Automotive cylinder head/gasket question

Hi folks,
I'm getting ready to reassemble a chevy 3.4L V6 that had a blown head gasket(2006 Equinox). It seems like there is some slight pitting on the block in one place, mostly between two water passages, but comes pretty close to the top edge of the cylinder. Is there any kind of gasket sealer that could be used under the head gasket? There is still about 3/16 inch of good metal for the "fire ring" (is that a real term?) to seal, but there is definitely some damage on the top of the block. Is copper coat used for modern automotive engines? I had the heads surfaced, but now I am concerned about whether it will hold.

Ray,
What I'm about to tell you sounds crazy, but I saw it work. Back in the early 70's a guy buys a new Ford pinto, with a 2 L engine cast block aluminum head. The dealer replaced the head gasket twice, while under warranty. A few thousand miles after warranty ran out, it needed another head gasket. Back then I never heard of silicone. They didn't make RTV silicone yet. This was a clear silicone. It took the two of us a 6 pk to do the job. One beer to remove the head. One beer to apply a very thin coat of silicone and let it dry. Another beer to put the head back on. If you are doing the math, 3 beers each. The guy drove the wheels off the car. It never needed a new head gasket after that.

So try what ever you want. If your attempt fails, try silicon the second time and post back.geo

For what it's worth, Both my 2005 buick 3.4l and my 2007 GMC truck with a v6 had the head gaskets replaced while under warranty. Think GM may have a head gasket problem?

Try lexell. Its like a new gen rtv

If you have 3/16" for the ring to seal on, should be no problem. Leakage between 2 coolant passages won't have any effect. Leakage between a coolant passage and an oil galley, internal crankcase passage, or external is a problem. You could put some sealer on the suspect area, won't hurt anything, but I would not coat the whole gasket. Be very sparing. Copper Coat is good as any.

Does that engine use torque to yield bolts? If so, go ahead and replace them, chase the holes with a tap, follow the torque recommendations exactly. I have reused the torque to yield bolts on my stuff, and they worked. But for customers I go with new, or if I'm in doubt, go with new.

yes I got new head bolts as well. Thanks for the replies.

And make sure you don't interchange the pushrods between the intakes and the exhausts. They are different lengths.

Funny I was just reading an old Engines Book from Petersen that said apply a little silicon sealer around those passages. but they meant directly to the block not the gasket.

I see what you are describing a lot, it has not been a problem in my experience with those engines. I myself would not use any type of sealer on the actual gasket but would add some GM Cooling System Supplement when the job is done. It is a leak stop type additive. I believe it is the same as made by Bars Leak , a tablet form. You can get the Bars Leak version at Napa for under 5 dollars.

Not a rare problem...



http://westernsealant.com/what_is_casting_porosity.html

http://teresasgarage.com/automotive-411/engine-block-porosity/teresasgarageonlinestore

Your call it may not be a problem I would use Permatex lock weld are JB weld to fill the voids...

Head gasket problems are inherent when different metals are used for the head and the block. This is because steel and aluminum expand and contract at different rates. That means that at times the clamping force of the bolts is greater than at other times - and at times it is significantly LESS than desired.
Torque to yield bolts and special gasket composition go a long ways to offset this problem, but it is just a fact of life that head gaskets will fail at some time on this combination of metals.
Torque to yield - also called "stretch" - bolts seem to help as they increase the clamping force applied. They are NOT re-usable - regardless of how many bubbas or Billy-bobs have gotten away with it. Once stretched to the yield point, they stay stretched. Re-stretching them will either break them or seriously weaken them.
As to the sealer thing, take a look at the gaskets. They are made of a layered composition. The necessary sealant is included within the gasket. When you deviate from the manufacturer recommended procedures, you are in uncharted territory - unless you think you are smarter than a 50,000,000 dollar engineering department.
As a general rule, "farmer fixes" are less than reliable on modern highly stressed engines. Look at the differences between an old John Deere tractor and a modern engine. Some of the old 2-cylinder JDs had over 500 cubic inches of displacement to make 35 or 40 horsepower. Your 3400 is about 215 cubic inches to make over 180 horsepower. The level of stress is the difference.

Given that you have had the heads resurfaced, and you use decent gaskets and new head bolts, you should be fine for another 100,000 miles if you put it together like the book says.

Our '01 Aztek went 225K before I sold it. Never had the heads off. Intake gasket issues, yes, headgaskets, no.

"Torque to yield - also called "stretch" - bolts seem to help as they increase the clamping force applied. They are NOT re-usable - regardless of how many bubbas or Billy-bobs have gotten away with it. Once stretched to the yield point, they stay stretched. Re-stretching them will either break them or seriously weaken them."

Who you calling Bubba?


From the Bubbas and Billy-bobs At Cummins;


I am not saying all Torque to yield head bolt are reusable but I have used these gauges that come right from Cummins many times to check and reuse head bolts and have never encountered a failure.

If there is a good surface for the fire ring on head gasket , then I usually go with it . if the area the fire ring sets on is badly pitted it probably won't hold long .silicone isn't going to hold combustion pressures . clean and dry on head gasket is best . we have used copper coat on all steel had gaskets with success at keeping coolant leaks at bay , but nothing I know of will hold combustion pressures but a good surface for fire ring to set on. Eo