Chronic Intake Manifold Gasket Failure

A few years ago I did an intake manifold gasket job on my 1996 Buick Regal 3.1L engine. I found the gaskets for each cylinder bank broke out at the bottom of the water passages which caused leak-out. I had read here in the cartalk forum that failed intake manifold gaskets are a very common problem. I did the gasket job, observing Chilton book instructions. It held for a few years with only minor leak-out, and some of this was from a cracked plastic radiator tank, no doubt a chronic problem with plastic radiators? But I have developed severe leak-out trouble again this summer from the left side of the intake manifold, just above the thermostat housing. I took the manifold off today and found the gaskets broke out at each cylinder bank at the left side, at the bottom of the water passages, just like the other time a few years ago. Is there any brand of intake manifold gasket I can buy that will hold up better? Is the torque value so extremely critical on the bolts nearby these gasket problem areas that I have to be extremely careful not to overtorque even a very little bit? I used a torque wrench on them, but it was a foot pound not an inch pound one and no doubt they are not accurate for inch pounds?

Any possibility the coolant is affecting the gasket material? Have you asked at the parts store if a updated gasket exists? have you made any manufacture inquiries as to what if any changes they have made in gasket construction.

Does the intake line up with the heads with out any prying or pushing? all threads chased on the heads? typical surface cleanup?

I am not going for a inch pound/foot pound problem,but perhaps dirty threads are skewing your readings.

Hmm. Could you try the dealer parts for this? They might be steep but the replacement cos. may not care to deal with this issue. Hopefully GM has a better part. Sorry but you might be stuck.

I had flushed out all the dexcool and changed to green antifreeze. Don’t remember for sure if I cleaned out the bolthole threads but if so I most likely used a round wire brush rather than a tap to clean the manifold bolt threads. I am quite sure I wirewheeled the bolt threads. I’ll chase the hole threads with a tap, wire brush them, and blow them out this time. The bolts did seem a bit loose when I removed them today. I had better check with a GM dealer rather than the typical aftermarket parts stores for any info about an improved gasket. Oldschool,are what you mentioned here the most common causes for GM manifold gasket failure? I am suprised that my oil doesn’t seem to have the milky color that it should if coolant gets past a failed gasket and into the oil returns under the manifold. It all seems to be leaking out to the outside of the engine!

Replace the gaskets with “Perma Dry Plus” gaskets made by Felpro. They are an improved design over the factory GM gaskets and work great. The torque specs on this job are crucial, if you don’t have an appropriate torque wrench, get one. Also when you refill your cooling system, refill with old fashioned green coolant instead of Dexcool.

You might check the mating surfaces of both the manifold and cylinder heads for any warpage with a precision straightedge. Within about .002 of a an inch it should be ok. Any more than that means it needs to be surfaced.

For what it’s worth, when dealing with aluminum I always use spray Copper Coat on all gaskets and after about a 100 miles go back and retorque the bolts as they may have a tendency to relax and loosen a bit.

I got the new intake manifold gasket at the GM dealer. I was glad to see that it has, in fact, been improved. There are metal inserts at the points where the original gasket would break, and the built-in silicone rubber sealing strips have been reshaped to seal better. And I have been using “old fashioned green coolant” rather than dexcool, since my first engine repair job 3 years ago.

Here is a picture of what a bad GM 3.1 liter engine intake manifold gasket failure looks like…