I took my '87 300D into the shop for new motor mounts, lower ball joints, and a general check-over. After the job was done, it is like a whole new car. So smooth! My old motor mounts must have been really shot.

But the wierd thing is, now the engine sounds different. There is a "roaring" sound that increases with the RPMs. It sounds a little like a 4wd vehicle in low gear. It's definitely the engine though, not the tranny. The only thing I know they did to the engine was to charge the A/C, which was previously void of refrigerant. The sound occurs when the A/C is not actively in use, though...

Any ideas?

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1987 Mercedes 300D ~200K (Greasecar & Biodiesel)
1993 Ford F-250 7.3 IDI diesel 165K (Biodiesel)
1996 Thomas/International Bus with DT466 engine