Figuring out if squeal is from belt or pump? - PeachParts Mercedes-Benz Forum

ps2cho · #1 11-18-2015, 09:17 AM

So I recently replaced my tandem power steering/SLS pump on my 300TE.

At the same time I found my tensioner was bad so I replaced it. Problem is that I have a squeal when the steering returns to center on certain turns and I don't know how to figure out whether the tensioner or belt is bad, or whether the pump is faulty.

How can I figure out what is making the noise? Any techniques from those with more experience?

It's most pronounced when doing u-turns. As soon as I complete the u-turn and the steering begins to spin back towards the center the damn thing shrieks with a high pitch squeal/groan...

TX76513 · #2 11-18-2015, 09:39 AM

Isolate a component by spraying some WD40 on the shafts and driving. Keep repeating till you find or rule out.

CarpeDiem51392 · #3 11-18-2015, 10:12 AM

A new belt is easy to try, if there is no change you can hold onto it as a spare or return to store.

Hit Man X · #4 11-18-2015, 05:40 PM

What brand of tensioner did you use?

ps2cho · #5 11-18-2015, 08:05 PM

It's a Febi tensioner...I gambled on it because there are no other choices. Febi @ $80 or Genuine MB @ $350...

That is why I am not ruling out the tensioner as just febi garbage, but since I changed them at the same time I want to try and figure out exactly who the culprit is.

Hit Man X · #6 11-18-2015, 10:00 PM

Well the one on the 300E I just picked up was not tensioned. I tensioned it, it held tight for a few days then broke.

The OE one I just tossed on the 300SEL is still working great.

Febi is in the same boat as Meyle to me now.

Is the squeal more pronounced with the AC on and blower on high speed?

76w115 · #7 11-19-2015, 12:49 PM

Not sure how you would do this while driving, but the easiest way I've seen to check for this exact thing is to wet the belt just a little bit while it's running. It'll spray back on you a bit of course, but it should quiet it down for enough time to decide whether it is the belt or not. I did this on a mercury Sable once that squealed through new belts, pulleys, tensioners, etc. Never could figure out why it wouldn't stop squealing. Once I wet the belt and that worked, I just left it alone til I traded it.

lsmalley · #8 11-20-2015, 02:56 AM

Get back under the hood and see if the belt still has proper tension. Aslo, as CarpeDiem said, a new belt is the easiest way to go, Or you can take off the one you have there now and try reinstalling it. Slim chance, but maybe something went wrong when you put it on.

ps2cho · #9 11-23-2015, 10:16 PM

Installed new belt today and redid tension. There is 100% no issue with the belt tension. Its tight and the pointer is set correctly to begin, and tightened until it reaches the left mark on the assembly. I drove the car, noise still there, and I reverified tension to make sure it didn't lose it.

I then used some garden hose and the noise is definitely coming from the pump.

Well looks like a replacement is needed now...

ps2cho · #10 11-25-2015, 03:25 PM

One final question just in case. How much deflection would you guys say is normal on the belt at the longest section?

How much can you push the belt down? I want to verify this isn't a pointer setting deal and the belts not tight enough even though the pointer is on the left side of the tensioner once it's tight.

Hit Man X · #11 11-25-2015, 04:26 PM

Quote:

Originally Posted by ps2cho

One final question just in case. How much deflection would you guys say is normal on the belt at the longest section?

How much can you push the belt down? I want to verify this isn't a pointer setting deal and the belts not tight enough even though the pointer is on the left side of the tensioner once it's tight.

Have a picture of the belt area you are depressing?

I have two M103s now, one with a low mile (sub 5k) OEM tensioner and a fairly new Febi that is dead so I should be able to provide you decent photos.

PM me your phone number if you can accept picture messages and I could send them faster.

lsmalley · #12 11-26-2015, 05:09 PM

I believe the deflection should be 1cm

ps2cho · #13 11-27-2015, 07:00 PM

Well put it this way, at fully tightened, I can push down the belt to touch the metal coolant pipe that goes out from the water pump...

So basically, can one of you guys just go push down on your belt and tell me whether you can touch the pipe with the belt?

I feel like I am leaning towards the tensioner is not tightening enough. Maybe on the sedans without the SLS it is more forgiving, but with this rebuilt pump, I have no room for any slack...

lsmalley · #14 11-30-2015, 01:03 AM

My belt can touch my water pump pipe if I press down in the center. However, I don't have any belt noise and my tensioner is shot. I didn't want to replace the tensioner until I did a p/s reseal so I removed the dampening shock and put a spring over it, sort of like a coilover. So the belt might not be to spec, but it keeps tension. Anyway you can post a video of the noise?

ps2cho · #15 12-06-2015, 12:53 PM

I just received today the Genuine MB Tensioner and I can see a slight difference on the the angle of the bolt in relation to the pulley compared to the Febi.

I will install later today and see if it tightens correctly now.