CoedNaked

So - the biggest hypothesis I have heard about the 3.0 is that the reason it blows headgaskets is because of additional heat due to the exhaust manifold design and crossover pipe dumping all the exhaust in front of the Number 6 exhaust valve.

When you look at the circumstances - some guys have reported burned #6 exhaust valves more frequently than other exhaust valves, and head gasket failures, it seems to make sense. But I would like to explore this hypothesis a little more.

For example, can't you get some sort of laser thermometer and point it at various places and it'll tell you the temperature of what you point it at? Or some other way of taking temperatures?

Also, what I would be interested in knowing is for those of you who have burned #6 exhaust valves, were you running the stock manifold and crossover, or were you running headers?

For those who have blown headgaskets, have you ever blown a headgasket with a set of headers on your engine?

I would also be interested in the type of headgasket failures. Are the warped heads or the failures of the headgaskets coming on the drivers side head, or the passenger side head?

These type of questions and answers can help shed light on the hypothesis that I have seen countless people recite but it's only really a theory right now.

I would also be interested in a comparison to the 3.4's stock manifold, which is designed in such a way that all the exhaust is dumped downstream of both manifolds, not in front of the #6 exhaust valve like the 3.0's.

What also might shed some light on the topic, is the 3.4 5vzfe and the 3.0 3vz-FE aren't known to have headgasket problems at all (the small run of headgasket issues/recall on the 3.4 for 95.5-97 models from my info was because the headgaskets were installed upside down supposedly). What are the inheret differences between the 3.0 3VZE, the 3.4 5VZFE, and the 3.0
3VZFE? I know they seem to be very similar engines in a lot of respects, but there are some differences. For those of you who maybe know these engines in detail a bit better, maybe you can point some of the differences out?

Answering this type of questions, can also help shed some light on the idea/concept of making a FI 3.0 potentially if we can figure out what exactly is the weak link in it's head gasket design. People say the head gasket is weak, but is it really weak, or does it suffer from being peppered from excess heat which really no aluminum head can withstand for very long.

pruney81

Mine failed at the #6 valve. It didn't warp the heads or overheat though. Mine was a 95 and wasn't covered under the recall so I guess it had the supposedly new and improved gaskets. Mine blew a 159k miles. I think the design was at fault like you said, too much heat.

Gonzo4Runner

Would the OEM TTY headbolts be a factor? Especially on the 2nd HG failure?

I had an 1988 v6 fail on me twice. 1st time in 1993 at 100k and then five years later at 200k. Paid for it myself the 1st time. Toyota picked up the tab on the 2nd replacement. I remember they said something about the headbolts being loose. I do not remember where the first failure was, but I remember something about the 2nd failure being between cylinders 3 and 5 (passenger side). The 2nd failure might be more attributable to re-using the factory headbolts.

toyota_mdt_tech

Its the aluminum head vs iron block. The aliminum head expands and contracts at a greater rate. When this happens, the head will slide across the gasket (laminated gasket) but eventually, it will start to tug on the gasket drawing it into the cylinder until heat gets behind the fire ring and burns it out. Area #6 is the most common, while #1 is the second. The gasket is thinnest in these areas. As for burning valves., Its alwasy been from too little exhaust valve clearance. Each time the valve closes, it allows the heat to excape into the head. If it doesnt fully close, cant get rid of the heat and the ends get red and melt down.

jriebe

I have heard a large number of people accredit the failure of many replaced head gaskets to the reuse of TTY headbolts. It seesm they become elastic and allow the head to stretch to a point where only the gasket is holding back the pressure without any support.

I am a firm believer that the heating issue is in fact due to faulty exhaust design. I am planning to do a ford style crossover farther back down the exhaust when i put my 3.0 in my 1981 PU. I think i will be able to reduce the engine heat considerably while maintaining a good exhaust flow.

another theory of mine is that there are a large number of "virtual" 3.0 owners. They hear the cons about the motor and then talk trash about it wothout actually ownig or working on it. In my experience, about 1 out of every 3 people who talk ☺☺☺☺ about the 3.0 don't own one, nor have they ever. I think this inflates the numbers of problems and makes the issue seem more sever than it is. I will not argue that the head gasket is an issue with this motor but I beleive there are ways to combat it that significantly reduce your chances for recurrence.

Hope this helps,

Jon

jriebe

do you possibly think that valve overlap is an issue with this motor? I was wondering if you could get a custom ground cam that might alleviate some of the heating issues?

Any thoughts?

Jon

saleen9973

I talked to ted for engnbdlr about a month ago. He said he put a electronic temp gauge on #6 and saw something around 900* on the outside of the head after a run. Hopefully he will chime in and confirm this for me.

fd59

FWIW - I just replaced the HG on my 3.0 for the second time in its life. This was at 293,000mi. Everything is still stock. The failure occurred on the #1 cyl. When I took the heads off everything else looked great. I think the HG failed because the prior owner ran the vehicle hot when the fan exploded and ruptured the radiator. I purchased the truck for $500 knowing what had happened and expecting to replace the HG at some point in time. I probably put 2-3k miles before the HG gave way.
I think the 3.0 is a good and reliable engine if cared for correctly. I have a personal theory that as long as you don't run the engine hot, keep it in tune, don't bog the engine down, and "blow it out" every "now-and-then" then it will reward you with a very long life. This holds true for any engine, however the 3.0 doesn't seem to be as forgiving to mistreatment.
I wonder what the ratio is on HG failure % on Automatics vs Manual trans. I find that people with autos (Especially Socer-moms) don't "blow-out/rev" the engine nearly as often a people with manual trans. I think that reving-up an engine really helps keep an engine in good shape by keeping the carbon blow-out of the engine.
Example - I can always tell when my wife has been driving my Isuzu Trooper (2.8l v6 w/267,00miles) for a week or so. She shifts at 2 to 2500 RPM and boggs the engine on a regular basis. No matter what I tell her she does it. When I drive it after she does, the engine just will not run smoothly. After I take it out on the highway and blow-it-out it is back to its old self. The 4runner stays in better tune than the Trooper so it is not as affected as much as the Trooper by my wife's driving, but I could see how that type of driving on a constant basis could cause the carbon buildup and eventually burn up a valve and cause HG problems in an already weak spot.

BTW when I refer to Blow-out / reving an engine I mean running it up to 4-5k RPM between shifts every now and then - not sitting still and reving the engine in neutral.

Topless4runner

I've had my '88 V6 4Runner for about 12 yrs. It's on it's second motor. The first one blew the HG at about 140,000 (around #6). The previous owner had run the engine very low on oil (drove it after putting a hole in oil pan & ran dry). I replaced 2 sets of connecting rod bearings before the HG & 2 sets after (I even ran synthetic oil). I've put about 100,000 on the new motor & I've had no problems with it. As for the "blowing it out" theory, I'm not sure but I do use the power setting (it's an auto) now and again & let it run up to the 4-4500 range. I dont beat the guts out of it but I do let her run now and again. Seems to work very well. Just my 2 cents.

^VooDoo^

I belive in the blowing it out theory, I keep the oil changed and cooling in working order and abuse it every which way from there, Havent a HG yet.
Oil still comes out clear most of the time.
I admit at this time its having issues from running leanout for 6mo but I really think its the wiring harness or burnt valves, not sure, But Ive seen alot of oxidized copper in the harness.
It still revs up to 5k fine and flys down the freeway, 2 ppl thought Ive done an engine conversion.
An engine is like a muscel, treat it soft and it will go soft.

TNRabbit

I had a headgasket fail @ 218,000 miles, but I'm pretty sure it began with an overheating and was finally done in by a localized overheating condition brought on by low coolant (temp neve rose, but it was pinging for about 5,000 miles & I never found out why). The #2 (Yes, TWO) cylinder blew out at the HG on mine. First one I'd heard of. Here's a link to my thread:
https://www.yotatech.com/forums/f116/crap-head-gasket-giving-up-ghost-108156/

WillRadford

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.

CoedNaked

Yeah but don't LOTS of engines use aluminum heads on an Iron block without failure or excessive failure?

WillRadford

I think lots of engines do use aluminum heads on steel blocks. Does the 3.4 L in 3rd gen 4runners and tacomas have aluminum heads?

Tigerstripe40

My personal hypothesis on the HG issue...

Back when the 3.0 liter engine was designed, a material that is EXCELLENT at heat absorbtion was being used for all sorts of things. From head gaskets, to brake pads, to clutches, etc.

This material is called Asbestos. And is one of THE BEST heat resistant materials known (and very inexpensive).

My hypothesis is that the 3.0 liter was initially designed for an ASBESTOS head gasket, then asbestos was banned and toyota had to find another material that, unfortunatly, wasn't up to the task.

rdharper

Anyone have a 3.0 HG failure with asbestos gaskets?

Tigerstripe40

Asbestos was banned before the 3.0 liter engine was released to the public.

toyota_mdt_tech

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.

shoes138

^^^^very well said!

mt_goat