My R4 compressor developed a massive leak around the outer seals. So I needed to replace with a new one. The compressor warranty requires that a new expansion valve also be installed. Whoever wrote the factory manual page on replacing the expansion valve in a W126 300SD should be !@#$% slapped.

He/she wrote:

1. Drain air conditioning system.

2. Remove cover at left under instrument panel.

3. Open housing by half.

4. Loosen all hose and pipe lines on injection valves with box end wrench first and then screw off.

The manual fails to address the large (6" diameter) tube that routes heater air on the driver's side that must be removed. This requires removal of the instrument cluster to get to the bolt that secures the tube on the right side. The manual fails to address the metal brace that is attached to the transmission hump with three bolts and is bolted up under the dash in two places. Not to mention the numerous bundles of wires that are cable tied to the brace. You cannot remove the brace to get it completely out of the way because of the routing of one of the wire bundles, so you are fighting the brace during the rest of the process as its natural resting place puts it right in the way. Also you need to remove several pieces of plastic ductwork just to see the expansion valve.

A 17mm flare wrench will work on one lower fitting on the expansion valve. I was able to use a 21mm crow-foot with a 6" extension on the other lower fitting. You cannot use a wrench of any type on the upper fittings. You can get a wrench on one of the fittings, but there is no room to turn the wrench. A 19mm crowfoot did work on one upper fitting. However, when you get that first fitting screwed out, it is still in the way so that even the 21mm crow-foot will not have room to slip onto the other fitting. I had to take a chop saw and grinder to my crow-foot and narrow down the sides to be able to slip it on the fitting. Then it was "turn the socket wrench handle about 20 degrees, then remove the crow-foot and reposition for another turn."

Finally the thing was out. Pic 1 shows the debris in the system. Note that the compressor had not failed--this was just a dirty system.

Took close to 2 hours just to get the valve out.

I drilled out the old valve so I could reinstall it to aid in flushing the evaporator. Worked great. Pic 2 shows the new undrilled valve and Pic 3 shows the old drilled valve.

Reinstalling with new o-rings was just as much fun as getting it out. I have left the brace, tubing, etc. loose until I can finish the project so I can check for leaks. Unfortunately, after installing the compressor and the drier, I discovered another leak, this one in the condenser, so I had to order another condenser. OUCH.

Attached Thumbnails

     

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1984 300SD 326,997 miles and counting . . . No wait, my odometer is still dead

The 126 has got to be one of the worst models to have to do an expansion valve on. I didn't have to pull the cluster but there was a lot of cussing involved during the removal. The 107 SL is a close second in difficulty.

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1980 500SE/AMG Euro
1981 500SEL Euro
1982 380SEL
1983 300TD
1983 500SEC/AMG Euro
1984 500SEC
1984 300TD Euro
1986 190E 2.3-16
1986 190E 2.3
1987 300D
1997 C36 AMG
2003 C320T 4matic

past: 1969 280SE 4.5 | 1978 240D | 1978 300D | 1981 300SD | 1981 300SD | 1982 300CD | 1983 300CD | 1983 300SD | 1983 380SEC | 1984 300D | 1984 300D | 1984 300TD | 1984 500SEL | 1984 300SD | 1985 300D | 1986 300E | 1986 560SEL | 1986 560SEL/Carat | 1987 560SEC | 1991 300D 2.5 | 2006 R350

Man I hate that you had to go though all that to get the expansion valve out. The W123 models are a breeze to get the valve out

At least you did get it done and did not have to pay someone.

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1981 300D 147k
1998 VW Jetta Tdi 320k
2001 Dodge Ram 2500 141k
1979 300D 234k (sold)
1984 300D "Astor" 262k(sold)
Mercedes How-To and Repair Pictorials
I love the smell of diesel smoke in my hair

According to the factory manual, it should be a breeze on the w126 also. Fortunately, I had tangled with that !@#$%^ heat duct before, when I replaced the ignition switch. That ignition switch is also much easier on a 123 model.

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1984 300SD 326,997 miles and counting . . . No wait, my odometer is still dead

One of the things I'm not looking forward to doing on the SD.

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I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

Hey,
I replaced my TX valve on my 300SD. What I did was position the seat so I could rest my right shoulder just on the edge and reach the valve with two hands.
Positioning the seat correctly makes a relatively easy and comfortable position to work in.
Also, a set of metric flare wrenches made all the difference in the world screwing the hoses back in.
I just reread your first post. I had no trouble with the flare wrenches on any of the hoses. If you do you may want to take a grinder to the neck and grind it down to make more room to turn the nut.

TIP: do the top hoses first then the lower hoses. You don't want to run the risk of dropping an o-ring into the valve before it can seat properly.
Don't ask how I know this.

Danny

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1984 300SD Turbo Diesel 150,000 miles

OBK member #23

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(='.'=) This is Bunny. Copy and paste bunny into your
(")_(") signature to help him gain world domination

I have metric flare wrenches. What I am saying is that there was no room to turn the wrenches, even after I removed the heating duct and the brace. Anyway that part of the job is done now, anyway.

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1984 300SD 326,997 miles and counting . . . No wait, my odometer is still dead

I need to have this information. Is there another post with more information on how to remove the expansion valve?? This is not something that I am looking forward to.

Thanks
Robert

i don't understand. i took the panels out and there was the valve. used a couple open end wrenches and a cresent to hold the valve and had it out in about 15 min.
no, not easy to reach up there, but i've had worst jobs..

haven't removed the compressor yet, it looks harder than the expansion valve.

now trying to figure out what oil to use for R134. what weight oil, etc. i bought some PAG 46 but not sure if i should use it.

r

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1985 300SD
1998 Jetta TDI
Previous: lots of diesel VW's, MB's, KW's, Pete, Freightliner


Walking isn't a lost art: one must, by some means, get to the garage.

I believe the W116 valve is even more difficult to replace.

DieselGiant has a write up on the expansion valve.
When I did it on my 84 300SD is was an absolute pain.
I also had to take an angle grinder to a wrench so that it would fit.

Jeff

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1984 300SD 300,000 miles--two tank WVO setup
2.88 diff & 500SEL anti-squat rear end

I have always wanted to put that information in but never figured out how to do it.

I am working on my 84 300sd

I would sure like to know how you did it and how did you get the Bordon (sp) tube back on the evaperator without seperating the housing??
Thanks
300SD

Ditto times 2.

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1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/diesel-discussion/10414-help-i-need-check-stretch.html

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/diesel-discussion/156207-photo-step-step-post-showing-w123-evaporator-removal-1983-240d-1982-300td.html?highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html

People are often prompted to replace the expansion valve (and receiver drier) in order to satisfy the requirements of a compressor warranty.

I did not have this level of difficulty on my 300SD. The job was done without disturbing any brackets or air ducts. It did require purchase of a set of Craftsman crow's foot wrenches, plus an on-line order for one larger one that is required on the top side. The pricing of this single one led me to comment that it must have been the crow that set the price for their foot.

One thing you get when the expansion valve is out is a much more forceful flush of the evaporator. I used a flush gun (fill with flush and pressurize with shop air) in one port and the other port had a piece of old garden hose over it running into a small bucket. Got lots of black stuff out of the evaporator.

There's no room whatsoever for regular wrenches to work. I used the crow's foot wrenches to get the fittings snug, then tightened them up with a long extension and socket wrench.

Ken300D

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1982 300D at 351K miles
1984 300SD at 217K miles
1987 300D at 370K miles