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Need help with mystery leak

155 Views 4 Replies 3 Participants Last post by  sefiro
I realize this is a longshot. My 1991 convertible (74k miles) has a slow but persistent oil leak when parked. It's been in several shops to no avail. They say it's not the main seal and now concentrating on the head gasket. Thanks in advance for any ideas.
scott in ny
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There are many, many possible sources for an engine oil leak. No one on the forum is better than your own eyes looking where the source of the leak is.

My recommendation to you is to get a couple of cans of engine degreaser, spray the entire engine down with it (protecting your distributor and your alternator from getting wet). Do this at a do-it-yourself car wash place. Let the degreaser soak 15-20 minutes. Then power wash everything with one of the pressure wands. This should clean off most of the oil on the engine. Then drive it a little and look for the highest spot on the engine that is wet with oil. Oil will always travel down, so the lowest may not be the source. I've always pinpointed the source of oil leaks this way. On a 5S-FE (2.2L) engine, it is not easy seeing up the engine on the firewall side, but this is often where the oil leak is found - often the valve cover gasket leaking on that side. Not saying that is your issue, but figure out a way to get under the car to look up the engine on the firewall side after cleaning everything up well. Using car ramps on the front would be a safe way to elevate the front of the car so you can crawl underneath it.
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The engine has been sprayed and cleaned repeatedly and completely (up on a lift) but nothing definitive has surfaced. I know it sounds crazy. I like your thought about the firewall side. The head was pulled about 12k miles ago to do the valve guide seals. I'm in a rural area, so no shops specializing in Toyota repair. The mechanic currently looking at it thinks it could be the head gasket, maybe it got damaged when installed 12k ago?
You are right, I don't get it. If the engine leaks liquid oil when parked, then the oil has to be on the engine - somewhere. The only times it was hard to pinpoint a leak is when the engine is so covered with old wet oil, the source can't be found. There has to be a drip point somewhere on the underside. That drip just needs to be followed up and/or across to find the source. At least understand if the drip point is where the transmission case bolts on, or that the timing belt end of the engine, or is on the oil pan - just have to look very hard.
  • front main seal
  • rear main seal
  • valve cover gasket
  • camshaft seals
  • distributor o ring

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