Replaced the evap on my 1990 300E a couple of years ago. Now, I have a big leak in my 1991. Topped it off (R12) two days ago and last night it would barely cool - heavy stream of bubbles in the sight glass.

So, I'm hoping maybe it is NOT the evaporator this time. Haven't yet tried to find the source of this leak.

What else tends to leak on these cars? Over the years I have had a compressor, expansion valve and evaporator leak in various 124 cars.

What's your experience? I wonder what percentage of time it is the dreaded evaporator.

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2012 E350
2006 Callaway SC560

I'm afraid you're taking the wrong approach for finding the leak. Looking for it based on the odds of what fails most is just NOT the way to find the leak.

There are two basic approaches, an electronic leak detector or UV dye. I use both and the electronic detector seems better overall, but there are times when the dye will find a leak that an electronic dectector might miss.

The problem is that it will run into several hundred dollars to get equipped for this. Don't you have a local auto a/c shop that can leak check it for you? They can do it in short order for not too much money and save you lots of time and money as compared to replacing parts based on past history of OTHER cars.

Best of luck with it.

It's Saturday (don't these things always come up on Saturdays?) and I haven't yet done anything with regard to finding the leak. I have a sniffer and the system has dye so next week I will hunt for the leak.

For now, I am just curious about other peoples' experience with leaks and what components are likely candidates. More of a rhetorical question, really. Certainly I would never try to "find" a leak this way.

Like I said, I have experienced leaky compressor, expansion valve and evaporator on these 124 cars. Just wondering what other folks have experienced.

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2012 E350
2006 Callaway SC560

The pressure switch by the receiver dryer has leaked for me on 123s and 124s.

Expansion valves have been known to leak. Replacing it is the only a/c system repair my 1993 300E has required.

I like the dye for leak detection, especially for slow leaks. Becomes rather obvious where the leak is ocurring.

The problem with dye is that it only works well when the system is full and functioning properly. So it's best to have it in there before you need it.

Like Jim Yuhn, I have replaced the expansion valve before. Make sure you sniff around in there. It's hard to get at if you have to replace it, but it can be done.

Just sniff around all the connections and everywhere you can reach. Sniff through the center vent with the system blowing and sniff through the condensation drain WHILE THERE IS NO CONDENSATION THERE. Condensation can ruin the element in your sniffer. Since you have dye in the system, put a UV light on the condensation drain water and look up in the drain tube.

Since you have dye in the system and a sniffer, I'm quite confident that you will find the leak. If the replacement evaporator was all copper and not the original dissimilar metal type, then the odds of it leaking again are not too high.

Good luck,

May I politely ask from whom does one buy an all copper evaporator for a 124?

Thanks.

Do some searching on this forum. There is a recommended brand, I think it starts with the letter "A."

Also, it's possible that the good replacement is not all copper, rather all aluminum. My point is that you don't want one that is dissimilar metals as is the factory original. That's why they gave trouble. Given that copper and aluminum expand and contract at different rates, they separate over time causing a leak.

The brand is ACM. You can purchase it from any WorldPac vendor (e.g. Fastlane). I used an ACM when replacing the evap in my 124 wagon and it fit perfectly. Even came with a new expansion valve already installed; a nice little bonus.

Jim,

Am I correct that it is all copper, or is it all aluminum?

Larry

Larry - I think it's all copper, but it has been quite a few years since I put it in. I just don't remember with absolute certainty.

- Jim

I put an ACM in my 1990 (since then it has been totalled in an accident) a couple of years ago. It was all Aluminum.

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2012 E350
2006 Callaway SC560

Larry Bible, all I can say is that you must be living right. While I'm sure they exist, I do not personally know of a single remaining 124 car with the original evaporator. Today I removed the blower motor so I could see my evaporator. It was a nasty oily mess on the driver's side where it's leaking, just like the one was in my '90 model. It's a big leak - goes down in about 36 hours.

So keep saying your prayers!

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2012 E350
2006 Callaway SC560

Hey - mine's orginal on an 86' model.


It may have seen some sealant in it's life. It did get a new compressor, dryer and hoses when the factory compressor quit functioning. I imagine it will get a new evaporator and heater core this fall/winter.

M