The 3.0 Hypothesis - if you've had a headgasket fail, read...if you have headers too
04-04-2007, 05:05 AM
#21
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I've done HG work on two engines.
1) The first had the factory HG recall done at 100k and I pulled the heads at 170k when it needed a valve job (HG still good). The valves that were the worst were the #6 and #5, most likely cause by the excess heat from the exhaust crossover. Vehicle was an automatic.
2) Bought a '91 with 165k miles (manual) with a blown headgasket for $1200. The factory HG recall was done around 110k or so. When I pulled the heads off it looked like the gasket had failed at the #6 cylinder.
I have heard that the aluminum heads against the steel block resulting in varying thermal expansion rates has a lot to do with the HG failures. I also don't think that the Torque to Yield bolts, or the reuse of said bolts, has anything to do with HG failures. If you've taken a Strength of Materials class, and therefor understand how stress-strain curves work, youd know that just because a bolt has been stressed to the point in which it yields, doesn't mean that it won't hold as well anymore. It just means that, #1) when the load is removed from the bolt it won't return to it's original length (it will be somewhat longer), and #2) the bolt is approaching its ultimate strength, or the point at which it will fail. So, what Im getting at is that unless the bolt actually breaks, its still good. Its still holding the head to the block just as good with the second use as it was with the first use.
Sorry for the Strength of Materials lecture, but I've reused head bolts twice now and haven't had any problems doing so.
1) The first had the factory HG recall done at 100k and I pulled the heads at 170k when it needed a valve job (HG still good). The valves that were the worst were the #6 and #5, most likely cause by the excess heat from the exhaust crossover. Vehicle was an automatic.
2) Bought a '91 with 165k miles (manual) with a blown headgasket for $1200. The factory HG recall was done around 110k or so. When I pulled the heads off it looked like the gasket had failed at the #6 cylinder.
I have heard that the aluminum heads against the steel block resulting in varying thermal expansion rates has a lot to do with the HG failures. I also don't think that the Torque to Yield bolts, or the reuse of said bolts, has anything to do with HG failures. If you've taken a Strength of Materials class, and therefor understand how stress-strain curves work, youd know that just because a bolt has been stressed to the point in which it yields, doesn't mean that it won't hold as well anymore. It just means that, #1) when the load is removed from the bolt it won't return to it's original length (it will be somewhat longer), and #2) the bolt is approaching its ultimate strength, or the point at which it will fail. So, what Im getting at is that unless the bolt actually breaks, its still good. Its still holding the head to the block just as good with the second use as it was with the first use.
Sorry for the Strength of Materials lecture, but I've reused head bolts twice now and haven't had any problems doing so.
Im not a metallurgist, so I can honestly say I don't know what I'm talking about, but when ARP states that a head bolt/stud needs to still be in its elastic phase when fully torqued, wouldn't it be considered bad that the TTY bolts are beyond their elastic phase? Ie - less overall clamping force?
04-04-2007, 05:07 AM
#22
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You are dead on! The abolishion of asbestos created lots of headgasket issues for other makers also. The 1988 3.0 and 89 and mid way throough 90 used asbestos, we had zero problems with these (keep in mind, a failure rate of about 7% in 100K miles was considered normal, headgasket is kinda like a normal wearing item). The worst gaskets were design 1 from late 1990 to 1993. In 1994, it was improved and 95, final design gasket was used) They have a print seal which was facing upward which made the gasket stick to the aluminum, and float on the iron as it expanded. Well, the aluminum expanded at a greater rate, design 2, same deal, but more reinforcement. Design 3, print seal was moved on the block side of the gasket, and even more reinforcement added which was bascially more steel and the head was allowed to float eliminating deformed gaskets. As for the 3.4, they did use a composition gasket, but around 99, they went to a laminated all steel gasket with a coating to allow slippage, but no gasket distortion. Problem solved.
speaking of HG replacement, and tps trouble shooting, did you get my PM?
How do I tell if I need to buy a new TPS?
[/thread hijack]
Id be williing to bet that all of these factors contribute to the 3vze's issues. Id also be willing to bet that if you address all of the issues, you'll have a great platform to start from to add FI.
Last edited by Bumpin' Yota; 04-04-2007 at 05:14 AM.
04-04-2007, 06:37 AM
#23
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Im not a metallurgist, so I can honestly say I don't know what I'm talking about, but when ARP states that a head bolt/stud needs to still be in its elastic phase when fully torqued, wouldn't it be considered bad that the TTY bolts are beyond their elastic phase? Ie - less overall clamping force?
Now lets say we torque a bolt which has a yield strength of 70000 psi (I have no idea what it actually is) to a stress of 75000 psi. Its been permanantly elongated, but when the load is released, it enters back into its elastic state.
Regardless of whether bolts are in their plastic or elastic states, they are still holding with the same force. Just remember that when you exceed the ultimate strength, bolts break. And the ultimate strength isn't much greater than the yield strength.
04-04-2007, 07:10 AM
#24
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AFAIK TTY bolts are a single use item. Re-use them, and you get to replace them sooner or later.
Not much clamping force to begin with on a 3.slow. Studs would help.
+1 on the bad gasket design, and +1 on the heat on #6. And +1 on valve adjustments; if the valve cannot quite contact the valve seat the heat has nowhere to go.... and the valve is quite thin on the edges, guess what happens.
Oh, and infrequent coolant flushes are deadly.
Even if you solved these problems (and you can), the 3.slo can't breathe anywhere near the 3.4.
(BTW, replaced two sets of HGs on two 3.slows, one 1990 4Runner @63K miles, one 1989 pickup at 112K miles - so much for the early HGs being good. Not my favorite motor. And one on a 22-RE, due to infrequent coolant changes and a deferred timing chain service which, if done by the factory procedure, would have replaced the HG)
Not much clamping force to begin with on a 3.slow. Studs would help.
+1 on the bad gasket design, and +1 on the heat on #6. And +1 on valve adjustments; if the valve cannot quite contact the valve seat the heat has nowhere to go.... and the valve is quite thin on the edges, guess what happens.
Oh, and infrequent coolant flushes are deadly.
Even if you solved these problems (and you can), the 3.slo can't breathe anywhere near the 3.4.
(BTW, replaced two sets of HGs on two 3.slows, one 1990 4Runner @63K miles, one 1989 pickup at 112K miles - so much for the early HGs being good. Not my favorite motor. And one on a 22-RE, due to infrequent coolant changes and a deferred timing chain service which, if done by the factory procedure, would have replaced the HG)
Last edited by Red_Chili; 04-04-2007 at 07:17 AM.
04-04-2007, 07:38 AM
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Yup, torque to yield bolts are really one time use only. By definition you've left the elastic phase and now the bolt is deformed. Reuse is going to result in a completely unreliable clamping force on the head gasket. It is possible to determine if a bolt is failed or not by measuring the relaxed length, but I don't know that Toyota specifies a TTY reuse spec on these bolts. The safest thing is use new bolts.
04-04-2007, 07:44 AM
#26
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Oh except that's an intake valve.
Last edited by mt_goat; 04-04-2007 at 07:52 AM.
04-04-2007, 07:50 AM
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Yup, torque to yield bolts are really one time use only. By definition you've left the elastic phase and now the bolt is deformed. Reuse is going to result in a completely unreliable clamping force on the head gasket. It is possible to determine if a bolt is failed or not by measuring the relaxed length, but I don't know that Toyota specifies a TTY reuse spec on these bolts. The safest thing is use new bolts.
Tell me if Im being annoying and should just drop it.
04-04-2007, 07:55 AM
#28
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I agree that TTY bolts become permanantly elongated after just one use, but can anyone explain to me WHY it is not safe to reuse them? Has ANYONE had a headbolt break because they reused it? I guess someone is going to tell me that they are not holding as well on the second use. But why is it not holding as well on the second use? And don't tell me its because the bolt is in the plastic region, because you enter the plastic region on the first use.
Tell me if Im being annoying and should just drop it.
Tell me if Im being annoying and should just drop it.
04-04-2007, 05:50 PM
#29
Bumpin, TPS, When Mine went bad the idle part of it was still good so it wouldnt throw a CEL, But it being a stick I had to clutch rev it to get it going, Or it would only increase in speed as the AFM would open, No passing what so ever unless I cluch revved it.
I would assume on an auto the kickdown would never work and would bawg badly.
That was 8mo ago, I just bought another I need put on because its seems to be doing it again.
I would assume on an auto the kickdown would never work and would bawg badly.
That was 8mo ago, I just bought another I need put on because its seems to be doing it again.
04-04-2007, 06:34 PM
#30
Yup, torque to yield bolts are really one time use only. By definition you've left the elastic phase and now the bolt is deformed. Reuse is going to result in a completely unreliable clamping force on the head gasket. It is possible to determine if a bolt is failed or not by measuring the relaxed length, but I don't know that Toyota specifies a TTY reuse spec on these bolts. The safest thing is use new bolts.
04-04-2007, 07:20 PM
#31
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ive also herd that the blocks of the 3.0 were machined with a dome effect on them. a guy who worked at a toyota dealership told me this. he said that is y they blew the head gaskets easily. the whole exhaust idea sounds like the problem. to me it looks like the worst designed exhaust ive ever seen. also i blew my engine and could never figure out what happen. all of my cylinders lost compression to 30 psi.
i would check the coolant alot on those engines. if you take a digital multi meterand check the voltage in the coolant and if its above .5v i belive is the spec. i would change the coolant and run a cleaner through it. it might also be a bad ground to the engine to the frame. that will also cause head gaskets to fail espically on allunium heads.
ill tell you this i would rip that 3.0 out and put a 3.4 in. thats what i just got done doing and i love my new engine. but it all cost money and i sure do know we all dont have that.
i would check the coolant alot on those engines. if you take a digital multi meterand check the voltage in the coolant and if its above .5v i belive is the spec. i would change the coolant and run a cleaner through it. it might also be a bad ground to the engine to the frame. that will also cause head gaskets to fail espically on allunium heads.
ill tell you this i would rip that 3.0 out and put a 3.4 in. thats what i just got done doing and i love my new engine. but it all cost money and i sure do know we all dont have that.
04-05-2007, 01:38 AM
#32
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Ted at www.engnbldr.com said he used to reuse them until the heads starting popping off the bolts. After re-doing about 3 head jobs, he quit. Check out his 10.9 bolts.
04-05-2007, 03:49 AM
#33
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I've heard that it's because of clogged cats...
https://www.yotatech.com/forums/f116/clogged-cat-cause-blown-headgaskets-108123/
toyota_mdt_tech, I'd really be interested in your opinion on this idea.
My source is John from Oregon Engine Rebuilders. He also stated that as the cat becomes clogged that your engine develops higher backpressure which would then result in increased valve knocking or pinging. Eventually the headgasket blows due to the high backpressure. I'm currently considering replacing my cat just because of this as I ping slightly even on 93 octane and I have every reason to believe that I'm still on the original cat and I am also pretty positive that my rings are leaking oil as I go through about a quart per 3000 miles. That can't be good for a stock cat with over 150k miles.
John felt like Toyota messed up during the recall because they replaced the headgaskets which only treated the symptoms instead of treating the problem which was the catalytic converter. (I hope I'm not misquoting him here. If there's any confusion I'll give him a call.)
Sorry to derail the thread but this ties back in to why 3.0 HG's fail...
I'm also willing to experiment by replacing my cat and seeing if my pinging goes away. Would be worth it just to go back to the cheap octane again! Too bad that I don't know a way to check how clogged up a cat is.
toyota_mdt_tech, I'd really be interested in your opinion on this idea.
My source is John from Oregon Engine Rebuilders. He also stated that as the cat becomes clogged that your engine develops higher backpressure which would then result in increased valve knocking or pinging. Eventually the headgasket blows due to the high backpressure. I'm currently considering replacing my cat just because of this as I ping slightly even on 93 octane and I have every reason to believe that I'm still on the original cat and I am also pretty positive that my rings are leaking oil as I go through about a quart per 3000 miles. That can't be good for a stock cat with over 150k miles.
John felt like Toyota messed up during the recall because they replaced the headgaskets which only treated the symptoms instead of treating the problem which was the catalytic converter. (I hope I'm not misquoting him here. If there's any confusion I'll give him a call.)
Sorry to derail the thread but this ties back in to why 3.0 HG's fail...
I'm also willing to experiment by replacing my cat and seeing if my pinging goes away. Would be worth it just to go back to the cheap octane again! Too bad that I don't know a way to check how clogged up a cat is.
04-05-2007, 03:52 AM
#34
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Ted at www.engnbldr.com said he used to reuse them until the heads starting popping off the bolts. After re-doing about 3 head jobs, he quit. Check out his 10.9 bolts.
04-05-2007, 04:34 AM
#36
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mt goat - When I ordered his Grade 10.9's as well as the top end rebuild kit, he said to do it exactly how the Toyota FSM says to do it. Tq to 33ftlbs first, then 90* and 90*. Most of them got to the first 90* with about 60ftlbs, and some took 75ft lbs though. The second 90* was interesting as most got there with only 85 ftlbs, but 2 of em took about 95ft lbs!
04-05-2007, 04:43 AM
#38
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Here it is, I saved it on my harddrive:
>>>*Other than simple overheat, the #1 cause of head gasket failure is clamping force variations.
Usually when I mention this, the answer is "I torqued it properly!"
*Yes, very likely, but torque, which is a twisting force, means almost nothing when we are talking about clamping force.
Dirt or machinery debris in the bolt holes will throw the clamping force off as much as 50% and more, even though the torque wrench reads perfectly normal.
The same happens when installing new bolts. The very best bolts made will show a rough mating surface at the threads when inspected under a microscope.
When installing new or used fastners, first be sure the bolt will spin in and out ALL THE WAY freely with simple finger pressure. Be sure they are lightly oiled, not too much which can hydraulic lock at the bottom of any blind holes and spoil your day.
Use this simple breakin procedure for any new bolts: Tighten all of them to 50%, back off 1/4 turn, then to 75%, back off 1/4 turn. Then take them to 100%, back off 1/4 turn and repeat. Do a retorque after full warmup.
*This procedure simply assures that the imperfections of the threads seat to the bolt hole threads.
Yes, time consuming, but much faster and less costly than another set of gaskets, the actual clamping force will increase vastly, even though the torque load is exactly the same.
The alternative is you may be additional twisting at the top of the bolt after the threads have come to a stop from excess friction.
If any single one does that, head gasket failure prematurely is gauranteed, plus it weakens the bolt....*EB
Usually when I mention this, the answer is "I torqued it properly!"
*Yes, very likely, but torque, which is a twisting force, means almost nothing when we are talking about clamping force.
Dirt or machinery debris in the bolt holes will throw the clamping force off as much as 50% and more, even though the torque wrench reads perfectly normal.
The same happens when installing new bolts. The very best bolts made will show a rough mating surface at the threads when inspected under a microscope.
When installing new or used fastners, first be sure the bolt will spin in and out ALL THE WAY freely with simple finger pressure. Be sure they are lightly oiled, not too much which can hydraulic lock at the bottom of any blind holes and spoil your day.
Use this simple breakin procedure for any new bolts: Tighten all of them to 50%, back off 1/4 turn, then to 75%, back off 1/4 turn. Then take them to 100%, back off 1/4 turn and repeat. Do a retorque after full warmup.
*This procedure simply assures that the imperfections of the threads seat to the bolt hole threads.
Yes, time consuming, but much faster and less costly than another set of gaskets, the actual clamping force will increase vastly, even though the torque load is exactly the same.
The alternative is you may be additional twisting at the top of the bolt after the threads have come to a stop from excess friction.
If any single one does that, head gasket failure prematurely is gauranteed, plus it weakens the bolt....*EB
04-05-2007, 04:52 AM
#39
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"Do a retorque after full warmup."
Who the eff is going to pull everything off their 3.0 to re-torque the heads after the first warm up???
That would be a gigantic PITA.
How 'bout it, Ted? Some clarification?
Who the eff is going to pull everything off their 3.0 to re-torque the heads after the first warm up???
That would be a gigantic PITA.
How 'bout it, Ted? Some clarification?
04-05-2007, 05:13 AM
#40
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TNR - hahahaha I was thinking that myself. (26scfm@90psi...grrrrr!! lol) But Ill bet you after 500 or 1000 miles you'll probably need to check the valve shim clearnaces and that would be a perfect time to retorque. I know my compression is all over the place and ive got a very loud tick in the top end so I definately need to check my clearances....
Mt - does the 1/4 of 100% refer to the 33ftlbs?
Mt - does the 1/4 of 100% refer to the 33ftlbs?
Last edited by Bumpin' Yota; 04-05-2007 at 05:16 AM.
