Burning oil diagnosis Con't....with pics....

[Dave M]

Background: Oil consumption high, using @ 1L/2000-3000km (90% highway cruising). Oil pan gasket needs replacement, so likely burning a bit less. Blue-ish smoke under vaccuum conditions (long periods of coasting in gear on the many mountainous roads b/w Vancouver and Calgary). Thin layer of black soot at exhaust tips. Cylinder head was replaced along with valve guides/seals @ 40,000km ago. I have seen oil on plugs #5 once. Normally all plugs are toasty brown. At this point, most opinions leaned toward valves/guides.

But....to preempt, I checked the compression and found low dry compression on #5 which improved when wet. I'm aware that this points to bottom end/rings, but I wanted to go a bit further with the suspicions of the top end.

Having posting probs so must split post...

[Dave M]

So.... heeding Bill's advice I removed the intake manifold (after a period under vaccuum conditions) to look for oil at the valves, indicating a problem with gides/seals. In the manifold, just beyong the throttle body was a small puddle of oil (estimate a couple of teaspoons). See below.

http://img.photobucket.com/albums/v11/dave_macisaac/Bimmer/Misc/Intakeoil2.jpg

Is this a problem? Related to oil consumption?

The valves weren't swimming in oil in cylinder #5 (or any others for that matter). Some had a 'healthy' crust of carbon, others were clean as a whistle. Not sure how it got there, but a small amout of clean oil filled a recess b/w #5 and #6. See below.

http://img.photobucket.com/albums/v11/dave_macisaac/Bimmer/Misc/Intakevalves2.jpg

[Dave M]

Compression values are not with me at the moment, but #5 was significantly lower (@30lbs lower dry) than the remainder which were all within 10lbs of each other.

So, I guess I'm looking for opinions on whether the oil consumption is limited to the lower end, or, whether the oil visible in the manifold and cylinder head recess could be contributing.

Just wanted to share my 'problems'. The vehicle runs great, gets 29-32mpg on the highway and will reach 500,000km this summer (original bottom end). I am not opposed to rebuilding and will take the winter to do it myself if need be. God knows I'll need a bit of time and courage.
Anyhow, thanks again for reading.

[Jeff N.]

..but the engines and the "way I got there" are completely different. Issue is oil consumpion ~ 1qt per 1000 miles, maybe a little more. Here's a quick summary:

Motor: M30
Block: 180k miles +
Head: 10k miles
Compression: all within 10lbs
Leakdown: < 3% with one at 7%
Engine gaskets and seals: all good

Observations:

- Blue smoke on startup, especially after extended sitting (+1 days)
- Very very slight blue haze on high RPM rev
- Slight amount of oil in intake passages near valve ports.
- Throttle body is clean
- slight oil crusting deposits on the plug electrodes

Thinking:

I'm guessing I have two problems really.

Blue smoke on startup suggests leaking guides. I think the valve guides on my head were set pretty loose by the rebuilder. The head's a performance rebuild with porting and also adjusts the position of the valve guides up a bit. Discussions with Bill R. have focused on how loose the guides may have been set by the builder. Builder doesn't think there is a problem with the head.

I'm also thinking that I've got some worn rings based on generally lower range compression (within spec but lower in the spec) and the fact that the car's been driven quite hard (track use, etc). I'm not getting much blowby as the throttle plates pretty clean. I think you see a lot of oil on it from the crankcase evacuation system if there was blowby. Head builder thinks I'm having problems due to the tight head and that I used an automatic tranny block for my 5 speed engine. States that ring wear pattern is different from a lower RPM auto to a higher RPM manual.

Net net - I'm not really worrying about it too much at this time. That and short of a full teardown, I don't know if I can prove the source of the problem beyond a shadow of a doubt. Car runs fine and if I have an excuse to pull the head (camshaft swap), I'll measure the valve guide wear and see what the story is on the guides.

Based on your mileage and your observations, you may have a similar issue.

Thoughts? Hope this helps...

Jeff

[Dave M]

Thanks for the play by play. At least your comp. vaues are more in line than mine. I consider a rebuild as I'd love to see a million km. Better yet, maybe my first born will get to see it.
You mentioned oil on the throttle plate indicating blowby. Would the pic below happen to be exactly that, or am I out to lunch? Mmmmm, lunch. plate.


http://img.photobucket.com/albums/v11/dave_macisaac/Bimmer/Misc/Throttlebody.jpg
Thanks again

[632 Regal]

Dave, the compression on number 5 can be caused by a couple different things as you know. valve lash/camshaft wear, rings and valves. make sure to check the obvious lash first and recheck compression.

the guides and valve job is only 40k old, leads me to think that either the seals are inferior and not doing their job or they knurled the guides instead of properly replacing them, in either case you will pull oil in.

That dead cylinder does bother me, my question is why just one being so much lower.

[Dave M]

Dave, the compression on number 5 can be caused by a couple different things as you know. valve lash/camshaft wear, rings and valves. make sure to check the obvious lash first and recheck compression.

the guides and valve job is only 40k old, leads me to think that either the seals are inferior and not doing their job or they knurled the guides instead of properly replacing them, in either case you will pull oil in.

That dead cylinder does bother me, my question is why just one being so much lower.

The dead cylinder bothers me as well, go figure. I am fairly certain that the consumption is centered in #5, whether top or bottom.
Regarding valve lash/camshaft wear. Would low compression due to either be alleviated in a wet comp. test? Since comp. values were boosted to the same as other cylinders when wet, should this not lessen the odds of the problem being valve related?

I would love for the problem to be in my head (pardon the pun) as I may have a case with those that did the head replacement.

Any input muchly appreciated,

Dave M

[George M]

what I would do is reperform a compression test for cylinder no. 5. This is an old stand by test to determine whether your oil consumption is top end or bottom end related. Perform a compression test conventionally for cylinder no. 5. Then put two tablespoons of oil into the cylinder and repeat the test. If your compression goes up measurably with the oil added, your issue is bottom end or ring related. If it says about the same you likely have bad top end valve seals for that cylinder. Your low compression in no.5 can also be head gasket related. Presume you have checked your oil and coolant baths respectively for cross migration of coolant and oil.
Good Luck,
George

[632 Regal]

well that was another subject that i didnt get into. when you say wet compression im thinking a small amount of oil or trans fluid, back in the day I tried this magic trick and got varied results because the oil wasnt enough to coat all the ways around all the cylinders giving false readings, too much oil could lead to hydro lock...not a good thing at all. Im also thinking (hoping) that #5 could be lower because when you shut the engine off that cyilinder may have been on a compression stroke and that in itself pushed the oil out of the rings. Im just guessing at things here and would like to know the answer as much as you would. Any more clues are good.

[632 Regal]

im getting double vision! mr blurrys in town.

[632 Regal]

it is also possible to have such a head gasket leak that its simply consuming oil somewhere as George stated.

[Dave M]

it is also possible to have such a head gasket leak that its simply consuming oil somewhere as George stated.

refering to a tablespoon of oil added prior to the comp. test. I tested each cylinder dry, then repeated each cylinder wet, while not onlt watching for the peak comp, but also the number of strokes to reach a relatively stable figure.
So, the burning under vacuum leads me to think upper (regardless of recent work in the area), while the low wet test leads me to think lower. Is the oil in the manifold just beyond the throttle body normal? What about the deposits on the throttle plate? Hmmmm, I wish I knew more.
Ah yes, I highly doubt a breach of the head gasket as I monitor coolant like a soup nazi and have seen nothing to suggest such a thing.
Short of biting the bullet and beginning to purchase rebuild tools (which wouldn't bother me in the least, I'd love a winter project and the chance to learn) I'm not sure what to do next.

[Dave M]

see/feel the camera that took these puppys. I believe its called the Kodak DigiKlunker. Better do some twelve oz. curls before you step up to the plate, she an oldie. It has to be rugged enough to survive tumbles down hills and bear attacks.

Anyhow, back to work.



im getting double vision! mr blurrys in town.

[632 Regal]

Is the oil in the manifold just beyond the throttle body normal? What about the deposits on the throttle plate?

I would feel safe to guess the answer to this would be a NO. But of course thats a guess and would be thinking along the lines of guides/seals and reversion, reversion is normal but it pumping oil back isnt normal.

[winfred]

oil in the intake is VERY common, it comes through the pcv system and it's the primary reason for the need to clean the throttle plate and icv, the crud will build up to the point that it will prop the throttle open and screw with the running, i've solved oil leaks on m50s by just replacing the rotted off line from the valve cover to the airboot, the m52 has a seporator (that screws up causing bad running) that runs the oil down the dipstick tube, most of the cars i work on just have the crankcase hooked to the intake, some have vapor seporators some don't (volvo guys lets hear it for the often forgotten flame trapp)


Is the oil in the manifold just beyond the throttle body normal? What about the deposits on the throttle plate?

I would feel safe to guess the answer to this would be a NO. But of course thats a guess and would be thinking along the lines of guides/seals and reversion, reversion is normal but it pumping oil back isnt normal.

[632 Regal]

hm yeah...just what he said

[winfred]

hell you own a m60, the master of crappy pcv systems that can suck oil, did a e38 740 that gulped about a quart of oil in 15 miles when the diaphram blew


hm yeah...just what he said