W203 Air con gas leak

[fwd]

Hi again...
Could a STAR diag machine pinpoint source of a gas leak at component level, ie condenser, pump etc?
I have a leak and can't locate it with dye as not able to pressurise the system sufficiently via a canister due to the large escape of the refrigerant and the short operation of the compressor due to the quick loss of pressure!

 

[brucemillar]

You could try a gas sniffer tool. If it's that big a leak you should be able to find it by pressurising the system and listening as you go. Usually the condenser rad is holed.

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[Davo]

In the same boat here, I learned a lesson on Saturday - I bought a W203 when it was 0 degrees outside and convinced myself that the aircon was just fine when an icy blast came from the vents!

Now looking through the service history I find a quote from MB at the last service offering to strip the heater housing to investigate an aircon fault for 20 hours labour. Having seen the clip on Youtube taking out the dash to get to this it seems the car was built around the damn thing.

The quote says 'on initial nitrogen test, possible failure of evaporator or expansion valve'. Not that I don't trust MB, but Halfords do a 'Superseal Air Conditioning Leak Sealant' for £19.99 - does anyone think this would be worth a punt on the offchance that it actually works?

 

[fwd]

Thank you both...
In my case, all was well and ice cool during the hot spell we just had (seems like years ago now) and suddenly one day there was a drop of almost 50% efficiency followed by no cooling at all the next day. Took it for a quick re-gas and was told that they could not do it as the system was leaking.
I subsequently purchased a charging adaptor, dye and canister and attempted to pinpoint the leak. System would charge and hold pressure but as soon as the AC is switched on, the compressor would run, the pressure drops rapidly and the clutch disengages due to loss of pressure before the dye has a chance to circulate and be detected using a UV light.
As the system needs to be charged for the pump to operate, the engine needs to be running and as such impossible to detect leaks audibly!
Was on the verge of coupling a metered supply of compressed air to keep up some pressure so that the compressor stays on and circulate the dye... is that feasible I wonder!!!
Having said all that, the purchase was not wasted as I have managed to successfully recharge our C250... so not all lost

 

[fwd]

Davo... while researching places that did AC re-gas, I am sure I read somewhere in the small print that leak sealant would not work if there was a large leak as only effective for small leaks past dry seals etc... but for 20 quid I suppose it worth the try.

 

[Davo]

Yes, worth a try I thought, just because MB think there is a leak doesn't make it so. If there had just been a gradual loss over the years I'm not convinced that would stop them charging megabucks to strip the system anyway.

Of course when the sealant goes everywhere behind the dash and all over the carpets I may think differently....

 

[E55BOF]

Fwd, if it lost 50% of its efficiency overnight, and gave no cooling at all the following day, there IS a leak, and a serious one.

How did you manage to get the system to 'charge and hold pressure' without running it? The proper way to fill it is to run the engine and compressor; the latter circulates the gas from the recharge canister. I don't think you CAN fill it without running the compressor.

"Possible failure of evaporator or expansion valve", eh? That's just an invitation to have it checked out at MB main dealer labour rates.

Most aircon leaks are traced to the evaporator, a.k.a. condenser. Take it to an aircon specialist; he will probably initially fill it with nitrogen and use a spray of soapy water on the evaporator/condenser to try to find the leak.

Personally, I wouldn't use leak sealer in an aircon system; it hardens to form the seal on contact with the air, and if you subsequently have to open the system up to replace a part, guess what gets into the system once the refrigerant is gone...

 

[ringway]

In the same boat here, I learned a lesson on Saturday - I bought a W203 when it was 0 degrees outside and convinced myself that the aircon was just fine when an icy blast came from the vents!

Now looking through the service history I find a quote from MB at the last service offering to strip the heater housing to investigate an aircon fault for 20 hours labour. Having seen the clip on Youtube taking out the dash to get to this it seems the car was built around the damn thing.

The quote says 'on initial nitrogen test, possible failure of evaporator or expansion valve'. Not that I don't trust MB, but Halfords do a 'Superseal Air Conditioning Leak Sealant' for £19.99 - does anyone think this would be worth a punt on the offchance that it actually works?

Replacing the evaporator is a huge job.

My previous S210 had a duff evaporator and after I sold the car (with the fault as known) Olly and Jack at PCS carried out the works. LINK.

If you go to John Delany Motors in Stockport, they will give a fair price to do the job. They are a trustworthy outfit and John the owner is a very nice guy. IIRC they quoted me around £900 for my S210.

 

[E55BOF]

OOOPS! My mistake (well, it was late at night...) The CONDENSER is the usual source of leaks, and it's an easy job to replace; the EVAPORATOR is at the other end of the system, inside the car

Get a proper diagnosis, which will include checking the condenser (and hope it's that...), before arranging for the repair.

 

[fwd]

Fwd, if it lost 50% of its efficiency overnight, and gave no cooling at all the following day, there IS a leak, and a serious one.

How did you manage to get the system to 'charge and hold pressure' without running it? The proper way to fill it is to run the engine and compressor; the latter circulates the gas from the recharge canister. I don't think you CAN fill it without running the compressor.

"Possible failure of evaporator or expansion valve", eh? That's just an invitation to have it checked out at MB main dealer labour rates.

Most aircon leaks are traced to the evaporator, a.k.a. condenser. Take it to an aircon specialist; he will probably initially fill it with nitrogen and use a spray of soapy water on the evaporator/condenser to try to find the leak.

Personally, I wouldn't use leak sealer in an aircon system; it hardens to form the seal on contact with the air, and if you subsequently have to open the system up to replace a part, guess what gets into the system once the refrigerant is gone...

Totally agree E55BOF, which is what I said. I could only charge the low pressure side of the system up to the compressor and as soon as the A/C is switched on, the pressure quickly decays indicating a high loss downstream of the compressor, and as such the dye I introduced in the system has hardly had a chance to circulate and be detected before the clutch disengaged and the compressor stopped (engine still running of course!)
That was also the reason for my question about the feasibility of pressurising the system with metered compressed air (continuous and free!!) while trying to pinpoint the leak either by spotting the escaping dye with a UV light or using "snoopy" type fluid/spray and looking for bubbles! as any audible detection would not be possible due to the noise from the running engine.

 

[andy27168]

Visually check the Condensor first, the one by the cars radiator (as opposed to the evaporator which is buried deep inside heater box deep behind dashboard).
A/C systems the engine is run and when being recharged are sucked out and held at a vacuum for a specific period of time half hour-hour, if it holds this vacuum then the system is recharged as well as specific amount of refrigerant and oil for the compressor is added, and 99 times out of 100 some UV Dye.
Recharging can only be achieved with engine running and system turned on, if in your case there is a drastic leak then it is I believe actually illegal for a company to attempt a recharge knowing this.
Common causes of leaks for the 203 A/C system.
Condensor, Compressor, Seals on pipe unions at compressor, and dryer.
Condensor is very very common, evaporator failure is rare, and I bet the utube video of the dash removal was for heater motor flap replacement rather than evap replacement.
The chances the car being on its original A/C charge I would of thought would be rare, so the chances are it had dye in it anyway.
Remeber now the system has a leak it is effectively open to the atomsphere and should have the Dryer replaced on system reinstatement.
Blowing compressed air through the system is a no go as compressed air is inheritently wet. I think that is why they carry out Nitrogen tests on A/C systems as mentioned in post above.

 

[Stratman]

As Andy said above, check the condenser first as it's the easiest and a common failure.

Just open the bonnet and you'll see the condenser in front of the radiator, it's the wavy metal tube. Examine it for corrosion and pinholes, also look for tell tale marks of escaping refrigerant.

 

[brucemillar]

Post #2

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[fwd]

Thank you all

andy27168: that rules compressed air then so back to the drawing board ;-)

Stratman: I'll have to have a good shufty and see if I can see any visual indications.

brucemillar: I hear what you say (post #2) but due to reasons mentioned earlier, I am unable to pressurise the system, so unable to either hear the leak or be in a position to sniff it out. ;-(