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Old 10-22-2001, 10:16 AM
Robert Boyer
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'88 420 SEL head gasket symptoms

Query: What would be the telltale signs that a head gasket is about to blow on this engine?

Notes: car has 167K, otherwise performs fine.

Upon startup, has a little grey (not black) smoke , which goes away after warm-up.

Sometimes there are some droplets of water (not antifreeze) from the tailpipe.

Any thoughts? Thanks.
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Old 10-22-2001, 10:24 AM
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The smoke you see is probably oil -- valve seals are in need of replacement -- 168k miles is about right.
The water is typical by-product of exhaust. Nothing to worry about and is more evident depending on the temp and humidity level of the outside environment.

Now if the car was blowing white smoke, that would be the head gasket.
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Old 10-22-2001, 10:31 AM
Robert Boyer
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head gasket symptoms, con'd

Thanks, W126.

Hard to say if smoke is really gray or white. This is difficult. It is not black, more a color in between gray and white.

I have been experiencing increased oil consumption the last few months. Maybe this helps.

Also, I think I seem to detect a sort of not hissing sound, but more of an air sound upon acceleration.

However, temp gauge stays rock solid at 80, or at times, just a tad higher. Even at stop signs or lights. (And I live in Miami).

I idi replace my own plugs (difficult), about 4 months ago, and although engine does not miss, one or two of the plugs I suspect might not be seated properly.

What do you think?
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Old 10-22-2001, 11:45 AM
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Black often denotes too much gas in the fuel/air mixture. I'm not sure what that sound is, hard to tell. Almost sounds like a bad fan clutch (?) Some other folks might have a better idea.

I'd make sure those plugs are seated properly. Also, how much oil is it using? A little is OK, considering it almost has 170k miles. Also, mild oil use is one of the symptoms of worn valve seals. Not a big deal, btw. It's A DIY job and not too expensive if you bring it to a competent shop.

Last edited by BlackE55; 10-22-2001 at 11:53 AM.
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Old 10-22-2001, 01:56 PM
MikeTangas's Avatar
Senior Member
Join Date: Apr 2000
Location: So. Cal
Posts: 4,430
Valve stem seals will give a puff of light blue (could look grey) smoke upon start up from oil settling in the cylinders. As was stated earlier, this iss likely the cause of your smoke.

As for the head gasket, check the coolant reservior for signs of oil in the water. Chances are if the head gasket is heading south, you'll spot it early on at the coolant reservior. Unless if you have a catastrophic gasket failure (yes they happen).

In the absence of oil in the coolant, you may see coolant usage, where you have to top off the reservior every couple days. This would indicate a coolant leak into an oil passage or into the combustion chamber (could even leak coolant externally at the head to block joint). Do you have any coolant in the oil? If you do you'll have a chocolate milkshake looking substance on the dipstick.
Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72

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Old 10-22-2001, 02:11 PM
Robert Boyer
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head gasket symptons, con'd

Thanks, Mike.

No, my coolant level is always high. No oil in the overflow resevoir, either. Oil is untinged at dipstick.

Could be the valve seals. I'd rather it be that than the head gasket.
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