I have the 250 straight six in my comet. I need to add a quart of oil every 200 miles or so. There are no external leaks on the engine. I had an extra catch can lying around, so I routed the pcv line through it to see if the pcv was sucking excess oil from the engine. It has only collected a negligible amount of oil. I removed all the spark plugs and found that they were all badly corroded with black soot, even though they had just been changed 1000 miles ago. I also noticed that they each have oil around the threads. I suspect the tube seals are bad, is it possible that the seals could be leaking oil through the spark plug threads, and into the cylinders? And if this is the case, is there any sort of thread locker I can use on the sparkplugs as a band-aid to keep the oil out of the cylinders until I replace the tube seals? Also, do any of the oil stop-leak treatments actually work, or are they all snake oil products?
does it smoke? if it smokes all the time your piston rings are wore out if it smokes at start up it is valve stem seals
Assuming the spark plugs are tight, oil on threads is almost always is forced upward from within the cylinder(we have that pressure thing working here)... It isn't hard to check the stem seals, removing valve cover and shining a light inside the springs will reveal broken or missing seals... If that the case, often are pieces laying on head outside the springs...
Alright Tom, that makes sense. I was thinking the same thing about cylinder pressure pushing the oil out through the threads, but at the same time I was thinking the oil was getting burned up in the cylinder, so it shouldn't be able to push "wet" oil out through the spark plug threads. I don't have an afternoon to spare this week, but maybe next week I can pull the valve cover off and check it out. Thanks!
If engine is using enough oil that it only gets 200 miles per qt, not all will be burned, at least not running at less than 2500 RPMs(idle, around town etc)... You're looking at the left over results...
Ok, i see. So the only way to know if the valve stem seals are bad is by visual inspection? I guess I could rule out the piston rings with a compression test. I'm not sure if that is a tool I can borrow from autozone. I'm also not sure if that would be any easier than taking off the valve cover. I'm assuming that I would need to hand crank the engine? Or maybe have someone turn the key while I watch the meter?
Compression is not a conclusive test for oil consumption... If cranking pressure were below 100 psi likely would a safe bet the rings are worn, but I've seen high oil users with nearly normal pressure(prob 125-140psi on your engine)... Valve stem seals prevent(or at least slow) oil being sucked into cylinder from around valve guides, have no bearing on compression... If your engine has never had the head reworked, it's almost a sure bet the stem seals are goners...
I highly doubt the heads have ever been reworked. When I got the car it still had a stock alternator! The guy I bought it from had a deep cycle battery hooked up, and would just charge it up after driving. Thanks for all the advice! I will get the valve cover off sometime in the next couple weeks and check it out.
I agree with Krazy Comet.....more than likely the valve stem seals. I have a thread on here somewhere about how to fix it.
I had a rear main seal leaking once it never leaked sitting still after you started driving it warmed up and leaked like crazy used a quart in ten miles i tore the engine down only had fifty thousand miles on it the owner had used ''QUAKER SLUDGE '' since new crud was packed in it to the top of the intake it took 3 days in a hot tank to boil all the sludge out of it. no ''Quaker Sludge for me ever.
My experience has been that if it smokes bad on start-up, then clears, that it's the valve seals. If it smokes constantly, it's the rings. Just my experience and a basic rule of thumb. Removing the valve cover is easy and it probably leaks now anyway. Might as well change the valve cover gasket while you're at it.
Something to watch for too is that broken bits of valve seal will find their way back to the oil pan via the oil drainback holes. Once in the pan, they can get sucked up by the stock oil pickup and jam the pump. I had that happen twice. I thought I got it really clean the first time, but there might have been a piece still in the head. The second time, I bought a Mellings oil pickup. It has a full screen across the opening and can't allow anything with any real size to get to the pump. The stock pickup is designed with a bypass feature (in case it gets sludged up?) that can allow this kind of failure. If you find a lot of broken pieces of seal, I would highly recommend pulling the oil pan and give it a thorough cleaning.
What does the bottom of your car look like? If it's oily then you know that it's an external leak. Could be last person who installed the flex plate/flywheel didn't use sealer on the bolt threads.
you can get dye to put in the oil and then it shows up under a black light it works really well a friend of mine uses it all the time on cars he works on for a car lot he also uses it to detect water leaks they make a dye for that too
