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Cross post: M104 Engine problem in my 300SE

3193 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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Thanks ClarkZ71. I will have my mechanic check it out.
Hey Clarkz71, my mechanic said he did cleaned and pressure tested the oil cooler using mineral spirits(?). That being said, would it be worth to try a new oil cooler? Am i right to think that it is highly unusual for an engine block or cylinder head to all of a sudden fail and start springing a leak? I mean, the car was running beautifully, it only has 91k miles, then all of a sudden I noticed a puddle of oil/coolant right below my passenger front bumper. That's when I popped the hood and saw the oil/coolant mixture coming out of the overflow tube on the coolant reservoir.
Ok, here is the deal being suggested by my mechanic. Right now I have a 2500.00 bill for the 90,000 mile maintenance and the work they've done so far to determine the cause of the oil, which included replacing the head gasket again. This is before the oil cooler install. They are quoting me another 1200 for the oil cooler and a new pipe by the oil cooler to replace the pipe that is partially siezed on mine and the labor to install. He is not guaranteeing that the oil problem is going to be solved by replacing the oil cooler as he is very confident the original oil cooler passed he pressure test. Another option he is giving me is to install a new to me used engine. He has one with approximately 37k miles and he will put it in for $1800. What would you do? I'm at $3700 if I go with a new oil cooler that doesn't guarantee the problem will be solved, or $5300 with a newer engine that will have a warranty. Or, I could just pay my bill of $2500.00 and walk away from the car as it will be pretty much worthless, unless someone wants a real nice 300SE with a suspect oil problem. It is silver with grey interior and in great shape...any value with the suspect motor? I think it is actually worth saving, but maybe you will tell me to run away. I'm thinking of going with the motor and at least have a chance to get some of my money back if I sold it.
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