OM603 engine swap, which belt to use? (Plus other interesting things) - PeachParts Mercedes-Benz Forum

Fulcrum525 · #1 09-09-2014, 11:57 PM

So the other week by tensioner pulley decides to grenade itself on my way to work. The engine in the 350SDL came out of an 87 300D which already had 400,000 or so miles on it but with a new head. This was 6 years ago now and another 150,000+ miles as the 350SDL itself just turned 322,000. Doing the job was relatively straight forward from the DIY posted here.

I had to use some creativity to hold the water pump pulley because Harbor Freight F^&*ing sucks and didn't stock the pulley holder and couldn't send me one in the mail on time despite spending almost as much on shipping as on the damn tool. (FYI my much larger parts order from Pelican ALSO shipped out from California on the same day. They charged me NO shipping and got it to me ahead of schedule) Today was the one day off that I had in order to do this job and I couldn't wait any longer for the tool to come in....

I used the old belt which was pinched when the pulley came loose so I had no intention of using it again. In this photo above there was still slack but by putting a small plastic electrical relay under the belt just above the headlight bracket it gave me just enough force to undue the cooling fan without using the weight of the G to pull it tight.

After removing the older tensioner I put on a spare pulley that I had from my original engine and put on the new belt. I will mention at this point that the serpentine belt went on fairly easy but that I still needed to use a good amount of force to get it over the last pulley. When I checked the tension I found it to be acceptably tight. I also started the engine briefly without the cooling fan and again, everything seemed fine.

Here is where things get frustrating though. While the above "Procedure" worked to remove the fan, I couldn't use it to tighten the fan. I had read that a few people have managed to hold the pulley by hand while tighting the bolt so I gave it a shot. I tried but was unable to hold the pulley and in my frustration I tried to hold the pulley by pushing down on the serpentine belt between the water pump and the power steering pump. What happened next is what has me perplexed and a bit worried. When I pushed down on the belt and tried to tighten the cooling fan I swear I could feel the belt stretch or otherwise become loose. Now the belt is definitely loose beyond acceptability and even occasionally chirps a little bit when revving it at idle. I won't be driving the car until that damn HF pulley holder comes in and I get this sorted. Is it even possible to stretch a slightly warm belt or even damage a pulley with was less then my full weight pushing on the belt?

My only (Hopefully) saving grace is that I may have ordered the wrong belt. The engine swap from a W124 has always made buying certain parts rather....interesting (Do I get them for the 350SDL or the 300D/300SDL?) In this case I ordered the 2145mm serpentine belt which is supposed to fit the 300D/300SDL. The 350SDL used a 2120mm belt. While writing this post I went through my older receipts and did find a return of a 2145mm belt and a purchase of a 2120mm belt.

Also I don't think it matters but I also swapped out the fuel pre-heater/thermostat which I think may have been letting air into the system. I will find out in the morning if it was...

Any thoughts will be most welcome.