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  #1  
Old 06-17-2008, 09:53 AM
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Join Date: Jun 2007
Location: North Mississippi
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Head Gasket Time! Questions!

It is finally time to replace the head gasket on our 300E! It is at the point that it uses 1 quart to every 500 miles if driven at freeway speeds and leaves quite a mess under it. At slow speeds, the car can travel around 800 miles between quarts. I have a few questions for the experts at doing these. First, the car only has 130,000 miles on it, should I replace the timing chain and the engine valve guides? I plan to replace the valve seals but have a hard time believing that the valve guides are worn out at this mileage as this engine should have the updated guides. Any input would help.

Aaron

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Old 06-17-2008, 01:30 PM
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What engine?
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Old 06-17-2008, 01:34 PM
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Year or engine (M103/M104) at least?

Head gasket issues existed with both engine configurations, but I believe the M103 configuration had valve guide issues.

Most techs will have the head and valves reconditioned while replacing the gasket...makes sense to get as much done while the engine is cracked open...cheaper too!

Don't forget to have the EGR tube cleaned out...far easier to access with everything out as it resides behind the motor.

My indie balked at doing the timing chain even at 160K for me. Said unless I was really poor with oil change intervals, they should be good for at least 200K.
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Old 06-19-2008, 07:11 PM
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Sorry,
I was thinking that this car was already in my profile. The engine is a M103 2.6 litre with around 130,000 miles. I have come to the conclusion that it will only need valve seals and guides. I am not going to do the timing chain. I do not see the need with such low mileage and the car has been well serviced all its life. After all, it made over 100,000 miles before it started leaking oil.

Aaron
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Old 06-20-2008, 07:13 PM
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Does it really need it?

Are you sure in needs a head gasket? Head gaskets are not generally responsible for high oil consumption. Perhaps all it needs is a valve cover gasket. Do all you can to stall that head overhaul. Besides being a real pia job, it will cost good money to get it into shape. If leaking from or down the side of your engine is the problem, I think it could be other then the head gasket.
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  #6  
Old 06-20-2008, 07:50 PM
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Location: Vancouver, B.C.
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M103 oil consumption

Hello Aaron;

Here is my prediction, based on tearing apart our 190e 2.6 twice (at 270,000 and 350,000 kilometers). Pure speculation, of course.

The cam chain will show no wear at all. Depending on age, the plastic cam chain guides may be brittle, or the tensioner may have lost its grip, but you would be hearing the awful clatter.

The valve guiides will show no wear at all. They should not wear much, since the valve train geometry places very little side thrust on the valves. Mine were still perfect at 350,000 km (220,000 miles). Everybody talks about replacing them, but I don't know why. Fear of not doing enough, perhaps.

At that mileage, the rest of the valve train is probably just fine. If it is clattering, there may be a sticky lifter. (Yes, it does have little hydraulic lifters built into the rocker arms.) The camshaft is probably not worn at all. You can see all this just by upening the valve cover.

The head gasket is still sealing well. However, the little front rubber gasket, under the distributor cap, is probably hemorageing oil. It could be causing your puddle. No need to change the head gasket: just try to seal up the front cover. I say "try" because it is notoriously leaky no matter what you do.

The valves could probably stand being lapped into their seats, if you feel like doing a tedious task and have the head off anyway. No need to take it to a professional to grind the seats and valves. (Except for the fear factor, of course.)

The valve stem seals are completely ineffective. The 15-year-old rubber is so hard that they might as well not be there. They are passing an amazing amount of oil, which is burning in the combustion chamber, fouling the plugs, upsetting the emissions (high unburned hydrocarbons), and is at risk of fouling the catalytic converter. You can get the seals replaced without pulling the head, but It is hard to do without special equipment.

So: I think that you probably have two problems: the leaky front cover causing the puddle, and leaky valve stem seals. For what its worth!

Andrew
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Old 06-21-2008, 11:27 AM
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Location: North Mississippi
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Thanks for the replies, the head gasket is definately leaking. The front gasket has already been done and is dry. You can actually start the car up on a rack, clean the right rear of the head and race the engine and see the oil bubble out the head gasket. The valve guides do worry me but I also realize that MB had a running change in the guides somewhere around 1990. Does anyone know when this occured?

Thanks,

Aaron
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  #8  
Old 06-21-2008, 09:53 PM
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I' doinf this on my 300SE and the valve guides need to be replaced. The valve stems are fine.

Head Work 1989 M103 300SE

more pics to follow.

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