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Oil Loss. No Smoke. No Leak?

03-24-2010, 10:28 AM
I'm fishing for ideas on this one. My 96 Civic EX is loosing oil quickly. About 1qt/250 miles! That's a lot I know. The real mystery is that there is no smoke from the exhaust and I do not see a leak. I read in a different post that it could be valve seals or blowby. I'm going to research those possibilities, but it seems to me that if it were valve seals I'd see smoke. I'm not sure what is meant by "blowby." Any help would be appreciated.

03-24-2010, 10:32 AM
It seems I'd see smoke if it were valve seals:

But, maybe not????

"Loosing that much oil, with no leaks, no noise, and no noticeable performance loss sounds like rings.
With rings sometimes there isn't much smoke. The oil will burn in the combustion chamber. It can burn out almost completely, making little smoke. When you get blue smoke, it is from the stem seals, especially the exhaust. the smoke is blue because the oil burns off the valve stem on the exhaust stroke so it doesn't burn very much, hence the blue smoke."

03-24-2010, 06:48 PM
I plan on doing a valve and cylender compression check as soon as I get my hands on a compression kit. I pulled the plugs to see if there was any combusted oil. The spark portion is a light gray and looks normal, the base portion has some black soot but I'm not sure if its normal or not. Anyone have any thoughts???? These are NGK and have only been in the engine for about 3 weeks. The stuff on the threads are anti-seize. (

03-24-2010, 07:45 PM
Also, I do have a P0138 (O2 sensor #2 high voltage = running rich). There is some soot in the exhaust and that may be what I see on the plug shown. I'm starting to think rear main seal possibly leaking when engine gets hot. I gotta get this compression kit to help narrow down possibilities!!!!

03-25-2010, 09:07 AM
When you say there is no leak, are you basing this on the fact there are no spots on your driveway or have you gotten underneath there and looked? I ask because I had a similar issue with not being able to tell where my oil loss was occurring. Once I got underneath the car and looked, I could see that oil had been running down the pan. I think I figured out the cause of my leak. I took out the PCV valve over the weekend and inspected it. It didn't rattle at all like it should when I shook it. So I installed a new one. After doing more research, I found that if a PCV valve fails, that excessive pressure can build up in the crankcase. Without the valve working properly to relieve this pressure, it has to find its way out of the engine somehow and will sometimes blow out a gasket. The best I can tell in my situation, it looks like it's the front right corner of the oil pan gasket. I'm assuming I never saw any spots in my driveway because it only occured when the engine was actually running. I plan on replacing the oil pan gasket. I'm certain that it is still leaking, but not as severe as before the PCV valve was replaced due to pressure relief. Anyway, just a thought. The PCV valve is located just above the oil filter. A new one is super cheap (like $2.xx) at AutoZone. Hope this helps.

03-25-2010, 10:28 AM
Ahhh, so that is what was meant by "blowby." I see you're still chasing your oil issue too. I replaced the VTEC solenoid & oil pressure gasket as well as the distributor O ring that we had talked about on a different thread. It looked like I had my leak solved until this started happening. I recall removing the PCV valve & hose when I removed the IM a few weeks ago. I didn't inspect it, but it looked to be in good shape. I'll be sure to check that before attempting to work on the rear main seal. However, it may be that if the PCV is faulty, it may have vented through the rear main seal? I know I need a new oil pan gasket, so I'm going to replace that and check the PCV, then do a compression and leak-down test. If I still loose oil and see the same oil wet area on the flywheel cover plate, I'll return to suspecting a bad rear main seal. My only hesitation in thinking it is a pan leak is that it only seems to do it when the engine is hot and my pan is clean except on the side by the tranny.

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