Noisy A/C compressor?

[Benzboy210]

Hi all,

1998 E430 - when I start the engine, I notice a slight squeaking noise coming from the engine bay. It is loud at first then gets quieter and after a minute or so it is barely audible. Pushing the EC button on the climate control silences the noise, so I am guessing it is the A/C compressor?

Bearings? Is this unit serviceable? A/C is working fine at the moment, nice and cold.

TIA.

[Matt L]

Before you do anything, check the clutch gap. An excessive gap can cause slipping upon startup.

[Benzboy210]

Originally Posted by Matt L

Before you do anything, check the clutch gap. An excessive gap can cause slipping upon startup.

Thanks Matt. I don't have a clue about the compressor, never worked on one. What should the gab be? Thanks!

[Matt L]

A typical compressor uses a .020" gap (.5mm). I don't recall seeing the spec in the FSM, but it must be there somewhere.

The gap grows with age, and is adjusted by changing (or removing) shims behind the clutch.

[Dave1965]

Originally Posted by Matt L

A typical compressor uses a .020" gap (.5mm). I don't recall seeing the spec in the FSM, but it must be there somewhere.

The gap grows with age, and is adjusted by changing (or removing) shims behind the clutch.

When I replaced my clutch, the instructions in the kit specified 0.45mm, +0.15mm or -0.10mm.

The preload of the belt will affect the gap so you'll want to finally set it with the belt installed.

Here's what I went through and the writeup I did about it:
http://www.mercedesshop.com/Wikka/W210CompressorClutch

[gregs210]

Originally Posted by Benzboy210

Hi all,

1998 E430 - when I start the engine, I notice a slight squeaking noise coming from the engine bay. It is loud at first then gets quieter and after a minute or so it is barely audible. Pushing the EC button on the climate control silences the noise, so I am guessing it is the A/C compressor?

Bearings? Is this unit serviceable? A/C is working fine at the moment, nice and cold.

TIA.

If you start by making assumptions instead of following normal diagnostic and troubleshooting steps you will spend lots of time and money or both.

Cycling the compressor loads and unloads other pulleys, so it is entirely possible it is your idler pulley, tensioner or even maybe the water pump or alternator.

So instead of sitting in the car and pushing buttons, grab your mechanic's stethoscope and carefully ISOLATE the source of the noise. If it is indeed the compressor then you can dig in further...

Take care and enjoy the ride,
Greg

[Matt L]

Originally Posted by Dave1965

When I replaced my clutch, the instructions in the kit specified 0.45mm, +0.15mm or -0.10mm.

The preload of the belt will affect the gap so you'll want to finally set it with the belt installed.

Here's what I went through and the writeup I did about it:
MercedesShopWiki: A/C Compressor CLutch Replacement

Thanks, Dave. I still haven't checked the FSM for the proper gap.

But Greg is right on yet again. Get a stethoscope and go hunting. You might need to have an assistant start the engine.

[Benzboy210]

Originally Posted by gregs210

If you start by making assumptions instead of following normal diagnostic and troubleshooting steps you will spend lots of time and money or both.

Cycling the compressor loads and unloads other pulleys, so it is entirely possible it is your idler pulley, tensioner or even maybe the water pump or alternator.

So instead of sitting in the car and pushing buttons, grab your mechanic's stethoscope and carefully ISOLATE the source of the noise. If it is indeed the compressor then you can dig in further...

Take care and enjoy the ride,
Greg

Good point, but would the compressor's load make that much of a difference? Either way, it's sound advice (no pun intended), so I will isolate the noise.

[Benzboy210]

So I tried to isolate the noise and it definitely appears to be coming from the compressor, but I can't be 100% sure. The other tricky part is that the sound goes away after a minute.

Matt - I can freely turn the front of the compressor with the engine off.

I think for now I may just leave it unless the noise worsens. I'll keep an eye (ear) on it. Thanks all.

[Matt L]

The compressor is actually turning when this noise occurs?