. One question for you. How's the head gasket holding up? I was thinking of getting the dealer gasket. Or would that just be a waste of money?

[timsrv]

I sold that van but last I heard it was doing good. I see it around from time to time. I would definitely spend the extra money and go with the Toyota head gasket. Toyota sells a "valve grind gasket kit" that comes with all the gaskets & seals you will need to complete the job. Tim

[Previa dude]

hey there Tim. i got bad new today from the machine shop. the head has a crack in it on the number 3 cylinder next to an exhaust valve. so i guess i need a new head:wall:. are all the heads the same for the n/a 2.4liter previa's ?:cnfsd: i was just going to pull a good head at the pick and pull and they have a few different years out there.

[timsrv]

Here's a quote from a similar thread:


There were only 2 heads made for all years of the Previa and as far as I know they are both interchangeable. Even the SC (Super Charged) and NA (Naturally Aspirated) Previas all years use the same casting. The difference between the two heads only affects some of the Previas that were originally sold in California. Other than the "California Spec" head (which I actually think is more common) they should be the same. Even then I believe they can be interchanged, but I'm a little fuzzy on what (if any) things that may (or may not) affect. Good luck. Hopefully somebody with more knowledge with chime in here.

PS: If you can get me the VIN numbers for both Previas (yours & the donor) I can tell you for sure if they are a match. Tim

If you end up using a head from an SC on a NA (or visa versa) you'll need to make sure and use your original camshafts. SC & NA are ground differently.

[Previa dude]

hey there Tim, just wanted to give you an update. i found a good head out at a junk yard, and its at tye machine shop now. the leak check i did at the yard showed the exhaust valves were leaking. common problem i heard with these heads. the guy at the shop said i should do a valve job on it. witch sounds right, right? the price is a bit more then what i wanted to spend (345 dollars witch includes a valve adjustment) on the van but then again the van was free.

So with that being said, is the investment worth the return on the miles i should expect to see. the van has 209000 miles on it( including the bottom half of the engine). i am hoping to get at least another 150000 out of her berfore i have change the hole engine. the automatic transmission is working great so hopfully i should not have any worries there for a long time.

[timsrv]

If the valves are leaking then it needs attention. As far as "adjustment", unless you are supplying him with the complete head (cams and shims included), he is talking about compensating for what he removes from the valves and valve seats by removing material from the stems. This "adjustment" is approximate and by no means a substitute for final adjustment. If the head is getting machine work, then it will need a final valve adjustment. For best results, this final valve adjustment should be performed AFTER the head is installed, torqued, and cams/old shims are installed. Of course I've never tried to do this with the head on the bench, so I can't say for sure if installing/torquing the head will throw it off :cnfsd:. Personally I'd wait until the head is installed (more potential variables removed).

To check valve lash, the engine should be stone cold and positioned to TDC. Feeler gauges are then used between the cam lobes and the shims to gauge clearance (you can only check half). After measuring and recording, rotate the engine 360 deg and repeat on the other half. Intake valves should have .006 - .010 in clearance, and exhaust valves should be .010 - .014.

If lash is off (and I'm betting it will be), you will need to adjust. To adjust, remove each shim and use a micrometer to see how thick it is. Then based on your initial measurements, you will need to add or subtract to determine the new shim size. Example: If you measured .018 in. on an exhaust valve, (.006 in. larger than the desired .012 in.), you would take the existing shim thickness (say .114 in.), add the .006 to it, buy a new shim (.120 in.) from Toyota, and install it in place of the old. If the "new" head came with shims, you could possibly mix & match shims to find the sizes you need.

There is a special tool to remove shims and reinstall. It's Toyota Part number SST 09248-55040 and it's available through Kent-Moore tools at 800-345-2233. Price is about $75. Tim

http://i8.photobucket.com/albums/a23/timsrv/IMG_7411.jpg

PS: I strongly recommend reading that section of the service manual before & during the final valve shimming. Good luck.

Edit/Update 3/25/16: I've learned the Kent-Moore tool (above) is up to $120 now. Here's a cheapy that will likely do the job just fine: http://www.coastaltoolsupply.com/product/SLY-88250.html. If anybody tries this, please reply to this thread as to how it performs.

[Previa dude]

thank you Tim. I will do just that. you haven't steered me wrong yet.

[beoutside]

When I pulled my head off 93 AWD Previa ( engine not removed) the shim I made to hold the chain and sprocket in place came off and the sprocket with it. Any tips on lining everything up. it's close to number 1 at TDC. Both cams have a locating pin placement I think is pretty much at 9 oclock or directly facing you .
thanks in advance!
Donny

[timsrv]

If you lost the position of the sprocket on the chain I'd probably just pull the timing cover and set it up from scratch. Better yet, since you're in that far why no put a new timing set on. When I did my head gasket the timing chain started making a bunch of racket shortly after. I ended up going back in and doing a timing set. Tim

[beoutside]

Thanks Tim , looks like it lost enough coolant to get overheated..... the valves are shot and head warped, with 260,000 miles I'm looking at a japanese replacement for 700,00. Wish you could put the diesel version in it ! 45 mpg sounds pretty good !!
DOnny







If you lost the position of the sprocket on the chain I'd probably just pull the timing cover and set it up from scratch. Better yet, since you're in that far why no put a new timing set on. When I did my head gasket the timing chain started making a bunch of racket shortly after. I ended up going back in and doing a timing set. Tim

[cvtroger]

The Looking for a timing chain kit and I am glad I came across this.

I clicked on that ebay link and the seller has some kits available.

I was looking at those Evergreen kits on amazon, but I was unsure about them.

I am glad to see that the timing chain guides are metal backed. The 1st year nissan 240sx had plastic timing chain guides and the timing chain would eat through that, then the timing chain cover, and where that was being cut was next to the water pump.

I am wondering if that kit is good for the S/C motors? Or there is no difference?

[Garth]

Hi guys, I noticed on the photos of the blown HG engine, that the coolant holes in the gasket, even comparing to the new gasket are all very small except around the back of the #4 pot. How come the casting holes are so much bigger than the holes in the gaskets? Is this anything to do with the country/climate the vehicle is sold? i am down under in New Zealand. Do the restricted gasket holes contribute to overheating or head cracking? Just asking, if anyone has any comments, I would love to hear them. Thanks.

[beoutside]

Update on motor from Japan,
After two years and now at 325,000 miles still runs like new.... I'll check my numbers but also seem to be getting better mileage then new :)


Thanks Tim , looks like it lost enough coolant to get overheated..... the valves are shot and head warped, with 260,000 miles I'm looking at a japanese replacement for 700,00. Wish you could put the diesel version in it ! 45 mpg sounds pretty good !!
DOnny

[beoutside]

The first thing I would check, which you may have already, is your radiator... with a digital thermometer to see if it has dead spots....
in my experience rigs with over 100,000 usually have radiator issues leading to over heating unless flushed regularly.... I know everyone says replace thermostat since it's cheap but it's critical to know the radiator is working as well.... Sorry if this is not related to you question.



Hi guys, I noticed on the photos of the blown HG engine, that the coolant holes in the gasket, even comparing to the new gasket are all very small except around the back of the #4 pot. How come the casting holes are so much bigger than the holes in the gaskets? Is this anything to do with the country/climate the vehicle is sold? i am down under in New Zealand. Do the restricted gasket holes contribute to overheating or head cracking? Just asking, if anyone has any comments, I would love to hear them. Thanks.

[timsrv]

Hi guys, I noticed on the photos of the blown HG engine, that the coolant holes in the gasket, even comparing to the new gasket are all very small except around the back of the #4 pot. How come the casting holes are so much bigger than the holes in the gaskets? Is this anything to do with the country/climate the vehicle is sold? i am down under in New Zealand. Do the restricted gasket holes contribute to overheating or head cracking? Just asking, if anyone has any comments, I would love to hear them. Thanks.

Restriction is an important thing when it comes to controlling flow. When they cast the block & head the main goal (regarding ports) is simply to insure they're there. The gasket is what's used to dial-in/control flow. Toyota spends a lot of money in research to insure they get it just right & sometimes product improvements continue for years. Messing with it by enlarging gasket holes would likely lead to other problems (you might be increasing flow to some parts at the expense of reducing flow to others). For best results be sure to use an unaltered OE Toyota gasket and you'll be golden. Check your head carefully for warpage and cracks before reassembly. I'd also recommend removal of the valves to check/inspect valve guides & valve seat condition. With the Previa, reshimming the valves on assembly is highly recommended and you should consider replacing the timing chains/guides. Good luck. Tim

[John A Feider]

Hey Tim.......Sorry about the incorrect posting, I thought I was posting to this thread. I hope I have it right now:yes: Glad to see you're still in the Prev business. I finally recovered from all my skiing and eye injuries and am back to putting my '92 Prev back together. I decided to rebuild the engine after an ignorant partial tear down to get the cracked head off. I read all the blog posts in this engine head forum but didn't quite come across an answer to my dilemma.

When I took the original factory head bolts off (owned since new) I threw them aside, almost lost, only to discover them maybe in the nick of time. I found them to have a washer with them and when I went to install the new head with new bolts (ordered for a Previa head) I was following the official Toy manual to the 'T' saying nothing about installing a washer:dizzy: It only said to wet torque them which I did. All ten are identical to the old and torqued just fine and they didn't come with washers either. Everything else I've come across says nothing about washers. I noticed in one of your replies to this thread you talked about wet torque, etc, but didn't mention the washers. What in your experience is maybe the answer or your opinion. You've rebuilt these engines? Have any broke or went bad after some time and/or miles WITHOUT head bolt washers? I've gotten conflicting opinions on this. Like if they needed washers they'd be perm attached or come in the package with the bolts. Does the extra few millimeters of torque spread out with the washers on the aluminum head matter? I haven't run the engine yet, it's still out and nearing completion.

Would really appreciate any guidance or info.....thanx much!

John

[timsrv]

Does it matter? Good question. Maybe? Too many variables to know for sure, but personally I wouldn't want to take the chance. Not having a washer would put the threaded tips of the bolts into new territory. Probably not much more restriction here (if any), but if there's any interference here it could affect final torque. Then there's the slipping action of the bolt heads against the hardened surface of the washers. Surface tension between those and the softer aluminum could also affect torque. Probably not by much, but it does add a variable. Personally I would remove each bolt one at a time, add washer, then reinstall/retorque. If you do each one while the others remain torqued, you wouldn't need to worry too much about messing up the head gasket and/or repeating the sequence (although I'd repeat the sequence giving each bolt the final 90º after all the washers were put back on). But that's just me, do what you feel is right. Tim

[John A Feider]

Thanx Tim for your kind input! I especially liked your thought about the head bolt slippage against the hardened steel washer. I also since your comment found in the Toy manual where it actually shows the washer in the illustrated breakdown of the head assy, etc, so I decided to install the washers. It took longer than I figured but like you said, better to be safe than sorry.

Also, if you don't mind....WHAT if any, is the reason for the block insulator between the block and the intake manifold? I'm guessing maybe for sound and/or heat transfer from the engine but not required for a specific engine function? Mine got destroyed some years ago but now that I'm rebuilding this thing I thought I'd better make sure. Do you know or have thoughts about this thing?

Thanx allot, John

[timsrv]

Actually I'm not really sure what you're talking about..........is it Toyota part #12581-76010? If so, you can get these for around $85 at the on-line Toyota parts sites. Tim

[previa94]

I have a 1994 Previa LE, in excellent condition, however, it apparently needs a head gasket. I say that because since it was diagnosed by a shop I never went to before almost a year ago, it still runs really great. I recently had the oil changed and that shop said there was a oil fiter housing leak. I have no technical knowledge about this, have owned this car since new. Recently had to keep putting in new coolant, but now is ok. Upon first startup, there is white smoke out the tail pipe - is this due to the leak or ??

[John A Feider]

I have a 1994 Previa LE, in excellent condition, however, it apparently needs a head gasket. I say that because since it was diagnosed by a shop I never went to before almost a year ago, it still runs really great. I recently had the oil changed and that shop said there was a oil fiter housing leak. I have no technical knowledge about this, have owned this car since new. Recently had to keep putting in new coolant, but now is ok. Upon first startup, there is white smoke out the tail pipe - is this due to the leak or ??


Hello 1994 Previa,

If you've been adding coolant and your Previa blows white smoke at all, it's burning coolant in the combustion chamber. This is due to probably one of two reasons or both especially if you have over about 200K miles on it....you either have a cracked head gasket or a cracked aluminum head. I had the same problem with my 92 Previa which was a cracked head and it will only get worse until you can smell the sweet odor of coolant. You have basically two options.....one is of course, replace the gasket and or head or pour some head and gasket sealer into the cooling system after it comes up to operating temp. Others have had varying success with this option and depending upon which product you select (there are about a dozen different ones) There are several U-tube videos on the subject dealing with the Previa engine. Some of them can clog up your cooling system.....I personally wouldn't try this unless I was desperate.

If it's a cracked head, in some cases it can be repaired if the crack isn't in the wrong place. The head can in fact be removed without removing the engine thru the maint panel under the front passenger seat. See Youtube still pix video access code CMH 1129 and get a maint manual preferably an official Toyota if you're going to try it yourself. Hope this helps.....

John in the Rockies

[previa94]

Hello 1994 Previa,

If you've been adding coolant and your Previa blows white smoke at all, it's burning coolant in the combustion chamber. This is due to probably one of two reasons or both especially if you have over about 200K miles on it....you either have a cracked head gasket or a cracked aluminum head. I had the same problem with my 92 Previa which was a cracked head and it will only get worse until you can smell the sweet odor of coolant. You have basically two options.....one is of course, replace the gasket and or head or pour some head and gasket sealer into the cooling system after it comes up to operating temp. Others have had varying success with this option and depending upon which product you select (there are about a dozen different ones) There are several U-tube videos on the subject dealing with the Previa engine. Some of them can clog up your cooling system.....I personally wouldn't try this unless I was desperate.

If it's a cracked head, in some cases it can be repaired if the crack isn't in the wrong place. The head can in fact be removed without removing the engine thru the maint panel under the front passenger seat. See Youtube still pix video access code CMH 1129 and get a maint manual preferably an official Toyota if you're going to try it yourself. Hope this helps.....

John in the Rockies


Thank you for the input, John. I did read elsewhere that it could not be the head gasket if I have been able to drive the car for over the past year. Perhaps there is some spiritual intervention going on ??

[tfreed1]

I started working on replacing my head gasket today using the leave the engine in the van technique. Here are some pictures of today's progress.

I got all but one of the exhaust manifold studs out. will work on the last one next time or take the head off with the manifold attached.
9221

I turned the engine to TDC and pulled out the distributor.
9219
9220

I decided to remove the oil filter mount so that I would have a couple of extra inches to lower the engine when I take out the engine mounts. I am going to replace the rubber gasket since I have it off.
9222
9223

[tfreed1]

I removed the exhaust manifold using hammer, chisel, and heat to get the last stud out.
9302

9303

Removing the oil filter mount was useful as it allowed me to lower the engine quite a bit. I did not need to leave wood spacers after removing the engine mounts.
9304

9305

Next time. I'll take off the head and see the extent of the damage.

Took out the cam shafts.
9317

9318

Took head off.
9319

The gasket had blown. The fire ring for the number one cylinder is bent and water passage leaked to the cylinder.
9320

There is some pitting in the block deck where the coolant leak occurred. I am not sure if this is something that the new gasket will fill or if there is some sealer that I should use in this spot with the new gasket. Any suggestions on this would be welcome.
9321

9322

[tfreed1]

Any suggestions about how to handle the engine block pitting?

9323

The new head gasket uses a metal frame around the water passages. Hopefully, this is a design improvement.
9324

[timsrv]

I guess it depends on how deep the pits are. Machining (decking) the block is always best, but that would require complete disassembly and then hauling the bare block into a machine shop. There is a product made for this: https://www.amazon.com/Permatex-80697-Gasket-Hi-Temp-Adhesive/dp/B000HBNUDQ/ref=asc_df_B000HBNUDQ/?tag=hyprod-20&linkCode=df0&hvadid=242122067968&hvpos=1o2&hvnetw=g&hvrand=12018598998084024873&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9033612&hvtargid=pla-569620038934&psc=1, but in my years as a mechanic I've never used it. I usually consider things in cans to be gimmicks and some even cause more harm than good, but there are exceptions........not sure if this one of them.

If the link above doesn't work, the product is Permatex Copper Spray-A-Gasket. It's available most places where auto parts & supplies are sold. Tim

PS: For quality you can trust I highly recommend OEM Toyota for your head gasket. Other brands may be good or possibly even better???, but I'd consider other brands a roll of the dice. Good luck with whatever you do/choose.

[tfreed1]

Thanks for the information timsrv. I don't really want to coat the whole head gasket just to address the small pitted area. I may use a small amount of the Permatex or something similar just in the pitted area under the gasket. I would like to let the gasket seal its self to the block rather than using some other substance to do the sealing.

I cleaned up the head and it looks to be in good condition with no warping when checked with a feeler gauge. The engine has never been over heated until the head gasket went at 244,000 miles. And it did not run more than 3 minutes at that point.

9325

[timsrv]

I agree. If I ever needed to use that stuff, I think I would spray it in the pitted area, let it dry, then sand or file it smooth (assuming that can even be done???). When I've had similar issues in the past I've either chanced it or I've had the block decked. Tim

[tfreed1]

Although I want to minimize the work on this job, I decided I better at least replace the valve seals since I have the head off and there are so many miles on the engine. I'm glad I decided to do this as the valves for the cylinder that took the most water were pretty well stuck in the valve guides. I got them freed up. I still have a few valve seals to change. Makes me miss 2 valve per cylinder engines. I did not lap the valves as I don't want to deal with changing shims.

9360

Finished replacing the valve seals.
9364

[tfreed1]

Cleaned up the block deck and it is in good shape other then the pitted area.
9365

After reading about possible options, I decided to use a small bit of JB Weld epoxy in the pitted area.It takes at least 15 hours to cure. I will file it flat before putting the gasket and head on.
9366

9367

Here is a SAAB TSB using this solution:
9368

[tfreed1]

I put on the gasket....
9369

Torqued the head bolts....
9370

And installed cams.
9371

Will work on connecting all the peripherals and getting the job finished as time permits.

[timsrv]

Here is a SAAB TSB using this solution:
9368

Well that certainly makes me feel better about it. If I ever run into that situation I'll likely give it a try. Looking good! Thank you for the awesome documentation and please keep us posted on how things hold up :thmbup:. Tim

[tfreed1]

Thanks. The TSB made me feel better about it too.

Some additional information that may be helpful:
I drained the oil the day after the gasket blew and there was quite a bit of water in the oil pan. I drained the coolant and refilled the oil and cranked the fresh oil around the engine using the starter. I did not want to leave water in the oil passages for an extended period of time. When (fingers crossed) the engine starts, I plan on running it for a while and then changing the oil again. I plan on adding straight water first, then draining it before adding antifreeze.

[tfreed1]

I finished getting everything together and the engine is running well after a few minutes of smoke from the antifreeze in the exhaust and the oil I used while assembling the head. I ran the engine for about an hour to check for leaks and to boil off the remaining water from the inside of the engine. When it cools, I am going to change the oil, drain the water, and add antifreeze.

9390

9391


I would estimate I've spent 35 hours of actual work time on this job. I spent time getting 26 year old bolts loosened and figuring out what needed to be taken out. I changed the front O2 sensor and had to drill out the studs that were too rusted to get out. I spent a lot of additional time researching how to deal with the head pitting.

9392

Leaving the engine in the van made the job possible to do on my own. I would not want to pull the engine without help. I also did not need anything other than a floor jack and jack stands to raise the van or the engine.

While under the van, I found these supports rusted on both sides and will repair them.

9393

I plan on using the van to commute to work and will let you know how it is doing.

[timsrv]

Awesome! Thanks for taking the time to document! :dance2:

[Previologist]

I hope no news is good news.

[tfreed1]

I have driven the Previa about 1200 miles since replacing the head gasket and it is running fine. It seems to have a bit more power than before and the gas mileage has increased a bit as well. It has not lost any coolant or oil since the gasket repair. I am going to take it on a trip for the holidays (about 1800 miles round trip) and will give an update after that.

I replaced the third member with one from a 96 SC last spring and the rear end ratio is 3.73 rather than 4.30 which makes highway driving a bit quieter. I want to see if my highway gas mileage is any better when we go on the road trip. The acceleration is acceptable.

[tfreed1]

Drove the van on a trip about 1800 miles of highway driving and it is still running well. Have about 4000 miles with the new head gasket. Van has lost no oil or water.

[peaquod]

Hi Tim and everyone on this thread. Which is excellent. I’m getting geared up to run this gauntlet and I’ve noticed that since the first time i looked, the photos from the original repost have disappeared. Are they still available anywhere?

Thanks

Ethan

[originalkwyjibo]

Welcome to the forum Ethan.
The most current explanation starts on page 2 of this (https://www.toyotavantech.com/forum/showthread.php?5031-New-Photobucket-policy-is-blocking-some-TVT-images) thread.

[tfreed1]

Hi Tim and everyone on this thread. Which is excellent. I’m getting geared up to run this gauntlet and I’ve noticed that since the first time i looked, the photos from the original repost have disappeared. Are they still available anywhere?

Thanks

Ethan

Hi Ethan,

The latest news on getting the photos back is here:
https://www.toyotavantech.com/forum/showthread.php?5031-New-Photobucket-policy-is-blocking-some-TVT-images

It looks like they will eventually be view-able again.


if you have any questions about the head gasket replacement, ask them here and someone should be able to help. Good luck.

Tony

[tfreed1]

Just an update

The Previa is still going strong 23,000 miles after the head gasket replacement. I have a new job that requires travel mostly around the east coast and been using the previa for work trips. I'm at 266 thousand miles now.

[tfreed1]

Another update:

Previa still running strong at 50K miles after head gasket replacement. Finally retired it as daily driver but use it when hauling is needed.

[Previologist]

Good news. That's a job I never want to do myself.