[yumling]

Have a friend with a W210 diesel with about 165K miles. He is have a very small oil leak and when we changed the oil, the pan was coated with engine oil. It is not the drain plug for sure because it in on tight with new gasket.

My question what are the usual suspects for such a slow oil leak on a diesel. as mentioned, oil coats the oil pan.

I will take a closer look but as I am not familiar with diesels any tips on where to look is appreciated.

 

[Kajtek1]

At this mileage I would supsect more of fuel lines leaking, than actuall oil leak. I traced leaks on my high mileage E300D for months, till finally decided that replaceing o-rings one by one is not a good solution. There are 6 clear tubings at fuel pump. The 5 that are easy to replace cost about $80 at Duval.
Fuel from this area runs down on oil pan and whole underbody, while washing the dirt looks like the oil.
The only way to pinpoint actuall leak is to wash everything and keep on checking.

 

[yumling]

You might be right. I did seem to smell some diesel fuel. Is changing the O ring a big job?

Also is there any running problems associated with a slow fuel leak?

At this mileage I would supsect more of fuel lines leaking, than actuall oil leak. I traced leaks on my high mileage E300D for months, till finally decided that replaceing o-rings one by one is not a good solution. There are 6 clear tubings at fuel pump. The 5 that are easy to replace cost about $80 at Duval.
Fuel from this area runs down on oil pan and whole underbody, while washing the dirt looks like the oil.
The only way to pinpoint actuall leak is to wash everything and keep on checking.

 

[Kajtek1]

Those engines are famous for small leaks, That's why driver side mount comes with a boot that protects it from fuel.
It is not the big job to pull the clip-on tubings, but require flexible fingers and/or very long nose pliers because of limited access under the manifold.

 

[LondonThing]

My old 300TD had these leaks. Eventually (6,500 feet up in the alps!) they developed into a full on rolling flood of fuel. The guys up a the local garage replaced the bottom half of the full pump - the plastic valve body - and the car came all the way back to London, and then another 3,000 miles without leaks after that repair.

 

[Kajtek1]

Funny thing you mentioned the elevation affecting the leaks. Each time I drive to ski resort and park it at 6600', in the afternoon the diesel hesitate very badly and smokes like a hell. I am not sure if elevation has something to do with it, but my suspicion is, that cold temperature make the fuel much thicker, therefore more suction in the lines opens more air leaks.
I go there in 2 days again with all new orings and most of new tubings. I wonder if I missed any.

 

[Kajtek1]

So after some additional driving.
Replacing fuel tubings with new ones definitely helped the engine. It runs much smoother and have better acceleration at low rpm. However I still have small fuel drip. Can't pinpoint it, but it is coming from shut off valve. After some more checking, (thanks Russians) I found there is one more oring between the valve and pump body (part 14 http://www.detali.ru/cat/oem_mb2.as...GM=717.446&CT=M&cat=19T&SID=07&SGR=045&SGN=01)
I am ordering the oring and few other small parts from Duval and hope for the end of those troubles.
For some reason the lower pressure at higher elevations magnify the problem. I started in the morning at the house at 39F. The car run fine with just slight hesitation for a moment. When restarted in the afternoon at 6600' elevation at 45F it was hesitating for about a mile.