First of all, I hope everyone had a happy Thanksgiving.

I managed to spend the better parts of the last 2 days getting everything disconnected from the top of the Eagle in order to pull the intake manifold... we were attempting a full power runup when, at about 3450rpm, I saw 3 puffs of black smoke from the left exhaust, and the aircraft owner (in the pilot seat) saw something cloudlike fly over the top of the fuselage.  He shut it down and we found, upon inspection, that there was coolant on top of the gearbox, obviously from a leak at the front of the intake manifold.  I did a compression check yesterday to verify that we hadn't blown a head gasket and that test yielded excellent results (all cyls 175psi +3 psi max), so the heads are ok.

I finally got the intake manifold off late this afternoon and found that they use o-rings to seal both the intake and coolant ports between the heads and the manifold.  The throttle body appears to be gasketed to the manifold only with a thin film of red RTV between the ground surfaces.  The o-ring grooves and the areas between them, however, were sealed with a light grey material, with a texture very like silicone, but it only stuck to the primed (I assume it's primed) inner surface of the manifold, not the ground surfaces that it mates to on the heads.  Is it possible that this is Hylomar?

I'm not sure about why the leak developed yet, as the gasketing all appreared to be ok... but I want to insure that when I put everything back together with new cork gaskets between the front & rear top edges of the block-to-mainfold junction and new o-rings on the heads that I use the proper sealant.  I was afraid that getting the manifold off was going to be a complete PITA but it actually popped off pretty easily, due to the sealant used and its lack of adhesion with the raw metal surfaces of the heads.  I'd like to insure that the next person (sure hope it's not me <g>) that has to remove the manifold has no harder a time than I did so would like to use the same kind of sealant. TIA for the help.

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