Leaking head gasket
 

Can anyone tell me what the symptoms are for a leaking head gasket? After telling my dealer that my SL320's engine was misfiring occasionally, suffering from terrible gas mileage (less than 10 mpg), and sputtering every now and then (remedy is to shut down engine and restart == problem usually disappears), my service advisor informed me that my head gasket was leaking and that the engine harness had to be replaced -- both of which he said were very large jobs. Given the extensive threads on the M104 engine harnesses, I wasn't too surprised that my harness needed to be replaced (1995 engine with about 55,000 miles). However, I was sort of shocked that my head gasket had failed -- my SL hasn't leaked a single drop of oil into the engine bay or my garage floor since I bought it. Are there any other telltale signs of a head gasket failure (other than dripping oil)?

Besides leaking a little oil (not much), the problem I noticed was oil in the water. Looking at the overflow tank, it looked like a chocolate milkshake. The car ran perfect. I have not heard of any leakage from the cylinders themselves, just oil leaking out of the engine and also into the water. I cannot seem how the "normal" 104 head gasket leak would give you the problems you are having.

As far as how big, rough figures are $1000 for each. Sometimes you get a break, others do not.

pfphipps -

thanks for your response . . . I'm told that the misfire, bad gas mileage and occasional sputtering are related to the faulty engine [wire] harness and that the leaking head gasket was just something they noticed when they were performing an oil change. My service advisor didn't really offer any explanation as to what happens as a result of a leaking gasket other than oil escapes from the cylinder heads (and that I should really consider replacing the gasket). Given that gasket replacement is covered by my Starmark warranty, I already approved the service, but am now wondering whether more problems are going to be created by the replacement (it's supposedly a complex job, requiring the removal of a lot of engine parts).

It all depends on the tech that is performing the work. I usually won't do a head gasket until there is noticeable loose off oil on the rear or front of the head resulting in spots on the client's garage floor.

Many times when doing a head gasket, I will find things out of place that other techs caused. So, it is possible to correct problems...

Benzmac,

Thanks for your response. If you did't have any obvious oil leakage on your garage floor, would you tell the dealer to hold off on the gasket replacement? My dealer hasn't started the job yet as they are still waiting on the replacement part (the gasket, I guess).

Take advantage of the "starmark" and get the head gasket done. Also, mention to them that you know that the wiring harnesses on these cars are known problems. The paperwork that came with my E320 shows the head gasket and wiring harness having been performed under warrently at the dealer at around 65k.

Wiring Harness
 

I just had the wiring harness replaced on the E320 and MB picked up the cost of the part. I paid the labor. I think I was told there is a national MB warranty for the harness. If you have the Starmark it might cover it regardless. I also had the head gasket replaced and there was noticeable oil leakage coming from the right front corner of the head. That was after the front cover had been resealed. Do both and you have accomplished repairing what I am told are the two most common 104 problems. Good luck.
BTW, the car had 106,000 miles on it when this work was done.

Redflash