Should I replace the receiver/dryer when cleaning the A/C system?
 

I was told that it is good idea to change the receiver-dryer/accumulator when I switch compressors and flush out the A/C system on my '89 300SEL. (This is to remedy a compressor failure.)

Is this good advice?

Thanks.
-Brett

As cheap as they are, you might as well.

Hi Larry. Thanks for the reply.

My hesitation was not the price, but the time it will take to get one, and a lack of understanding as to why it would need to be replaced.

Without replacing it I can be done today. But if I need to replace it, the part is at least a day or two off (nobody around me seems to stock MB parts - even an air filter is a special-order item).

-Brett

do the expansion valve , too... not much cost there, either

You should always replace the drier when you open the system, and ESPECIALLY after the kind of work you have just done.

You need to replace it to get new desiccant. Yours will have absorbed some water, and will absorb more with the lines disconnected.

The reason for replacement is what Matt said. The purpose of the drier is to remove moisture from the refrigerant and it can only do it as long as it has not absorbed tons of moisture already which is what would happen when the a/c system is opened and kept open for an extended period of time and also during flushing. If you dont replace the drier, excessive moisture in the system would damage the compressor and also fine tubing in the condensor as well as the evaporator. Replacing the expansion valve is also a good idea though not absolutely necessary. And ofcourse replacing all the seals (o-rings) around tubings that are opened should always be done. Replace the inserts of the schrader valves also.

They may not be removable so don't tear them up trying to get them out.

Thanks guys. Now it makes sense to me.

I've ordered the receiver/dryer, expansion valve and a seal kit (all the o-rings, etc.). It was about $60 total (which seemed reasonable to me). Now I just need to wait a few days.

Thanks again.
-Brett

MB offers these guidelines...if the system is over 5 years old & is opened for any reason, the drier should be replaced.

If the system is left opened w/o charge OR vacuum for over 24 hrs the drier should be replaced.

Leaking Compressor-to-Condenser Hose
 

The compressor-to-condenser hose from my York compressor ('77 280E) has just developed a leak where the metal tube goes into the metal shroud that connects to the rubber part of the hose. Is there is seal in this part of the hose that I can replace? The system recently was given a charge just before the leak started.

If it is a Schader valve, like the one in our bicycles, the inserts should be removable. You just need a special tool, available for sure at home a/c supply stores. The insert has to be rotated to remove.

a/c goes hot if car is not moving and stays that way
 

I am tracking like a freight train on the idea of replacing the drier and the receiver and even the expansion valve and the seals. My issue is past that. After opening the system and vacuuming it down and refiling the freon, I am lost. My 16v is switched to R134 and until this week has always been ice cold. It has been 95 -97 each day and if i let the car idle or have to stop for an exrtended period of time, the a/c goes hot and stays hot until I stop the engine. Then after a short shut down, even 5 minutes, I restart the car and the ac is typically ice cold again. ANyone know what my issue might be. I am working on getting the new drier, reciever and seals and valves, but I dont know what is causing the hot ac on idle or car not moving.

Christopher, the first things I would check are the fan/clutch and the electric aux fan.

After you shut down for a few minutes and on restart when the a/c works again, does it work on idle for a while ? When the a/c stops blowing cold air, do you see the compressor cut off ? I am trying to understand whether it is mismatch in the engine and the compressor RPM that is causing the compressor to shut off and therefore causing a loss of cooling OR is it the engine temperature OR high compressor outlet pressure (possibly because your aux fan may not be working) that is causing the compressor to shut off.

Info on non-removable valves: Click Here

The 16v I have dose not have a visco fan clutch, it has the magnetic clutch and it was replaced 2 months ago and appears to still be working correctly. the aux fan also seems to be working as it should. It is also on when ever the A/c is turned on as it should.
The engine temp does not seem to be any hoter than normal, 80-90. I seem to have a 16v 190E that actually has no overheating issues as of yet.
As far as if the compressor is kicking off when the ac goes hot, i am not sure. I have been in traffic most times and can stop easily and check.
I think the a/c is staying cold for at least a while even while idling after the car is shut down and restarted and the a/c has gontten cold again. I would say that it stays cold at idle for at least 10-15 minutes, not really timed it, usually, I do a restart and it is cold and I am off. I will start checking it. I typically dont use it as a daily driver so I am just starting to get the whole issue defined. I used it for a 2 hour trip last week on the highway and it was 95 outside and the a/c was freezing us out the whole way, not a single issue. Now it seemed to go hot and then cold again, then hot 4 times in 2 hours today alone.

There is a 3 pole switch on the coolant manifold, it could red or Green.
If IT thinks the engine is overheating it can shut the compressor off.
Try disconnecting the single pin connector & see if the A/C stays cold.

Huh !! Never seen a schrader valve whose insert cant be removed, but clearly they do exist. Yes, then have to be careful as brewtoo said, otherwise the whole hose/fitting could become unusable.

I will try the temp switch trick MB Doc. Is it the sensor up on the top front of the engine, where the other sensors (100deg temp, vac switch over, etc and thermostat is? I'll go look at it.

A/C expansion valve
 

I want to consider replacing some prevent maint items when I replace s few seals and the drier and temp/pressure switch at drier since the freon has to be exacuated anyhow. Can anyone give me advice on how to replace the expansion valve on my 16v? I know where it is, expansion location, but I have never dug to it or replaced one. Is it worth the trouble and time?

If it's not broken, don't fix it. No reason to replace the TXV as routine maintenance.

You would not enjoy getting it out, anyway.

I figure it is difficult to get at and get out. Just didnt know if it was worth the effort to replace it...it is 22 years old and I am opening the system anyway. I think I will probably leave it off my replacment list