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Oil leaking on engine

Hi, I have a quick question. A few weeks ago I took a long trip and sat in a lot of traffic with my 1992 Toyota Corolla. When I finally arrived and I got out the front of the car smelled bad, like exhaust. Today, my mechanic just told me the engine is leaking oil and it is probably leaking from one of the seals–that are usually changed when the timing belt is changed-- onto the engine. The leak can’t be very big, because when we checked the oil on our trip the level was fine. This car is not one in which we want to put a lot of money. So the basic question is: if there is a leak there, is it dangerous to keep driving it around town as is (by town, I mean NYC) or is it okay, so long as I don’t take the car on any big trips. I didn’t notice this smell on any shorter trips. Thanks, Cranky Toyota

Are you sure a 1992 Toyota is a belt engine and not a chain? I would have trouble with a oil leak that could degrade the belt.

You say you smell “exhaust” do you really mean the smell of oil smoke? If the smell is oil smoke I cant see how a leak in the timing belt/chain area comes in contact with a area that is hot enough to smoke it.

I would be thinking more likely a valve cover leak,this could easily allow oil to contact the exhaust manifold and smoke.

Valve cover gaskets are not very expensive to get changed. Probably 1hr and parts (use a real gasket not some RTV stuff).

Thanks very much for your reply. The mechanic called it a timing belt. I have since found out that it was indeed replaced less than 60,000 miles ago, which is what is apparently required. In any case, this mechanic that I went to now himself changed the valve cover gaskets a few months ago when I took the car in for inspection. At the time, he noticed an oil leak and said that this was the cause.

He isn’t saying that it’s a leak in the belt this time. Sorry for the confusion. But rather he says since he replaced the valve cover gasket it must be a leak in one of the seals in the engine: cam seal, crank seal or engine seal. He doesn’t know which one without going inside the engine, but he says these are routinely replaced when the belt is replaced, which it was.

As for the smell, to me it smelled like when a car has a bad exhaust smell, only it was coming from the front. It may very well be oil smoke. I wouldn’t know the difference, unfortunately.

So, in other words, the mechanic thinks that one of those seals named above is leaking oil onto the engine. And I just want to be sure it’s safe enough to drive around that way, at least around town, since I don’t want to put a lot of money into replacing the seals (labor alone for that, says the mechanic, is around $450).


I suspect that your mechanic is spot-on (pardon the pun).

You don’t say how many miles your Corolla has, but at 17 years young I would not be at all surprised if you had some blow-by im the cylinders. Blow-by is gasses passing by worn rings and cylinders during combustion. The gasses are being blown by the rings under the pressure of the explosions, and they can cause elevated pressures in the crankcase. Couple that with the wear and shrinkage that normally occurs in rubber seals with rotating parts spinning in them, and oil can get pushed through. It’ll happen more on a long trip because driving down the highway is when the crankcase pressures will be at their most elevated, and the oil its thinnest.

This whole thing can be exascerbated by a PCV (Positive Crankcase Ventilation) valve stuck closed and not allowing the crankcase to ventilate. The PCV valve is dirt-cheap and worth changing, although a stuck one can be unstuck by bathing in a solvent. Or even washing down with a spray carb cleaner.

It is not a dangerous condition. But you do need to monitor your oil usage and bring some extra if you take another trip.

If you’d like to confirm my suspicion, a simple compression test could reveal a lot, although I’d have to point out that while it’s an overall good check for wear it checks only compression rings and not oil rings.

Yes definitly a belt is in use. If either of these cam seals (there are two) are leaking the oil could get on the belt which would be bad for the belt but again I don’t see how this oil would touch anything hot enough to make smoke.

Any of the seals in your engine can leak even if your crankcase is not being pressurized by excessive blowby and a non-functioning PCV system. The edge of the seal (the sealing part) simply wears out and allows oil to leak by.

That’s true.

I guess point I was trying to emphasize was that on an engine this age there could be, and probably are, more than one contributing factor. And that it isn;t a dangerous condition, only one requiring vigilence in checking oil, but I also agree with a new belt and seal.

Was I too wordy?

I have had a few older toyotas and they leak a little and it drips down onto heat shield, that is where the smell is coming from.
You must keep oil level checked and fill with correct oil but I have never heard of fire happening.
I would not worry about it one bit.

Yes, a '92 Corolla has a timing belt. Some people replace the cam seals when they replace the timing belt, and some don’t replace them unless they are already leaking, which means they may not have been replaced.

If the leak is small, I wouldn’t bother fixing it. Yes, oil might contaminate the timing belt, but even if it does the worst case scenario is a broken timing belt, which will make the engine stop running, but won’t damage any internal components. This is not an interference engine.

You say the oil level isn’t going down, or at least not much, so the leak can’t be too bad. Your mechanic would have to remove the timing belt cover to figure out which seal is leaking, but if you’re going to go to all the trouble of removing the cover you might as well replace the timing belt and the seals.

My daughter had a '91 Corolla, almost identical to yours. The crankshaft seal started leaking at about 150K miles. I’m sure the timing belt must have had oil on it, but the car was still running well at 175K when she sold it, and the new owner is still driving it and adding oil as necessary.

I suggest you monitor the oil level closely, add oil as necessary, and continue to drive the car. When the time comes for another timing belt, then your mechanic can replace the seals.

Thank you everybody for all your responses. They are very helpful, and I will use the info not only to keep an eye on things, but to know what to look for or ask the mechanic to look for the next time I bring it in. And it’s very good to know that the condition is not dangerous. By the way, someone asked about the mileage on the car. I forgot to say that it has about 111,000 miles on it, which is not that much considering everything. Thanks again, Cranky Toyota