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  #1  
Old 09-01-2003, 04:23 PM
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Join Date: Jun 2002
Location: Monrovia, CA
Posts: 490
Need Help Changing W124 Expansion Valve

Help!

What's the trick to getting at the bolt that holds on the A/C expansion valve in my '86 300E? Do I need to remove the brake booster (I hope not)? Does it take a 10mm wrench or 11mm? I've tried a double ended 10/11mm box wrench that's about 8" long and I can't get enough rotation to get it to drop over the head of the bolt. Do I just need to go buy a real short handled wrench? There just doesn't seem to be any room back there to get at it with anything.

Thanks for any help.

Gary
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  #2  
Old 09-01-2003, 04:43 PM
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Join Date: Aug 2001
Location: Evansville, Indiana
Posts: 8,150
Yup, it's a pain in the butt.

Remove the little plastic clip that holds the vacuum lines beside the brake booster -- this will reduce the amount a skin removal considerably.

You will have to get either a thinwall 10mm socket on there or use a short 10mm on it, nothing else will work. Have a care not to drop the nut, it will vanish down into the darkness. I never did find mine, had to use a spare.

Once you get that nut off, you must also remove the clamp on the low pressure hose further down to pull the manifold off the expansion valve.

Underneath are two 4mm (I think, may be 3mm) flathead screws that hold the expansion valve to the evaporator. Use ONLY a good hex driver that fits securely, if you strip these you are screwed. I used a plain hex key from a cheapo set, but it fit securely. If you have a swivel, you can use a hex driver on a 1/4" drive, but you will want to cut the key off short so that you can get it all the way into the screw and completely seated.

Not the best design I've ever seen, very difficult to reach.

DO NOT overtighten the screws going back in, they will be stuck something fierce then next time you have to do this!

Peter
__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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  #3  
Old 09-01-2003, 06:12 PM
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Join Date: Jun 2002
Location: Monrovia, CA
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Thanks very much!

Gary
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  #4  
Old 09-01-2003, 10:45 PM
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Join Date: Aug 2001
Location: Evansville, Indiana
Posts: 8,150
If the screws aren't stuck, this is fairly easy once you figure out how to get your hands in there....

Peter
__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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  #5  
Old 09-02-2003, 12:58 AM
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Join Date: Jun 2002
Location: Monrovia, CA
Posts: 490
Just finished the job of replacing the expansion valve, receiver-drier and the entire A/C Manifold/Hose Assembly - what a chore!

Once I took off the vacuum line holder behind the brake booster it made it just barely possible to get both sets of fingers back to the exp. valve to remove the bolt and then the two 3mm allen screws. The new valve uses a stud and nut instead of a bolt and, sure enough, I lost the first nut down under the brake booster, never to be seen again. It's a little tricky getting the nut started, but once you do it goes together easily. The receiver-drier is a no-brainer and easy to get at.

For anyone who replaces the A/C hose assembly with the fuel cooler on an early 300E, plan to spend the better part of the day at it. And here's a tip - before you start, take off your gas cap, and make sure you have a 27mm open end wrench. One of the first things I did was to get under the car and disconnect the fuel lines from the fuel cooler on the old A/C hose. I routed the inlet hose upward so it was at the highest level it could be, well above the level of fuel in the tank. As the morning progressed, I realized that I needed to go buy a 27mm wrench, so off to Sears I went. When I got back about 45 min. later, there was a very strong smell of raw fuel in the driveway. I looked under the car and there was about a 3 ft diameter puddle of gas and more dripping all the time. Seems that as fuel heats up in a closed container, it expands - gee, who woulda thought? As soon as I popped off the gas cap, the gas stopped leaking, but the damage had already been done to my asphalt driveway. It just ate away about 1/2 to 3/4 inch from the surface of the asphalt, and now it's real crumbly, so be warned.

It was a bit of a job to get the new hose in place as the bends were slightly different from the original as well as having a small chamber near the cooler that the original one didn't have. It's already crowded under there and this just made it a little more difficult. The hardest part was routing the pipe to the condensor. The bend was a little different, the bracket that bolts it to the inner fender didn't quite line up and the pipe interfered with my trans cooler lines that I installed last summer. I also had to reshape the plastic shield that mounts just to the left of the radiator as the new pipe fouled it and wouldn't let me remount it in it's original position without grinding some additional clearance in it

But all in all, I'm glad I did it. I saved probably four to five hundred dollars easily in parts and labor over dealer prices and at least I know the job is done right. BTW, someone in a reply to an earlier post I made suggested a product called Nylog for sealing all the o-rings and threaded couplings. I went out to my local friendly refrigeration supply house and bought a 30ml bottle of Nylog Red Label (for R12) for a whopping $4.85. This is probably a lifetime supply for me. You use just a little bit at each junction and it looks like it will probably seal better than anything else I've seen. It's basically a mineral oil base with something added that makes it thin but very stringy. You apply it to threads by touching it one spot then wrapping it around. Neat stuff. Has a shelf life of about forever. There's more information about it here:

http://www.refrigtech.com/nylog.html

That's it for now. Next weekend I'm replacing the parking brakes and rear discs. Should be a cinch after this.

Gary
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  #6  
Old 09-03-2003, 02:11 AM
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Join Date: Aug 2001
Location: Evansville, Indiana
Posts: 8,150
Gary:

I guess that means I should keep the expansion valve I took out of the 300TE, it was a replacement! Probably leaking, though.

I hope you don't find the same problem I did on the 300D -- rear rotors STUCK big time, never did get them off (replacing links on the suspension, not doing brakes).

Peter
__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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