W126 AC compressor issue - PeachParts Mercedes-Benz Forum

LandYaghtLover · #1 06-22-2012, 08:22 PM

Before I replace the compressor/clutch....

For a while my compressor has been a bit noisy. But nothing extreme I would say. The only issue was the belt screeching from time to time when it would cycle on. Given my SLS pump leak I figured oil contamination on the belt. A cleaning and tightening and all was well for some time.

Then a couple days ago it starting screeching again, but I had been adding a lot of fluid to the SLS system, so figured I needed to clean the belt again. Maybe even tighten it. It was a new belt. But then things changed, the compressor itself got pretty noisy. It also seems to have gotten rather warm. At one point I had smoke from under the hood. I dumped some water onto the compressor and it cracked and sizzled just like putting it on a hot exhaust manifold! I am not sure how hot the compressor normally gets, but I think that is not right.

So now I have an AC system that if I dare operate for short durations (just to test!) blows cool. But its noisy, so I dont normally operate it. Pressures look good, but at idle it does not blow as cool as it should.

So would I be right to guess the compressor is on its way out in short order if I run it? I would not think it would just be a clutch issue - but want to be sure. A clutch is a bit cheaper than $319 for a rebuilt compressor with clutch.

If I do replace, and really feel I should anyway, I will replace the drier and expansion valve as well as clean out all the lines, replace o-rings and add oil in the right places. Can I use the updated green o-rings?

pawoSD · #2 06-23-2012, 10:04 AM

Maybe low lubrication in the system? Or it could be just wearing out.....if that stuff is happening I'd just get the components replaced.

Air&Road · #3 06-23-2012, 04:07 PM

Are you sure it's not overcharged.

LandYaghtLover · #4 06-23-2012, 05:59 PM

I dont think so Larry, even when cooled down now overnight it still noisy now. I can certainly evacuate some from the system. But I think a new compressor and parts may simple be the way to go.

Air&Road · #5 06-24-2012, 10:03 AM

Noises and vibrations are the most difficult things to deal with on a discussion forum. Even posting audio doesn't really help. I would have to hear it.

It depends also on the compressor type. These compressors are QUITE robust. If the noise is not bad, the pressures are good and it cools well, I would tend to just turn up the radio and drive it, but then again, I have not personally heard it.

I don't know what to say. Best of luck with it.

LandYaghtLover · #6 06-27-2012, 07:59 PM

Well the compressor is locked up now. Horrible screech when I turn it on. When I got home I did so to visually verify. Quickly I will add.

So looks like a new one for me. I found I can get a whole "kit" for $400 which includes the drier, expansion valve, flushing fluid (although I will order MANY more cans), and orifice-filter thingy. I can ever choose my oil type.

This was not something I had in the budget this summer. But I guess I gotta get it done! If I have the time I will take pics.

Hit Man X · #7 06-27-2012, 08:13 PM

Changing that TXV on the late W126 will test your patience. You better have a great set of stubby wrenches, flares, and crow's feet.

Air&Road · #8 06-28-2012, 07:28 AM

Under such circumstances you need to completely flush the ENTIRE system, replace the r/d and TXV and spread the required amount of oil throughout the system as it is buttoned up installing the r/d last thing.

You also might investigate adding a suction side filter.

The reason for all this is that when a compressor catastrophically fails, they typically spread debris throughout the system that will destroy the new compressor.

Sorry to be the deliverer of bad news that goes on top of your already bad news.

hbofinger · #9 06-28-2012, 07:59 AM

You can handle the expansion valve in an afternoon - I have done it. Here is my writeup:

Removal and Replacement of Expansion Valve

I found a Denso rebuilt two years ago for about $250 on the web, so look carefully for the compressor. It has held up nicely. Did not even have to send in the core!

LandYaghtLover · #10 06-28-2012, 08:47 PM

Larry, well aware of what can happen and already planning to flush lots! Hence my note above. I will attempt to make the system as new as possible and replace every part within reason. I am betting it will take the better part of a day.

But sounds like the TXV will be a huge pain. Is that thing inside the cabin? Is it something maybe I can leave or are they prone to fail?

Hit Man X · #11 06-28-2012, 08:56 PM

Better budget more than a day, this is a weekend project.

LandYaghtLover · #12 06-28-2012, 09:34 PM

Ugh....

Air&Road · #13 06-29-2012, 07:50 AM

Yes, it is a big project, but it's hard to say just how big.

It is quite common to replace the TXV in the case of a catastrophic compressor failure due to debris commonly collecting in the restriction.

IF you were able to flush the components leading away from the compressor and find that they are SPOTLESSLY clean, then you might get away with letting the TXV be, but with the compressor locked up, the chances of that being so are EXTREMELY low.

Start when you flush the components, put a white towel or paper towel over the outgoing end of the component to filter so that you can see if debris is coming out. It might only be a fine powder, but that is enough to wreck your new compressor.

You might also invetigate putting in a suction side filter. This is an aftermarket filter that goes just before the inlet to the compressor to catch whatever might be floating around. You can not do this in lieu of the flushing procedure because it can then easily plug up.

I've never changed the TXV in one of the big cars but I understand it is challenging. Just make sure you use a back up wrench and preferably tubing wrenches to prevent buggering up the nuts.