mj1pate

I have the pass seat removed about to prep for full AC system flush. I have the rear AC solenoid removed. I need advice please:
1) the solenoid is full of original oil and I’m changing to 134a. What should I flush the solenoid with? Ester oil? Standard AC solvent flush?
2) how to more safely flush the refrigerant lines inside the cabin? The area around where the solenoid has been removed is the lowest point for the refrigerant lines. But how to deal with flush that flows down so close to the floor? How to evacuate flush coming down so low in the cabin?
Thanks for advise!
1986.5 with auto transmission

ammonman

When I had all my A/C lines rebuilt (off the car) and flushed the system I used brake cleaner followed by lacquer thinner. I knew someone had added "leak stop" at some point and I wanted to get as much out as possible so I used a pretty aggressive solvent mix. Get some lengths of clean vinyl hose to clamp over the various tubes, then pour/spray the solvent and blow out with compressed air. I cleaned everything that would get new hose crimped on before I took it to the hose shop. Be sure to wrap the "discharge" end of the clear hose in a mass of towels to catch the solvent and oil. I cleaned the rear evap out of the car but the front evap and condenser stayed in place with hose attached to introduce the flushing solvent and catch the waste. Once everything flushes clean let the system sit for a couple of days so the unions are free of solvent. Then, lube and install new o-rings before closing everything back up. Once closed, attach a vac pump and let it run 24 hours to vaporize any remaining solvent. Break the vacuum with 12 oz of refrigerant to collect any remaining moisture/debris/solvent, then vac again for 24 hours. Charge in the appropriate amount of liquid refrigerant and enjoy your awesome A/C!

mj1pate

Thanks!
the rear AC solenoid is full of r12 oil. What is the best way to flush out the solenoid?
can it be flushed with AC solvent flush? Or flush it out with ester oil?

AirtekHVAC

TSI Supercool 27361 A/C Flush Gun with Flow Control Valve and Improved Spray Head https://a.co/d/7CoSQnT

something like this is what you want..

mj1pate

thanks… I actually have them. Not expected to harm the solenoid ?

FredR

Michael,

Some pointers from my perspective-
1. The flush solvent of choice is acetone- as I am aware it is what is inside the proprietary flush cans and works well.
2. The rear ac solenoid is easy to remove and push a little solvent through it.
3. I have one of those flush guns that Ron linked you to- they are very useful- driven by compressed air.
4. Once you have flushed through the system as I understand it is important to replace all the O rings to ensure no damage from exposure to the flush solvent.
5. It is not clear what you intend to do to get the old oil out of the compressor. I susect the easiest way is to drop the compressor and its hoses and flush externally.
6. When I did my system after a compressor grenaded/seized a couple of years ago I chose to remove the condenser to assist the flush process.
7. For the rear ac it is easy to remove the evaporator for the flush process.
8. I flushed the main evaporator by removing the expansion valve and using an old expaansion valve I drilled straight through it and then mounted it to provide a clear flow passage.
9. The rear ac unit makes flushing a bit tricky- I made a couple of blank connections to blind of the piping to the rear unit so that I knew the flush medium had gone evenly through the system. Note my system had previosuly been converted to R134a and I use PAG46 oil.
10. There is a short section of hose on the fllter drier discharge that sort of loops around the side of the radiator- this is captive and is nigh on impossible to replace with the egnine in situ. The hose itself gets saturated with mineral oil from the R12 useage and thus acts as a "barrier" that system experts reckon holds solid even after flushing but it remains what it is- "old hose". I have not had any problems with mine that I know of post flush but...?
11. Leaving the system on full vacuum for 24 hopurs does no harm albeit I personally believe such is not needed but for sure the system should hold vacuum for ever and a day and think it is a good practice.
12. When you come to fill the system not that if you connect the fill cylinder to the systen and purge any air in the hoses it takes about 200gms of gas to bring the system up to pressure in equilibrium with the fill cylinder. Once such amunt of gas is in the system you can then fire up the ac system and it will work. I typically run the system and introduce more gas until the total is 1kg- that seems to work nicely on my GTS, Theoretically R134 takes a bit less gas than R12 weight wise but...?

Trust the above helpful

mj1pate

Thanks Fred… flushing the internal of the compressor is ok? With AC flush? Or should I repeatedly drain and fill with ester oil to dilute the old R12 oil?

FredR

Michael,

I would think the best way is to remove the end caps of the compressor and wash/rinse the internals directly with the flush media then fit new body O rings and a new seal. Then you can fill with PAG46 as specified. The ester oil route is a sort of half way house solution [as I understand] in that you drain out the old mineral oil and then stick the ester oil in on the basis that it is compatible with any remaining mineral oil and also with R134 gas. Doubtless others may have some more definitive views.

mj1pate

I would also like to pressure test my compressor before I install it.
is pressure testing if with pretty dry (5 micron element + desiccant) air suitable? Directing 100 psi air thru a manifold into both high side and low side. Any issues?
thanks

FredR

The compressor is designed to take full test pressure in the static condition. Testing with air at 100 psig is pretty much meaningless- as I understand they are factory tested at something like 350 psig probably with nitrogen. I tested my rebuilt compressor with air at 300 psig- saw no need to condition the test air as the compressor was going straight back into my motor after the test and then new drier, vacuum etc. Under normal operation the compressor typically see something like 230 psig and usually there is a healthy margin between normal operating pressure and design pressure that is controlled by the setpoint [relief pressure] of the safety valve that protects it

mj1pate

As regards pressure testing the compressor, I am going to try and attach R134 fittings to the R12 ports on it, so as to attach a manifold. The stem on the discharge R12 may be to short to fit an adaptor onto it.
Are there adapters for the compressor hose ports that will allow applying air pressure there?

Hilton

I flushed mine without the compressor attached - flushed the loop both ways using the compressor end of the hoses as an inlet and an outlet into a bucket. I actually flushed first with odorless mineral spirits, then with dry cleaning fluid to end up with no residue. Be warned - getting all the liquid out of the lines with compressed air is nigh impossible, use a vacuum pump to vaporise it, but expect the vacuum pump to suck some solvent into its oil on draw down, so watch its oil level carefully and replace the oil in it before final vacuum.

Also - after flushing and evaporating any residual solvent (I just reattached the compressor hoses without mounting it back on the bracket for this), plan to take apart and replace every single o-ring in the system, a new drier, and add the correct volume PAG oil to the (rebuilt or new) compressor. If your AC lines are old, get them rebuilt with correct barrier hose too.

My r134a conversion has been great even in Aussie temps - altho' I have manual 928's with a larger condenser than auto, which helps.

mj1pate

So, I think I finally have suitable r12 to r134 adapters so I can plug my manifold directly into my compressor and pressure test it thru the r134 fittings. But how do I seal off the refrigerant hose ports on the compressor for the pressure test?

FredR

The pressure test is a static test in that it only takes one flow path to pressurise and the low pressure side of the manifold set, if used, should be isolated or it may well be over pressured leading to mechanical damage.

For the pressure test a blanking plate is used on one of the compressor ports, usually the low pressure port that is physically bigger and the test media is introduced via a port adapter of some kind. One could test the entire circuit if one wished to do so but the main source of leaks is the compressor and particularly so the lipseal. I think it is better to test the compressor demounted and then do as we did, immerse the compressor in a bucket of water to test for leaks, That way you will pick up even the smallest of leaks. If you can test using R134 so much the better as I understand its molecules leak easier than those of air or nitrogen but it is all relative.

mj1pate

Just a follow up on system flushing.
I had disconnected the rear evaporator and flushed both the low and high pressure lines with flush directed into the rear evap line openings, with flush exiting near the (removed) condenser. The flush exited both lines looking clean.
…then I removed the under chassis lines feeding the rear evaporator and oil poor right out of the low press line as I lifted it out. Gravity really holds oil in those under chassis lines. Just be aware.
yes, once removed I flushed these lines individually.