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Cross post: M104 Engine problem in my 300SE

3191 Views 5 Replies 2 Participants Last post by  oaklandw140

I just posted this on the W140 forum but wanted to include it here because the M104 was also available in the W124 chassis. If anyone has any ideas on what might be happeneing to my car, I would appreciate anyh input:

I have a 1992 300SE with 91,000 miles that has a mysterious problem, according to my mechanic. Two weeks ago I found oil in my coolant reservoir and the oil in my engine was down about 2 quarts. There was no coolant in the engine oil on the dipstick. I called my mechanic who suspected it was a head gasket. I was disappointed because he had done the headgasket 14 months earlier. So, he went ahead and replaced the head gasket and he tested the oil cooler. He just called me and told me after putting the engine back together and flushing out the system, he is getting the same issue...oil is somehow entering the coolant and the engine oil level on the dipstick is showing about 2 quarts less. He is baffled, I'm not very happy, and I'm hoping someone here has had a similar experience and can shed some light on the problem. The engine is the M104 and has been running fine, no overheating. my mechanic suspects that something suddenly happened to either the cylinder head or the engine block and is hesitant to tear the engine down again to try and chase a bad cylinder head.

Any ideas out there? I would appreciate any insight.
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Poss oil cooler problem

I checked WIS and there's a complaint of oil in coolant
and the cause is the oil cooler between the oil filter housing and block. (#5)

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Well, I'd say trying a new cooler is a lot quicker then pulling the head and having a machine shop test it for cracks.

That and the fact that MB knows about problems with the cooler.

I've never seen a problem with M104 heads. It's your call though.


1994 E420

Mercedes Benz Technician since 1982
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