Re: Mysterious Oil Loss, 97 Tercel

Gord Beaman wrote:

>>Tercel Owner wrote: >>>Gord Beaman wrote: >>>>...any pressure escaping past the rings could be >>>>pressurizing the sump and if the PCV isn't doing it's job then the >>>>sump will pressurize and possibly force oil out of your main >>>>bearing seals...do as he suggests and if there does seem to be >>>>quite a bit of pressure there try changing your PVC again. >>> >>>...not sure how to recognize too much pressure. >> >>...I'd sort of think that there shouldn't be any pressure there to >>speak of though. >> >>...you might ask a friend with a similar vehicle to do this test and >>compare results?... > >I'm the odd ball. Most people I know have American cars. I'll give >it a whirl anyway. Thanks.

Leo snipped-for-privacy@Hotmail.com wrote:

Cut out a smooth piece of cardboard to amply cover the oil filler >opening. Slobber it with oil and hold it lightly over the oil filler >opening. Check whether the cardboard is pushed up or whether air is >being forced out of the opening.

I tried a couple of other things prior to sampling the pressure at the oil filler cap. I checked the all spark plugs against pictures in the Haynes manual, and even brought it into the parts guy in an automotive store. It was fine, no residue, blistering, or flaking, or structural degradation. After reading what there was to it, I was worried about crossthreading, but that didn't happen.

I then put the front end on a pair of jackstands and revved the engine for just over 2 minutes. I looked at the seepage coming from the rear main seals (or the transmission, not sure which), and it didn't seem any worse than before. In fact, it seemed less. So revving the engine for 2 minutes doesn't contribute noticably to the oil loss, at least not when it's free from loading.

I was all set to "test" the sump pressure by pressing an oil-drenched cardboard against the oil filler opening. Then I realized that I had only tranmission fluid. I used the filler cap to test the overpressurization hypothesis. Basically, before the filler cap is fully screwed down, there is some vertical play. Pressure from the head should push it up a smidgen. But it doesn't. As I screw the cap down tight, there is no hissing of gas to indicate a high pressure inside.

To further test the PCV (beyond shaking the valve to listen for a rattle), I took out the valve and hose (as a single unit) and blue from each end. Air blew through readily in the forward direction, less readily in the reverse direction. (I read about this in Haynes, which suggested not putting one's mouth in contact with the PVC parts; rather, use a clean rubber hose to direct one's breath into the parts).

To test the PCV beyond any reasonable doubt, I replaced the parts and used my hand to pinch the hose, with the engine idling. The engine did not sputter as expected, but I heard a distinct clicking sound, which I assume was the valve. Every time I pinched the hose, it clicked. I have no idea whether that behaviour makes sense, but at least I know it's responsive.

As a final test of the PCV, I yanked it out and idled the engine. The engine cyclically revved up and down, in about 3/4-second cycles. I assume that is the computer algorithm going around in circles, since it is calibrated for an engine with PCV in-place. But at least I know the PCV forms a closed system, since the cyclic revving stopped as soon as I put the valve/hose back in. It did not seem to matter whether I pulled out the valve end or the intake manifold end in this test.

I think I can safely discount the hypothesis that overpressurization of the crankcase amplifies the seepage at the rear main seals when the car is running.

The only remaining possibility is that the oil is entering the combustion chamber, burning, and being expelled with the exhaust. As I mentioned, there is lack of any indication of bad rings -- engine does well on compression & leak-down test, exhaust is clear, analysis of exhaust allegedly shows normal composition, and no oil on spark plugs. Furthermore, there is no indication of head gasket problems -- no loss of coolant, no white gunk on spark plugs, no rusting of spark plug threads, no cross-contamination of oil/coolant,

I visited the local master guru in town, the one that suggested reporting back to him after a 2-hour drive. He said that in order for oil to show up on the spark plugs, I would need to be burning around

1L/300km. Yeesh. He also said that in order for exhaust to be unclear, the amount of oil being burned would need to be in the same ball park as the amount of fuel. So the absence of these 2 signs doesn't detract from the hypothesis that oil is burning in the combustion, though neither does it resolve the fact that compression and leak-down tests are good. Say the rings are good; if the oil is getting into the combustion chamber through an isolated bad spot in the head gasket, one would expect this to show up on compression/leak-down tests.

Another local Toyota technician suggested using oil dye. This kind of dye glows when illuminated with UV, so any leakages that are hidden from the naked eye can be found. Before putting this dye into the oil, the engine should be shampooed and air dried, which should take about half an hour, I'm told. After that, it's a matter of running it for a week and waiting for the dye to work its way out at the leakage points. This is definitely worth doing to eliminate the possibility of barking up the wrong tree and changing the engine for nothing.

I am considering having an emissions test done to corroborate the fact that the oil is not showing up in an analysis of the exhaust.

Anyway, the costs for these individually are small, but I've done quite a bit of this and it is just adding up. I'm wondering whether it's wise to just throw in the towel and let the engine be changed. I'm just concerned that it will be crappier engine, with a worse result in compression/leak-down tests (definitely the valve seals will be worse, as the current ones are new), and the problem of loss oil and caustic fumes might not even be solved.

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Tercel Owner
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