Well, after a thorough evaluation, it has been determined that my evaporator core needs to be replaced on my 87 300D. I have read numerous threads about this topic but I still have a few questions. Are there any special tools required to remove the dash and everything else which has to be removed? I have torn the dash out of the wife's 84 300D and my old 85 300D, but have not yet ventured behind the dash in my 87. Are there any precautions I need to take when removing the evaporator? Once I put the new one in, how can I go about pressure testing it to ensure there are no leaks? i am assuming I need to replace the dryer and expansion valve at the same time, am I correct in this assumption? Any words of wisdom, or just plain moral support will be appreciated.

Mike

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Mike

'80 300D
'84 300D
'85 300D
'87 300D

Oh My Gosh, I know one thing for sure.... you should test the new evaportor for leaks BEFORE you install it... All that work and THEN find out it leaked... Just could not stand that heat...

It sounds like you have more experience in this department than anyone else I know of ... there was one student i think in Florida who took his apart and put it back together TWICE... but I have not read of anyone having attacked two different dashes... and live to tell about it...

ANYTIME the system is opened up the Reciever Dryer is supposed to be considered KAPUT... it takes almost no time out in the open for it to get saturated with moisture... and the oil in it does not give up its moisture when one evacuates a system in the normal way...

The expansion valve would not have to be replaced... but it is cheap ... and if you wanted to that would be the logical time...

Good luck... and take lots of digital pictures both for you sake putting it back together and for us to see...

Glad to hear that if I am going to do this, it will put me in a higher standing...wouldn't want to do this for nothing? How do I go about checking the evaporator for leaks? Do I simply plug one and pull a vacuum on the other? How do I test the whole system for leaks before taking it to someone to have it charged?

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Mike

'80 300D
'84 300D
'85 300D
'87 300D

You will need to plumb up something which does not leak and either pull a vacuum or pressurize it.... then see how long it holds whichever..
Since it is the connections between the different parts of the overall system which constitute the usual culprits when looking for leaks there is no way to check it until you put it all together... However, I do think it is wise to hook up a ' jumper' across what would be the Rec/Dryer....
Yes, just cap one end of the Evaporator and place a valve and guage on it where you can disconnect from the pump...and be able to read the guage on just the evaporator....
Be sure all the other connections are good... then put the Rec/Dryer in the circuit and close up..and vacuum immediately... that is what the manuals call for... leave the Rec/Dryer sealed until the last possible moment... then uncap and install.... and start vacuuming right then.... so the moisture in the system can't contaminate it...

Did you know that many rental places rent the legit vacuum pumps ? Then you know exactly what it was pulled to.. and how long....
I hate to sound distrustful of mechanics... but.....

I run a calibration lab and our forte is pressure so I have access to all of the pumps and gauges one could ever need. I think i will do the work, then take it down to the lab and hook up to one of our pumps and pull a vacuum on the system. Hopefully I won't run into any major problems. Thanks for the advice.

Mike

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Mike

'80 300D
'84 300D
'85 300D
'87 300D

That is amazing... why don't you keep notes on the sizes/threads which are required for whatever buttoning up you do in order to do your tests ....
At some point people will be able to do all these things ahead of time and know what to order...

Sometimes pulling vacuum to determine if a component leaks or not, is not enough. Ideally you should both pull a vacuum, as well as pressurize it.

The reason being is that if for example you have a hairline crack, than pulling vacuum, may cause the crack to close, preventing a leak from being detected. Pressurizing on the other hand, will keep the crack open, and allow the leak to become evident.

Once you are in there, you should also consider replacing the climate control vacuum pods. These are impossible to reach otherwise, and do fail after 10 - 15 years

Phil

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'95 E300 Diesel, 264,000 Miles. [Sold it]

Pulling a vacuum and seeing that it holds is a good "gross leak" check. If you want to pressurize it, use dry nitrogen along with two ounces of R22 and then use an electronic leak detector. The leak detectors can find R22 much more easily than other refrigerants. This is actually a legal thing to do. The EPA figures that releasing two ounces of R22 is better than leaking a large quantity of 12.

This will allow you to check the entire system with about 200PSI of pressure.

Although on the 124 this is a time consuming procedure, if you have the MB service information printed out and close at hand, there is not really any mystery or magic to it. I have never pulled the dash from a 123 car, so I can't offer a comparison between the two jobs.

When I did my 124 I learned that it's pretty easy to pull the steering wheel and get it out of the way. Many of the guys here leave the steering wheel in place and just extend it as far as it will go before disconnecting the battery. My brother in law is an MB dealer tech and he encouraged me to pull the wheel. I was glad that he did, it made it much easier to deal with the instrument cluster connections and just generally be able to access things easier.

When removing the Allen bolt in the steering wheel center, make sure that you hold the wheel against your wrench, rather than just loosening the bolt with the opposing force being applied to the lock mechanism. This can in some cases put bur on the lock mechanism which will cause it to work poorly.

Good luck,

I don't know how large the evaporator is.. it may be pretty small... so instead of messing with the refrigerant... just put it under water the way they check for leaks in tires at the station. A drop of Joy detergent will make tiny leaks show up dramatically with bubbles. You can probably do this in a regular dishpan... if necessary diagonally...
I offer this because many people don't have electronic leak detectors available.. ( I don't ).

All of this advice has been quite helpful as I build up to this great adventure. I do have access to freon leak detectors. We repair them in our lab regularly. How exactly do you remove the steering wheel on a 124? The 123 is easy because you simply take off the center cover and remove the bolt. The 124 has the airbag in the center of the wheel so how do you get to the bolt?

I agree with you Larry, never turn the wheel against the stop. The center bolt for the steering wheel is usually on there pretty good and you could do some serious damage if you pulled hard enough. I usually use a two foot breaker bar and have someone firmly hold the wheel as I break the bolt loose.

The 123 dash is relatively easy. The first one I pulled took about 12 hours to pull and put back in. The last one took about 3.5 hours. The hardest part is getting the stupid thing over the steering column and lined up right. It is a job I would do again if needed. I did it the first time because my mechanic wanted to charge me $1200.00 to replace the pod which controls the center vents. The price my mechanic wanted to do this job was three times as bad, thus the motivation to do this one myself also.

Leathermang, we use the dunk method regularly a the lab when trying to find leaks in pressure calibrators. You can use all of the "snoop" and other methods you want...the dunk method still prevails.

Mike

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Mike

'80 300D
'84 300D
'85 300D
'87 300D

sublet,

My posts have been made with the assumption that you have the factory manuals available. Removing the steering wheel PARTICULARLY requires the manual, in order to know how to SAFELY remove the airbag. You MUST disarm the airbag properly following the factory manual. Once the air bag is disarmed, removed and safely stored, removing the steering wheel is the same as removing a 123 wheel. With the manual disarming and removing the airbag is a quick job.

I am probably one of the worst there is for tearing into things without service manuals, but this is an operation where the manual is almost mandatory IMHO.

Best of luck,

Larry,
I've been out of town all week and this is the first chance I have had to get caught up on things. I too am really bad about not refering to manauls, and this time I don't even have one to refer to. Which manual is hte best for this car and where can I acquire one? I am in the process of ordering a whole bunch of parts for my two cars and now is the time to get what I need.

Mike

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Mike

'80 300D
'84 300D
'85 300D
'87 300D

I have the Mercedes manual on CD. I don't think there any other manuals that would be helpful for pulling the dash, but I'm not positive of that.

Good luck,