An interesting maintaince problem... - PeachParts Mercedes-Benz Forum

Pooka · #1 03-30-2009, 03:40 PM

Crusing down the Interstate in a 1981 240D and all of a sudden there are VERY loud noises coming from under the hood. Temp gauge pegs out and alternator light comes on. Being a smart guy, I decided to pull over and take a look.

The plastic fan had all of its' blades broken off, the belts were hanging from the part of the engine that was not busted and the crank drive pully was laying in the fan cowl. Using all my mechanical powers I sized this up as not good.

Towed the car to the house and found the problem: The bolts holding the crank drive pully had sheared off. Everything turned OK, so I just started removing things until I got the parts to where I could get the remaining parts of the bolts out and then I just replaced the bolts with the strongest I could find. Of course I also replaced the fan. While I was in there I also replaced the front crank seal, but that was just because I was in there.

I am aware that on 114/115 cars the bolts holding the steering gear need to be replaced now and then, but are the crank pully bolts a normal wear item?

Anyway, I just thought I would post this so others could know about this problem. Replacing the bolts is an easy job (unless they are sheared off) and might be something to plan on. I don't remember the size of the bolts, but you could pull one out and take it to a bolt and fastner retailer and they could order them for you.

Charlie20 · #2 03-31-2009, 09:34 AM

I had almost the exact same thing happen to me. I attributed it to my having adjusted the A/C belt too tight. I would not think the bolts wear out so long as they do not exceed a certain shear force.

pawoSD · #3 03-31-2009, 10:26 AM

To tightly adjusted belts. I keep all of ours on the loose side just because of that risk.

Rashakor · #4 04-01-2009, 08:54 PM

as long as the belts are not slipping there should be some 1in play on them.

pawoSD · #5 04-01-2009, 09:02 PM

I usually adjust them to where they are slightly slipping, then go ever so slightly tighter from there to stop the slipping. I stay as far away from "tight" as possible.

marfa300td · #6 04-01-2009, 09:51 PM

Quote:

Originally Posted by Pooka

Using all my mechanical powers I sized this up as not good.

Where did you get schooled on those mechanical powers? Really funny post.

toomany MBZ · #7 04-02-2009, 12:07 PM

When something similar happened to my 240, the fan was okay, as were the bolts.
I believe it was the thrust bearing, but the fella I sold it to replaced the front crank seal and JB welded the casting, so far so good, but I don't know if he takes it on the highway.

Pooka · #8 04-02-2009, 03:28 PM

I had not considered that the bolts might have been over-toqured. I was not the original owner so I really can't say. They were put in correctly when I did it, but that is neither here nor there.

I always tighten the belts to where you can grab then between the drive pully and the pully being turned and see if I can turn the belt 90 degrees. If so it is OK, if it will not turn that much it is too tight, if it turns too much it is too loose.

Mercedes recommends that a tensionmeter be used on every belt, but in over 50 years of repairing autos I have never seen the need for one. (Please be aware that if you are changing the timing belt on a Porsche 924 or 944 the use of such a tool is manditory unless you like replacing water pumps.)

I am glad to see only a few resonses to this thread since that must mean this is not a common problem.

By the way: I drove the car for about a mile before I could pull over. The steering effort went up of course, but the engine suffered no ill effects. Those 240D's are tough.

Pooka