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

pwood999 · Aug 12, 2023

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 ?

kermit_rr · Aug 12, 2023

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

pwood999 · Aug 13, 2023

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

pwood999 · Aug 13, 2023

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.

kermit_rr · Aug 13, 2023

Can you check the heat exchanger in the cabin?

pwood999 · Aug 13, 2023

kermit_rr said:
Can you check the heat exchanger in the cabin?

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.

kermit_rr · Aug 13, 2023

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

Rubberknees · Aug 13, 2023

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

Or just sit there smoking a ciggy

Mark Piercy · Aug 13, 2023

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.

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.

Mark Piercy · Aug 13, 2023

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

Datatek · Aug 13, 2023

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.

pwood999 · Aug 13, 2023

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 !!

Grrrrrr · Aug 14, 2023

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.

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

kermit_rr · Aug 14, 2023

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

It can't do that, can it?

Grrrrrr · Aug 14, 2023

kermit_rr said:
It can't do that, can it?

I would imagine there's a safety valve somewhere.

kermit_rr · Aug 14, 2023

Grrrrrr said:
I would imagine there's a safety valve somewhere.

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

Datatek · Aug 14, 2023

Grrrrrr said:
I would imagine there's a safety valve somewhere.

Not that discharges to the atmosphere.

pwood999 · Aug 14, 2023

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.

pwood999 · Aug 18, 2023

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)

pwood999 · Aug 19, 2023

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.

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

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