Cracked head

After doing the head gasket last year on my 94 AWD non supercharged engine, I went 550 miles and my head cracked in three places. Or maybe they just got bigger. There are now three obvious hair line fractures: Two of them at the #3 spark plug hole on combustion chamber side;These start at the plug hole and go into each of the two exhaust valve seats at that cylinder. The other one goes from the intake valve seat to the exhaust valve seat on the rear end of engines #3 combustion chamber. See the three red marks on this picture below to the rt.

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when i took the exhaust apart just under the manifold, coolant came spilling out. You can see from this picture how much coolant was getting into the combustion chamber by the steam cleaned piston #3.

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I don't see any evidence of coolant getting through the used gasket here:

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I did notice when i loosened the head bolts they were only torqued down to 680"lb.

This seemed too low to me and could be why it cracked???

Anyone got a good cylinder head for my Previa?

You might be able to see the three tiny cracks if you click on either one of these pics:

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It too late to know if the cracks were starting before. Like i already mentioned, it did make it 500 plus miles into my road trip before showing a temp problem. Then things went bad really quick.:pissed:

Should have done a "QA inspection cleaner" test for any evidence of the start of these tiny fractures. I think they were there before but just invisible. Any Ideas?http://www.toyotavantech.com/forum/i...isc/pencil.png

That's a lot of wasted work. I hate doing jobs twice, sorry you're having this problem. I've heard of Previa heads developing these cracks before. Thankfully I haven't had the misfortune yet (and hope I never do).

I did the head gasket on one of my Previas and frankly I was a little distressed with the head torquing procedure. The FSM said to torque them, then crank each bolt another 90 deg! This seemed like an outrageous amount of torque to me and I feared breaking a head bolt, but they all held and so far the van has been holding up fine. If I were in your position I would consider purchasing one of those "low mileage jap engines". Most major cities have an importer of these things and they are supposed to have less than 50k miles on them. If you're paying somebody else to do the job, your total cost would most likely be less too. Next time I need major engine work I'll most likely go that route. Good luck. Tim

That confused me too about the 90 degree torque on the head bolts in the FSM.
Called the dealer and they want a grand for a new head and will take a month.

It was way easier to just drop engine down and pull the head.about 90 percent less to take apart(seems like 90.did not actually make a list) and won't have to deal with movin engine around too.

sounds like i'll look for a low miledge engine or just pull a head from the junk yard.

any ideas on what year heads are compatible?

I'm not 100% sure on this but I believe all naturally aspirated heads are the same. Tim

PS: I'm getting one of those "low mileage" jap transmissions for my All-Trac and was considering getting an engine at the same time. Nothing wrong with my existing engine, just has a bunch of miles on it. I was thinking I could swap the set in one weekend then not revisit these things for a long time to come. Tim

I just found a previa that this guy uses for work. The interior is shot and body is not that great but only 170,000 on engine and he wants $900.

I'm wondering if his engine and trans will work with my 94 all trac. his is a 93 2wd NA engine.

I know there were a lot of changes between 93 & 94, but I don't think any of them affected the engines or trannys of naturally aspirated Previas. Like I said, I'm not 100% sure, but I'm at about 90% pushing 95%.

even the same trans for 2wd and all trac? I could see the engines being the same. I just would not automatically think for transmission too.

I would assume trannys stayed the same too.......of course you know what they say about the word ass u me :LOL2:. All-trac trannys are different from 2wd trannys, so you couldn't do a simple swap over there. I suspect the internal parts are mostly the same, but the back half of the cases and tail shafts are different. Tim

PS: Naturally aspirated trannys are different from supercharged trannys......SC trannys are built tougher and also use a different gear ratio.

So being that the SC transmissions are tougher, maybe if i go the complete engine route instead of the quick fix of just a used head, then i should look for a SC hook up. Anyone ever done this? I know the computer would have to be swapped out. just curious what else. maybe its not worth it. I would like to have a tougher trans though.

SC Previas utilize different gear ratios on the differential(s) to compensate for the gear ratio change in the transmission. You could use the SC tranny on a chassis that was originally NA if you also swapped out the differential(s) (or at least the gears inside). Personally I would prefer the engine to remain NA for economy/reliability reasons. SC engines seem to hold up okay, but there are more things that can go wrong. IMO the superchargers on these don't increase power a tremendous amount anyhow. Tim

Here to chime in. You can buy a used JDM mileage engine for pretty cheap. I'm talking $600 or less. They are supposed to have low miles and they usually will come with a 6 month warranty too. They are pressure tested before they are sold. Most of these engines have low mies but noone really knows exactly how many miles are on them. You could have 30,000 miles or 80,000 miles. Most people will say 60,000 miles. Anyway, I've seen places here in So. California selling engine and auto tranny together for around $650. Previa trannies can be had for $200 or less. Most around here for the N/A van are going for around $150. BTW, check E-Bay. Many of the distributors are selling on there too.Good luck.

The way it was described to me is Japan places a huge tax on vehicles that exceed 60k miles. Due to this tax it's often cheaper to salvage the vehicle and get a new one rather than keep it and pay the tax. This is what I was told by the JDM outfit in Lynwood, WA. Tim

I couldn't remember if it was 60,000 miles or 60,000 kilometers. Thanks Tim.

Quote:

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Originally Posted by terbennett

I couldn't remember if it was 60,000 miles or 60,000 kilometers. Thanks Tim.

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That's a good point. The lady I talked to said miles..........perhaps she already converted from kilometers??? Perhaps she didn't know what she was talking about??? I've never really looked into this before, but I have friends that have used these and had really good luck. Maybe somebody else here has more info on these things? If so I'd like to find out more. For prices like that, I think I'm going to swap both the engine and tranny together. Tim

Those are great prices. The ones i have been given so far from other internet parts places have been around $800 for my engine and another $800 for the trans. free shipping and warranty. there is no way i'm going to spend that much on an engine with 130,000 miles. A friend told me about http://www.car-part.com and there are some really cheap places to get used parts. That's probably where I will get the head. I don't see the point of pulling the motor and not put in newer, low miles, trans and engine.

Just got a quote from internet jdm place. i waited 20 minutes on the phone and at first the sales guy told me they don't have motors that old. i pressed him and he said o yeah they have 3 motors but they don't have transmissions. 1 year warranty and less then 50,000 miles and provides vin #. They want $1950.00

I can get the engine for $749 & the Transmission for $495 Both delivered to my door. The company I'm dealing with said they only have one or two transmissions at this time so I'm waiting on posting that company's info until after I get mine :wnk:. They said the engine and tranny will come on 2 different pallets (not married together).

I talked to the woman there a little more about the mileage claims. She said that Japan taxes vehicles based on how many kilometers they have. As the kilometers go up, so does the tax. At some point (usually between 70,000 & 95,000 kilometers) the tax becomes too expensive and the vehicle gets recycled. They purchase engines and transmissions and have them shipped over here for resale. When you convert kilometers to miles, this works out to about 45k - 60k miles, but there's no way to really know for sure what the history was. I'm still a bit skeptical, but it does make sense considering the roads (or lack of them) in Japan. I think it would take a really long time to rack up the miles because they don't have a huge highway system like we do (it's an island). Tim

To buy a refurbished head with valves and warranty is $350.00. I don't want to go this route. It will save time but not deal with the weak link of an overheated motor with a good head. If i'm going with the quick fix then a good used head with the same miles is all I need. But I want to put my hands on it before i buy it.

I found a van in a junk yard only a couple miles from me:

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They say the lady drove it to the yard. I could see from the damage to the top rear that it was too costly a repair for her, but internally everything is fine from the wreck. Hardly anything has been parted off of this van. 200,000 on the odometer 2wd federal emissions NA engine built in December 1990. If we do this, then the compatibility question will be answered with a 03/94 NA motor.

They will sell me the whole engine for $250.00. The passenger side is sunk in the mud so to save on hours of labor time i'll just yank the head for $250.00. I have a power outlet and they will let me cut out the top above the engine with my diamond bit angle grinder to lift the intake then bend the paneling back and the head hopefully will come out the top. They won't sell the whole van and its future is the crusher, so I'm not so worried about cutting it up. If this quicker fix does not work then I'll consider to finish pulling the entire engine out or going with low miles JDM. $250.00 and the van going soon at 200,000 or $1300.00 way more labor and down time but with trans and motor at 60,000?

I want to hear how this engine at the junk yard sounds before i pull it apart but not sure of the gas supply situation. The tank is sunk in the mud. I have a extra fuel pump from one of my plow trucks. It's a W series 87 dodge ram pickup. I have all the fuel connectors to go inline to the previa. Is this a stupid idea? I have never done a fuel pump and i can't find any electrical diagrams for how my dodge pump is supposed to be wired. Do These fuel pumps take 12v directly? I have all the plumbing and electrical components to do this. Obviously extreme caution must be taken when running voltage to a fuel container then fuel into a motor. It will be fun and exciting but maybe there is an easier way to check a junk yard motor without fuel supply.

If the yard is following EPA rules they would have drained all the fluids out of the van before placing it in the yard & often times they don't bother putting drain plugs back in their holes. Make sure there's oil in it before starting. If you put oil in it, make sure the drain plug is there and it's tight. I'm guessing they wouldn't want you putting oil in it there because then they'd need to drain it out again.

I don't know anything about your style of fuel pump, but it needs to be capable of around 50psi. If it came from a vehicle with a 12vdc electrical system, and it has 2 wires coming off of it, then yes, you could simply hook it up to a battery and get it to run. Do all the wire hook-ups at the pump 1st, then hook up the leads to the battery at a distance (you don't want any sparks right there next to the fuel and the pump). The plumbing between the pump and the engine fuel rail needs to be sealed and capable of holding around 50psi. If you can handle all of that, you have a good cranking battery, and they let you bring that stuff into the yard, then you should be in business (assuming none of the crucial parts and/or wiring have been removed). Tim

All fluids except gas are still in it. The guy at the yard told me that with ethanol they put water in it so it corrodes fuel system. Never heard that before.

Great point about the electrical being done last away from the gas and pump.


I do have a question about the injectors once the head is out: To test them do I just put 12 volts directly for them to open with a 50 psi pressure?


Plan to go to the yard tomorrow.

It's kind of hard to test injectors without a test bench. It can be done but there are challenges. I have a write-up over at TVP of doing this with a van, but I think it may have messed with my FPR (Fuel Pressure Regulator) because it failed shortly after putting it back into service. Here's a link to that post: http://www.toyotavanpeople.com/forum...=shezam#p40263

If I were to do this again I'd do it without the pulsation damper or the FPR installed or I'd simply take the injectors down to a shop with an ultrasonic cleaning machine and an injector test bench. It would cost you about $50-$100 to have all 4 cleaned and tested. Tim

That's just what i needed to see. I'll try it with the previa if it works. Let you know how it goes.

I just thought of something about putting in a used cylinder head. Even the ones that are pressure tested and shaved. What about the cams? The head would need its original cams and bearing caps and the piston looking shims. Wouldn't it be a problem using old cams from a different head? I know your not supposed to mix up the bearing caps. Using a different head and cam combination would have a different wear pattern and cause trouble. Right? (the wear on the head where cam runs 180 degrees under bearing caps).So I also should use the cams and shims and bearing caps from the donor head. So Its not a good idea to just order a random used head without it's cams and bearing caps.

Yes, all valid points. I'm not exactly sure about Toyota's procedures, but typically all the caps are installed and torqued, then the cam bearing surfaces are line-bored together. Once line-boring is completed the location and orientation of each bearing cap is set for life. As far as bearing surfaces go, changing cam-shafts wouldn't be such a big deal, but then all the valves would need to be re-shimmed to match the cam (preferably with new). Of course that would re-initiate the high wear of break in on an old cam (and that's a bit risky), so keeping all used parts together with their original mates would be much preferred.

So unless you plan on re-shimming valves, having machine work done, buying new expensive parts, etc be sure to keep all parts in their original order and orientation. If you're going for an inexpensive lasting repair, installing a good used head complete with all of it's components would be the way to go.

I try to be conservative and re-use as many old parts as possible. But, considering the fact this engine needs to be removed (or mostly removed) to change the head anyhow, IMO it's hardly worth changing a head (at least not on a high mileage engine). Especially while there are low mileage Jap engines available for reasonable prices.

BTW, I tried to order an engine and transmission today from www.foreignengines.com but found they are out of the naturally aspirated All-Trac automatic transmissions :cry:. So now I'm on a waiting list. Perhaps I'll look around at some of the other importers. Tim

Quote:

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Originally Posted by timsrv

I try to be conservative and re-use as many old parts as possible. But, considering the fact this engine needs to be removed (or mostly removed) to change the head anyhow, IMO it's hardly worth changing a head (at least not on a high mileage engine). Especially while there are low mileage Jap engines available for reasonable prices.
Tim

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I want to try something different. I very well might kick myself for trying it this way. I will try to document my process. And if anything it can be a way not to do it.

This is what I did today one hour before the yard closed. Please note this engine is not dropped down:

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It took me 45 minutes to take out the driver seat (passenger seat removed already and spark plug cover) and cut out the carpet (higher risk of fire) and once i made the 16" cut bridging the two access openings (included in the 45 minutes labor time), the panel lifted easily with my hands. The yard is going to bring this van to the crusher. For 45 minutes of work, I am seriously considering doing this to my Previa( I would have to figure how to bolt back down ) and see how long it takes to drop this head in from the top on my 94. Let's see if it comes out the top first on this one. In no way am i saying it would take anyone this same amount of time to expose the top of the engine like this and make this single cut. To buy the tools and equipment new would be around $125.00. And fortunate for me the previa was only 3 cars from my work van (86 2wd) and 50' from a power outlet to run my diamond bit outfitted angle grinder. This $50.00 diamond cutting wheel moves quickly through wood metal or stone and it lasts forever. I used a face shield, ear protection and $20.00 3m painting mask for the fumes and metal dust. Had a fire extinguisher just in case, and it made the yard owner feel better; diamond wheels don't spark like other abrasives and iv'e never had a fire. I use this tool all the time. My Makita cordless impact made quick work of the bolts that had to come out to prep for the cut and beyond. Just have to crack most of the larger bolts loose with the socket wrench first. Going back tomorrow, and I will try my best to document everything i still need to do to get the head out and how long it takes. The converter is already cut out at the flex pipe so the exhaust is free and i plan to leave the exhaust manifold attached for install and weld into new converter. It looks like everything else still needs to come loose to just get the head out.

This is where the head needs to go: Keep in mind, for this head removal i dropped the engine and head came out below,which was quite a bit of work but may not be necessary for future intake access. That's if the cut out works:

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I'm not sure what's up with your pics but they don't show. I'm very interested to see these. Tim

Sorry the pics did not work. When i go to edit the post I can see them fine. Is there a help thread for the best way to post pictures on this forum?

I spent 4 hours getting the head ready to come out today, and I have many more photos. Everything is separated from the head. This being the 3rd time i've taken off a previa head this was by far the easiest and quickest. The van was not lifted all that high either. There was no wheel on the front here so i had to lift it. but I wonder if there was a tire there would it even need to be lifted. Worst case just the front rt wheel.The only bolt that was difficult to get to was the 12mm (one of two) that holds the wire harness onto the head just above the distributor. It was just tight fitting my hands in there . And if i remember correctly this was hard to get to even with the engine dropped. My point is, compared to the last two head removal jobs this bolt was the least of my worries. Actually everything went really smooth. Egr tube came off easy. Oil return hose at the front passenger mount did too. (compared to other times) . did not even need to take loose any engine mounts and or lift the engine. I checked the clearances on the shims and all is good. Tomorrow take the bearing caps off and loosen the head bolts,lift the intake and it should lift right out or just go down like i've done in the past. I should have the head out of this van in 6 hours total labor time. I know it can be done quicker.


Ps. are these going through? this is the area where i had the most access trouble just above the distributor at one of the bolts for harness bracket. The last picture is where i left off today. Cams, head bolts,lifting intake and timing chain are all thats left before it will lift out:


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Here are the things i had to take off on the right side (front of vehicle) of the head:

coolant hose into head(hose into water pump does not need to come off for head removal), oil return from head into oil pan and timing chain tensioner:

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The second picture above is the bracket for the oil return which has 12mm bolt which bolts into the engine mount (it's technically not the engine mount but what the mount bolts too.) and can be removed first, then the 12mm studs in first picture and the other end is at the oil pan pic 6. once everything is loose i just stuck my pry bar(big screwdriver would probably work too) above the oil hose in pic 6 and under the engine mount and pryed down and once hose came off there then the metal part at head with the two studs pic 1 came down and the whole thing came out. Did not need to touch the engine mount. Same for the tensioner. I did need to use a 1/4 inch universal and extension 12mm short socket to get around the nut closest to the block. Picture below shows access point with universal to tensioner bolt/stud then the tensioner studs:

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Had to be careful around the 16 inches of sharp metal where i did the cut out. Went along it with a hammer afterwards but still got cut here:

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I took the 3 coolant sensors off. 22,19 and 17 mm opened end wrenches worked good (as those are the 3 sizes of these sensors). I broke one last time when the wrench slipped and also wanted to avoid getting any broken during head removal. Have some extras now:

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Nice. Looks like all the pics except 1 came through this time. Thanks for taking the time and effort to post them :thmbup:. Tim

PS: Looks like you fixed the ones in your previous post as well. I can see all of those now too.

Thanks Tim,

I'm trying. Wish I could do a better job on the pictures and describing what i'm doing. Just not familiar enough with all the parts and names and such. It's just going to take some time. What is the best way to do this? Just keep editing the upper post adding pics and comments to it or should it be done another way?

Spent two more hours on the head today and got it home. It lifted right out the top with only the 16" cut as shown already. Here's also how I attached my lift chain to the rt or front end of the head.lifted it up and out with my hands. wasn't too heavy. find the left side chain picture later.

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The entire job was done with the van being even lower then with tires. It really did not need to be that high up because most work was done from up top and the head is on the end so to get underneath to the right or left all i really needed was my arms and head under there. Here's a picture of how high the van was.
who would have thought? There was a brick under the rotor passenger front. I can't find the pic now. i'll put it up later.

Here is a better image of the cut out. Notice the double layer of sheet metal at the both ends of the cut where the access panels meet. It took a little longer to get through on these ends. The middle went through like butter.


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Awesome! Nice Job...........now the real fun begins :)>:.

The gasket on this van had just been changed before it was wrecked because it looks new. I was curious to see what the head bolts were torqued to and they must have done them like it says to do in the shop manual. This could be why my last head failed because I had only torqued them to 680" lb (which seemed a lot to me ). These bolts were at 1224" lb and the bolts did not break and no signs of failure with its latest head gasket job either. In a couple a spots I had to use a 3/8 extension because my shortest 1/2" was a bit too long .So for clearance without the engine drop a 6" long 1/2" extension is too long for a couple or more of the head bolts. I would mark the bolts(really I just marked the socket) and then loosen a bit then re tighten to measure torque at original position. This is what happened to my 3/8 extension(use 1/2" extension shorter then 6") when I tried to set a bolt back where it was to original torque position:


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I finished up at the junk yard and had to put off the project for a few days. Here's where i'm at with the donor engine. I lucked out and got a rebuilt engine. all the seals and gaskets are new and the cylinders have been bored and i think there are new valves and seals too. I know the bottom end had been pulled too because the gasket is new on that cover as well. a mechanic friend told me that the deposits on the pistons is oil getting through because rings have not fully set in yet. I did notice a lot of oil or tar like residue in the exhaust manifold pipes:

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Have to put off this project for a few weeks. Something else has come up. will return later.

I'm late in getting around to this. The head is done. Put around three thousand miles on it now and no problems.

Here are some pictures of testing the injectors before the new head went in (the picture does not show gauge under pressure but when activated read aprox 50 psi ):

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Here is the cold start injector test:

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Then some more pictures of electrical test wires fuel system check before head goes in switches activates injectors with 12V and the other switch 12V to fuel pump:

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