Piston Slap: Essex Archaeology, Scorched Earth Supras

TTAC Commentator Scorched Earth writes:

Hi Sajeev, my buddy has a manual-transmission, non-turbo 7M-GE MKIII Supra with about 150,000 miles. Supposedly the previous owner had replaced the head gasket at least once. About a month ago it started smelling like burning oil, and the engine is known for being overly prone to blown head gaskets, so he decided to play it safe and take it off the road within 2 hours of the symptom appearing.

Draining the coolant reservoir revealed a sludgy black substance, which we assumed to be oil, within the coolant. Another strike. The spark plugs, too, were swimming in oil. The rest of the coolant, however, was fine. We could not find any coolant mixed in with the oil, either. Furthermore, there was no greyish/whitish substance around the radiator cap.

Still, we went through the arduous process of removing the head. When the moment of truth arrived, the head gasket was found to be undamaged. And at this point, we’re clueless.

The head gasket needs to be replaced regardless since we’ve taken off the head, which will cost about $500. If we can find out what the source of the issue is, that’s fine. But if not, it may make better financial sense to junk the poor car.

Any idea what problem could be posing as a blown head gasket?

Sajeev Answers:

I cut my teeth on this whole Internet Car Writing thing by moderating a nice little corner of cyberspace called LincolnsOnLine.com. I am also waiting for my mail-order Archaeology degree. In the meantime, I suspect my years of dealing with old Lincolns driven by old people, neglected by their second owner and eventually scrapped by their third, puts me in a unique position to understand what/how/why this happened to this Supra.

Check it: the Essex 3.8L V6 in the 1988-1994 Lincoln Continental, also known as the “Essex Machine”. While these motors are well-known head gasket munchers, Wikipedia says the same darn thing about the 7M-GE ( http://en.wikipedia.org/wiki/Toyota_M_engine#7M-GE_) in this Supra. Aluminum heads, iron blocks and poor repairs by a previous owner have a common language, no matter what the car.

Here’s what happened, because I’ve seen it with Essex Machines: the previous owner cooked the motor so hard he blew the head gasket and warped the head. (Which, unlike the Essex Machine, isn’t that hard to do with the super long casting of an I-6 cylinder head.) Unfortunately, the previous owner didn’t upgrade the head bolts, upgrade the head gasket or didn’t have a machine shop check the block/head for warping.

Or a combination of any of the above, which is an ugly scenario. With any luck, all you need are a new gasket, head studs, and a machine shop to deck the head. Not a big deal, if you actually spent the effort to pull the head in the first place. So do it, or consider the alternative:

That’s right, either an LS-X or a 2JZ-GTE swap. That’s what I’d do if I had a busted Essex Machine and an LS-4 powertrain in my garage. Yeah, baby!

Send your queries to mehta@ttac.com