A/C compressor belt tension

[obone]

Went to replace A/C compressor belt but cannot figure out how to loosen/tighten the belt . does anyone know the secret?

TIA

[Merkin]

You need to loosen the A/C Compressor. There's a bolt on top and a two on the bottom. I had to loosen all 3 before I was able to get the belt on.

[obone]

Merkin thanks for the info. I had lossened the bolts on the bottom and had two bolts on top ('84 633) that I loosened and still could not get compressor to move to relieve belt tension. Any other secrets? Where is the bolt on top that you mentioned?

[Merkin]

That's what my A/C compressor looks like, I'm pretty sure. You can see the attachment on top and the two on bottom.

I had to use a lot of force to move the compressor, don't be afraid to really yank on it.

[songzunhuang]

This thread never got resolved. I also have a 84 633CSi and I can't figure this out. I found the 2 top bolts and loosened them, but the compressor wouldn't budge.

Can someone confirm that I am loosening the right bolts?

Any help would be great.

[dwcains]

After you loosen the top bolt, you need to loosen those 2 bolts on the bottom, too. One bolt is a pivot, while the other is the adjuster. If you look closely at the adjuster bolt, you'll see it has teeth which mesh with teeth on the bracket. You adjust the tension by turning the bottom bolt which causes it to move along its track in the bracket.

[songzunhuang]

After you loosen the top bolt, you need to loosen those 2 bolts on the bottom, too. One bolt is a pivot, while the other is the adjuster. If you look closely at the adjuster bolt, you'll see it has teeth which mesh with teeth on the bracket. You adjust the tension by turning the bottom bolt which causes it to move along its track in the bracket.

So are you certain the 84 had this? Basically you've described the same system as the power steering and alternator for tightening the belts. I was under the car looking for a similar setup for the compressor and I didn't see it. Maybe it was so close to my face that I somehow didn't get it?!

I did loosen the two lower bolts but I didn't see a toothed track like you describe. I'll have to look again I guess. Thanks for the response.

[dwcains]

Well, that's the original, but not necessarily what's on the car now. My '85 has an aftermarket bracket to adapt a modern Sanden-type compressor. They were once fairly common, but now NLA. There are other alternatives, too, including adapter brackets to work with the original mount and a Sanden compressor.

[sansouci]

Song,
As part of the alternator or aircon compressor work, you can buy the toothed nut as they are a bit too soft and should be replaced as a matter or course. Also lube the pivot points.

[songzunhuang]

Song,
As part of the alternator or aircon compressor work, you can buy the toothed nut as they are a bit too soft and should be replaced as a matter or course. Also lube the pivot points.

OK, the 84 633 does not have the toothed nut. Today I crawled under and around the car loosening every bolt and nut I could fine. There are 2 bolts with nuts at the bottom and this appears to be the pivot point. There's also another bracket and nuts on the bottom that I am not entirely certain of their necessity or function. It just seems like and extra bracket.

On top, I spotted two (2) 13mm bolts and they were on a bracket with a slot in it. Hmm, the slots look promising. So I loosened these top 2 bolts as well and discovered that if I really lever it hard, the compressor moves and the belt tightens. There's no good way to hold it in position while holding tension on the belt. I ended up tightening the bolts enough to create friction to hold the belt in place.

So in the end I tightened the bolts a bit, levered the compressor to tighten the belt and then tightened all the bolts. The belt appears to have kept the tension. Weird that the engineers created such a cool system for adjusting the belt tension on the alternator and the power steering pump, but then neglected to do anything for the compressor. What's up with that?!

Anyhow, I now know how it works. I can confirm that there is no toothed nut on a 1984 633CSi. You tightened the belt for the compressor in the "old school" way. Also, there was no need for me to lube the pivot points. My compressor was covered in oil. I've got an oil leak to track down. It's small, but it's definitely there.

[dwcains]

If you think you want to tackle swapping the bracket on there for the extra one I have, it's yours for the postage. If you want a few more pics to verify fitment, I'll post some. Let me know.

[hornhospital]

Song, yours may not have the toothed nut/geared rack to adjust the tension, but it most definitely is supposed to have it. My '84 633 does, as does every other E24-2 I've seen.

[sansouci]

Song,
German engineers didn't know squat about aircon. Willis Carrier was an American genius.
Oil leak? Likely to be failed compressor seals.
Based on some of your previous posts, hi performance wipers are more important than aircon (lol).
Happy New Year.

[songzunhuang]

Song, yours may not have the toothed nut/geared rack to adjust the tension, but it most definitely is supposed to have it. My '84 633 does, as does every other E24-2 I've seen.

Anyway for you to get a picture of the toothed rack and where it's suppose to be located? Is it on the bottom or top of the compressor? Everything on my car has been pretty stock so far. I'd be surprised and wondering why the aircon was not made with the same adjustment options. It's not aftermarket or anything.

[songzunhuang]

Song,
German engineers didn't know squat about aircon. Willis Carrier was an American genius.
Oil leak? Likely to be failed compressor seals.
Based on some of your previous posts, hi performance wipers are more important than aircon (lol).
Happy New Year.

Maybe it's all mixed up with other fluids, but the drops that I wiped off of the compressor seemed liked engine oil and not the compressor oil. So far, my compressor appears to be holding pressure and the aircon has worked the few times I have turned it on. Note that here in California, I don't need air-con most of the year, especially in the winter.

I've got a slow oil leak somewhere and I fear it's a front seal. I've replaced the valve cover gasket and it's very dry around the perimeter over the past months. The suspect place is the front cam cover (upper or lower I can't tell) and the front seal. From what I can tell, replacing these will not be an afternoon job. I'm living with a small slow leak until I have to deal with it.

[hornhospital]

Anyway for you to get a picture of the toothed rack and where it's suppose to be located

Absolutely, as soon as the monsoon lets up. Southwest Alabama (Mobile and the Eastern Shore of Mobile Bay) has had over 81" of rain this year and it's still coming down. A lot of it's come in the last month.

The adjuster is on the bottom IIRC.

[dwcains]

The pic I posted on 12/21 shows the adjuster, and it's positioned under the compressor when mounted on the car.

[sansouci]

Song,
Brush or scrub with Gunk GP to clean the suspect area. You can hose it off and it becomes soap-like. Second choice is Simple Green. Send pics
Happy New Year!

[songzunhuang]

Ok, here's a picture of my compressor lower mount. I used some degreaser and a brass brush to get a lot of the gunk off so that you can see the assembly pretty clearly. As you can see, there's 2 bolts where it pivots and then there's the bracket that doesn't seem to do anything.

The top area I couldn't get a picture of as easily. It's way in there, but there are definitely no toothed nuts for adjusting. Oh well.

View of the lower compressor mount. It appears different from the descriptions I've seen on the forum.

Compressor Mount.png (850.94 KiB) Viewed 5751 times

[hornhospital]

That is totally different from any AC compressor mount i've seen on any M30 engine. It appears to be adapted from some other mount, especially the spacer where the smaller bracket is attached close to the oil pan mounting bolt. The compressor itself looks like no other BMW-applied compressor, either.

[dwcains]

I don't know what that is, either. It looks like that bottom bolt is just a pivot point, though, and not a sliding adjustment. Any pictures from the top?

[songzunhuang]

I don't know what that is, either. It looks like that bottom bolt is just a pivot point, though, and not a sliding adjustment. Any pictures from the top?

Now you understand why I was confused with the instructions I read. You are correct that the entire bottom mount is a pivot point. There is no adjustment to tighten the belt from here.

I'll see if I can get a shot from up top tomorrow. There are 2 bolts and the one closer to the firewall is clearly mounted in a slotted bracket. The one near the front I couldn't really tell if there was a slot. I loosened it anyway and was able to get some movement to tighten the belt. Again, I was able to get the belt tightened a bit, but there wasn't a clever toothed nut to do the job easier and more precisely.

OK, more tomorrow. Thanks for the responses.

[GripGreg]

I hope after all this, that you did change the belt??

Also, for all of my compressor & alternator belt adjustments I always used a two or three ft. crowbar. Always! More leverage makes it easier.

[Da_Hose]

That looks like some kind of custom build. Notice how the bottom tabs look welded onto the compressor.

Jose

[sansouci]

Looks like a bit of shade tree mechanic's work.
You may have a bit of "undoing" to do. Is it functional at all?