Hi Everyone, I am new to this forum and was hoping someone could help me out. I have an automatic 1979 300D and need to change the fan belt. The current fan belt snapped off and as a result I need to change it. I am not sure how to remove the other two belts in order to place on the new fan belt. Any posts or information would be appreciated. Thanks

Since your fan belt broke, it's safe to assume that your other belts are in need of replacement as well. Belts cost very little - on the order of about 6 bucks each - so it is silly not to replace the others. First, go to the parts store and request all the belts under the hood. Have the parts guy mark down what each belt is to on the sleeve that the belt comes in. Next, look at each component that a belt goes to. They will be the alternator, power steering pump, fan and air conditioning compressor. Note the brackets that these components are attached to, and loosen the bolts a little so that the adjustment bolt can be backed-off to produce slack in the belts. Back it off extra as the new belts will be tighter. Remember the way the belts are routed, some cars have a diagram on the front of the car somewhere under the hood. when you tighten the new belts, do so so that you have about one inch of play at the belts longest run between two pulleys. This part is important, since overtightening can lead to very costly repairs. hmmm, try to get manual that has this procedure in it, a haynes or chilton. Actually, my haynes doesn't have it, so check the chilton. Good luck, and never be afraid to try it yourself, but don't be afraid to continue to ask questions either. Adam

Fan belt drives alternator and water pump/fan, PS belt drives PS pump, AC belt drives AC compressor. PS and AC are loosened by loosening the bolts on the appropriate brakets and swinging the pumps away from the belt. The fan belt is adjusted at the alternator (lower passenger side) by loosening the pivot bolt (bottom) and the slide bolt (top) -- the belt tension is set with either a star bolt and rack or a long bolt that goes between the alternator and block.

I don't have a W123, so can't be real specific, but the PS pump usually has bolts front and rear that need to be loosened, and the AC will, too. There will be a bolt front and rear in a slot, and one that is the pivot -- all must be loose. You don't have to take them out. Usual size is 15 or 17 mm, sometimes 19.

You will need to remove the other two belts to replace the alternator belt!

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

that is good advice about not overtightening as belts tighten as they warm up and can put stress on bearings.....
William Rogers...

I always thought belts loosened (expanded) as they warmed up; as the molecules would move apart with the increases kinetic energy. Maybe I'm wrong.

Adam (ATLD)

maybe one of the techs can comment on this but it's my understanding that rubber belts strech when new but shrink when warmed unlike most other materials......
William Rogers.....

V-belts DO get larger when warm -- in both directions. Sitting in a tapered goove, the increase in length is compensated for (more than compensated for, in fact) by the increase in width -- the belt rides higher in the goove and self-tightens.

They don't grow all that much in length -- Kelvar doesn't expand much.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

ATLD guess we were both right....
William Rogers...

I really enjoy being part of a think-tank this efficient. Thanks all.

Adam T. L. Delecki (ATLD).

You learn something new every day!