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Pulled my expansion valve...

Started by 1980sdga, 18 June 2011, 04:26 PM


I'll post pics if anyone's interested (Daughter took off with the camera).

Anyway, It wasn't really that bad. Don't know what I was worried about. The hardest part was getting all the "dum-dum" off of it without making a mess of the interior. Kind of like doing suspension work in the front seat  :o

I was expecting an inlet screen but didn't see one  ???  It's a little gunky inside but not too bad.

I timed it and it took an hour and a half from start to having the part on the bench  ;D  It helped that I'm semi-pro when it comes to removing the instrument cluster  :P

And I swear, it looks as if there is a clip that holds the panel that the evaporator lines run into.  'Twould be great if that sucker would slide out. Looks like it may...


I would love to see some pics. I plan to do this myself this weekend!!


I'll post some pics this evening. I wish I had the camera while doing it  :P

Anyway, I started by pulling the door duct parts that are in the drivers footwell. Don't know if you've ever done it but you need to be careful and proceed with caution when pulling all that stuff. There are some screws that are sort of hidden and you can break something if you force the parts.

Aside from the obvious screws there is one phillips head screw on the far left (LHD car) which fastens to the kick panel. There are also some screws along the right side which hold the panel to the center ducts.  Once you get all the screws you can wiggle the door side of the part out and tug the center part loose.

When you get that out you can reach up and unscrew the speedo cable, pull the instrument cluster wiring/ oil pressure line and take the cluster out.  It really does just pull straight out!

Oh yea, pick up some rubber gloves. The black sticky stuff that covers the valve is STICKY and NASTY!  Getting that stuff off without getting any on my interior was actually the worst part of the job!  I used a ziplock bag and CAREFULLY pulled it off piece by piece and stuck it in the bag.  I may be able to re-use it.

I'll check out what wrench sizes were needed and post back...


Jon, the sticky stuff is called "grease tape", you should be able to find it at a good a/c supply store.




Thanks Joe. I thought it was stuff we always called "dum-dum" which was used on US auto AC systems. But I did notice that some of it came off like tape.

I'll have to round some grease tape up!

So Grant, why are you pulling your valve?



the shop tested my system and said there was pressure on the high side but no pressure on the low side. They speculate debris in the expansion valve. I have decided to replace valve, drier, and compressor and call it done.


What car and what type compressor etc.?  I'll post some pics before the weekend.


1979 300sd

The parts came in this morning. I picked them up at Oreillys, but the compressor does not seem to match what is on my car? The computer said it was an A6 model?


Does yours look like this:

If so then it's an R4. The parts store catalogs show an A6 for some reason...


That's the one!!! Thanks so much. any tips on removal?


rgrant 78,

300SD compressors are always R4, in fact all Turbo-Diesel MB's with the OM617 engine use it, the A6 is used on the V8's




I found removal was really easy!  Just a few long bolts going through the bracket into the rear of the compressor.  If your system has been evacuated there is a single bolt holding the hose manifold in place.  You can get to everything pretty easily from underneath the car.

There are some spacers that go between the bracket and compressor so I'd be careful not to lose them.

I actually removed my PS pump assembly because I'm working on fitting a different type of compressor to my engine.


after putting the system back together, where do i put the oil? what kind of oil? how much oil? Then i plan to take it to a shop where they will put a vacuum on the system and then charge with freon. How much freon does our system take?



Whooaaa... Slow down.

You really should do some research and maybe get your AC shop involved.

Ken should be around soon  ;D

What type of oil you use depends on the refrigerant used. R12 uses different oil from 134a and some of them are not compatible!  You also need to know exactly how much oil is in the system because too much and it won't cool, too little and it could damage your new compressor.

The only way to know how much is in the system is to flush all the old oil out of each component and start fresh.  Since your system is apart this won't be that big of a deal.

I believe the general rule is 2 oz. of oil in each component. 2 in the drier, 2 in the evaporator, etc. You have to spread the oil throughout the system because it needs to circulate in order to lubricate the compressor properly.

I'm still learning this stuff so DON'T go by what I say.

Did you get the proper compressor?


Hehe, hey Ryan, welcome to the fun. Well it's your fun at the moment, anyway, if you have a new compressor I would check that it is not already charged with oil. Going by the MB a/c manual for the 116 model, the compressor

for the engine 617.950 came with 170cc of oil precharged. If yours has no oil I would not bother trying to buy it and put it in yourself, you will probably need to buy a litre/quart as a minimum and it's not the kind of stuff you get

at your local parts store. You need to decide which refrigerant you are using and make sure you have the right oil, if you use R134a you MUST have synthetic POE or PAG type oil, if you use R12 you can use mineral or

synthetic. If you have a shop that will vac and charge the system for you I would leave it to them to put the oil in, but make sure it's not already in there.

Check the climate control manual in the library, look under the manual a/c section (section 1), job 83.520 gives the specs you need.

Good luck,