Excessive oil consumption - part 2

Mike R said:
My car barely uses a half a qt between 7-10K synthetic oil changes since the rear main was replaced, used a more than a qt prior. The car has 202,000 miles on it.
Click to expand...

a rear main seal could be expected to leak with that high mileage. however, can it be checked easily, say without removing the engine or trans?
 
flash75 said:
How do your spark plugs look? The fact you have good compression doesn't necessarily mean the rings and cylinder walls are good. In a compression test you are using the cylinder to pump a small amount of air into a gauge, the gauge traps the air to give you a reading. The combustion process has a much greater pressure and it happens at a much faster engine speed than a simple compression test.

You said the leak-down test showed within the green limits but air was blowing out the dipstick hole. I have one of those gauges with a green zone at anything above 40%. That means you could have 40% percent of the air blowing by out the valves or around the rings and be considered OK. A good healthy engine should not exceed 10%. Anything greater should be suspect. Any good engine build shop would be looking for less than 10% leak-dowm

What I see in your photos looks like some pre-emission engines I have torn down. I don't consider it clean for a modern engine.

I don't think you are going to solve the problem by removing the EGR or blocking the PCV. I believe your engine needs a rebuild. Sorry.

Clifton
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thanks for the reply. the spark plugs are sooty just like the upper intake. one time I pulled them one or two had oil on the threads. I assumed at that time that the valve seals were leaking.

I'm not so confident in the leakdown test results. 40 percent conflicts with the steady performance and best average mileage to date. Plus the test directions weren't as clear as I hoped.

if it needs a rebuild, i'll wait until ii have a better reason and some more time. I have brake and electrical issues to tackle first.

thanks.
 
iluvmacs said:
a rear main seal could be expected to leak with that high mileage. however, can it be checked easily, say without removing the engine or trans?
Click to expand...
You can look at the line where the bell housing and engine meet and see if there's any oil film there. It usually appears long before oil drops on the driveway. I may have another way to check it - this one's a little out there.
My rear main is about shot - say 500 mpq and leaves a mess. So of course I was dilligent about keeping the oil level up. But then coming back from a trip I didn't have any oil handy and the level was almost down to the add mark. I said, well I can make it the 300 miles OK I think. When I got home, the level was - just above the add mark! Then I was reminded of my old 626 that would leak if you went past about 1/2 way between the marks. Anyway, you may be able to let the oil level dwindle and see if consumption lessens to verify the seal is bad. As for me, I'm just gonna run it low, check it often, and change oil a little more often.
 
One time I didn't check it between fillups and it was below the low level on the dipstick. I'm going to keep it filled up.

Thanks for the reply.
 
Status update:

Oil consumption has NOT increased. Friends behind me have noted blue smoke.

I can see a smoke cloud if I leave the car overnight, facing up a hill (steep driveway), and it's cold outside (40-50F).

I had a suggestion that the head gasket might be the problem. I always assumed that the water jackets would be closer to the cylinder than the oil channels, but after looking at a head gasket, I'm not sure.

Can anyone tell me what each of the holes in the head gasket are for, or describe how the head oiling system works? I know that there is a main oil source in the middle of the head, but how does the oil return?
 

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You know strangely enough, when I moved from PA to FL my oil consumption is back to
normal.
But the difference is, even though my daily commute is more than 10 miles longer than it was in PA, it's nearly all done at 65-75 mph; the 'rush hour' stop-and-go traffic is not part of my regimen any more...
 
Protephile said:
You know strangely enough, when I moved from PA to FL my oil consumption is back to
normal.
But the difference is, even though my daily commute is more than 10 miles longer than it was in PA, it's nearly all done at 65-75 mph; the 'rush hour' stop-and-go traffic is not part of my regimen any more...
Click to expand...

valve seals??? puffing out smoke on acceleration maybe from a stop? I don't know really. My old p5 didnt seem to burn any oil with around 170k on it.
 
Protephile said:
You know strangely enough, when I moved from PA to FL my oil consumption is back to
normal.
But the difference is, even though my daily commute is more than 10 miles longer than it was in PA, it's nearly all done at 65-75 mph; the 'rush hour' stop-and-go traffic is not part of my regimen any more...
Click to expand...

So you left PA too huh? Haven't heard from you in a while.

I'm doing the same type of driving, and I really haven't seen much change in oil consumption. However, when I drive back to PA (every 2 weeks since January) I don't get as much oil consumption, maybe half.
 
StealthWyvern said:
valve seals??? puffing out smoke on acceleration maybe from a stop? I don't know really. My old p5 didnt seem to burn any oil with around 170k on it.
Click to expand...

If I'm pulling the head to do valve seals, I'll do a head gasket and new studs for sure.

Wish I could afford a borescope to see where the oil comes from.
 
I'd like to know exactly what the problem is so that I can get all the replacement parts lined up and minimize the time I don't have a car to drive. If the rings are bad I need to do a heck of a lot more. If it's valve seals or head gasket, I don't have to mess with the bottom end.
 
I just measured the valve clearances. Every exhaust valve is within spec, except 1 is high at .012 mm. EACH of the intake valve clearances is less than or equal to .007 mm, which is .002 mm below the tolerance band.

I wonder if when the engine heats up and things expand, the valves can't fully close, and oil gets sucked in during the intake stroke.

I'm going to swap the shim from the exhaust with the worst on the intake and get some new ones. Do I need to go to mazda, or might someone else have them?

Thanks
 
I believe you are quoting inch measurements, not mm. The valves clearances will change when the engine heats up but probably not enough to prevent them from closing.

You are concerned about the intake stroke, the intake valves are not supposed to be closed on the intake stroke, they are always open when on the intake stroke. The tight intake valve lash could cause some problems but are not likely to have any effect on your oil consumption.

It's not a good idea to randomly switch adjustment shims. You need need to determine what thickness shim is in the out of tolerance tappets. Next you need to compute the thickness of shims you need to bring the clearances within tolerance. After those steps you may find you will have some shims that will work in another location.

Do not use any used shim if it appears to be worn, if worn it could ruin your valve lobes

Clifton
 
Good point about the intake stroke. Still, there's vacuum to draw the air in, and air will come in through the path of least resistance.

I wasn't going to switch them randomly. I can't find my calipers right now, but from what I can tell, all the shims are the same exact size. They're all in fantastic shape too. Absolutely no signs of wear.
 
yep, sure did. engine rebuild. took it to a machine shop. old machinist ripped it apart said the rings were done, didn't have any spring to them. rebuilt it but he mixed 2 rid caps so a mile down the road it bound up and I had another rebuild and a crank grind. the sealed power rings had too much gap, like 4x normal. had a baby on the way and needed a car so I said screw it. got 2 years and 29-25k miles before too much oil burning. was running really rough and misfiring a lot. rebuild 3. I got the sealed power rings for 050 oversize an files them down to the right gaps. I also meticulously measured the bores an pistons. they were tapered and wide but at the ragged edge of in spec. engine running now but I had the parts out so long that something either clogged an injector or the injector gaskets dried up and it's misfiring on cyl 1.

I was going to enjoy this car, I thought. now I'm thinking I should take it to the auction as soon as it runs right. got 2 kids now and 6 acres of land that are taking all my time.
 
Heh, the old ex-Pittsburgher shows up again. I feel your pain.

I love the car but I have the same problem. How much did all this cost you? I have to think at this point it may have been cheaper to just
swap a lower mileage FS-DE and be done with it. Kinda where I am leaning. My car spent too many winters in the 'burgh and as much as I'd love
to rebuild the top end with better performance parts, there is a couple grand in body work that I just can't do myself.
 
I've been in sc longer than pgh now! no way I'd put another fsde in it. it's either going to the auction or getting a klde v6.

I just did a post breakin leak down test and I'm so happy that all the rings are tight. u fortunately I have 1 cylinder with intake valves leaking by. bad enough the ecu trips the code for misfire pretty quickly. if there's anything I can do besides a valve job I'd love some advice! also would like to do oversize valves if I have to get machine work done.
 
I did the valve job this year (yeah, finally) and got the car back on the road. It's running great now. Took me long enough. It's unfortunate that the factory rings were so bad and caused so many people to burn oil. If I would have known I would have sold the car over a decade ago. Now it has a fresh engine but the entire bottom is rusted. I ended up replacing the entire fuel system and broke nearly every bolt. I now have to deal with rusty and gunky bolts on basically everything now, so every repair job is going to take 4x the time. I still enjoy driving the car though. It handles better than anything else I can afford!
 
That was at 114k miles. I just turned I've 118k and its burning oil again.

I'm pretty sure the source of all these problems is the cylinder to piston gap. I had perfectly gapped rings from the last rebuild. However I did notice some cylinder taper and ovality that was within the factory spec in the service manual. I think that when I'm tired of burning oil that what it and all our cars need is an overbore and new Pistons.

Also since the rebuild I have an issue with the obd II code for camshaft sensor when comes on pretty consistently if I rev to 5000 rpm. I did some searching and believe the timing is the cause. I'm going do a belt, tensioner, the whole works this weekend and hope that solves my issue.

I also notice a hissing noise at high rpm which I'm assuming is the crankcase gas blow by traveling through the pcv catch can and other small plumbing. I do get oil in the can and in the pipe to the intake as expected but nowhere near the amount it's burning

I think the Majority of burning is happening at BDC intake stroke where the gap is big, the cylinder vacuum is the greatest, and the oil squirters are closest. Just a theory though.


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