Belt started making a squeling noise when idling and low rpm and goes away at speeds above 2000 rpm. I have seen postings discussing could be belt or idler pully or even broken tensioner spring. Will not be able to look at until late tonight. My fisrt question is can the belt be changed with out removing the vicous coupler/fan assembly?

If issue is not the belt, but the idler pully, does any one have experience with how long the pully will last once it starts making noise?

Thanks,
Lee

You can change the belt on a 603 in ten minutes if you know the path perfectly. No removal of the fan is required.

I have no speculation on how long a failing idler will last. My '86 currently has belt issues and is making a horrible racket..........I'll be pulling all those components off the engine very soon.

Yeah there was no sticker for the path on my Euro car, oops. So if there isnt make a quick drawing it will save quite some time. On my car feeding the belt between two of the pulleys to go around the tensioner was a real mother. And be prepared to be covered in black diesel goodness from the front of the engine. On the tensioner, if you have the big stainless spring style, taking a pair of vise grips to the hook and clamping on to it and just pull up is the easiest way to remove/install it. No problems with the fan either, just try not to bend any fins when you shimmy the belt by the radiator.

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2003 Dodge Ram 2500 Cummins - Georend fully built trans, Banks Big Hoss Bundle, Smarty Tuner, 5" turbo back exhaust. 500 HP and 1100 ft/lbs to the ground.
1979 Mercedes-Benz 300CD - Lost to a four car pile up on 275, Thank You Michigan Drivers.
1986 Mercedes-Benz 300D - Sold, Euro non-turbo car.

The trick is to start at the tensioner and slide the two sections into the tight spot near the water pump pulley. You can't get the folded nose of the belt through that spot without damaging the belt, IMHO.

Couldn't agree more, start at the tensioner and slide each side of the belt through the opening one at a time. There is no way to just jam the belt between the two pulleys

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2003 Dodge Ram 2500 Cummins - Georend fully built trans, Banks Big Hoss Bundle, Smarty Tuner, 5" turbo back exhaust. 500 HP and 1100 ft/lbs to the ground.
1979 Mercedes-Benz 300CD - Lost to a four car pile up on 275, Thank You Michigan Drivers.
1986 Mercedes-Benz 300D - Sold, Euro non-turbo car.

Yes, there is something of a trick to it. I'm not sure where I picked it up, maybe from a manual somewhere, but the trick is to form a small loop in the belt and get that pushed through the very tight space described above. Since there's no way to push the loop directly between the pullys, you have to form the loop in front of the pullys, then slide one side (one belt-thickness) through at a time. Seems to me it is a reverse loop too, with the belt turned inside out.

But its been awhile since I've done this.

Ken300D

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1982 300D at 351K miles
1984 300SD at 217K miles
1987 300D at 370K miles

Thanks for the good words. I will carry a spare with me as I go around until I can take a little time to change it.
Lee

When I checked the belt, I found that the tensioning spring was broken. I ended up driving the car about 140 miles prior to installing a new spring. It worked ok and the belt never came off the pulleys. I ended up traveling that much because the local dealer did not have it in stock and it took a couple days to get it in.
I need to change the water pump soon, so I will go through the rest of the belt items when I do the water pump.
Thanks,
Lee

There is a difference between the original idler pivot bolt and the replacement bolt. If you order a new idler pivot bolt from FastLane, you will also need to buy the washer to properly space the new idler assy away from the front of the engine. Contact Roy for details because the washer isn't shown in the FastLane parts lisings.

Here is a diagram for the 603 belt routing: 603 belt

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Never a dull moment at Berry Hill Farm.

If you buy a Goodyear Gatorback belt, the package has a belt routing diagram for a 603.

Sixto
87 300D

Our 603 had the idler replaced along with the belt. Within a month, a squeal started in that area. The mechanic tried spraying some silicone on the belt, which made the squeal go away for a day or two, but then it returned. I took the car back to the mechanic, who replaced both belt and pulley on warranty. The squeal went away and has not returned.

Jeremy

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"Buster" in the '95

Our all-Diesel family
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