W176 Persistent Leak/Low Refrigerant Noise

[matthewins]

Hi folks,

Bought a w176 in April 2020. A/C wasn't working from the outset. Took car back to dealer, it was leak checked and re-gassed. I knew this wasn't the end of it but all appeared to come good for the time being except the A/C made the hissing noise it makes when the system is low on refrigerant. I ignored the hiss for a bit until a few months later, the A/C starts to perform poorly. Took the car back to dealer, siting the original issues with the A/C and further leak checking saw the condenser and expansion valve replaced, along with relevant seals. System serviced to full yet the noise remained. Much back and forth ensued and car now back to dealer again and they've had it for the last six weeks. More leak checking to no avail yet the gas level has dropped again apparently. I'm assured they've leak checked everywhere they can but they're drawing blanks and everyone is losing patience. Is there a known hidden source of leakage that might not be very obvious to a car supermarket mechanic (he seems reasonably switched on, to be fair) that somebody here might be able to share please?

Many thanks in advance

Matt

 

[rf065]

I had a Ford Ranger regassed 6 times over a 6 month period. The garage kept insisting there were no leaks and simply regassed it every time. Reluctantly they investigated further and guess what, found a leak!
Having the equipment to service air con does not mean you know what you're doing.

 

[matthewins]

Thanks rf065. I can't doubt they've been looking for leaks. It's a very long story but four different garages have had a go thus far to no avail. Hoping someone here has some direction they can share.

 

[matthewins]

Correction. Bought car April 2021! Stupid new year.

 

[rf065]

Thanks rf065. I can't doubt they've been looking for leaks. It's a very long story but four different garages have had a go thus far to no avail. Hoping someone here has some direction they can share.

Maybe you need an Air Con Specialist and not four garages with air con equipment?
I was told years ago that the equipment most regassing places use, checks for a leak by applying a vacuum which can also hide a leak and show the system as sound. Where as a proper pressure test will expose any leak in the system.
None of this would explain why any of these garages cannot find the leak with ultra violet light and the dye inserted with a regass that is designed to show exactly where the leak is?

 

[LostKiwi]

None of this would explain why any of these garages cannot find the leak with ultra violet light and the dye inserted with a regass that is designed to show exactly where the leak is?

Exactly this.
A UV dye and UV light will soon find it.

 

[matthewins]

Thanks guys. I'm aware of the dye process and understand this had been used but you've got me wondering now so will have this confirmed.

 

[LostKiwi]

If they've used dye and can't see a leak under the bonnet it's almost certainly the evaporator inside the car. The usual place for hard to find leaks are the compressor seals but that usually sprays dye everywhere.

 

[matthewins]

Thanks LostKiwi. The evaporator being behind the dash, I guess? Doesn't sound like fun. Any experience on replacement/checking it for leaks? The current mechanic seems to be focused on replacing condenser seals, even though we've replaced the condenser, but you're saying compressor seals a good shout too? I've tried to send him the way of the compressor but I'm speaking through a non-technical aftersales lady and not sure the message getting through. I'll need to confirm if dye has been used for leak checking. Really appreciate your thoughts. Thanks

 

[mattkh]

. Really appreciate your thoughts. Thanks

What type of referigerant is it..?
Also, what is the mileage..?

 

[LostKiwi]

I'd imagine it would be r134a in a 176.

 

[matthewins]

R1234yf. 2016 plate, 14000 when bought in April '21. About 16/17000 now. Low miler. Often wondered if that hasn't helped.

 

[matthewins]

What type of referigerant is it..?
Also, what is the mileage..?

R1234yf. 2016 plate, 14000 when bought in April '21. About 16/17000 now. Low miler. Often wondered if that hasn't helped.

 

[LostKiwi]

R1234yf. 2016 plate, 14000 when bought in April '21. About 16/17000 now. Low miler. Often wondered if that hasn't helped.

Interesting. It's the replacement to 134a.

 

[mattkh]

Low miler. Often wondered if that hasn't helped.

Possibly, if only used on very short journeys.
Can the previous owner tell you what use the car was put to..?
I think it points to seals as they can deteriorate over time.

 

[matthewins]

The low miles and marks on the IsoFix hooks suggests driving to the local shops and baby groups! Not a bad shout but car was bought from a car supermarket who I suspect picked it up from an auction, ex-PCP, etc so not sure how easy it would be to contact the previous owner.

 

[matthewins]

By way of an update, compressor, expansion valve, condenser, evaporator (dash removal) all performed, along with countless leak checks, and it still leaks. Where's the secret leak location, that so far everybody who has worked on my car has been unable to find?

 

[joderest]

Perhaps there is a crack in one of the pipes

 

[mattkh]

Perhaps there is a crack in one of the pipes

Are you saying the crack will not show when using a dye, which has been done .

 

[joderest]

If its concealed and cannot be seen, or perhaps under the pipe.
As said before, any decent air con engineer worth his salt will find it, a lot come to your home.