SeanR

Solinoid valve full on one side, clear on the other which means that the desiccant didn't make it up to the rear A/C expansion valve.

davek9

That was a good find and will save you more flushing

Sean do holding a vacuum over night (using a HF Pump and gauges) give an indication of where the leak could be?

thanks!

SeanR

Nope, if it holds vacuum over night then you will be fine. If it leaks pulling vacuum then you will have to change things out until you find it. Long and tedious. If I were you I'd go in and change all the seals, vacuum it down and if it still leaks you are left with hoses or the compressor. That's where it gets expensive. Figure $500.00 on a good rebuild compressor or get yours done for $200 or so. You can get the hoses rebuilt if you have someone who can do it good. If $$'s no object, order the hoses from Roger, replace all the seals and don't worry about it for the next decade.

dr bob

I'll toss a few thoughts in here...

The "holds vacuum test" has a maximum differential pressure across the leak of less than 15 PSI. The system is static at 100 PSI or so on a summer day, and might have pressures as high as 350 PSI on the high-pressure side on a hot day sitting in stopped traffic. In addition, the vacuum will actually tighten o-ring connections slightly, while higher pressure in the system will push those connections apart. Bottom line is that passing the "vacuum test" says that you don't have any -big- leaks.

UV dye for leak checking is an acceptable method, but relies on having all the connections clean, accessible, and directly visible. The dye mixes with the oil in the system, and tracks out of the leaky connection, fitting, seal, or hose with that oil. To find the trace of dye that's leaked out, you need a good UV light and an otherwise-dark workspace. You get to inspect every connection, fitting, seal, and hose with the UV light to see if there's a telltale glow from the dye. As Sean mentions in his description of the solenoid valve for the rear air, that means that the pass seat comes out, rear console is apart to expose the rear expansion valve and the evaporator connections, car is on a lift or stands to see the lines from the firewall connections to the bulkhead fittings under the seat. That's just for the rear system. In the front, the lines are tucked next to the passenger side of the engine by the coolant lines, up under the passenger side exhaust to the compressor, at the fuel cooler on the firewall under and behind the air filter, and under the cowl cover for the expansion valve and the connections to the evaporator. Plus the condenser and drier connections in front of the radiator. Except for the connections by the radiator, no connections or hoses are visble for UV inspection without some disassembly. Good News is that you can disassemble and clean all those locations, reassemble, add the dye, run the car for a day, let it cool, disassemble and inspect everything with the UV light to ID the leaks (note the plural).

For all that work, in my opinion, you might as well do the same disassembly and clean, replace all the old o-rings and seals with new type, rebuild the hoses, and know that you stand a fighting chance of having a system that will work for a while. Original systems will have multiple leaks, as every o-ring seal on a connection or hose is now 20+ years old. Replacing the first one or two you find now is a band-aid on a festering wound. No AC leak is self-healing, and small leaks only get bigger. The leak that carries oil out with dye in it has been carrying oil out for as long as it's been leaking, so you don't really have a clue how much oil is left in the system and how much needs to be restored. All these things point to the need for serious attention, especially for systems that have just been "topped up" with refrigerant to keep it going a little longer. Need a winter project? Got one for you!

SeanR

Good points on the vacuum leak vs pressure leak. It's been a while but I did have one leak under pressure but not under vacuum, that might have been the one where I went ahead and got the nitrogen set up. Now I always pressure test the system before pulling down then filling. Easier than pulling a vacuum on it and waiting to see if it holds and then repeating the process but not everyone has access to that stuff.

davek9

Understood, well at least both cars are clean so a leak should be easy to spot once I dissemble to expose as advised.
So far I have replaced most O rings w/ the assemblies when I did dryer and expansion valves on both cars, I've not replace any hoses as yet or compressors.

Time to buy some dye

Thanks guys!

Dave