[Walt Fricke]

Fanaudical - you are thinking of the spring guide which is part of the oil pressure system modification which Porsche did starting with the '76 or 7s. Just about everyone who rebuilds the earlier motors does this modification to them.

Among other things, this involved a different oil piston (two, actually), and a longer spring for the pressure setting part. To keep the longer spring from buckling, a tube is inserted into its bottom end. All this is in the vertical drilling which comes out at the top of the engine where the idiot light sender is, and at the bottom of the case where there is a plug with an odd and infuriating sort of screw driver slot (usually unsecrewed with a pipe wrench by us shade tree types - the later motors had a cap with a nice hex head on it)..

I thought about that sleeve, too. But 1) it is steel, and a magnet would glom onto it. 2) It has a flange at its bottom which sticks out beyond the spring. Hard to imagine how the tube could break off of the flange. There is very little force involved there. 3) it would have to get by the piston to get higher up in the engine and into any other oil passages. And 4) this drilling is parallel to, but not the same as, the hole in the bottom of the thermostat bore - too many corners to turn. If the piston were missing, you'd have no oil pressure anyway.

That about exhausts the possibilities. There is at least one steel tube cast into the case oil system in that area. Possibly more. If the one I am thinking of were to come loose, you'd have oil all over everything on top of no oil pressure - it would kill the motor, plus it can't really come loose anyway. If there are others in any of the vertical machined passages back there, they, like the one I am thinking of over by the oil cooler, are much much larger in diameter than your mystery.

I am guessing this is a foreign object which somehow fell in during some previous work on this motor. Replacing the O ring on the thermostat is part of dealing with the inevitable oil leaks in this area on top of the case (the others being a failed idiot light, a leaky breather hose, or sometimes the oil drain from the air box if you overfill the oil tank).

By the way, if you put the thermostat in a refrigerator (I use the freezer) to be sure it is really cold, and then toss it into boiling water, and there is no change in the position of anything, then the wax cannister inside is toast. You can purchase just this cannister (it is also used on the external oil thermostat which controls the right front fender oil cooling system), but I am not sure just how one would disassemble the housing you have.

I think the good news is as DB Cooper suggests - since it has been in there so long without causing problems, chances are good it wore into little tiny particles which did not plug any oil passages (because the engine hasn't blown up) and were within the embedability capacity of the bearings. The smallest passages I think are the oil spray bars over the cams, and the piston oil squirters. The cam spray bars you caneasily test and clean as part of your top end rebuild. As long as your oil temps are within spec (a working thermostat will help) and so are the pressures, and you don't get rod knocking sounds and whatnot, drive it until you decide it is time to split the case to replace bearings.