Arrgghhh! What am I doing wrong? - AC belt - PeachParts Mercedes-Benz Forum

Ether · #1 08-30-2007, 10:01 AM

It seemed like such an easy task, replacing the belts on our 84 300D. Not so fast my friend................

The AC compressor belt has turned into a nightmare job. I loosened the pivot bolt and both of the adjusting bolts and the compressor did indeed slide in a bit and the old belt became loose. But not loose enough to slip off. After struggling a while I eventually gave up and just cut the belt. The problem now is that I can't get the new belt on.

I have used a pry bar between the compressor and body to try and gain that last desperate inch but all I end up doing is moving the entire engine. The clamp that attaches the oil cooler lines to the mount has been removed in the hope that that was restricting the movement but no dice.

I keep thinking to myself that this can't be this difficult. I must be overlooking something simple that is keeping the compressor from sliding all the way in the mount slots but I haven't been able to figure it out.

I have the correct replacement belt (13 x 925) so I'm sure that's not the problem.

Any insight would be appreciated.

rrgrassi · #2 08-30-2007, 10:18 AM

Did you loosen the 10mm adj nut?

Ether · #3 08-30-2007, 10:22 AM

Quote:

Originally Posted by rrgrassi

Did you loosen the 10mm adj nut?

Yes.

Although it did occur to me last night after I gave up the fight that perhaps I didn't back it out far enough. I'll check that this evening before I go at it again.

Junkman · #4 08-30-2007, 10:34 AM

My 85 SD was a tight fit. I ended up putting the belt on the crank pulley & partially on the air cond pulley. Then rotate the engine by hand using a 1/2" ratchet on the crank pulley. Be sure to rotate in the direction engine turns when running. You have something that isn't loosened or is in the way if you can't get close.

Whiskeydan · #5 08-30-2007, 10:38 AM

It's pretty tight in that area around the ac comp but, I suspect one bolt still needs to come out a bit or there's a (grease covered) rock or something lodged behind it.
Viewed from a different angle with better lighting may reveal the problem.
Good luck, and let us know what you find.

spark3542 · #6 08-30-2007, 10:56 AM

Quote:

Originally Posted by Ether

Yes.

Although it did occur to me last night after I gave up the fight that perhaps I didn't back it out far enough. I'll check that this evening before I go at it again.

I had the same problem until I found the 10mm adjusting nut...not just the bolts in the slotted area.

LUVMBDiesels · #7 08-30-2007, 10:59 AM

On the 300SD, there are three bolts that have to be loosened before the compressor will move inboard far enough to get the belt on. I think the mount for the compressor is the same on the 300D.

Take a look at the pdf files below...

Ether · #8 08-30-2007, 11:27 AM

I have all 3 nice and loose.

Now that I have the benefit of a nights rest to think about it, I'm betting on the 10mm adjuster not being out far enough.

vstech · #9 08-30-2007, 11:41 AM

don't go too far!!! it's a pain to re thread that sucker.

Junkman · #10 08-30-2007, 12:25 PM

PO broke my adjuster & welded non-metric threaded rod on. That's a parts car problem fix.

JimmyL · #11 08-30-2007, 01:27 PM

It boggles the mind how far that 10mm adjusting nut has to be backed off in order to buy just an extra mm required to get the belt on. Certainly not a lot of extra slack!!

toomany MBZ · #12 08-30-2007, 02:20 PM

Quote:

Originally Posted by Junkman

My 85 SD was a tight fit. I ended up putting the belt on the crank pulley & partially on the air cond pulley. Then rotate the engine by hand using a 1/2" ratchet on the crank pulley. Be sure to rotate in the direction engine turns when running. Clockwise as you stand in front of car.

I do this when belts are tight to get on, except I use one of those handy trigger engaged bump starter things, it rotates in the correct direction. Also when adjusting valves.

Ether · #13 08-30-2007, 09:54 PM

Well,
I ran the 10mm nut all the way out and sure enough I was able to slip the belt on. Woo hoo!

dmorrison · #14 08-31-2007, 02:14 AM

Glad you got it done.

I find a couple of things help.

Of course loosen all bolts in the back.
Loosen the 10mm bolt ALL THE WAY.
Make sure you unbolt the clamps that hold the AC hose to the frame, this just gives you a little more.
I then use a large crow bar from below against the frame and compressor to push the compressor a little more towards the center of the car and I can get the belt on.

Dave