sound from front of engine, AC compressor, vac pump? - PeachParts Mercedes-Benz Forum

michaelwoodcock · #1 08-27-2012, 05:34 PM

Hey guys,

I just got an odd sound from the front of the engine that sounds somewhat akin to a snare drum if it's barely hit, and it's not constant, every couple of engine revolutions it seems to do it. I know it's not a rod bearing, I unfortunatly know that knock sound all too well

Just prior to noticing the sound, I was pulling out into traffic and had to bury the throttle as the car didn't seem to shift to first, it was sluggish as if it had started from second.

It's a little hard for me to determine where the noise is coming from on a diesel engine, as the engine volume is already pretty high, any help would be greatly appriciated!

Thanks,
Mike

sixto · #2 08-27-2012, 06:41 PM

Does the sound persist if you remove all the V-belts? Does each pulley spin smoothly and quietly by hand?

Sixto
87 300D

eatont9999 · #3 08-27-2012, 07:14 PM

A mechanic's stethoscope might help. If you disengage the A/C, that should help with the diagnosis. Which side is it coming from?

michaelwoodcock · #4 08-27-2012, 08:52 PM

It sounded like it was coming from the vacuum pump side, around the AC, power steering, and vacuum pump. I had just put a new AC belt on as the car came with inoperable AC and I am in the process of replacing it. I also just did a power steering flush, I will look into it more when I have daylight. Thanks for the help guys, I was getting really nervous about the possibility of the vacuum pump about to go out!

Thanks,
Mike

vstech · #5 08-27-2012, 09:19 PM

My pump made zero noise until it died... then it made quite a ruckus as my car coasted to a stop...
I had warning ahead of time, via the brakes being slow to build vacuum and difficulty shutting the car down.

did I listen to my car? nooooooo... such was the faith I had in the mighty 617... poof...

sixto · #6 08-27-2012, 09:35 PM

The pump took out the engine? I thought that only happend to 60x's.

I got an '83 300SD for free because the pump was dead. Engine ran fine.

Sixto
87 300D

TMAllison · #7 08-27-2012, 10:25 PM

If the mech stethoscope doesnt find it right off, pull all the belts. Then add one belt at a time and check each added accessory each time.

Harbor Frt has the stethoscope for ~$5, or use any long screwdriver, breaker bar or cut down broom handle you have laying around.

eatont9999 · #8 08-28-2012, 10:53 AM

I wonder if that is the reason why the A/C belt was disconnected.

michaelwoodcock · #9 08-28-2012, 03:53 PM

Hey guys,

When I got to work this morning, the power brakes didn't work! (Vacuum pump?) On my way home, they would work just fine for the initial application after a few minutes of driving. But, if I repeatedly apply them witihin a short period of time, they begin to have little effect with normal pedal effort, and require me to really bear down on the pedal. If I pump the brakes, it will get to a point where I can hardly stop the car from moving forward at idle speed in drive. Vacuum leak, or vacuum pump?

Thanks guys,
Mike

eatont9999 · #10 08-28-2012, 04:01 PM

Strange noise coming from vac pump area, then no vac the next day. Sounds like a vac pump to me. I wouldn't risk it. Stop driving the car until you can replace the vac pump.

To test for a leak, disconnect the tube going to the vac pump, pull a vac with a mighty vac and see if it holds. Could be a bad brake booster but that would be a heck of a coincidence.

Chris_ · #11 08-28-2012, 04:41 PM

Replace the vacuum pump - they are not cheap but better than losing your engine and then you will know you have a good one going forward.

michaelwoodcock · #12 08-28-2012, 05:28 PM

Hello,

what do you think of a vacuum pump rebuild kit? The price difference is staggering, and I would like to disassemble mine, and powdercoat it while I'm at it, to help keep a clean look under the hood

Thanks,
Mike

michaelwoodcock · #13 08-28-2012, 11:44 PM

gentlemen,

hate to be a bother, but is an electric vacuum pump a possibility? I was considering this one: Summit Racing SUM-760150 - Summit Racing® Electric Vacuum Pumps - Overview - SummitRacing.com
I would gut the OEM one, put it back on the engine and simply put vacuum caps on the outlet. I would feel more comfortable having something on the engine that is rebuilt for under $15, and won't take out the engine if it fails

Thanks,
Mike

sixto · #14 08-29-2012, 12:10 AM

Dang, is that what 617 pumps cost now?!?! Put a WTB listing in the parts forum then rebuild yours as a spare. I'd probably not work around a part that served over 200K miles. These pumps aren't known for taking out the engine when they fail as are the 60x pumps. Yours failed the engine isn't the worse for it.

Sixto
87 300D

michaelwoodcock · #15 08-29-2012, 05:59 PM

Hey guys,

Thanks for all the advice & suggestions! I went out today and hooked the mityvac up to some vacuum lines under the hood. Here's what I found so far:
Black line to transmission: leaks fast
line to top of injector pump plastic thing: leaks slow
line from bottom of injector pump plastic thing: holds no vacuum at all
Big clear vacuum line that has a U joint off the main line out of the vacuum pump holds vacuum forever.

I'll keep testing and see what I come up with. But this thing leaks like a sieve. I guess a long day with new vacuum lines is in my future!

Cheers,
Mike