Squeaking near the front of an M103 - PeachParts Mercedes-Benz Forum

Jim Anderson · #1 10-01-2004, 10:53 AM

I hear squeaking near the front of my M103, usually when the engine is warm, and usually when its idling. I can't tell exactly where its coming from, but its in the general vicinity of the water pump. I changed it semi recently and was introduced to the tensioner. I've managed to get some oil to the tensioner pulley, but there's not much of a pattern of noticed squeaking so I couldn't really tell if it helped. I pulled the belt off and checked all the pulleys in that area and they all seemed okay, but the engine was cold.

Could it be the water pump? I've never heard one squeak, is that possible?

Could it be the tensioner? If it is does it indicate a possibility of seizing and leaving me stranded? Can I change just the tensioner pulley and not the whole$ thing? Why couldn't it fail when the water pump was changed?

sixto · #2 10-01-2004, 06:07 PM

The noisy fellow in my case was the idler that hangs off the timing chain cover. IIRC you have to replace the assembly that attaches to the timing chain cover. You can't replace just the pulley.

Could also be the belt shock starting to go.

Sixto
95 S420
87 300SDL

John Plut · #3 10-01-2004, 08:12 PM

I had a sqeaky serpentine belt on my '92 300e recently. I tried tightening the belt and the squeak got worse. It turned out that the tensioner was shot.

The tensioner is a weak link on the M103 and fails fairly often without warning. The only way I know of telling if the tensioner is bad is that it cannot be adjusted (either the pointer arrow will be off or you will run out of threads on the adjuster rod).

Cost of a tensioner is about $150 and it took me about 5 hours to change.

Gilly · #4 10-01-2004, 08:51 PM

Yeah, could be a handful of things:
Fan bearing bracket, as it's called. This has the hub and bearing that the cooling fan itself rotates on, it also has the idler pulley as part of it, over on the right side (all one housing, although the idler itself I can't remember if it's included or not). If it gets bad enough the fan bearing can fail and cause all sortsa nice damage (fan, radiator, et al).
Tensioner or tensioner shock (as mentioned)
Alternator bearing
water pump
serp belt itself dry or cracking

Gilly

mpolli · #5 10-01-2004, 08:57 PM

I had a high pitched squeak/squeal that would come and go on my C230. A couple of nights ago I came home and noticed it was pretty loud so I thought I would track it down. I put my mechanics stethescope on everything I could think of and couldn't find any bad bearings. In fact the loudest one was the alternator which was the only place I was pretty sure it was NOT coming from. (Didn't really sound bad, it was just the loudest) I moved all around the car trying to localize the origin of the sound. It just seemed to be coming from everywhere the belt was. I had inspected the belt just a few days before and noted that the tension was good but the surface looked a little old and had tiny cracks in it from age, even though it is only about 2 years old I think. Anyway, I considered that it could be just the belt itself. As an experiment I dipped a toothbrush in water and touched it CAREFULLY to where the belt goes around the tensioner, where the V part is on the outside. ** Do not do this at home !!** Might not be safe on other cars!!! Anyway, as soon as I touched the belt, the sound would stop for about 2 seconds until the water dried off. I imaging you could do the same test with a spray bottle and that would be a lot safer! I have ordered a new belt and I believe that will solve the problem.

Mike

Jim Anderson · #6 10-04-2004, 10:33 AM

Well, I found and ordered a pulley from Fastlane. I'm assuming since its available that it is replaceable, but how do I even get to it? It doesn't look like its in a very user friendly place.

Gilly · #7 10-04-2004, 10:39 AM

What exactly did you order?
Are you sure what you ordered is the source of the noise?

Gilly

Jim Anderson · #8 10-04-2004, 11:55 AM

I ordered G6020-31276 Acc. Belt Idler Pulley for 201.029 103.942
VIN:WDBDA29D0MF813954

No, I'm not sure, I'm making an educated guess based on approximate position of the noise and when I oil it (that was an effort) I'm pretty sure it stops for a little while, and its the least expensive part near there by far. If I'm wrong I can either return it or consider it preventive maintaince and exploratory surgery.

Jim Anderson · #9 10-05-2004, 10:36 AM

It only squeaks when its warm so last night I took the belt off, again, but this time while the engine was warm (ouch) and its the water pump that squeaks. I didn't think it was the pump because I changed it 13 months and 24,000 miles ago (its still clean.) The pulley has a just barely noticeable amount of play, and the weep hole has just a touch of dried coolant.

What does this all mean?

I bought the pump from fastlane, is there a warranty?

Can I lubricate it, and with what. I'm worried about oil cause it might dissolve the seal, but what about synthetic oil? I was also thinking about graphite, silicone, and Teflon as alternatives to oil that may be nicer to the seal.

Does this mean imminent threat of pump failure?

Lots of questions.

Gilly · #10 10-05-2004, 11:15 AM

The usual warranty on MB parts is 1 year unlimited mileage.
I don't know of a good way to service that pump bearing, it's packed in grease and doubtful anything would help, so kind of on your own, try what you like.
I'd still bet that it's the fan bearing or maybe the idler you mentioned.
You can get one of those mechanics stethoscopes like Mike used (Mpolli) or use a long skinny screwdriver as a cheap alternative to a stethoscope, that's what I use (hold screwdriver handle up to ear and the tip of the screwdriver as a probe.

Gilly

Jim Anderson · #11 10-05-2004, 11:41 AM

Now there's quality control, a 12 month warranty and it fails after 13 months. I'd expect only Mercedes could be capable of such precision. Defiantly a case of over-engineering.

Like I mentioned, I took the belt off and while I was there I checked everything that was near there. While the bad news was that the water pump squeaked, the good news was that everything else was quiet and tight, except for a slight front to back play on some pulleys.

So how exactly is a water pump bearing built?

And I'd be kind of nervous about putting one end of a screwdriver in my ear and the other end near something spinning

mpolli · #12 10-05-2004, 01:18 PM

What I used for years and years (until I just got my official stethoscope) was just a "sounding stick". Basically any stick or rod will work. Often I would use whatever was lying around, a yard stick or any small stick about 3 feet long. I would hold it with my fingertips on the end and hold that in my ear. Works really well! Actually I find the stethoscope too loud usually. Main advantage of the stethoscope is you can pinpoint what you are listening to better.

Mike