W210 buzzing on startup (WITH VIDEO)
 

I get a buzzing noise for 1-second (or less) on engine startup. Thought it might be coming from the power steering pump but I'm not yet sure. Perhaps it's the oil pump? Seems to happen more often on colder mornings (perhaps a pump is starving when the fluid gets cold/thick)?

Anyone else with a w210 have this problem?

I would describe the PS pump as more of a whine, than a buzz if a little low on fluid.

Mine had a leak at a hose clamp and got a little low and whined making turns when cold.

Something vacuum related maybe?

video
 

here's a video.

http://www.youtube.com/watch?v=gaM3AmVIXlo

buzzing starts 1-second after engine starts and lasts about 0.5 second (for this video)

It's always different - sometimes the noise is immediately at startup and can last a full second

BUMP


to answer your question, it sounds like a slipping belt to me. MY 300SD did the same on start-ups and i later found out it was a slipping belt. They were old weared away belts so i replaced them and they stopped making that buzzing noise.

Don't think it's the belt, but I will look into that. Good suggestion.

Vacuum related will be tough to track down. As heard in the video, the noise doesn't last long enough to do much tracking.

I know the whining noise at the PS pump that you speak of. I also had this noise when turning the steering wheel and my fluid was low. The fluid is no longer low. This current noise doesn't correlate to turning the steering wheel.

I only have this noise when starting the engine. I only get the noise on the first start of the day (more noise on cold mornings than warm mornings). Subsequent starts do not make this noise.

I hear a short flutter a half sec after the engine starts that may be tension from startup comming off the belt and the belt fluttering as the engine settles into idle.

You could test that if you are brave by using an 18-24" tight fitting bar and releasing the tensioner bolt and holding the tension of the belt with the bar after the engine is started. One MUST be carefull to have a good grip AND control of the lever one is holding. This is easier with a longer rather than shorter bar.

By slowly reducing tension while running I'll bet you can duplicate the noise you are hearing.

I've done this to test for vibration at the tensioner assembly. It is easier the second and third time you do it.

ps: all my tensioner woes were due to bad motor mounts. i burned up numerous tensioner components B4 discovering that. If yours are OE you might want to check the tops of them for cracks/separation.

Sorry, I've never had a noise like this but as mentioned above it sounds most like a belt. Some Diesel Purge will clear up your heavy knocking, though ;)

I sprayed some belt dressing on. I'll have to wait till morning to see if that helped. If not, I'll try a new belt.

I ordered some Lubro Moly Diesel Purge and I should receive tomorrow. I'll be going thru the purge procedure also tomorrow.

These are the directions I used for running DP:
http://www.peachparts.com/shopforum/showthread.php?t=113596
Just some advice from personal experience:
If you don't have an extra of the line that runs between the in-head heater and the prefilter (as I didn't) and you choose to disconnect it at the fuel heater, MAKE SURE to put a piece of duct tape over the opening on top of the heater! If you don't (as I didn't) all the fuel will drain back to the tank, filling the supply line with air.....it was the biggest purging job I've ever done, ended up with a brand new battery charger because even my excursion couldn't supply enough power to crank it. Also don't let the DP supply line suck air, the running engine will fill your whole IP system with tough-to-purge air. This is also where I went wrong.

Aside from my mistakes, DP worked well and cleared out a boatload of carbon and the engine runs better than it has in a long time.

Great tips! Thanks for taking the time to post.

Very easy to check if its the belt. When cold, remove the belt and start the engine. No more than a few seconds, and do not let the engine get hot.

If theres no noise, you know its belt related.

appears to be the belt
 

Thanks for everyone's help. It does appear to be a noise coming from the belt. I half-heartedly spayed on belt dressing and the noise mostly stopped.

This did not sound like the belt squeals I've heard in the past. For future trouble-shooters: The video/audio file picked up the true sound fairly well.