AC leaking from... ?

[632 Regal]

95 530

My AC has always been on the warm side but did work for years like that. Last year I charged the AC because I found a couple cans of R134. Was a fail due to my manifold hoses being loose. So 2 months ago I charged it with 4 12oz cans and it worked great. Not a big fan of AC and I only use it to defrost the windshield. Today it's raining and the defrost / AC trick didn't work so I turned it all the way cold and nothing, just outside temp air. So low the compressor wont even turn on.

Where are common AC leaks found on the E34? Compressor seemed fine, no noises or oil around the pulley but it's leaking somewhere and pretty fast I would guess.

Any help, guesses or advice appreciated.

[shogun]

pipe connections between engine bay and the cabin. Basically you have to check all this http://bmwe32.masscom.net/johan/aircon_o-rings/aircon_o-rings.html

[632 Regal]

Egads. I think I'll try a can of stop leak first. It's R134a with a dye and some PA100 oil. Read good things about it sealing O rings.

https://i5.walmartimages.com/asr/743d8edd-38fb-4f5e-96c1-569b29e65c5a_1.83adef8affc0006f1231bc618a87b41d.jp eg?odnHeight=450&odnWidth=450&odnBg=ffffff

[genphreak]

I usually add an amount to reach correct pressures using a top-up can and valve, and then drive the car around in the heat for a week or so: If there is refrigerant noise in the cabin (I guess this is boiling fluid in the evaporator lines under the dash), I add 10g at a time, until it becomes quiet.

I do if I'm not going to evacuate the system, as it is hard to evaluate the right amount of refrigerant and gas to add. The pressures simply do not tell you enough about the volume of liquid refrigerant in the system, and there is no other way without doing a full recovery/recharge.

Of course the right way is to replace all the line seals like Johan32 does, but I replace the valves and the drier as well. They are cheap (US$6 or so) (not like the little shrader valves in most cars) on eBay. Doing this requires removing the compressor, draining it of oil. After adding new o-rings, a new drier and buttoning it all up, evacuate and test for leaks. That takes hours before you can begin to recharge (weighing the amount that goes in, as well as adding the correct volume and grade of PAG oil through the line, assuming its not had an ester based oil added at some point (very rare around hereabouts)

I've always suspected and changed the high and low pressure filling valves (they come complete with a sealing rings) on the lines near the bulkhead. I feel they leak at age- the internal seals can only last so long.

Recently I stopped doing o rings on non-R12 E34 and just recover the gas left the system, replace the fill valves, drier, R134a and oil.

So far so good, but won't know for a few years more for sure. I'd normally do the TX valves always, except on RHD E34 doing this (and the other o-rings all the way through the circuit) takes too long as the TX valve requires dropping the steering column as well as everything else. This introduces hours and hours of extreme contortions that are really well worth avoiding.

[632 Regal]

I've always suspected and changed the high and low pressure filling valves (they come complete with a sealing rings) on the lines near the bulkhead. I feel they leak at age- the internal seals can only last so long.

Checked mine at top off and did the spit test on both valves and was good. Plus the caps have a rubber seal. I'm guessing the O-rings at the bulk head are a problem. Going to try the fix a flat before tearing into anything.

[genphreak]

Checked mine at top off and did the spit test on both valves and was good. Plus the caps have a rubber seal. I'm guessing the O-rings at the bulk head are a problem. Going to try the fix a flat before tearing into anything. If the system had charge, the only way to know if the valves leak gradually is to test under serious pressure (hot day/run time/spit will dry real quick).

Or if the system has been working fine and you wait till everything is cool and quiet and you listen for a an ever so slight hiss when removing those cover caps. I've come across enough of those alone to not trust those valves- and even with a drop of PAG oil in those little sealer caps. There is just no way they can resist the run-time pressures if the main rubber in the valve is compromised, but they will certainly pressurise if the valve is leaking- hearing it is the hard bit, unless you can rely on a green dye to point you to the problem.

[632 Regal]

If the system had charge, the only way to know if the valves leak gradually is to test under serious pressure (hot day/run time/spit will dry real quick).

Or if the system has been working fine and you wait till everything is cool and quiet and you listen for a an ever so slight hiss when removing those cover caps. I've come across enough of those alone to not trust those valves- and even with a drop of PAG oil in those little sealer caps. There is just no way they can resist the run-time pressures if the main rubber in the valve is compromised, but they will certainly pressurise if the valve is leaking- hearing it is the hard bit, unless you can rely on a green dye to point you to the problem.

The fix a flat supposed to have a dye in it which I will keep an eye out for. Not sure the time frame for me to get the goods either but hopefully soon.

[winfred]

a cheapo uv flashlight really makes the dye pop, the ones that project purple light don't need the yellow glasses like the "nice" blue ones that are usually too bright to see small leaks, my favorite is the $9 one thats usually by the registers in lowes, purple aluminum 3 aaa's, about 5" long, i call em a piss light as they are usually billed for finding pet "spills" (this light works much better then the $50-110 ones off the tool trucks, which really annoys my coworkers that i suggested to go get the $9 piss light) you can also turn off the lights and gross out the ol lady by walking around the house or motel room at night, esp if you have pets

evaporator leaks are not uncommon, but the 4 o-rings at the expansion valve attached to the evap is common, a juicy leak can be seen with dye at the condensate drain tubes on either side of the trans (exhaust side would be the valve side) lower corners of the condenser are not unheard of but the oil staining will be visible without dye (btw the dye is water soluble so enough rain driving can wash it off, also the condensate in the drains, but usually a little will hang around)

[632 Regal]

Thanks Winfred, going to check these out.