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Figured I might as well create a thread for all my blown head gasket stuff. Gonna try to keep the forum nice and tidy :LOL2:
Here were some of my previous threads that were related:
http://www.toyotavantech.com/forum/s...hite-and-brown
http://www.toyotavantech.com/forum/s...shaft-bolt-off
http://www.toyotavantech.com/forum/s...oil-pan-gasket
A bit of good news: I got my head off today. Found out it had > 0.30mm warpage near cylinders 3 and 4. :no: Odd thing is that I called 2 different machine shops and they told me different things. The first one said that the head wouldn't be salvageable because it had too much warpage. He said that usually it would be okay if it was 0.10mm - 0.12mm warpage and that I'd also have to worry about the top of the head warping, where the camshafts are. He recommended I just get a new head or one from the junkyard. The 2nd one I called told me that it'd actually be okay to shave it off flat. He said that if it were twice the amount (0.60mm) of warpage, then it'd be troublesome. Which one is correct? Perhaps I misunderstood one of the machinists?
my 2c? The first guy is correct.
Beyond .1mm (.004") out-of-flat and your head is questionable. Beyond .2mm it's toast.
Try putting a camshaft in its journals (after pulling out the lifter buckets and putting them in something like an egg carton so you can keep track of where they came from). It should turn freely. Now bolt the cam journal caps on. Does it still turn freely? If not, your head is toast.
Yup looks like you were correct. The 2nd machinist called me back again today. Told me that the head was in really bad shape. On top of the warpage, there was also a leaking intake valve and leaking exhaust valve. He recommended that I get a new head or one from the junkyard.
Saw this snippet in my '93 Previa FSM about inspecting the head for flatness. It said maximum warpage for the head surface is 0.15mm and for the manifold surface is 0.20mm. If the warpage is greater than maximum, replace the head.
One thing I'm worried about is that since my head was in such bad shape that my engine block may be toast as well. What's the best way to check the condition of the lower half of my engine (cracks, etc)?
it takes a lot more heat to warp the iron block
measure the trueness of the block the same way you would with the head... the shop manual explains this
I was able to get a junkyard head that had < 0.10mm warpage, so not too shabby. I did it in just under 6 hours too :). The Previa I got it from had 287k miles on it. The reason I chose it was because when I took off the valve cover, there didn't seem to be any milky white oil in it. The 1st Previa I got to actually had less miles, but once I started working on it, there was a bunch of milky white oil leaking out.
So I dropped off the junkyard head at the machinist, but the machinist called back again today, and said that there was slight leakage in the valves. If I were to do a valve job, he said he could do the job for ~$650. It would include doing the valve clearances, exhaust valve guides, and valve stem seals (already gave him the parts for that). The machine shop has both my original bad head and the "newer" junkyard head (not really newer since junkyard head had 287k miles on it, but at least it was less warped!). I'm guessing he would re-use any parts from my old head in the junkyard head. This is from the machinist that said that 0.30mm was OK.
Regarding the 0.30mm warpage being OK, after talking to him more, my impression is that he might have misheard me on the phone, because talking to him today he made it seem like 0.30mm was way too much. The guy seems like he knows what he's talking about, but I've just been wondering about everything he tells me ever since that episode. What do you guys think?
Also curious about the price. $650 feels like a shot in the gut, since I've already done all the work for pulling off the head both on my own car and at the junkyard. And he's got a lot of the parts in front of him. If he were to do the job, I don't know if he would go out and purchase any new parts, since he's got 2 heads in front of him.
- What's the normal cost for a valve job like this? I've looked around on the net and found a couple different quotes from $200-300 for a 4 cylinder to $700 total on a Tercel all labor included for pulling the head off (I've already pulled the head off though)
- Since $650 seems pricey (but I would do it if you guys recommend it), should I just get another junkyard head? One of the commenters here said it'd be easier to just buy a used head from the junkyard. I have a 30 day warranty on the head that I pulled. It only took me about 5-6 hours of work, and I have 2 other Pick'n'Pulls within 30 minutes I can check out.
What do you guys think of the situation? Should I just do the valve job? Just get a another junkyard head from a different Pick'n'Pull? Get a quote from the 1st machinist that was upfront with me about the original head being junk? I'm really debating what I should do and hoping for any advice Thank you!
Also:
- Is the cost of a valve job dependent on which valves and number of valves are leaking? Or do machine shops typically do all the valves? If it's dependent on which valves are leaking, I guess I wouldn't be able to get an accurate estimate from the 1st mechanic because i don't know which valves are leaking.
- I found this posting from Corey over at the Previa Yahoo Group, where he said that he would only mill a non-cracked head and not bother with valve job. I am not sure if he was referring to OP's specific situation or in general. Here's the quote:
https://groups.yahoo.com/neo/groups/...s/topics/54304Quote:
If you can find a non cracked head, I would only mill it . all that valve work is not needed. Having the head milled is $50 to $60 . there are several heads listed on www.car-part.com . a call to the yard that is selling it to verify that the visually inspect for cracks near the valves and spark plug threads would be necessary.
That has me even more confused now. Thoughts?
I've been down several roads with Previa heads, and have taken them all to the same shop. I've used them for many years on many projects and never been disappointed.
One only needed to be cleaned and surfaced, and have the seals replaced.
One was warped and declared junk.
Most recently, a head was inspected and found to be flat but with some leaking valves. The work involved cleaning, grinding all the valves, replacing the seals and surfacing. All for around $300. $650 sounds steep to me, but the difference may be the exhaust valve stems. If they really need to be replaced, that might well be the difference.
I bought a "rebuilt" head on ebay this last year (to replace the warped one), but that seller no longer lists them. It was $300 with free shipping, including the return shipping of my old warped core. I haven't even started that engine yet - long story. So this seemed like a great deal but until that engine has miles on it the jury's still out.
Took my heads over to the 1st machine shop. Just felt more comfortable with them and charges seemed more reasonable.
Doesn't seem like there's too many Previa heads for sale on EBay anymore. Maybe there's a market opportunity there next time I get another 50% sale at the junkyard. :LOL2:
Got my head back from the machine shop a few days ago. Head is resurfaced. The machinist also did a vacuum test on it, and told me that it was leaking a little bit, but probably not necessary to do a full valve job.
I did want to address the leakage with some lapping though. So I did a water test to figure out which valves were leaking and found that most of my intake valves were pretty good, but nearly all of my exhaust valves were leaking a little bit. I spent the last few days lapping my exhaust valves so they could seal better. Also changed out my valve stem seals while I was at it.
Here were the tools I used.
https://i.imgur.com/JHmseHO.jpg
From left to right:
a) paper towels - to act as a cushion for my home-made valve spring compressor. Also to clean oil and valve grind compound off.
b) 17mm socket - put this underneath the valves I was working on, so that it could be as a counter-balance for valve spring compressor
c) PVC pipe w/ center portion cut out - 2" long, 3/4" diameter. I used this as my valve spring compressor. Only cost me 51 cents at Home Depot.
d) magnetic pick up tool - when using the valve spring compressor, inserted this through the cut out portion touching keepers, to make sure keepers don't fly everywhere.
e) pick - this was used to take out the old valve stem seal.
f) 1/4" extension - on installing the keepers, this was used to keep the keepers in place, while I pressed down with the PVC pipe.
g) Permatex valve grind compound 80036 - $4 at the auto store.
h) power drill with 5/32" vacuum hose - only needed 6 inches in length to attach to the valve stem. Vacuum hose was $1.25 per foot.
I also originally bought a Lisle 21200 small lapping tool, which turned out to be complete crap. I would not recommend at all. The suctions didn't work, so they weren't even able to turn the valves. I ended up using the power drill method, which ended up being cheaper anyway.
I lapped all of my exhaust valves, and after a re-test of the water test, SUCCESS! No more leakage! I think I'm ready to install my cylinder head soon. :)
Nicely done! I love the minimalist approach to your tooling.
I've a couple of questions:
What did you use to press the PVC pipe down?
It looks like your 1/4" extension has a deep socket on it. What size? just big enough to straddle the keepers?
I guess the vacuum hose has a ID small enough to grip the valve stem and allow the drill to spin it. What's with the flared portion on the end?
I actually only used my weight and a little arm strength to push down my PVC pipe. My workbench was waist high, so that made it convenient for me to just lean over and press in. I think that a C-clamp could actually work as well, provided that it is large enough, but pressing down on the PVC seemed worked well enough for me. I used paper towels on top of the PVC pipe, so that it wouldn't dig into my hand too much.
For the 1/4" extension, I used the drive end of the extension. I have a 10mm deep socket on it, but I didn't actually use that end. If I had to take a guess on the socket end, I think anywhere from a 8mm to 10mm socket could work. Also, for installation, what I did was push down the PVC pipe with one hand and with the other hand push down the extension and wiggle it. It can be a bit tricky sometimes and requires a little practice, but it is similar to what briansmobile1 does in this YouTube video (@8:48 mark): https://www.youtube.com/watch?v=VIwmf0nhljU&t=8m48s
I took a picture of the vacuum hose after i had already finished lapping, so it was already enlarged by the valve stem and that's why it looks flared. Originally, I had used a 7/32" vacuum hose and that fit snugly over the valve stem, but it wasn't snug enough to actually rotate the valve. So I got the smaller 5/32" and just kinda shoved it over the valve stem, and that seemed to work perfect for me. It's possible a 3/16" vacuum hose might work, but my auto store didn't have any more in stock, so I wasn't able to try that.
Also, I forgot to mention I had to use an air compressor for doing the water test. I already had 10 gallon compressor from previous work I've done, but I think that's the only piece of specialty tooling that I used. I used the method described in this video to do my water test: https://www.youtube.com/watch?v=DkH4cNAahZQ. Water will actually leak out of the spark plug hole, so I just placed my thumb over the hole to plug it up and prevent water from leaking out while I was doing the test.
Got my head bolted down. But having trouble with getting that EGR pipe bolted to the head though. It just doesn't seem long enough to get that stud to fit into the hole on the pipe. Oddly, I don't remember the pipe being too hard to take off. It just kinda lifted out. Could I be doing something wrong?
I had the same problem on my 92. I Had to get help pushing/prying on pipe with pry bar from above through access hole while I was underneath with another bar... Just enough to line it up to get a bolt started, then it went on. It was a bit scary, but it worked.:(:
Got it, thanks! The way I did it was I used a C-clamp to get enough horizontal force to finally get the EGR pipe on the stud. After getting the hole onto the stud, the rest was pretty easy.
So now I'm working on my distributor. I already broke one of the bolts from over-tightening, so I'll have to wait a little bit while a new bolt comes in from the dealer.
Well not so good news. I finally managed to put most of it back together, but wanted to do a quick compression test to see if all my issues had been resolved. Originally I had 0 compression in cylinders #3 and #4. Well now, it turns out I've fixed cylinder #3 with 155psi, but still have low compression in my cylinder #4 with only about ~70psi in that cylinder.
Debating what I want to do next... Thinking maybe I should do a leakdown test to check my valves again..Or maybe my piston rings in that cylinder are shot from when it overheated and blew the HG?.
Wow, that's pretty disheartening.
Did you check your valve clearance after getting the head back and putting the cams on? Maybe you have some valves that aren't closing completely.
I hope it's that simple.
I didn't check, but I think that might be exactly it. Reflecting back, I now remember using my original exhaust camshaft, rather than the "new" junkyard cams I had gotten. Basically, what happened was that the 2 "mini" gears on the junkyard ones were kinda mismatched from each other because I forgotten about using a service bolt when I was at the junkyard, and rather than trying to fix the mismatched gears, I just opted to use my old exhaust camshaft. At the time, I didn't know if leaving junkyard valve lifters in there would make a difference, but now I'm thinking I should have also changed out those lifters too, so they would be matching. I'm gonna take a closer look at those clearances. Hopefully it'll be as simple as swapping out some lifters.
Aha.
If your valves were ground, they sit deeper into the seats, and unless the stems were ground shorter by the same amount, the clearance to the cam through the lifter and shim will be less. Change the cam and other random clearance changes will occur as well.
I had a head done recently by my shop, and I didn't take the cams in. They ground the valves and ground the stems as well. When I put the cams on I checked the clearances. All were within spec, but a few were on the edge. I swapped a few shims and bought a few new ones to nail the clearances all around. This took a while. I bet I had the cams off and on four or five times.
You're going to wish you did this with your head on a bench!
Actually after seeing your post about valve clearances, I felt 10x better this morning. Yesterday, I was all ready to book a trip to Mexico and my heart dropped when I saw the compression numbers. Even if I just have to take that cam out a few times, it'll be much better than tearing that whole head down again! :yes:
Checked my valve clearances today, but there's a still a little bit of a mystery here for me.
Spec says that it should between 0.15-0.25mm on the intake side and 0.25-0.35mm on the exhaust side. All of my intake clearances were in spec. All of my exhaust clearances were out of spec. Seems to make sense since I only did lapping on the exhaust side and none on the intake side. Also, I had used the old camshaft on the exhaust side.
Anyway, here's what I found on my exhaust side today (2 valves per cylinder):
Cylinder 1: 0.13mm...0.15mm
Cylinder 2: 0.23mm...0.21mm
Cylinder 3: 0.10mm...0.04mm <--- !!
Cylinder 4: 0.20mm...0.13mm
While all exhaust valves were out of spec, the weird thing for me comes in that my worst one is actually cylinder 3, not cylinder 4. But in my compression test, I had I had 160psi compression in cylinder 3, while I only had 70psi in cylinder 4. Because cylinders 1 and 2 (both about 155psi) and 3 were all out-of-spec, but also still had decent compression, that leads me to believe something else might still be wrong with 4. I do remember doing a water test on all the cylinders after lapping to test for leakage, so for some reason I think the valve seats should be okay? I am actually not sure on this one. Any ideas :cnfsd:
perform a leak down test to determine where it's leaking
Well, my theory's blown. If you have any clearance at all, then the valves are closing. Fine-tuning the clearances won't fix your compression issue.
I think TheMAN's suggestion is a good one at this point. If the valves are sealing, you are either leaking at the head gasket or past the rings.
Found my leak today. It's the piston rings. I had a ton of air coming out of the oil filler cap and oil dipstick hole. A tiny bit of air, but noticeable, was also coming out of the throttle body too.
I had done a leakdown at the outset of all this, but guess I did it wrong originally. Now it looks like I'll be needing to work on the bottom half of the engine too.
Hello all
Reviving a rather old thread as I prepare to replace a blown HG on my '94 N/A egg. I plan to take Samay's approach and do the work w the motor mostly still in place.
I've been looking through related posts here for more info on what to replace while I'm doing this work but haven't landed on a succinct list. So far I am thinking h20 pump, t'stat, and any other hoses that I can access. I wish I could do the timing set but I don't think I'll be able to remove the whole engine and trans. I'll need to replace one plug as cyl 1 is the culprit per a pressure test, and I have ordered a new prepped head in case the old one is cracked. My motor has over 150K on it, though it's the second engine in this van which is showing 309 on the odo.
Are there any preferred vendors for these parts? I've read that the OEM HG is the 'only way to go' so I won't skimp on that. What about water pump and other parts?
Quote:
Originally Posted by maestro123