Occurs at startup and on and during acceleration; sitting.

So far - moved car to WV where ethanol gas is really bad. Shortly after first tank: over-heat and white smoke. Pulled the vacuum hose and no fluid and sucked on it and plugged with my tongue and it held and could pulled no fluid into the hose. I drained, flushed and replenished the collant and it seems to hold its level. Pulled plugs and no water and none blew out upon crank without plugs.

Seemingly; I have eliminated trans fluid and anti-freeze being blown out the exhaust.

Next: would a plugged cat converter do this from bad gas?

There has to be a source. O2 sensor affect???? What am I missing? What checks can I make?

Telling us what kind of car you have would be helpful.

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1989 300CE

1995 SL 500. I though I left something out and.......... you beat me here.

Is this frustrating or what

New try: 30 min ago. Start, fine w/no smoke but some water coming out tail pipe. But, the water level was exactly where it was yesterday w/new thermostat (80 C).

82 for 20 min and gradually climbs and still water or condensate coming from tail pipe and taste basically like water but makes the tongue dull for 10 seconds.

Climbs to ~100C and still no smoke. It did this same thing before I replaced the thermostat.

Can ethanol gas clog the cat convt and cause this phenomenon? O2 sensor???????????? at wits end.

You can safely use gasoline with ethanol content up to 10%. Are you using fuel with more than that? If you are only driving the car short distances, you could be burning off the condensation from the engine.

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1989 300CE

I am afraid to drive the car off the property. I just drive around here and it does good and gradually moves to 82C in ~20 min.

Then goes to 85C and hangs or moves slowly to 95 and then on to 100C and starts missing. (actually starts missing at 90C; just gets progressively worse).

Leads me to believe maybe more than one problem; but, I tend to inculde the cat convt.

Replace the thermostat and see if your 500SL still overheats.

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Fred Hoelzle

Replaced it yesterday. No change.

Does the car consume coolant measurably? How many miles on the car? Any leaks on the ground? Are all the cooling system parts original? Cooling fans working?

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1989 300CE

It just started happening to me too. Out here in So Cal...it turned cold (65 degrees is cold here) and rainy and I have to burn off some white smoke every morning now. I'm sure something is leaking into something and causing this now. Another thing I need to fix! They just keep coming! '91 300E.

Steve

Replaced thermostat: no change. ~92,000 miles '95 SL 500 R129. Both aux cooling fans work and the engine fan seems OK as it spins.

Can't seem to see any lower level of coolant - or, doesn't seem to consume coolant although my wife says it smells like anti-freeze. But, not to me nor does it taste like anti-freeze.

It does not appear to be sucking trans fluid from the vacuum line of modulator best I can tell.

Kicker: I started this AM; no smoke but a tiny amount of vapor. Water still drips out the exhaust pipe. Again; no taste but some chemical to affect the tongue for ~5 seconds mildly.

If temp climbs it starts with a miss-fire and gets worse as temp rises.

Does it go beyond 100C? Not sure where the M119 normally sits engine temperature wise. Moisture is created in the combustion process and it sounds like it is being burned off. Continue to monitor coolant level. When was it last changed? Are you using the correct MB fluid? Not sure about the misfire. Plugs, filters, wires are a good place to start if they haven't been done in a while. Is your wiring harness original to the car?

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1989 300CE

the combustion cycle does create water vapor but not that much.

Orig wiring: new plugs. Thanks for the help.

If it gradually starts missing as it gets hotter, it could be a pre-ignition or detonation problem from carbon buildup on the pistons. I experienced this with a 119 engine in my 400E and it was completely solved by running two bottles of Chevron Techron in a full tank of gas. It is a cheap fix and you don't have much to lose by trying it.

Also, during periods of higher humidity, I have noticed in both my 400E and E420 that water does drip from the exhaust pipe. It may not be the coolant leaking into the combustion chamber, but the humidity of the air that the engine is intaking.

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1993 400E, 256,000 miles (totaled)
1994 E420, 200,000+ miles
1995 E420, 201,000 miles

Add an OPPS:

Added the Chevron TEchron. Now; engine has vapor and then 95% clears up and seems to run OK (not great) but now the RED check engine light comes on.

Think it will clear? Ignore and keep driving or _____________________suggestions.