Need Help Replacing Belt - PeachParts Mercedes-Benz Forum

jmann.arch · #1 10-14-2012, 09:59 PM

Hey Everyone -

I am looking for a little bit of advice - as I am having a hard time getting the serpentine belt reseated/replaced on my '87 300TDT. I had some other mechanical problems so the previous belt was no longer on the pulleys.

I took out the old belt that was already off the pulleys, released the tensioner pulley, and then looped the new belt between the fan shroud and fan. I didn't have any trouble getting the belt basically reseated on the all the pulleys to the left, but I don't have enough slack to get it around the power steering/self leveling pump pulley - which is the easiest to access for me.

I have tried to partially seat the belt then move the pulleys by hand to get it to pull the belt on but it has not worked.

I have replaced this belt before - but from a worn still seated belt - and I just don't remember having this much trouble. I have rechecked the part number - and it should be correct.

Am I missing some step to get more slack from the tensioner pulley?

Is there some other trick to get it seated?

I appreciate any advice you can give me.

Thanks!

Jimmy
'87 300TDT

vstech · #2 10-15-2012, 05:52 AM

do you have the belt routed correctly?
OM603 Serpentine Belt Routing
also, the spring has to be off the tensioner, and the tensioner needs to be TOTALLY pushed down. BUT you need to have the belt ON the tensioner BEFORE you push it down, or there is not enough room to feed the belt through the space between the WP and the Crank...

jmann.arch · #3 10-15-2012, 09:50 AM

Thanks for the response vstech -

Yes, I have it routed correctly. What I don't have mechanical skill I make up for in reference material.

I will try taking the spring off the tensioner - but in pushing down on the tensioner it doesn't want to go any further. I have been pulling on the belt and trying to push the tensioner further down to no avail. I am wondering now if it is possible that something is blocking it from going to the furthest slack position.

Another option I saw out there in cyberspace said to put the belt on the alternator pulley last because it is smaller and easier to get the belt around it. Not sure if that will work in my case, as I didn't take the fan/shroud off, and I think it is going make getting it on that pulley difficult, but it might be do-able.

The pulley for the power steering/self leveling tandem pump I have been trying to put the belt on is a lot bigger, and has a edge ridge making it probably the most difficult to get a belt onto - but it's the most accessible one.

Brian Carlton · #4 10-15-2012, 11:29 AM

If you are sure the belt routing is correct, a proper belt will slip over the last pulley (usually p/s) without any effort or struggle.

If the routing is correct, you presumably have the wrong belt. There is a very similar belt for the 603.970 that is a bit shorter than the belt required for the 603.960.

The issue with the inability to install the belt on the 603 is legendary, however, and it always results in the failure of the mechanic to fully understand the belt routing, despite his ongoing protests to the contrary. One member had the vehicle out of service for more than one week until someone assisted him with the routing. Translating the diagram to the vehicle is fraught with risk.

vstech · #5 10-15-2012, 11:36 AM

what is the length of the belt? the link I put in, also shows the different lengths of 60x belts... you should have a 2045mm belt if you have the 603.97x belt it'll be a 2020 and the 602/1 belt will be a 2000.
also, if you have a larger alternator than stock you may be outboard too far to install... that was my issue with a car recently, and getting a 602 wp pulley fixed the problem for me..

jmann.arch · #6 10-15-2012, 12:40 PM

Brian - Thanks - but I am positive I have the routing correct. It is exactly what vstech posted, and matched the diagram I was using - but I did not measure it to check if it is 2145 mm - nor am I positive a pulley or component hasn't been replaced.

vstech - Basically for the belt I went to a local chain auto parts store and picked up a belt, just like I did last time I replaced it. I went with what their computer recommended, and I did go back and verify last night that the package code matched what their website said it should be - but I never thought about the possibility of component or pulley being replaced throwing off the length. The packaging however does not indicate the length of the belt.

I am going to try and see if I can get the belt around the alternator pulley - but if I can't I am going to take it back off and compare it in length to the belt I removed. I guess I just got lucky last time I replaced this.

I had never thought about the fact that components could have been replaced throwing off the length of the belt.... duh...

It is entirely possible the last belt was also too tight - as the entire reason I am going through this exercise is the belt split when my tandem power steering/SLS pump broke off it's mounts. It had no rear bracket - just the front two tabs for bolts - those broke loose. I had the pump rebuilt last year - so I have reinstalled all of this before. Main problem is you can't go out and buy a tandem pump - so I had the tabs welded back to the body, and I have fabbed a rear bracket for this pump - which likely was in place prior to my ownership.....

Will let you know what I find out looking at this later - also may take a fabric tape measure to the check the length required.

Thanks for the feedback!

vstech · #7 10-15-2012, 12:47 PM

I've got tandem pumps...
if the belt was tight, CLOSELY INSPECT YOUR TENSIONER ASSEMBLY!!!!! the shock, the spring, the arm, and the pulley... ALL will have been loaded heavily, and damaged.
you should also check your a/c clutch/pulley, and the alternator bearings.

jmann.arch · #8 10-15-2012, 01:23 PM

I know I have had a pulley or pulleys replaced before on this before as it used to squeal - and I was the one that found the cause to the squeal on this forum (somehow I think the tensioner pulley) - and had my mechanical at the time fix it. I don't have the squeal anymore - but it sure doesn't look like the tensioner pulley or anything on it was replaced.

I am hoping a comparison of the belts is going to show a difference in length - and I can make my adjustment there.

I posted something on the forum about the tandem pump coming off it's mounts back in July - to no responses. So I went and got it welded back together. Basically a $45 fix versus an expensive pump - particularly when I know the pump works. I am hoping adding the rear bracket holds - but I am okay to "test" it and see.

To be fair the pump broke loose after a 16 hour drive up to NJ and an 8 hour drive half way back. Yes - it would have been nice to get back all the way home first - as it was no fun having to drive back 8 hours to go pick up a car and get it home. I am thinking it failed due to no rear bracket, and a 25 year old aluminum body pump - just heat stress from the long drive gradually cracked the mounting tabs.

I guess I will go back and check the other pulleys to see if anything is loose, or not spinning correctly. Again - I haven't had any noise from the pulley's that would lead me to believe something is wrong.

jmann.arch · #9 10-15-2012, 03:42 PM

Okay - went home at lunch and the belt that was recommended to replace it with is a 2145 mm belt (6pk2145). It is also the same belt that was on there that failed, and the last rib came off of the rest, but is now shorter than the middle of the belt - so the outer rib didn't stretch as much. I measured the old belt - as difficult as it is - to pretty close to what it should be approx. 84-1/4 to 84-1/2".

I am going to remeasure with a string hitting all the pulleys with the tensioner disengaged, and engaged to see what I get - and get a belt with a little more slack in it.

jmann.arch · #10 10-16-2012, 09:26 AM

Well guys - I am not sure what changed - but I took the belt off, rechecked my adjustment and movement of the tensioner pulley, and took string and measured with the tenioner engaged and disengaged - and will you guess what.... the belt was exactly the length it should be. LOL

I put the belt back on, and tried leaving out the alternator pulley till last. I still had to get some slack out to get it on there - but I got it installed.

So I don't think it was too tight - as it wasn't too bad getting it on there.

I am not sure if in rechecking the tensioner I somehow got more slack in the there - and I know this really brings up more questions about my mechanical proficiency - but I wanted to share - for all out there that have had trouble getting the 603 belt on there - put it around the alternator pulley last.

The belt is on and the car is running again which is the main point.

Thanks for the advice!

CDL · #11 07-07-2021, 02:43 PM

I am looking at putting a new belt on a 300TDT Seems a bit low clearance down in there. Should the rad shroud be removed ? Any other hints/tips to have this go smoothly? I do see the routing from the previous post. Thanks!