83 300D - R4 compressor on its way out? - PeachParts Mercedes-Benz Forum

ah-kay · #1 12-23-2011, 08:21 PM

The 300D is now in San Diego. My daughter came home for Christmas from Santa Cruz. It has 346K and it made the 500 miles trip with only 1 incident. Charlie in Santa Cruz replaced the clogged secondary filter before the trip. Now the car is here I would like to give it a good go over it while it is here.

I tested drive it today and found the R4 compressor is noisy when it is ON. Otherwise A/C works well, it has been converted to R134 by the PO. It gives a rattling noise. Is it something of concern? Shall I change it out as a preventive maintenance?

tangofox007 · #2 12-23-2011, 08:23 PM

Tighten the drive belt.

DeliveryValve · #3 12-23-2011, 08:26 PM

^^ yeah and make sure all the bolts are there.

.

ah-kay · #4 12-23-2011, 10:49 PM

It is making the noise while the clutch is engaged. There is NO sound when it is free wheeling. I would expect noises if it is missing bolts.

DeliveryValve · #5 12-24-2011, 01:52 AM

I had one with a bolt came out and it didn't make any noises when off. However, it was plenty noisy when it was on.

.

tangofox007 · #6 12-24-2011, 08:13 AM

Quote:

Originally Posted by ah-kay

It is making the noise while the clutch is engaged. There is NO sound when it is free wheeling. I would expect noises if it is missing bolts.

What is your current belt tension?

ah-kay · #7 12-24-2011, 01:02 PM

I am not sure. I think it is correct, I push the belt in the middle and it goes in about 1/2". All the belts were changes about 15K ago when one was frayed. I could not describe the sound, it may be a rattle or something but it is a strange noise I do not expect when the clutch is engaged. A/C still cools OK so it is not catastrophic but I just do not feel comfortable.

I will check the bolts when I am not so busy next week.

Yak · #8 12-24-2011, 02:06 PM

There is nut that is sometimes there/sometimes not on the center shaft for the clutch. I've got a Harrison R4 guide that shows NO bolt in the assembly/disassembly instructions; but the M-B guides DO show a bolt there. You can rent/borrow the clutch tools to set clutch plate depth and adjust the R4 clutch from Autozone and/or O'Reilly's. I recall one or two forum members who have reported losing that center bolt and then having clutch failures.

But I've also read that noise is a common complaint with R4's, so what you're hearing might be normal-ish.

New R4's can run about $300, so it'd be a pricey "preventive maintenance" swap if it's currently cooling okay. If you go that route, a complete flush and re-fill with the proper quantity of oil would be prudent since lack of lube due to previous oil loss may be the root cause for the noise. If your daughter's driving it and it's out of your control, a few hundred dollars may be small price for piece of mind, though.

Are there any traces of oil leaks on the A/C system? Maybe drop the passenger panel to look at the TXV near the evaporator?

Some people might say 134 in a W123 that "works well" in California is an abnormal condition. Have you put gauges on the system to check pressures?

Are you sure the compressor is making the noise and it's not from one of the other pulleys due to the extra load when the compressor is engaged?

tangofox007 · #9 12-24-2011, 02:12 PM

Quote:

Originally Posted by ah-kay

I am not sure. I think it is correct, I push the belt in the middle and it goes in about 1/2".

Procure a belt tension gauge. You will be shocked at how inaccurate the various shadetree tension measurement methods are.

irishflyer · #10 12-24-2011, 04:12 PM

Look at aftermarket AC places, I noticed a Sanden with a GM back part A4 I believe for 199.00

rrgrassi · #11 12-26-2011, 12:21 AM

Quote:

Originally Posted by irishflyer

Look at aftermarket AC places, I noticed a Sanden with a GM back part A4 I believe for 199.00

Have a part number or compressor model number for the Sanden? I recently came across a Sanden 508 and mounting conversion bracket for the OM617.95x.

Ah-Kay, do as Tango advised. He is typically spot on.

My current R4 needed a new idler pulley bearing. It was caused by an overcharge, so the head pressure was too great, and the compressor stopped turning, but the idlerh did not, so it smoked the clutch and over heated while the engine was idling.