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Old 12-30-2003, 11:23 AM
Registered User
Join Date: Nov 2003
Posts: 111
strange smoking problem

1974 450 SEL, 256,000 miles. Down on power, uses a little oil
(but not excessive). Recently a strange problem has developed.
When I start the car cold, everything is normal. No visible smoke.
Then I'll drive about a mile or two. First couple of times, I'd drive to a store, shut it off, come out, start it and there would be an
excessive cloud of blue smoke. Then as I drove on there would be no smoke. Last couple of times, it would start (no smoke), then after 1 or 2 miles at most, if I stopped at a light and then accelerated there would be the excessive amount of blue smoke. Drive on and no visible smoke. When I say excessive, I mean a big cloud, so much that if there were a cop behind me he would probably stop me. But at cold initial startup and when the car is warm there is no visible smoke.
At first I thought there might be a stuck ring. But because there is a regularity to the problem (only does it 1 or 2 miles after startup) I don't think that's it. Also, wouldn't seem to be valve guide seals, because wouldn't that smoke right at startup?
Might there be some emissions related thing that is sucking oil
somehow, or a leaky power brake booster or something?

I'm stymied. Any ideas?
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Old 12-30-2003, 01:00 PM
Registered User
Join Date: Aug 2002
Location: La Quinta, CA
Posts: 271

Sounds like a classic case of valve guides/seals being worn out. My car would emit a little smoke at startup but it really put out a cloud after idling for a few minutes at a traffic light. Oil consumption was light. Car ran great. But the smoke finally make me do the repairs.
1986 560 SEL (159K miles)
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Old 12-30-2003, 07:06 PM
Registered User
Join Date: Dec 2003
Location: Rogersville, Missouri
Posts: 143
Another possibility is when a cam oiler tube pops off, the valve cover slowly floods with oil and then the intake guide suck the oil into the combustion chamber. This would take the 1 to 2 mile drive for this to occur. The oil fills the rear of the cover and overloads the intake seals. Oil would be noticed on the rear spark plugs of the affected bank. Additionally this car did not smoke at cold startup.
1987 190E-16v,
1988 260E Gone after 19 years of service,
2006 C280 4MATIC Gone to another
2006 OM647 Dodge (Mercedes) Sprinter
Time to find another car
29 years Mercede-Benz Technician, Retired Master Technician/Master Wrench
Master Guild Technician once/ SLR Technician Nine cars serviced
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Old 12-31-2003, 07:09 AM
Registered User
Join Date: Jan 2003
Location: Matthews, NC
Posts: 1,356
I had this exact problem on my 84 500 SEL.
Turned out to be the modulator valve in the transmission.
The valve is located on the left side close to the shifter linkage. It has a vacumn line hooked to it.
84 500 SEL (307,xxx miles)
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