RJC

I'm amazed none of the techs that frequent here can help with this awful sound that comes from my AC compressor. I've mentioned that since my car was new (04 CLK500) the AC compressor emits a buzzing noise very similar in sound to a neon sign running. The dealership replaced the compressor once and the noise remained. I took the sage advice of someone hear and used a rubber hose to listen for where the noise is coming from and it's right at the upper front of the compressor, the closer I put the hose to that area the louder the buzzing was. The noise is almost always consant and only with the AC on and stops within a few seconds after switching the AC off. I would greatly appreciate some help with this.

TECHNICIAN

Can't help you unless I hear it personally. Sounds like a bad compressor. Did they change the clutch?

RJC

Thanks for the reply. The noise sounds just like a neon sign when turned on and is 100% from the compressor.

I went to an independent AC shop today, they showed me freon was leaking through the vents (but from no where else) using a very cool instrument and determined the evaporator may be leaking. I was also down 10 oz's of freon; they added it and the noise seems to have gone. They said I may also be down on compressor oil too but would have to open the system to add it. Since my car's warranty is still good I will inform MB of the issue and let them deal with it.

Here's where I need some advice. They tell me to replace the evaporator the entire dash and most of the center stack needs to come out! I really don't want that messed with as I have 0 rattles squeaks etc plus it's all stone colored which shows every dirt mark imaginable. My question is, since I may be switching the car either very soon or within a year can I just keep adding freon/oil when needed ? Also is it as big of a job as they tell me to do the evaporator and what's involved? Is it bad to be breathing the leaking freon/oil when driving while the AC is on? FYI the leak is quite small; 10 oz's in a year.

Thanks

TECHNICIAN

yeah the dash has to come out. No way around it.

RobertG

Breathing freon is not 100% harmless even is such a small amount,on the other hand youre breathing far more dangerous stuff just sitting in traffic(Fumes, brake dust or clutch dust, cigarette smoke and etc.)

RJC

RJC

Thanks. Until I get it fixed (if I do) I'll not use the recirc feature anymore but let outside air in using the charcoal filter option.

mleskovar

I've heard of people fixing small holes in car AC systems successfuly with available products that are put in with the gas and solidify when they hit air....kind of like radiator stop leak. Interesting that the added gas stopped the noise and that MB couldn't figure it out. If they truly replaced the compressor they would have recharged the gas. Did the noise go away for a while when you first picked up the car after the compressor change?

RJC

Thanks for the reply, I was wondering if there was a product like what you mentioned. Well tonight on the way home the noise came back . I've also been noticing a plasticy smell in the cabin coming from the dash area and the more I checked the more it smells like some kind of light oil!! I'd bet the evaporator box has got compressor oil in it leaking from the evaporator, hence the smell and noise from the compressor! The car goes in for service on the 6th and we'll see what's up. Youre right, it is amazing MB could not have figured this one out, but since the air has always been blowing cold they were never too concerned. The AC shop just used this cool gun and pointed it at the vents and the thing starting making all kinds of noises which indicating a leak.

I'm not too happy about MB removing the dash etc but it must be done. My lease is up in May and I was trying very hard to get the right 06 E55, but the car did not make it to the dealer by today's cut off so I'm going to see how MB fixes my car and if its good I'll just extend the lease another year (MB offered a great renewl rate) or I'll just get a new CLK550 in Aug.

My car is so perfect inside and out with 0 rattles; I hope they don't screw it up

Is this the product you were referring to?
http://www.sherco-auto.com/TLC.htm

Tim Timko

Get a second or third opiinion. I have seen a rash of "you need to replace the evaporator" in the last few years. I can make the sniffer go off by contaminating the area before you sniff it. Common scam. The evaporator job is the most expensive. $500 for the evaporator and $400 labor to put it in. Then when your not looking, just top off the refrigerant and tighten a small leak they found and charge you out the a$$. Two of my friends were almost caught up in this. I found one bad o-ring on a junction of the hose to firewall connection on both cars. (both Chrysler products.) Changed o-rings ($.59 each) had the systen vacuumed and recharged $50. No problems ever since.
As far as a car that new leaking from the evaporator?? Come on.. Its hidden, nothing can get to it to MAKE it leak. I have cars from the mid eighties that don't leak from there. (BMW) And you expect me to believe a Benz A/C leaks? I would place my money on a condenser in front of the radiatior to leak first due to a stone hit.
But.. Its your hard earned money.

RJC

Thanks Tim:

The compressor oil smell from the vents has been an issue for sometime now (long before the AC shop got involved) and so has the compressor noise; so everything is beginning to add up and make sense. I watched the AC shop do all the tests plus they knew my car was still under warranty and MB would be doing any repairs at no cost to me so I doubt they tried anything funny but I'm sure in other situations there are lots of scams going on. It goes to MB soon and we'll see what happens.

TECHNICIAN

Don't listen to that retard. He is just an internet mechanic.

The evaporators DO go bad. They DO leak. It has NOTHING to do with its location in the car. Its alot more then $400 labor by the way.

MB evaporator problems go back to the W140 and have gotten better since but they occasionally do leak.

Tim Timko

Excuse me? A retard?? How do you know? My 190e finally died at 350,000 miles, I did all the maintenance and repairs. Internet mechanic? haha good one. I have experience in Mercedes, BMW, Alfa Romeo, Lancia and I currently own 2 Maserati Biturbos that I just got from an estate.
Lemme guess your an ASE certified technician.(25 years old too probably) Right? A computer diagnoses the problem for you while you change parts to try and fix the problem. Me? I'm a trained mechanic. Trained to diagnose the problem myself, remove the part, repair or rebuild the part, reinstall it, and charge the customer according to flat rate standards.
Here's a test for you.. Quick list the 5 reasons a Bosch L-Jet injection systen would run rich.
Didn't think you would get them all.

Moviela

That buzzing sound might be the compressor trying to compress water. Since water doesn't compress, the valve vibrates. If 134a is leaking out, air and moisture are leaking in.
The moisture turns the 134a into an acid that screws the entire system. I'd be worried the whole thing is toast, and just turn it back in on the lease end.

As for the L-Jetronic system running rich, I can think of more than five.....

ECU hybrid control circuit (most often faild part of the ECU)

Airflow meter

Ambient Temperature Senssor

Coolant Temperature Sensor or Head Temp Sensor in air cooled cars.

Thermo-time switch, that little devil controls the cold start valve.

Engine revolution sensor

Throttle position sensor

Oxygen sensor

Any of these can fool the ECU into pointing to the wrong area of the "map" and inject too much fuel for the air flow. There are also mechanical problems like fuel pressure regulators, leaky injectors, corroded contacts in the injection harness.

Mike Hawk

At least he is not an oozing sphincter like you, Mr. Technician.

Not everyone can be a Master Certified MB Tech, from what I have experienced when dealing with Benz hacks like you, it takes a special kind of douchebag to attain that status. A golden combination of greasy personality and pompous incompetence. Someone who can find time to take cheap shots at people just trying to be helpful in between working, wanking and restacking the chips on your shoulders.

A guy like you could learn a lot from a retard.

RJC

I there anyway they can tell if moisture/water has infiltrated the system? Could the noise just be from the compressor running low on oil (especially since I can smell oil in the vents and cabin)?

Thanks

Tim Timko

If any did, it should have been handled by the dryer built into your system. When they repair your evaporator, they will pull a vacuum on your system before recharging it. That should be more than sufficient to remove any moisture (the minute amount that may be there). There shouldn't be any, as your system is under pressure.
On another note, I forgot you mentioned that you said it was a warranty job. I hope you get your buggy back the way you love it. Just hope I helped.

Tim Timko

Ding, ding,ding... We have a winner. I knew there was more, but at the instant I was posting that I could only think of 5. Lemme guess you were searching pretty hard through your Bosch Injection manual, weren't ya. LOL
Well, Its finally warm and sunny here in Ohio. Going out to play with one of the Masers.
http://smg.photobucket.com/albums/v2...aserati_27.jpg

RJC

How many hours are involved for replacing the evaporator in a CLK500?

TECHNICIAN

Its the ignorance of some people around here that pisses me off. There is so much mis-information on this forum its rediculous. Everyone knows everything. You really think just because the evaporator is behind the dash it won't leak? Are you kidding? You think every dealer and every tech is a hack, doesn't know anything, and can't fix anything. Dealerships or "stealerships" as they are called here are all evil and worthless. etc...

Thats fine... I'm done here. I figured I'd sign up and maybe help out a few people in my spare time. I take pride in my work and training, and take my job seriously. I make sure to the best of my ability that **** is fixed and fixed right. Some people don't, I don't argue that point. But since everyone here knows everything thats fine......I'm gone.

Good luck with your A/C problem by the way. None of my comments were directed to the original thread starter.

RJC

Don't leave...unfortunately the internet causes things to get a bit out of text and misunderstood sometimes; we've all been though it I'm sure. I truly appreciate everyone's advice and thoughts. We need current MB tech's here to help all those with recent model cars

mleskovar

Don't let a few jerks **** you off enough to quit participating. Remember, this is the internet and everyone has their opinions. Some people post here looking for help when all else fails, some because they like futzing with their cars, some because they can't afford dealer prices, and some just because it's an area of interest.

Moviela

You are correct! Mercedes Gemersheim sends them to the US by the pallet full for warranty replacement.

It is difficult to measure the moisture in the system with workshop tools, but you can inspect the interior of the evaporator when it is removed to see if there is corrosion. The drier is only effective for about one small drop of water, and should be replaced anytime the system is opened for more that a few moments.

After the work is done, a [I]decent[I] vacuum pump needs to be connected and run for at least an hour to boil and remove the moisture in the system.

Don't be concerned about the dealer taking out the dash and replacing the evaporator. While there might be a random gripe, 99.9999% of the time they get it right the first time.

RJC

Thanks for the info. Since I've been losing compressor oil too (I smell it in the vents and in the cabin after the AC been on) and the compressor has been making this awful buzzing sound for about 2 years steady, will it need to be changed from the lack of lubrication?

MBTech21

First I wanted to point out, actually it does take a lot, we are not all 25 years old (it's actually almost impossible to be Master at 25 by the way). Of the roughly 200 Master Guild techs in the country, which is the real top title, very few of them/us are under 40, and very few are arrogant or pompous...now that I have that off my chest. Here is your answer..

The buzzing was coming from the compressor control valve, the 209 uses a variable displacement compressor, so it was trying to keep up with the demands of the ACC. At full displacement, but with low refrigerant- it buzzes, its not from lack of lubrication. When they replace the leaking evaporator and dryer(which takes about 4-5 hrs BTW, but pays more than that- this disclaimer is to stop all --no way, I can do it in 2 hrs, but I paid 8 hrs BS), and fill the system with the replacement oil (can't remember what an evap adds, I want to say 4 ounces), your car will be fine.

Hope this helps...