P38A AC suddenly lost pressure - Now re-gassed but got strange noises

Some time in last two days my AC stopped working. Checked the pressure when I got home yesterday, and it was down to about 10psi.

Decided to pressurise it & do the soapy water check for leaks, but cannot find any. Yes I will be pulling a vacuum afterwards before doing a proper refill !!

So far it's held 100psi for over an hour. Any ideas why it might have suddenly dropped ?

Assuming that's running pressure? I'm no expert but the low side shouldn't be that high, as far as i know. What are the pressures normality?
Dodgy valve or compressor can do that

No that's the empty system pressurised with air so I could check for leaks . . .. . . but cannot find any !!

Update: This morning it was down to 50psi, so something is leaking. Also sprayed soapy water all over the gauges & no signs of bubbles. It's clearly a slow leak, so gonna need UV dye to find it. I have vacuumed is down to -30 on gauges & see what happens today.

Can you check the heat exchanger in the cabin?

kermit_rr said:

Can you check the heat exchanger in the cabin?

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AFAIK Not easily without pulling the dash. While it was under pressure I got my step-son to listen for hissing using his younger ears - nothing !! Not sure if I can see it with glovebox removed, but will check.

Could you pressure with propane? If it's leaking in the van you'd soon smell it. Molecules might be too big to leak though

kermit_rr said:

Could you pressure with propane? If it's leaking in the van you'd soon smell it. Molecules might be too big to leak though

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Or just sit there smoking a ciggy

pwood999 said:

AFAIK Not easily without pulling the dash. While it was under pressure I got my step-son to listen for hissing using his younger ears - nothing !! Not sure if I can see it with glovebox removed, but will check.

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You can get a sniffer tool for behind the dash and for checking vents but it'll need to be charged somewhat to detect a leak inside the car.

Any green oil traces around the compressor connections, the compressor casing or condenser?

Top right corner of the condenser seems to be a favorite place for pin hole leaks.
On one of mine, a recharge would last 2 weeks, the vac test at the garage showed nothing. The dye in the recharge located the pin hole.

No dye traces anywhere. My guess is Kwik**** didn't put any in when they re-charged it earlier this year. Got some dye coming this week, so will suck that in & then pressurise to see what I can find.

No signs on condenser. I removed the foam water trap when I replaced it a few years ago. Still looks like new apart from the bugs in the front !!

pwood999 said:

Update: This morning it was down to 50psi, so something is leaking. Also sprayed soapy water all over the gauges & no signs of bubbles. It's clearly a slow leak, so gonna need UV dye to find it. I have vacuumed is down to -30 on gauges & see what happens today.

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Thermostatic expansion valve on the bulkhead knackered so it is venting to atmosphere to protect itself?

Grrrrrr said:

Thermostatic expansion valve on the bulkhead knackered so it is venting to atmosphere to protect itself?

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It can't do that, can it?

kermit_rr said:

It can't do that, can it?

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I would imagine there's a safety valve somewhere.

Grrrrrr said:

I would imagine there's a safety valve somewhere.

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Maybe.. on/in the compressor? I don't know

Grrrrrr said:

I would imagine there's a safety valve somewhere.

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Not that discharges to the atmosphere.

On GEMS there is a pressure relief valve in the high pressure line from the compressor to the condenser. Item 9 in the diagram.

No signs of leaks there with soapy water. I sprayed every joint & pipe, except the inaccessible evaporator. Might need a more soapy mix until I get the dye in the system.

Update. System held vacuum for 5 days with no problem, so got it re-gassed today at ProTyre. Their machine definitely knew the correct P38 gas & oil quantities, so that was good. 20min vacuum test at -1000mBar passed, and the machine proceeded to fill & eventually pressure hold test. They assured me it usually adds UV dye, although I didn't see much change on the UV bottle. We will see how long it lasts this time.

On a side note, I left my gauges with all valves closed & 100psi in them for 4 days in the garage. Gauge needles have only moved about a needle width, so they seem to be sufficiently leak free.

Wondering about buying one of these 2kg or 5kg cylinders so I can do the other family cars that I get nagged about. (My P38 project, BMW 120D & Corsa Hatch)

Need to check idler pulleys tomorrow, but getting a strange tinkling noise when AC is on. It goes away if I switch AC off, or unplug compressor.