603 serp belt shreaded - PeachParts Mercedes-Benz Forum

a2t · #1 08-12-2009, 01:25 PM

I recently replaced my 603 fan clutch w/a 606 unit, and kept metal fan. I also changed serp belt out for new 1. All this was ~2k miles ago. All was fine, coolant temps were lower than 100C.

I noticed last week that coolant temp was beginning to pass 100C, and even hit about 110C briefly (its been real hot here). I shut down hot and could spin metal fan about 1 full turn or so, definitely NOT like it was went I 1st installed it – it would not spin more than a few fan blades. The brand is ACM and its from worldpac. Worldpac is kind enough to replace the part for 12 months if I tell them its bad. Maybe I should swap it out for 603.

So…as Im sitting there idling at lunch talking to wife, I start hearing a peculiar racket which gets worse and worse until the entire serp belt shreads itself under the hood. Luckily I have a spare in the trunk but Im wondering why this happened. I wonder if the fan clutch bolt has come loose (was I supposed to use locktite?).

I have a new tensioner, spring, and damper in there too. For some reason the belt rides about 1/16” off the front edge of the tensioner pulley, I cant figure out why either. I will have to dig into it tonight in the parking lot so I can leave work. Sucks balls.

Brian Carlton · #2 08-12-2009, 02:21 PM

Quote:

Originally Posted by a2t

For some reason the belt rides about 1/16” off the front edge of the tensioner pulley, I cant figure out why either. I will have to dig into it tonight in the parking lot so I can leave work. Sucks balls.

The '86 would do exactly the same thing. I concluded that the bearing allowed the pulley to tilt slightly forward and the belt was forced a bit forward. Replacing the tensioner will likely cure the issue...........if you remember to reinstall the spacer washer behind the tensioner............

Billybob · #3 08-12-2009, 02:42 PM

Quote:

Originally Posted by a2t

I wonder if the fan clutch bolt has come loose (was I supposed to use locktite?).

I have a new tensioner, spring, and damper in there too. For some reason the belt rides about 1/16” off the front edge of the tensioner pulley, I cant figure out why either. I will have to dig into it tonight in the parking lot so I can leave work. Sucks balls.

"was I supposed to use locktite?"

This would be a good application for it! The bolt; new from the factory, is micro encapsulatd with thread locker.

"I have a new tensioner, spring, and damper in there too"

Assuming the washer behind the tensioner has been installed. Is the tensioner pulley new also? When looking from straight above does it appear straight and in line with the other pulleys? If the tensioner pulley bearing is failing the pulley itself will run cockeyed and because of the induced angle the belt will be constantly tying to "run off" the pulley.

Billybob · #4 08-12-2009, 02:54 PM

If you don't already own the factory tool and if you have a Harbor Freight near by you will find $7.99 a very good investment!

If you have a Harbor freight close by get this tool:

Pulley Spinning Tool ITEM 66385-0VGA $7.99 on Sale now!
Ideal for holding or spinning the crankshaft and camshaft on motors using deep forged pulleys.
Applicable for Mercedes Benz, VW, Audi, BMW, Ford, Opel, Peugeout, Renault, Volvo and Japanese cars
Long handle for extra leverage
Overall dimensions: 13-1/16" L x 1-1/2" W x 1-1/2" T; Handle length: 4-5/8"; Jaw opening: Min. 1/4", Max. 7/8"; Pry bar dimensions: 13-1/16" L x 1-5/8" W x 15/16" T
Weight: 0.87 lbs.

a2t · #5 08-12-2009, 05:19 PM

Thanks guys, yes its a brand spankin new from the MB dealer tensioner w/pulley so I dont know why it doesnt sit properly with the belt. I guess I can add a few more washers behind the pulley to shim it fwd.

I got a spare belt installed (from my trunk) so that should get me home. Its always fun to wrench on your benz in 100 degree parking lot wearing business casual. Sheesh the shreaded belt was lodged into the fan clutch and a/c clutch so bad it took me an hour to pull it all out in 100 peices. Not fun...

That tool is to hold a pulley while removing the bolt? As in for the h20 pump pulley when removing fan clutch bolt? Mine was not that tight so I just held it by hand.

Billybob · #6 08-12-2009, 06:05 PM

Quote:

Originally Posted by a2t

That tool is to hold a pulley while removing the bolt? As in for the h20 pump pulley when removing fan clutch bolt? Mine was not that tight so I just held it by hand.

Yeah, the tool cams and holds the water pump mounted pulley in place so counter force can be applied to the fan clutch's 8 mm Allen Head bolt.

The first thing to ascertain is that the correct washer is behind the tensioner, as that determines how far outward from the timing case the tensioner pulley ultimately sits. Then, if the tensioner pulley does not line up straight as opposed to; at an angle, you will continue to have a problem I'd think because any tension on the belt will always exert force causing it to "run off" the pulley. If the entire tensioner is not square and that is the cause of the tensioner pulley being at an angle then you should probably give a very good look at the area surrounding the tensioner’s bolt mounting boss integral to the engine’s timing cover.

The tensioner’s bolt is M10 X 1.5 thread, if you obtain a bolt or threaded rod 6-8’ long and thread it into the mounting boss you might be able to see if it appears straight and therefore perpendicular to the faces of the other pulleys. You could hold a square between the bolt and a pulley If it is obviously not straight you might very well be in need of a new timing cover.

This is the best thread regarding this particular issue:

http://www.peachparts.com//shopforum/showthread.php?t=109058&highlight=broken+timing+cover

Good Luck!

a2t · #7 08-12-2009, 06:41 PM

is it a special washer that goes behind the tensioner? or will a regular home depot washer do the trick? anyone know how thick it is supposed to be? looks like i need about 1/16" or so.

Billybob · #8 08-12-2009, 07:01 PM

Quote:

Originally Posted by a2t

is it a special washer that goes behind the tensioner? or will a regular home depot washer do the trick? anyone know how thick it is supposed to be? looks like i need about 1/16" or so.

It's about 3 or 4 mm thick, about 1/8" thick. I don't think you'll find a substitue easily, it is a machined steel spacer rather than a washer actually, with pretty exacting tolerence's I'd supect. At the very least I'd suspect both its' faces are machine flat and parallel in order to prevent cock-eyedness. Shouldn't be more than $40 at the dealership! No seriously probably less, although I just purchased two small washers for someone's a 113 convertible top at $8.73 each!

a2t · #9 08-13-2009, 11:20 PM

well im pretty sure there was no washer back there, maybe it fell out into the black abyss and i didnt notice. i'll see if i can make due with 2 or so washers stacked in there to shim it out. A few thousandths out of parallel wont make a difference (i hope). ahh hell I'll call the dealer 2, see if they got 1. dont really want this happening again.

a2t · #10 08-13-2009, 11:21 PM

Quote:

Originally Posted by a2t

well im pretty sure there was no washer back there, maybe it fell out into the black abyss and i didnt notice. i'll see if i can make due with 2 or so washers stacked in there to shim it out. A few thousandths out of parallel wont make a difference (i hope). ahh hell I'll call the dealer 2, see if they got 1. dont really want this happening again.

wait...if i replaced the WHOLE tensioner unit from the dealer, that came with a new pulley already attached didnt it? cant remember...it should of already had spacer in there. maybe im forgetting something.

Brian Carlton · #11 08-13-2009, 11:24 PM

Quote:

Originally Posted by a2t

wait...if i replaced the WHOLE tensioner unit from the dealer, that came with a new pulley already attached didnt it? cant remember...it should of already had spacer in there. maybe im forgetting something.

The spacer is a separate part.........easy to forget on the installation.

sasquatchgeoff · #12 08-13-2009, 11:30 PM

Quote:

Originally Posted by Brian Carlton

The '86 would do exactly the same thing. I concluded that the bearing allowed the pulley to tilt slightly forward and the belt was forced a bit forward. Replacing the tensioner will likely cure the issue...........if you remember to reinstall the spacer washer behind the tensioner............

My tensioner originally did not have a spacer washer behind it so I didn't put one on (had no idea it was needed) when I replaced it. After first crank I noticed the belt was riding a little over the pulley, so I de-tensioned and adjusted the belt. Seems to be riding perfectly even now that the belt is broken in. The 602 FSM does not show a spacer with the new style tensioner and EPC shows no spacer for my engine number - just the pivot pin and tensioner.

a2t · #13 08-15-2009, 03:28 PM

when you say you "adjusted" the belt, uh...how ?

All you can do is slip it over the pulleys and connect the spring tensioner. The only way I see to "adjust" the fit of the tensioner pulley is with some sort of spacer.

And I wish I had take it apart and put in the spacer because this morning on my way back from mtn biking my spare fan belt also let go, this time taking out a bunch of vacuum connectors at the top of belt, the upper rad hose (G*DD*AMMMMIT thats a dealer only 2 day lead time and it was brand new!) and also ripped out the 2 pigtails (long gone) connecting to an a/c pressure switch. Bits of shreaded fan belt lodged into clutch and ac, didnt I just spend an hr on that 2 days ago??! Guess i should quit procrastinating and fix this thing.

So to remove the tensioner and shim it out, I need to remove the whole fan/clutch right ?? Oh what fun...Im getting good at removing the radiator on this thing ...

sasquatchgeoff · #14 08-15-2009, 04:16 PM

adjusted - pushed the belt further onto the pulley - I guess "adjusted" was the wrong term - should have said "realigned."

sorry to hear of the failure -

with new tensioner, dampener, and pulley, and the spacer behind the tensioner, if appropriate for your engine, all should be good. As others have said I would be looking at the timing cover for obvious signs of distortion. When disassembling, before removing the tensioner I would double check to see if the pivot pin is torqued to the correct 100 nm (about 74 ft lbs) and that the threads on that pin are sealed using the spec'd thread locking compound (I used red loctite) When I disassembled mine for the first time, the pivot pin was only finger tight - I about fell over when I discovered this. no wonder I had oil all over the front of my engine.

a2t · #15 08-15-2009, 07:20 PM

i hear ya.

so I do need to remove the fan clutch to get at the tensioner right?