Subject vehicle is a 2008 ML-320 CDI with 70,000 miles.

This vehicle has experienced the infamous Exxon Valdez oil cooler leak, followed by a high pressure fuel pump leak, followed by a rerun of the oil cooler leak, followed by the intake tube oil leak. No more leaks at present, but I have learned that I need to watch it closely.

Dealer says that the front differential mounts are cracking and need to be replaced due to all the oil. OK, I can believe that. They also claim that the differential is "seeping" and they want to reseal it. Well, I don't think I ever saw a differential that didn't seep at least a little bit. Furthermore, everything I have heard in the past tells me that resealing an MB differential does not have a high success rate due to the tolerances involved.

Estimated cost for this job is about $1600, of which $1300 is labor and $300 for parts. Question is, should I just have them replace the mounts, or should we go ahead with the reseal, knowing that there may be a chance of failure and even a possibility of making it worse?

If it's just a seep without a drip, I'd personally leave it alone. Don't fix what ain't broke. IMHO, if you had that much oil spraying about under the hood, it's entirely possible that the oil "seeping" from the diff is actually from all the leaks and not actually the diff.

If it were mine, I'd have the engine mounts replaced, then go in there and clean everything up with degreaser and give it a good bath, then watch it and see how much of a "seep" you really have. If it's just a "sweat" of oil around the gasket, leave it. If it's enough to form a drip, it may be worth having them do the reseal. 2008@ 70K miles seems awfully young to have a diff oil leak big enough to worry about.

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Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)