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Registered
1991 500 SE
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61 Posts
Discussion Starter #1
Guys,

I've been holding off before asking for advice...

Around 2 weeks ago I drove the 560 over a distance of 300kms on the highway with the cruise set at 100mph/ 160km/h. It was a nice warm day - 25 deg C.
At the end of the journey I accelerated to @ 180 km/h for @ 5 kms and then 200km/h for the last 5 kms. Upon slowing down from 200km/h to turn into the ranch on a slight down-hill I happened to look into the rearview mirror... well I almost freaked when I saw light blue/grey smoke coming from the exhaust on overrun - not blinding, but def visible. I immediately shifted into neutral and as I turned off the road, with the motor now idling, there was still a bit of smoke coming from the exhaust for @ 10 seconds.
Oil pressure and idling was good and everything sounded fine.

I parked it for the night, with my mood sagged into my shoes...
The next morning I checked the engine oil and it had turned from see-through light brown into almost black and it now has a slight burnt smell - however the level is still where it has been during the last 2000 kms since its service - full. It burns no oil.

I started it up and took it for an extended drive - trying to simulate the previous day's driving style... well, I burnt the snot out of it and never saw a puff of smoke during hardcore accel or on overrun from high speed. I parked it and checked the oil after 10 mins - spot-on and slightly lighter in colour but still with a black tinge.
I am bleak and the car has sat since.

I must admit I have adjusted the vacuum modulator for softer shifts by 1 and 1/4 to 1 and a half turns... could this have caused it to suck tranny oil into the engine? Would that cause a slightly burnt smell on the engine oil?
I checked the tranny oil while cold withthe motor not running and it read between F and L:confused: I will check it again tmrw to see where its at.

I am contemplating an engine oil change and maybe a new modulator???

What do you guys think?
 

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Registered
1991 500 SE
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61 Posts
Discussion Starter #2
BTW, it runs on 20w50 and it got new valve stem seals and cam oiler kits at 200 000kms in 2004.
 

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Registered
W126 500 SEL 9/85 W124 E320T Brabus
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2,057 Posts
Hi RSA560,

its always the same - a half done job!:surrender:

First of all - It burns oil! Thats your blue smoke.

BTW, it runs on 20w50 and it got new valve stem seals and cam oiler kits at 200 000kms in 2004.
Thats the half job! I will try to explain and hope my english is good enough for this.

After 200kkm the valve guides have been widened up and the valve is tumbling in it. When the piston
goes downward, it sucks oil along the valves into the combustion chamber and burns it. So if you only change
the seals, the valve keeps tumbling. The seals wear faster and leave space for the oil.

The blue smoke only appears, when the engine turns with high speed and then suddenly the acceleration stops.
The pistons suck the oil - and so on...

Upon slowing down from 200km/h to turn into the ranch on a slight down-hill I happened to look into the
rearview mirror...
Thats the situation ;) To get rid of this, you have to do that job again and change valve guides and valve seals!

Roland

with a little help from babelfish :D
 

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Slightly creased
2015 ML 400 x 2
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16,602 Posts
now, there was a revival of an old thread recently by shrimpton who had similar symptoms and it turned out to be a very simple fix of the oiler tubes. Kodiakj2 had a similar story - search on both those user names for posts about this in the last month or so.
 

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Registered
W126 500 SEL 9/85 W124 E320T Brabus
Joined
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2,057 Posts
now, there was a revival of an old thread recently by shrimpton who had similar symptoms and it turned
out to be a very simple fix of the oiler tubes. Kodiakj2 had a similar story - search on both those user names for posts about this
in the last month or so.
What will happen, if the oiler tube separates? The camshaft will run dry (extreme situation) and the oil goes
back to the circulation. But how should it get into the combustion chamber?

Roland
 

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Registered
'84 500 SEC Euro 040 black Lorinser 2005 sl500
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2,516 Posts
What will happen, if the oiler tube separates? The camshaft will run dry (extreme situation) and the oil goes
back to the circulation. But how should it get into the combustion chamber?

Roland
The oiler tube on my 500 SEC was not separated completely, just loose at the very back cam oiler "clip" or prong if you will. I guess the cam bearing was not getting it's full load of oil, but nothing happened to it that I can tell.

Same thing was happening to my car as well as Shrimpton's. Running about 70-80 with heavy acceleration just prior to getting off the freeway and down an off ramp. Pretty heavy braking, sit for a few seconds then hit the gas. Result would be a big ol' plume of smoke.

My top end had been completely rebuilt by Mercedes with genuine Mercedes parts (bought the car from the dealer, 2 months later the chain jumped with a valve hitting. Split the $6,000.00 usd bill with the dealer).

After reading Shrimpton's discovery that the fix was actually just the left bank oiler tube repair kit, I also replaced mine since my heads only had about 60,000 miles on them at the most. Wouldn't think the seals would go that quick. After I did the oiler tube the problem has vanished for the better part of a month or so.

The premise is that the oiler is spraying heavy in the cam cover due to the loose oiler tube clip. When running hard, then pitching the car forward the oil runs forward in the cam cover and gets sucked up through the blow-by tube from the valve cover to the intake via the cold start valve/idle valve area.

All that I can say is that it worked for me. What a relief!

Good luck with yours,
Greg
 

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Registered
1984 500 SEL euro, 1989 560 SEL, 1980 450 SL, 1981 DeLorean, 2013 F10 BMW
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1,253 Posts
Years ago I had a similar situation while driving to New Orleans. I had been driving at a reasonable 75 mph and after several hours I had picked the pace up a bit. In the middle of MS. and nowhere near anything I noticed a large plume of smoke rolling out the back. I pulled the car over rather quickly and called my tech/friend who helps me with my cars.

Come to find out the trans fluid had foamed from the vent and hit the exhaust thus 'big smoke'.

Word to the wise, make sure you use a non-foaming trans fluid!!

Regards,
 

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Registered
1991 500 SE
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61 Posts
Discussion Starter #8
Thanx for the replies, guys!

I have been following those threads, but for some reason I'm thinking my valve guides COULD be stuffed.
But why the blackened oil with a burnt smell then?I guess you guys are ruling out my fiddling with modulator then?

BTW, upon cold start-ups the motor makes a slightly deeper sound in the top-end than just a tappet noise - somehow metallic. Most people wont notice it, but I do. It goes away once the motor has warmed up - to the point where there is absolutely no tick or beat and the motor runs as quiet as a new one.
Consequently, I'm sure the cams are still good.

Also, would a thicker oil kinda mask the worn valve guide symptoms in the short term - IF that is the case?

Your help/ideas are greatly appreciated.

I'm going to check the tranny oil now...
 

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Registered
1991 500 SE
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61 Posts
Discussion Starter #10
I'm sure they're good - I know what that sounds like and have never heard that on this car.
As I've mentioned that metallic noise isn't very audible - but I know its there... AND it isn't only audible for a few secs after start-up - it only dissapears once the motor has completely warmed up.

FWIW, the PO had it from 160 000 kms in 2002 untill 298 500 kms a month ago.
And he really is an old boring doctor and the service records show it never wanting for anything, except perhaps guides and chain... so I presume the car hasn't been driven hard during the last 7 yrs.

BTW, I've just checked the trans fluid level and it reads an inch above the full mark. I checked it 3 times and each reading was positively an inch above the full mark. Note the car had been sitting for 2 weeks now - so its ice cold.
Also, the engine oil is upto the full mark.
 

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Registered
1991 500 SE
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61 Posts
Discussion Starter #11
Good news guys!!

I went to an established Benz dealership yesterday and spoke to a service technician - a very friendly and very knowleagable guy. It is not often that I trust someone, but he definitely new what he was talking about.
He is positive that my short high speed run caused it to burn off carbon on top of the pistons - hence the smoke on overrun and black oil. He says I should only use Wynns engine flush and change the engine oil/filter - and Bob's your uncle!
I bought a new filter from them at ZAR42 which is equal to @ $4,66 US

I asked about the possibilty of worn valve guides - he said unlikely at that mileage!! And because of the fact that it doesn't burn any oil. He says these engines just don't give problems.

On the subject of oil.... they only use Castrol GTX 20w50 mineral on these older Mercs - and Castrol SLX 5w30 full synthetic on the new Mercs. This is at an alititude of 1 800m above sea level where temps in Winter drop to @ -3 deg C with highs of @ 25 deg C.
Lows in Summer of 18 deg C and highs @ 30 deg C

Timing chain and guides.... he says leave 'em 'till ya hear 'em!
He says guys fuss over it too much.
So I'll leave mine 'till I hear it - end of story.
He could easily have persuaded me to have the job done, otherwise

And they never change diff oil.
 
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