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Old 03-25-2003, 09:53 PM
Posts: n/a
Unhappy SL evaporator replacement

So its starting to warm up, and that means I have to replace the evaporator on my 1990 300SL that has been leaking since late last summer. My local MB shop quoted $3400 to R&R, and another independant shop wanted $2900. So it looks like it will be a DIY job. I know it will take a considerable amount of time, as the shop quoted 22 hours to do the job.

Questions - can anyone tell me the order of removal of parts from the dash to get to the evaporator? Start with the radio, climate control then center console? I understand there are a myriad of wires and servo's, and I'm sure if they are removed in the right order it would make things much easier.

My plan is to replace the parts and let a qualified shop evacuate and charge the system. What parts should I replace besides the evaporator? Dryer, maybe?

Any help would be greatly appreciated!
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Old 04-20-2003, 11:22 PM
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Vacuum lines

Well, I have removed the dash, console, wiper assembly, fresh air assembly, and finally the heater/evaporator core case. I am replacing the evaporator, heater core, expansion valve and the dryer. I am planning on driving the car to a local shop to have the system re-charged with 134a (it was previously converted).

My question is will I damage anything driving the car with several vacuum lines disconnected, as I dont want to put everything back together until I have the system charged and checked for leaks. If I do need to plug the vacuum lines, are there any tricks?
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Old 04-21-2003, 07:10 AM
it leaks, its german
Join Date: Mar 2002
Location: raleigh nc
Posts: 1,111
hopefully you replaced the heater tube o-rings while you were at it.

Project Smoker, '87 603 powered wagon
Hauler, 96 CTD can you say torque?
Toy 73 Cougar xr7 convertible
Acme Automotive Inc.
Raleigh NC
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Old 04-21-2003, 07:23 AM
Posts: n/a
That's right, golf tees to plug the vacuum leaks so the engine will idle okay.

Since this is such a massive job, you definitely need to check for leaks before putting everything back together. Once the evaporator is in place and connected, take it to the shop and have them evacuate and see if it holds vacuum for 30 minutes. This will be a worthwhile step and expense given the massive scope of this job.

You deserve at least a nomination for the DIY award of the month.

Good luck,
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Old 04-21-2003, 10:09 PM
Posts: n/a
Sorry I wasnt clear on my last post (at least I think I wasn't). I am talking about the vacuum lines that attach to the various locking and airflow actuators in the interior of the car. I believe they are supplied with a vacuum from a pump inside the car, and not directly from the engine. Most of them have plastic connectors on the end, and I dont think a golf tee will work (unless I remove all the plastic connectors). I was wondering if having these lines disconnected might damage the pump, as I understand they are very expensive.

Oh, and I did use new O-rings for the heater core. Funny, the heater core must have had a re-design, as the new one has a separate inlet at the top, but it came with a metal plug to seal the hole. Took me a few minutes to find the plug though, so I thought they had sent the wrong one.
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Old 04-22-2003, 08:06 AM
Posts: n/a
No, the vacuum source is indeed the engine vacuum.

To plug your plastic connectors, just get a length of vac tubing that will slip over the end and then put the golf tee in the vac tubing.

Good luck,
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Old 04-22-2003, 08:52 AM
Registered User
Join Date: Jan 2002
Location: Colorado Springs, CO
Posts: 1,006
Anytime the A/C system is open to the environment you should replace the drier. My W124 has a separate (electric) vacuum pump for the door locks, but that's it. I'd replace the vacuum elements that control the heater door flaps/vents since you alreayd have the dash off. Or, at a minimu, the ones that are impossible to get to without taking most of the car apart. When my mechanic does an evap he does this as standard practice. He usually finds 1-2 that don't work anyway.

Brian Toscano
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Old 05-02-2003, 11:49 PM
Posts: n/a
Good news: AC is charged and cooling well. I have re-installed the under hood items (fresh air intake and wiper motor, etc) and installed a new ACC Filter.

Bad news: The car has developed a miss at low and high rpm's, but only after it has been run for at least about 10 minutes, and then the miss stops after about twenty minutes. It has done this on 3 separate trips now. The first one, I was driving to have the AC charged, the engine started missing so I turned around to limp the car back home. On the way back, it started running smoothly. The next day, I am driving the car to get the AC charged again, and after about 10 minutes of the 15 minute trip it started missing again. I drove the car around for about 10 minutes and it stopped missing again. Oh, and the miss happens whether the AC is on or not.

Any ideas? All I have left is to re-install the dash and I would like to find the problem before I put the dash in, only to find I have to take it back out to correct the problem.
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Old 05-03-2003, 07:35 AM
J.HIDALGO's Avatar
Registered User
Join Date: Jul 1999
Location: Jax, FL
Posts: 1,785
Vacuum leak?

Apply vacuum to a main line and see if it holds...Autozone has a the tool to "borrow, if you don't have one.
'86 300E
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