The a/c pulley DIY that fizzled [Archive] - Bimmerfest - BMW Forums

: The a/c pulley DIY that fizzled

09-15-2012, 06:38 PM

I've been getting bad bearing sounds from the a/c pulley, when the a/c is turned off.
My plan was to remove the a/c pulley, replace the bad bearing and claim success.
BMW actually only lists the entire a/c compressor for replacement - quite expensive, too.

Here is some information on the a/c system that may be usefull, if you decide to try this for yourself.
The a/c compressor on my 745li (2004) is a Denso 7SEU16C
The pulley is called PV4
Other numbers of interest are the BMW PN 64509175481
but its also known as Denso 471-1483

The bearing size of the pulley is 35x52x12 (unconfirmed).
You can get this bearing size at

Sooo. I took off the fan and moved the dynamic drive hyraulic line to have better access.
The masterplan was to
(a) remove the front bolt of the pulley
(b) take off the coverplate
(c) remove the ribbed belt to the crank
(d) remove the snap ring inside the pulley
(e) remove pulley

Next I planned on pressing out the bearing on a press. Replacing the bearing with red loctice (only to the housing). Reassembling.

HOWEVER the bolt holding the coverplate in place is ROCK SOLID in my car. :yikes:
I tried everything to get that bolt off. PB Blaster, Hammer, center punch, breaker bar...

Then I stopped not having good luck and started having bad luck. The bolt head rounded itself with the use of the breaker bar. Further efforts of vice pliers, a bolt extractor, torch (carefull with that), dremel, and even brazing on a nut to the bolt head were futile. :mad:
I'd like a word with the Denso engineer that picked the undersized bolt.

I've ended my attempts to replace the pulley alone and will now start planning for a full scale a/c compressor replacement.


09-16-2012, 04:57 PM
Since the bolt head is already trashed, you might consider using a drill and that Dremel to chop away at the bolt head until you have it entirely off, since the bolt head is the main binding surface that keeps the bolt from turning. Without the bolt head on, everything should just pop off, or you could at least use the bolt extractor and get better results. Good luck!

Sent from my SCH-I535 using Bimmer App

09-16-2012, 08:56 PM
Hello Keif,
thanks for looking into it. I must admit, the thought had crossed my mind in the sense of "what is there to loose".
I put it aside as the accessiblity within the engine compartment is less than optimal, especially for drilling.

When it's removed from the car I'll give it some more tries.

Regards, flash_n

11-04-2012, 05:48 PM

after replacing the entire compressor, I thought I'd try to disassemble the compressor to
a) give it a shot at repairing
b) take it apart to maybe help someone with more details of the inner workings

after dremeling the entire bolt head off, it was still stuck beyond belief. I hope I was just unlucky and the bolt does not doom any other attempt of just replacing the bearing.
I took the screwdriver and simply broke the tappet (?) off.

Basically the main shaft is attached to the tappet via the bolt.
The tappet in turn connects to the pulley with damping rubbers in between.

To take off the pulley, I'd strongly recommend a proper tool. The surface the bearing is seated on is aluminum.

The bearing size is 52x35x12mm.
The bolt size is 7mm -- as measured on my replacement a/c.
The legible number on the pulley is 047451-xxx.

If you open the compressor, you'll be surprised at how much is still in there, even after you thought you had drained it.

03-17-2013, 08:26 AM
Did the prongs in the “tappet” connecting to the rubber dampeners in the pulley appear capable of slipping for a period of time without permanent damage? Do you think the tappet was designed to be non-removable?

03-17-2013, 08:43 AM
@ flash n... just wondering for future knowledge: how did you distinguish between the pulley making the noise or the compressor?

03-19-2013, 12:08 PM
My guess would be that the tappet prongs would survive. The rubber dampers i'm not too sure of.

I don't think it was designed to be non-removeable. But definately undersized.
Happens often in design IMO.

03-19-2013, 12:12 PM
To distinguish between the compressor and pulley:
If the A/C is on, the pulley spins in sync with the compessor. No relative speed.
If the A/C is off, the pulley spins but the compressor does not. This is when you should hear the bearing in the pulley.