No, you should not have to lay out over a $1000. And yes, you expect your Mercedes air conditioning system to be as reliable and function as well as a Toyota Corolla or Hyundai Excel.

But the reality of the matter is if you have a W124 vehicle with the original factory all-aluminum evaporator and you live in the deep South, you have a problem. And if you fix it improperly at first, it will come back to haunt you. The system's components are intolerant of abuse. If you want reliable air conditioning at the lowest cost, you either do it properly now or do it properly later.

Heres the lowdown -

* M-B's all-aluminum evaporators, used in W124, W140 and R129 series vehicles, superceeded the indefatigable copper tube/aluminum fin evaporators used by the prior generation vehicles - W123, W126 & 107. Unfortunately, the all-aluminum units had an Achilles tendon - under the right conditions (aka, routine use?) the units starting leaking like sieves. The problem was prevalant in (and perhaps facilitated by) climates with high ambient temperatures and humidities. These aluminum evaporators were manufactured by Behr (in Kentucky?) and contained no external anti-oxidation/anti-corrosion coating. And leaks started developing. From the outside in. Tube wall integrity loss has been attributed to poor quality materials.... design defects.... corrosion... phase of the moon.... bacteria ... mites. I've spoken with many service techs, parts and M-B field reps (in the U.S., U.K. and Germany) over the years and received many different explainations. But one thing was consistent: at the service and parts level there was always the acknowledgement that a problem existed; at the management level, the opposite: "We do not have a problem with our evaporators" and
"Evaporators can not be expected to last more than 80-100K miles". But the most important finding was that the leaks invariably developed from the outside inwards.

* The W124 refrigerant compressors have no oil sump; lubricating oil is circulated throughout the system. Spring a leak? ... you can loose both freon and oil simultaneously. System not cooling well? Recharge with freon! But did you also replace the lost oil? One accompanies the other. The compressor's pistons are coated with teflon, which, in conjunction with the oil, prevents seizure. When the system runs low on oil, the teflon is abraded off and the pistons seize in their bores. The compressor self-destructs and sends metal particles throughout the system. Then you have to replace everything. Flushing can't effectively remove all the metal particles.

* Can the sealer truly prevent new leaks from developing? Particularly when they originate from the outside in? If the evaporator is leaking, replacement is the only remedy. Especially if the leaks are parasitic in origin.

Haven and Benzmac are right regarding the detrimental effects of the sealer on system components. Go to your A/C repair facility; ask to see a disassembled Nippondenso compressor. Note the internal clearances. A factory rebuilt, without clutch, is $500, plus labor. Is it worth the risk?


My service recommendation, from someone who has been there (more than once):

1) If you haven't done so already, thoroughly leak test the entire system. Now. While everything is still functioning. In particular, look for leaks at the evaporator, expansion valve, freon pressure switch located at receiver drier, and suction manifold hose assembly (bolts to compressor).

2) Check system pressures (high and low side). Confirm that you have a healthy compressor.

3) If you have a healthy compressor and an evaporator leak, then bite the bullet and replace the evaporator. And you don't have to use a factory evaporator. Save big bucks and purchase an aftermarket unit with copper tubes. My M-B dealer long ago acknowledged the evaporator problem (unlike MBNA) and began to offer a choice of factory or aftermarket evaporators. If your suction manifold assembly is leaking, replace it. But with an aftermarket remanufactured unit; its available at a fraction of the price of a new manifold.

4. Ensure that the balance of your system is thoroughly flushed. Its the only way to get your system's oil level to zero so that you can accurately load the factory specified quantity.

5. Replace the receiver/drier. Period. No questions asked. And replace the expansion valve and freon pressure switches, even if they aren't leaking. They will eventually. They're inexpensive and installation time is minimal.

6. Refrigerant? R-12 is still available. If you can stomach the price, use it. With the upgraded evaporator and new style expansion valve and freon pressure switches the system should remain leak free for several years. R-134a typically requires a larger evaporator to offer cooling comparable to R-12; in the heat of Miami's summer R-12 will offer the best cooling from a factory stock system. Additionally, R-134a requires higher pressures; a compromised compressor will eventually fail under the additional load.

7. Regarding your concerns about someone messing around under the dash ... no need to worry. Just make sure you go to a reputable, high volume repair facility, whether dealer or aftermarket. So many W124s have sprung evaporator leaks that techs are quite familiar with the repair procedure. Ask for one who has handled a substantial number. One won't be difficult to find.

8. Feel Lucky? Real Lucky? - Take the car to your dealer for a A/C system check. If the diagnosis is a leaking evaporator, request that they repair it for free. After they decline, call MBNA Customer Assistance Center (201.476.6212) and complain. MBNA has been silently performing out-of-warranty ("Good Will") evaporator repairs for years. On W124, W140 and R129 vehicles. In some cases, they cover everything; in others, parts only; or some combination. At this point, you probably don't stand a chance with a 10 year old vehicle, but your odds wil improve if you are the original owner, had all or the majority of the vehicle's maintenance performed by a dealer and previously complained about poor A/C cooling related to freon loss. MBNA will assign a Field Service Rep to inspect your claim; the Field Rep will make a recommendation after reviewing the vehicle's records. The Rep's decision is final and normally cannot be appealed. There appears to be no rhyme or reason to the decision making process; perhaps there is a quota: in one case a friend's '92 400 E out of warranty evaporator repair was paid for in full by MBNA; a week later another's '92 300 D 2.5 was declined. If the Rep says no, then ***** at the dealer. I am aware of one case ('91 300 D 2.5) in which the Rep denied the claim but the dealer subsquently offered the owner the parts at cost and reduced the labor charge from 16 to 10 hours.

Given the number of vehicles that have suffered this problem, I am surprised that a class action suit has never surfaced. Early W140 owners suffered front end problems which resulted in legal action and a settlement with MBNA. All three of my W124s ('87 300 TD, '90 300 D 2.5, '92 300D 2.5) developed evaporator leaks, with the earliest occurring at 55K miles. A friend's '91 500 SL starting leaking at 32K; another's '92 500 SL, at 46K miles. In all, I can tally 27 W124 and R129 vehicles of family, friends or colleagues, encompassing MY '86-'95, that have developed evaporator leaks; most leaks occurred before 75K miles.

This information is culled from my own experiences and is offered with the hope of being beneficial and that a moderator will step in and correct any inaccuracies that may exist.

Good luck.

[This message has been edited by jgl1 (edited 04-08-2000).]