Well, the saga of the 97 Tercel (manual tranmission) continues.
Review: Engine burned out due to oil leak, combined with lapse in checking oil. Engine was replaced with a used engine. Oil was then being lost at 0.7L/1000km. Valve seals were changed, which reduced oil loss to 0.6L/1000km. Oil was dripping from rear main seal, which (for some reason) was greatly reduced by changing oil pan gasket. Currently, loss is at about 0.65L/1000km. This is the approximate upper limit of acceptability according to some people, but considered quite excessive by others (and by the mechanic himself). Things that have been tried to identify the cause include:
- Color of exhaust -- neither black, blue, nor too white (Exhaust invisible on a warm day) * No cross-contamination between oil & coolant * No loss in coolant * PCV valve changed
The mechanic has checked the following
- Exhaust was analyzed for composition (was within acceptability) * Spark plugs have no black or white crud on it * No signs of oxidation on spark plug threads
The only outward signs of any leak is the remaining seepage from the rear main seals (leaks down face plate of transmission). Never enough to drip, but very fresh every time I see it. Perhaps the agitation of the movement of the crankshaft, combined with high pressure during operation, causes leak when car is driven, but stops when engine turned off. Seeing as it is leaking down the faceplate of the transmission, however, it could also be gear oil, but that would eliminate the only clue I have as to where the engine oil is disappearing to.
As this has been trouble-shot for many months, the mechanic plans to replace with yet another used engine. I am concerned that the engine might not be the problem, due to the lack of clues pointing that way. The replacement engine could very well be worse than the current engine, which passes compression test and leakdown test with good results (and has new valve seals). If the engine is changed, that would burn up good will with my mechanic without really solving the problem. An instructor of a basic car-care course agrees with this concern. He (and others) have checked through the engine from the top-side and from down under (car lifted) and can't find any other signs of external leakage besides the seepage down the transmission face plate.
Is it a big job to change the rear main seals instead of the engine, or is it the case that the engine might as well be changed at the same time, due to difficulty in getting the rear main seals changed?
Related question: Are there separate seals on the engine block side and the transmission side, where the two meet, or does "rear main seal" refer to a common seal for them both? If it is the former, would it be easy to change the seal on the transmission side, in case it is gear oil that is leaking?
Finally, is there anything more that can be done to track down the source of the engine oil loss?
Thanks.
P.S. Oh, yes, another possible clue is the aggravating fumes coming in the intake vent, which I've posted alot on. I believe it is coming from the engine compartment. Mostly just aggravating to lungs, throat, nasal passages, and eyes, gets very serious after a few days. Sometimes, there's not much of a smell, sometimes smells like hot oil, sometimes like burnt rubber...though it might be the case that the aggravant is separate from the smells.