1xsculler

I've determined that my GL450, 120k, '07, burns a quart of oil every 1000 mi.

Will the engine last me to 200k or should I trade it in? The compression is even in all cylinders albeit a little low at about 120 psi. It doesn't smoke and it runs very well. I'd hate to get rid of it but I will not buy a new engine for it. I got it with 100k on it.

alx

according to mb a quart every 1000 miles is acceptable.

in my mind it is not - especially for a non-turbo engine.

120psi is borderline. you probably have cracked/ worn oil piston rings.

as long as compression is even across the cylinders you should be all set.

BlownV8

I have over 200k miles on my 450 and I don't have to add any oil between 10k mile changes. It may be considered "normal" from an MB liability/warranty perspective but it should not be burning that much oil.

a2j

I don't have to add any oil between changes as well. And I hear that 320 should burn more oil than 450.

alx

Yes, diesels like to sample their oil on a constant basis- just to make sure it is still good A quart every 10k miles is about right for the om642.

Oil consumption on its own unless a particular cylinder is low on compression is not bad. The problem is that things on the exhaust track get plugged up. Expensive things.

eric_in_sd

That's my fear. My oil consumption is steadily worsening. Flirting with 1 qt/1k miles. 2007 GL450, 128k miles. Haven't checked the compression, but the plugs looked uniform at 100K miles. It's hard to imagine the cats not complaining at some point.

1xsculler

When your GL was burning 1 qt/1k miles did you notice any blue smoke from the exhaust?

eric_in_sd

Not was; the most recent four quarts have been at just over 1k miles.

No oil smell, no smoke, no drips anywhere, and at 100k, which was when it was at about 1500 miles/quart, no oil on the plugs.

The consumption bounces around a lot, at least according to the "check oil level" message. For example, it's now been 1k miles since the last quart, and the dipstick shows 1/3 quart above minimum. So I'll bet this interval is more like 1,500 miles.

1xsculler

I've found that I can drive about 800 mi after the check oil light comes on before the oil on the dipstick is at the very bottom of the safe level. I have no smoke, smell, fouled plugs or drips either and the car runs beautifully.

Your statement about having to replace expensive exhaust parts like catalytic converters, etc. does scare me though. I'll trade it in for a Toyota Sequoia before replacing expensive parts only to eventually have to put a new motor in it.

BlownV8

Aftermarket cats are cheap but doesn't sound like you need them. Just keep using Mobil 1 0w-40 and check the level every few thousand miles.

eric_in_sd

I remember someone said they had put in aftermarket cats. Was that you, even tho you're in Cali? I looked again at the CARB lists and found nothing for GL450.

I've been sticking with 0W-40 (vs. 10W-30) for about 10k miles now and the consumption hasn't changed. Continued the miles/quart downslope. I have a supply of the 0W-40 so I'll just use that up and see where I'm at.

eric_in_sd

I'll post back with how many miles from here to the warning light. By "very bottom" you mean the MIN on the dipstick, right?

If you aren't in Cali the cats shouldn't be too much of a concern. We have to have our cars smogged every two years. The whole state suffers to help Los Angeles have clean air.

eric_in_sd

Got 300 more miles, for a total of 1,300 miles.

The tranny started to seriously act up, and my icarsoft told me turbine speed sensor was pfft. So I took it in to a shop today (I'll update the transmission thread separately) and while I was there I mentioned a few other things, including oil consumption. The guy mentioned the PCV valve and said they'd check it out. I saw your other thread asking about this, with no replies; I'll let you know. It's a pretty easy replacement, and a $50 part, so if this works, I'll be one happy camper.

One thing makes me think this is a more likely culprit: If oil is getting past the rings, you'd be getting oil in the chamber on all or most of the piston strokes. Thus more likely the plugs would show oil fouling. But if it's coming in on the intake, it would be more likely to be cleanly burned.

eric_in_sd

Compression tested very strong: 180s across the board.

Which raises a very interesting question: Where is my oil going?

BlownV8

No oil.drips under the engine? If not, it must be going through your intake and getting burned in the ignition process.

eric_in_sd

They sent me a picture of the plugs and they looked kinda black. But the motor has been at a shop, started, stopped, started again ... so I dunno.

If oil is going in through the intake, it would only get mixed in with the fuel in the intake stroke, so it should burn more cleanly than if it's getting in past the rings or leaking through an intake manifold gasket.

I changed the separator, and it was a MESS. Very interested to see how the oil consumption holds up. I'll kinda miss tracking the oil consumption, tho.

1xsculler

If oil was going through the intake wouldn't there be black soot on the sir cleaners?
What is the separator?
My wife's ML350 with 80k on it uses no oil between 13k oil changes. My GL450 goes through a qt every 700 miles. When I run a finger around inside her tail pipes or mine the black soot looks the same. Neither are oily just black soot.

eric_in_sd

Not necessarily. The crankcase vapors, with oil, enter the manifold after the throttle. So they pretty much always are sucked into the combustion chamber. I should have checked the air filters, though. They're due for being changed fairly soon, though, so I'll give it a look.

I'm not sure how it works. Some call it the PCV valve, but I don't see anything valve-like about it. "Centrifugal separator" is also used. It's on the upper rear passenger side of the motor.

Carbon from incomplete combustion and semi-burnt oil look very similar. I didn't look closely at the picture they sent me of the plugs.
If the tailpipe were actually wet with oil, the oil would have to be entering during non combustion strokes and making it past the catalytic converters. So your test is ruling out something very terrible.
Changing the separator (and cam housing plugs, while you're at it) is easy, if you're mechanically inclined. I took a couple of hours to do it, and I'd be fired first day on the job at a repair shop.

eric_in_sd

Welp. After changing the valve / separator at the back of the engine, still burning oil. 2 qts in 2800 miles. Not sure about the next step.

The crankcase ventilation system on this motor bugs the heck out of me. I can't figure out how it works.

1xsculler

eric, Maybe we're trying the same experiment to get a grip on ridiculous oil consumption.

I just installed a new separator and all three cam housing plugs (Ebay, about $30 for all) (none of them had been leaking) to, hopefully, eliminate one possible element contributing to 1 qt/1000 mi.

I won't know if changing out these parts helped for another 1000 miles, or so, but I will repost then.

I'm pretty much convinced that my oil burning problem is worn out valve stem seals on my 124k, 2007 GL450. My compression is strong and consistent in all cylinders, i.e. 185 psi +/- a couple of PSI and the only time I notice any blue exhaust smoke is when I first start the engine after it's been sitting. Then I get a little blue puff. With four valves/cylinder = thirty-two valve stem seals I can understand why this might be the problem. Considering the excellent compression and strong running of this vehicle I can't believe this much oil is blowing by the rings and that leaves only the valve stem seals as a possible cause unless someone on this forum can convince me otherwise.

I figure it will take one day and an insignificant cost to do the job myself as I am a total DIYer and never take my care in for anything except stuff like tires which I don't have the equipment for. If you take these cars to the dealer as they recommend they cost a fortune to own and I'm not buying into their program.

alx

Valve guide seals are a common failure on the v8. They are also not very hard to replace. The blue puff upon start is a good indication that your seals are bad. Rings usually blow blue smoke on hard accelleration...

eric_in_sd

Are either intake or exhaust seals more prone to leaking? It would seem to me exhaust seals would be much more prone to causing smoky exhaust. I've got no exhaust smoke.

I think I'm going to get a borescope to peek at the intake valves. Dunno if the fuel spray would wash the back sides of the valves, though.

eric_in_sd

I found this thread on valve seal replacement. Different motor, but he said it was a non trivial job:
https://mbworld.org/forums/w211-amg/...placement.html

Is it easier on this motor?

a2j

I did this on one of my vehicles. Blue smoke on acceleration symptoms. I used one of these https://www.amazon.com/Lisle-36200-K.../dp/B000P0ZJIS

alx

It is easier as there is no blower and coolant to remove/ drain. A competent tech can do the job in 8 hours taking his time. It looks intimidating, but once you start doing it is not very complex, does not require strength, just tedious. Once you do the first cylinder the rest will go faster.

Once you are in there you might as well do both intake and exhaust seals.