Re: new head and gasket seeping already??

Posted by TheRealRon on August 19, 2004 at 09:53:09 from (69.179.0.225):

In Reply to: Re: new head and gasket seeping already?? posted by Allan in NE on August 19, 2004 at 06:19:59:

Allan, I've built hundreds of engines and you are way off base here.

Most MODERN engines use non-retorque gaskets for the obvious reason. All non-retorque gaskets do NOT use sealer. Nor do they contain a built-in sealer. In fact, the exact opposite is true. In the "old" days heads were glued to the block with gasket cement on the theory that they should never move in relation to one another. This theory was wrong. Modern thinking is to use non-retorque gaskets which are especially made to be slippery... hence, Teflon, silicone, and graphite. This allows the head to move across the surface of the deck without tearing the gasket and therefore provides a perfect seal for the life of the engine.

Far from being a scam, sealers are mandatory where they are required, for example, many older tractors are being rebuilt with NOS or even OEM gaskets. Some new "retorque required" gaskets also demand sealer.

Further, the mating surfaces must be flat. If they leak, they are not flat. By overtorquing them all you are doing is warping the head (making it conform to the deck). Sure, it MIGHT seal temporarily, but as the engine goes through some number of thermal cycles, the uneven clamping forces cause the head to move. This tears the head gasket and almost always dumps coolant into the crankcase, destroying bearings in the process. Might take 5 minutes of engine operation to destroy it, might take 5 years. It's a matter of degree.

All of us who actually do this for a living use a "steel" (think giant straightedge) to verify both the deck and head for flat. The spec is always in the service manual. It's usually something like .001" per lineal foot of head. Gaskets will not seal gaps greater than this.

While reinstalling a head seems like a trivial process, it is far from it. I feel very sorry for the guys who post here with the old "my engine blew a head gasket so I replaced the head gasket and now the gasket blew again". Of course, without a proper head and deck surface, it is a near 100% certainty that the gasket will blow again.

There's an old saying... "any job worth doing is worth doing right". People who refuse to follow this sage advice almost always end up doing it over... and over... and over.

Follow Ups:

• Re: new head and gasket seeping already?? Allan in NE 12:04:15 08/19/04 (2)
  • Re: new head and gasket seeping already?? TheRealRon 05:51:36 08/20/04 (1)
    • Re: new head and gasket seeping already?? Bob 07:25:46 08/20/04 (0)

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