V12 Drinking and smoking problems

[anonymous-user]

Hey guys, I've never posted in here but long time lurker of some interesting engine related threads, I thought I'd pick some brains

Soo... I have a 2007 Mercedes S600 that has developed a drinking problem secondary to its taste for Super unleaded and a smoking problem to rival my own

The car is now using about 1 litre of oil per 100 miles .

I get a big blue puff of smoke under load/boost coming entirely from the left hand bank. No smoke on idle and off boost, and I had the engine upto 3,500rpm on overrun and again, no smoke issues.

I have had some suspicions about the blow by from my PCV system and/or out of the engine filler cap is a little excessive when doing the diag for the misfire. Compared to a car with half the miles I do have considerably more gases being vented out of the system, but even with the PCV system vented to atmosphere and blocked off to the inlet, I still get the smoke.

My thought always has been that I knackered a piston ring by washing the bore with fuel when it was misfiring. That, coupled with the 225,000 miles the engine has covered, was the only thing that made sense. So today I carried out a compression test.

Compression test results (12-14bar the tolerance for a new engine, 10bar the limit. Taken from cold as opposed to warm as the workshop manual advises. 7-12 are the bank that are smoking.
)
1 - 14bar
2- 14bar
3 - 14bar
4- 14bar
5 - 14bar
6 - 14bar
7 - 9bar
8- 13bar
9 - 12.5bar
10 - 12.25bar
11 - 13bar
12 - 13bar

Cylinder 7 is obviously low, BUT, I have a suspicion it may be caused by carbon fouling on the valves. Why? Check out the plug!

|https://thumbsnap.com/6uHmaa84[/url]
.

But it gets more confusing. Cylinder 11 had one of the highest readings of bank 2, and check out its plug



. .



Other plugs on Bank 2 where fouled and black, but no where near as bad.


And now I'm honestly running out of ideas... In my head, A failed ring is going to cause much less compression than 9bar... right?

I then think it could be valve stem seals but, I have no smoke at start up or idle... and its using so much oil I wouldn't have expected stem seals to cause THAT much consumption... right?

Given the consumption I was expecting something definitive on the compression test but now I'm more confused that ever, BUT, I'm siding with it being stem seals.

Any thoughts or input would be greatly appreciated.

Thanks for your time .

Edited by anonymous-user on Sunday 28th March 20:10

[robseagul]

Good evening .
Turbo on the left bank knackered wouldn’t you say.
Can you remove the intake pipe work to the turbos for a comparison?
Rob

[anonymous-user]

Hi rob.

The pipe work and intercooler for the turbochargers is about the same bank to bank - A little oily but nothing to suggest the amount of oil it is eating.

Charge side both intercoolers feed into the inlet manifold at a single point, so If it were picking up oil on the intake side of the turbo I'd expect a more even distribution of smoke? My issue seems be coming entirely the LH bank

If the plugs were clean i'd have expected it to have been pulling oil in on the exhaust side, but something strange is definitely happening in the combustion chambers to cause those plugs.

[robseagul]

Good evening.
Ok I see what you mean.
A large cloud upon acceleration could well be valve stem seals however that’s normally comes with clouds upon starting when left for some time.
I’m a motor man but merc trucks and have yet to have an s600 .
Is it too much hassle to remove the actuator /pipe feed to the turbo on the left bank and see what occurs?
Although it will run rough if the smoke reduces with a non spinning turbo it may provide an insight.

Check absolutely all breathers too .

Sadly it’s a engine out for turbos right ?
R

[robseagul]

What oil grade are you using by the way??

[anonymous-user]

robseagul said:

Good evening.
Ok I see what you mean.
A large cloud upon acceleration could well be valve stem seals however that’s normally comes with clouds upon starting when left for some time.
I’m a motor man but merc trucks and have yet to have an s600 .
Is it too much hassle to remove the actuator /pipe feed to the turbo on the left bank and see what occurs?
Although it will run rough if the smoke reduces with a non spinning turbo it may provide an insight.

Check absolutely all breathers too .

Sadly it’s a engine out for turbos right ?
R

I adore all Mercedes vehicles, I think that they are one of the most diverse manufacturers in existence and when they really try to build something well, they do it - I think a 225,000 mile, 517BHP V12 that is still ((mostly ) within new compression tolerances speaks volumes.

As you say, my indication for valve stem seals would be smoking on start up, but there isn't anything noticeable on start up or idle. The smoke issue at least can be "driven around" but I'm not sure if its a matter of it constantly burning oil and me just not noticing until the revs are built up, BUT, as i mentioned, it didn't smoke on overrun - 3500RPM should have been plenty movement to expel lingering oil.

While I have it apart I want to replace the oil centrifuge on the end of the camshaft. Its about the only apart of the PCV system that's left at this point, then I'll put it back together and disable a turbo as you suggest.

Indeed, engine or at the very, very least subframe out and a lot of swearing to get the turbos off. I do have a ""spare"" engine that I can rob parts from, but dropping the engine on one car is daunting enough, let alone twice. I think at the point of a double engine drop and swap I might have to call time on the "project" to save my sanity .

Oh, oil - My first two changes were on Elf 5-50W. It is now (or was) on petronas 5-40w but its been watered down with various "top ups" as required with it drinking issue

Edited by anonymous-user on Sunday 28th March 20:08

[GreenV8S]

If you're confident you carried out the compression test correctly then it is pointing clearly to the cylinder with the problem. You can follow it with a wet test to see whether it seems like a ring sealing issue. You can also do a leakdown test to see whether it's leaking past the rings or the valves. A worn valve stem seal would account for oil consumption but not the low compression so the evidence doesn't point to that. Worn rings or bore/piston damage unfortunately seem more likely.

[stevieturbo]

Considering the engine, this is one of those cases where you need proper diagnostic gear and abilities. Guessing will cost you a fortune.

There could be many causes of a loss in compression, rings are a possibility. Whether one piston alone would be the cause of the huge oil consumption...seems unlikely.

But absolutely check every aspect of the PCV and crankcase breathing.

To determine where any leakages are occurring, a scope and pulse sensor in the crankcase would hopefully at least identify which, if any cylinders are leaking excessively into the crankcase.
Likewise in the intake/exhaust it would give an indication if there are leakages occurring through either of those routes

But the lower compression could also be a red herring in terms of oil use.

You are also mentioning a misfire, but do not state which cylinder is misfiring and when ?

Get the PCV working correctly, put new plugs in it....no point trying to take too much from extremely old plugs.

[robseagul]

Good evening.
To be fair I have a conti gt here with the same scary turbo Engine out scary prospects so you have my sympathies.

[anonymous-user]

GreenV8S said:

If you're confident you carried out the compression test correctly then it is pointing clearly to the cylinder with the problem. You can follow it with a wet test to see whether it seems like a ring sealing issue. You can also do a leakdown test to see whether it's leaking past the rings or the valves. A worn valve stem seal would account for oil consumption but not the low compression so the evidence doesn't point to that. Worn rings or bore/piston damage unfortunately seem more likely.

Thank you for your reply.

Is it naïve for thinking that a worn ring or serious piston/cylinder damage should cause more of a compression loss than what I'm seeing? While its 3bar down on the next lowest and a cause for concern, 9bar doesn't seem all that horrific, especially when I see the plugs on that cylinder in that state - My mental gymnastics has me thinking that those deposits could be causing a valve not to seat correctly thus a small loss of compression.

I'll invest in a leakdown tester and do a wet test for my next mess around with it .

stevieturbo said:

Considering the engine, this is one of those cases where you need proper diagnostic gear and abilities. Guessing will cost you a fortune.

There could be many causes of a loss in compression, rings are a possibility. Whether one piston alone would be the cause of the huge oil consumption...seems unlikely.

But absolutely check every aspect of the PCV and crankcase breathing.

To determine where any leakages are occurring, a scope and pulse sensor in the crankcase would hopefully at least identify which, if any cylinders are leaking excessively into the crankcase.
Likewise in the intake/exhaust it would give an indication if there are leakages occurring through either of those routes

But the lower compression could also be a red herring in terms of oil use.

You are also mentioning a misfire, but do not state which cylinder is misfiring and when ?

Get the PCV working correctly, put new plugs in it....no point trying to take too much from extremely old plugs.

I'm a roadside mercedes tech by trade so my diagnostic gear and abilities are little bit higher than most DIYers, but I have to work within the constraints of not having a workshop (or special tools) or a ramp, so "big jobs" are still a little daunting.

The misfire previously was unrelated to this fault - The ignition system on these are very temperamental, I had at least one coil pack fail. I replaced both packs, the voltage transformer and plugs prior to my "shakedown" before becoming aware of the oil consumption. THOSE are new plugs. They maybe 400 miles on them.

The PCV valve was changed as well. Same issue with the original unit, one from my donor car and now a brand new unit. The last part to change is the centrifuge but we are clutching now with it only being a PCV issue.

Edited by anonymous-user on Sunday 28th March 21:00

[anonymous-user]

robseagul said:

Good evening.
To be fair I have a conti gt here with the same scary turbo Engine out scary prospects so you have my sympathies.

Haha, awesome.

I did my apprenticeship at Jack Barclay Bentley in London... When it comes to engine outs, YOU have my sympathies .

They are amazing machines though, nothing comes close to the attention to detail you get in a Bentley or Rolls Royce.

[stevieturbo]

That's some state for 400 miles !!.

Can you re-route the crankcase breather system so that no oil crankcase vapours at all get drawn into the inlet ? Even if only for another test period to see if it fouls up the plugs like that again ?

Or if it absolutely must get drawn in/PCV, add a decent filtration can to ensure only clean air gets through.

I think I recall someone years ago mention about the coil packs on them, it's a single pack for each bank ? mega expensive ?

but again...identify which cylinder is misfiring, and see if it ties in with any compression tests readings, although a CR test might be of limited use here.
Check properly for spark quality at each cylinder.
Likewise at 225k....maybe worth pulling injectors and having them tested/cleaned ?

But first off, establish if the oil consumption ( and plug fouling ) is breather related or something else

Can you get a visual inside the intake, or down the ports to see what each runner looks like ? remove injectors and stick a camera in there ?