Leaking Air Con System


Active Member
Jul 25, 2002
W211 E320 CDI
About May/June this year I had the air con system regased but to find it not working again only two months later. I called the air con specialist back to check where the leaks are. He used the ultra violet light and spotted a gas leak on the air con radiator inside the engine compartment. As the specialist could not tell me exactly how much he would charge and it may invalidate the warranty, I have to take it to the dealer and have it looked at.
After 7 weeks' wait ( that's how long I have to wait for the appointment), the car is booked in the workshop for 4 days. I dropped the car there 08<img src="http://www.mbclub.co.uk/iB_html/non-cgi/emoticons/wow.gif" border="0" valign="absmiddle" alt=':0'>0 on Tuesday morning. Called the dealer at 16:30 on Tuesday and they told me they have not started on the car yet - what a waste of a whole day.
Wednesday morning they called back and said they couldn't find any leaks on the radiator but the evaporator could be leaking but reluctant to take the whole dash out because it is an involved job. I then pointed out where the leak is but they said it is probably coolant. Then I mentioned the UV light and they said OOOOH! let us check it again.
Obviously they are not equipped for the leak detection but how come they insist the flourescent dye to be included as part of the gas recharge?

Other items need fixing/replacing in these 4 days :-
1. Faulty petrol gauge sender
2. Gear slipping - I have been told a faulty sensor
3. One of the Catalytic cconverters

1998 E240 Elegance 68K

Tony M

Active Member
Nov 20, 2002
Porsche 997 Turbo Cab
Generally ,flourescent dye is not added to any system new or recharged unless the person initially detecting the leak cannot find the leak.

Leaks are normally detected using an electronic device which, in the crudest sense, 'sniffs' the presence of leaking refrigerant and it 'Beeps' accordingly.The closer to the leak, the more frequent the 'Beep'.Sometimes one can't find exactly where the leak is, and 'Dye is introduced which shows up when a UV pen is used.

Don't be too hard on the garge that could not detect the leak. some seals only leak under movement, some leaks only occur under full pressure when the system is working hard, and there is no way anyone can poke a leak detector into an engine running at full throtle.

If you have an undetectable leak, the first step is to have the system pressurised with oxygen free nitrogen. the standing pressure can be taken and rechecked say 8 hours later. if the pressure has dropped ............There is a leak.  

Once a leak is confirmed then a standing charge of refrigerant can be added to the system and a 'Sniffer' leak test carried out around all pipe joints ,seals and 'U' bends at the ends of the evapoator and condenser. If a leak is found, all well and good as it can be repaired or the component replaced.

If that fails to show a leak, then a mix of refrigerant and OFN can be added under high pressure to try and find the leak.

If that fails the sysem should be partially disconnected and broken down into say 3 parts, and the process repeated for each section of the system.

If that fails to find the leak, as last resort try Dye.

If that fails, then sell the car !!!   <img src="http://www.mbclub.co.uk/iB_html/non-cgi/emoticons/alien.gif" border="0" valign="absmiddle" alt=':alien:'>

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