4Runner Help

DriverSound · May 28, 2009

Hey guys, I know this is a Tacoma Forum but I also have a 4Runner and I know you guys have or have had 4runners too. I currently have a 1995 4Runner sitting in the driveway due to a blown head gasket. It's been replaced once already along with new heads and apparently this is a common problem with this 3.0 3vz-e motor. Can anyone recommend a fix for this? Brand/type of gaskets perhaps? I'd really like to keep it but I don't want to have keep fixing the same problem also. Thanks guys!

Hotdog · May 28, 2009

try to find out who did the previous replacement. One of the important things to properly replacing the gasket will be to properly torque the bolts.

Hotdog · May 28, 2009

from http://www.aa1car.com/library/gasket_failure.htm

Bimetal Stress
One factor that makes many engines hard to seal today is the use of aluminum cylinder heads on cast iron blocks. Aluminum heads save weight but expand 1.7 times faster than cast iron when they get hot. The difference in expansion rates creates a lot of motion and scrubbing between the head and block. If the head gasket cannot handle this motion and is not strong enough to withstand the shearing forces that occur every time the engine is started, run and allowed to cool back down, it will eventually leak.

A few recent examples of this kind of problem include the OEM head gaskets in the Dodge Neon 2.2L, Ford 3.8L V6 and Toyota 3.0L and 3.4L V6 engines. Going further back, we all remember the problems GM had with the 2.3L Quad Four head gaskets. All of these engines have experienced a high rate of premature failure because the OEM head gasket could not keep a seal. Fortunately, the aftermarket developed replacement gaskets for all of these applications that solved the original problem.

If the surface finish on a bimetal engine head and block is too rough and digs into the gasket too deeply, it can literally tear the gasket apart over time. That is why surface finish is so important on today's engines.

For bimetal engines with composition gaskets, the recommended surface finish is 20 to 50 RA. This compares to 60 to 120 RA for cast iron engines with the same type of gaskets.
head gasket

Equally important is the design of the head gasket itself. One way gasket manufacturers deal with the scrubbing problem in bimetal engines is to add a nonstick coating to the gasket. Teflon, molybdenum and similar low friction coatings prevent gaskets from sticking to either surface. This allows the head to expand and contract without ripping the gasket apart.

This is the opposite approach to what is done with many head gaskets for cast iron engines. On these applications, the rate of thermal expansion for the head and block is the same so there is much less movement and scrubbing at the gasket surface.

Raised silicone, Viton or fluoroelastomer sealing beads are often applied to the face of the gasket to increase the clamping pressure in critical areas. This improves the gasket's ability to form a good cold seal when it is first installed, and helps it maintain that seal by holding the gasket firmly in place.

On many late model engines, graphite head gaskets are used because graphite has natural lubricity that can handle the differences in expansion between aluminum heads and cast iron blocks. Graphite is a relatively soft material that provides good conformability for cold sealing the engine, and it can withstand high temperatures and draw heat away from hot spots to reduce thermal stress and loading.

Hot spots tend to form in areas where exhaust ports are located next to each other. Heat buildup in these areas makes the head swell. This can crush the gasket between the cylinder bores causing the gasket to leak and fail. To prevent this from happening, gasket manufacturers may use a gasket material such as graphite to dissipate heat away from the hot spot and/or reinforce the most highly stressed areas of the gasket with a shim so it will not crush.

Head gasket durability can also be improved by using stronger or reinforced combustion armor, tougher, high temperature fibers such as aramid and Kevlar in composition gaskets, and adding extra reinforcements to critical oil hole grommets.
Click to expand...

So, it looks to me like you want to get a nonstick gasket.

DriverSound · May 28, 2009

lsocoee said: ↑

try to find out who did the previous replacement. One of the important things to properly replacing the gasket will be to properly torque the bolts.
Click to expand...

The 4runner was passed down to me since it was broken but a shop did it the first time. I think the mileage was around 150K or so and now 20K later, the same thing. I won't know what gaskets was used until I tear it down. I know its either the metal ones or the cheaper graphite gaskets.

Hotdog · May 28, 2009

from what I was reading, they seemed to prefer the graphite gaskets for this application.

DriverSound · May 28, 2009

I think I might have to go that route also but from the looks of it, this is gonna be a pita kinda job.

Hotdog · May 28, 2009

you might be able to find someone on one of the forums that has done one before that is located close to you.

DriverSound · May 28, 2009

lsocoee said: ↑

you might be able to find someone on one of the forums that has done one before that is located close to you.
Click to expand...

Thanks for all the info. I'm sure I can do this myself. I'm just not used to working on Toyotas. I've done plenty of work on older Chevys and Fords though. It's just that this 4runner has all kinds of stuff to remove just to get to the heads. I might even do DIY since I'm gonna take pictures for referrence in putting it back together anyway. Thanks again.

Hotdog · May 28, 2009

I doubt it will be hard, maybe just time consuming.

Toy4Life · May 28, 2009

I've heard multiple thoughts on why there is a headgasket issue with the 3.0 v6. I've heard the routing of the exhaust or the headers is part of the problem. I have also heard that it is imperative to keep your cooling system in tip-top shape to avoid the headgasket issues.

TacomaWorld is my home, my family, but when I recently purchased my 92 4Runner, I joined YotaTech. There is a lot of info there on the older Yotas...can't hurt to look.

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