E300 D 1996 strange noise - PeachParts Mercedes-Benz Forum

radunegru · #1 04-17-2010, 08:27 PM

I did a serpentine belt replacement last week including the little shock in front of the engine. All went smooth, I put all back nice, then I took a 600 miles road trip. When I got home the next day I discover a strange noise at the front of the engine similar to "a pump that runs dry of fluid". The nose continue like 4-5 seconds after the complete shut off the engine. I was thinking at vacuum pump.
What else I should check. I few days I will take another long drive and I don't want any surprises. Car has only 124k and am trying to find what could be. Please help!!!!

KarTek · #2 04-17-2010, 09:08 PM

Radu,

These cars have a couple of vacuum actuators that operate various components. The actuators have vents with little filters. When you shut the engine off, the vacuum escapes through the filter vents with a slight "purring" sound.

This may be what you're hearing.

radunegru · #3 04-17-2010, 11:09 PM

Yes I know what are you talking about but this is a cyclic noise taht increases with rpm and I was never there before.

radunegru · #4 04-18-2010, 10:32 AM

I was starting the engine this morning and no noise at all.
Can this be an intermittent problem? Or is not the vacuum pump?
Should I just change it as a precaution measure? Car has 125k now on the original pump.
If yes, could you give me some info about the replacement...what tools I will need, what thinks I should worry about etc... Please help ... I use this car for long trips for work and I need no surprises.
Thanks for your help.

pimpernell · #5 04-18-2010, 10:33 AM

Quote:

Originally Posted by radunegru

I did a serpentine belt replacement last week including the little shock in front of the engine. All went smooth, I put all back nice, then I took a 600 miles road trip. When I got home the next day I discover a strange noise at the front of the engine similar to "a pump that runs dry of fluid". The nose continue like 4-5 seconds after the complete shut off the engine. I was thinking at vacuum pump.
What else I should check. I few days I will take another long drive and I don't want any surprises. Car has only 124k and am trying to find what could be. Please help!!!!

Just a stab in the dark, but when you installed the little shock, the shop manual recommends that you orient the shock in its normal installed position, and move the piston in and out fully a couple of times to purge any air that may be trapped, but even failing to do that step would not cause the noise to continue for 4-5 seconds after shutdown. Good luck!