j.fonder

I've muttered those words under my voice more than once, lol. He is a friend and trust me when I say, he knows these AC systems better than you or I.

ofelas

You forgot to mention 100% antifreeze equalizes the low & high side refrigerant pressures, you are slipping big time

Bruce M

Mark,
Your old R12 compressor is still working great in my 90 Dodge.
Have not had to add R12 to the system for the last 3 years

maybe368

Glad to hear that Bruce, the old girl lives on. How is the cooling system experiment going? Any problems?...Mark

Bruce M

Mark,
How often do you change your antifreeze?
Still using the original 100% with no problem at 100 degrees F and above.

maybe368

That is a good question, I ran the same antifreeze in my Fairlane for many years. I changed the antifreeze in the Cummins a few years ago, I posted a thread called "this is why I don't add water to antifreeze" or something similar, where I changed my antifreeze while replacing other cooling system components. The antifreeze looked so good that I still have 3 gallons of it in the truck for emergency use. So, to come up with an answer, run it as long as you are comfortable, for me it is many years...Mark

Edit: Here it is: https://www.dieseltruckresource.com/...freeze-313866/

edwinsmith

Just to horn in on the antifreeze question. I ran water when I was a kid until a radiator shop friend showed me what happens to your radiator without the rust inhibitors that AF gives you. Now I run 50/50 with no problems in most everything, I buy it premixed, except for my Kawasaki KZ 1300 which had an aluminum engine which I ran 100% AF with no problems at all.

SO my advice, use at least 50/50 but 100% ain't gonna hurt anything.

maybe368

Thank you...Mark

j.fonder

for the sake of beating a dead horse, i edited your quote.

edwinsmith

Well, I bought a new Expansion Valve, a new Receiver Dryer and new PAG 46 oil. Then I opened the system and took off the hose to the high side of the compressor. I ran about an ounce of PAG oil in it and then I started the truck. I ran the compressor about a minute at idle to blow out the old oil and flush the compressor. Then I poured the AC Pro flush liquid in the top of the Evaporator and let it set for about an hour. I corked off the bottom hole to get the maximum amount of flush in it. Then I blew it out with compressed air. I blew out the condenser and other hoses with air and then I reassembled everything.

The studs on the Receiver Dryer were messed up so one of them had to be swapped out with one from the old unit. When I pulled a vacuum on the system it had a leak. It wasn't bad but I didn't know if it was my gauges or a leak in the system. I added the oil with the vacuum method and pulled a vacuum again. Then I added 2 cans of R134a (24 oz) and I took the temp inside the outlet of the A/C. I got about 55 degrees. I added more R134a until it got down to about 42 degrees which was about 3/4 of the third can then I stopped.

It was then that I noticed seepage from the high side of the receiver dryer.

I torqued the nut down again as hard as I could and it seemed to stop but I have a feeling I'll be changing it again. I think I'll try a unit from a different vendor. Murray makes theirs in China and both the new ones had messed up threads on the studs where the lines attach.

The pressures seem normal now. The high side gets to just over 200 PSI and the low side is around 50 psi when it is running. as a test I added 1 can then stopped the compressor and the pressures equalized to about 75 psi on high and low. Then I added the rest of the R134a.

I'm very happy with it now. I just hope the leak is stopped. If it all leaks out I have more and I'll just buy another Receiver Dryer and slap it on.

I saw no obstruction in the Evaporator at all and the dryer seemed to be flowing so I don't know what the problem was unless it was a bad EV which I couldn't tell by looking. I'll disassemble it later on to see if I can find a reason.

Has anyone else had problems with the Murray parts from O'Reillys?

Thanks everyone for your help.

Edwin

Jim Lane

I have had a lot of problems with leaking receiver/ driers getting the flanges to seal, it is important to use the correct nuts, they have to have the big washer attached to spread the clamping force evenly.

When I flush my system, I tried using commerical flushes, one was citrus based, it did not work well and then I could not get rid of the smell.

So now using a flush gun I purge all of the components using acetone from both directions, I let it sit for about 5 minuets and then blow it out until it is dry this removes all traces of the old oil.

Remember, never flush the compressor or the drier.

I took an old H-valve and removed the metering valve then tapped the outlets to accept my fittings, this makes it a lot easier to connect my flush gun and air lines.

As I said before, I rejected quite a few evaporators until I got one that passed my QA even then I had to work with it in a vise to make it fit the housing.

Jim

edwinsmith

I have the correct nuts. I am also using the Nylog Blue sealant. The problem seems to be the studs on the dryer are damaged to the point that it is difficult to tighten the nut down enough to seal. It's still working today so it may be good. If the refrigerant leaks out eventually I'll try replacing the studs but the thread locker they used made it nearly impossible to get the bad stud out of the outlet side. The inlet side was then leaking.

My next little job is replacing the serpentine belt because the oil splashed on the current one makes it squeal very loudly. Got to figure out how to work the tensioner since the square slot it difficult to get at.

Edwin

edwinsmith

Today I replaced the belt to stop the squealing because of all the PAG oil that had been sprayed on the old one. The I took it out for a spin. While waiting at one of SoCal's luxuriously long lights the Pop OFF valve went off again and sprayed the new belt with oil.

I got it back home, it's still cooling BTW, and checked the pressures. The high side was over 300 Psi. The low side was around 50. I noticed the 30 amp fuse I had placed in the line for the aux fans I put in front of the condenser was blown for the third time so I replaced it again. The high side pressure dropped immediately to around 200 Psi. I went and got some aluminum foil and wrapped the fuse in it and I'll begin the search for a slo-blow fuse. I think the high temp in front of the condenser is melting the fusewire. I may have to relocate it to a cooler place.

I don't think I lost more than an oz. or two of oil so I think I'll run it that way. I may go and get an oil charge and put in it later on when it cools off. It's 98 degrees here now. Doncha just love SoCal?

Edwin

j_martin

Yer right. a fuse is a low melting point metal, so it doesn't get hot enough to start a fire before it parts. An extra 50 degrees in it's environment makes a big difference.

Be sure you have enough overhead in the wiring and fusing for fans. If they draw 25 amps, a 30 amp fuse and 10g wire would be pushing it.

Obviously you figured out the spring loaded idler pulley. I use a 1/2 drive ratchet and a piece of pipe.

edwinsmith

I have one with a 3/8 hole so I use a 3/8 ratchet. I have to pry the shroud away with a crowbar to get the ratchet in then I use the pipe method. After a sufficient amount of skin off my arms and knuckles is removed I got it changed. I used Brake Parts cleaner to get the oil off the pulleys and the new belt was quiet as ever.

After the oil spray on the new one it squeals a little but nowhere as bad. I hosed it off ASAP so hopefully it won't be to bad. I drove up to Ridgecrest today with the air on. It's not as cold as I like so maybe a bit more R134 is needed since some was lost. I'll add a can of oil charge which is about an ounce just to be on the safe side. I'll be moving the fuse also. Yes I have #10 wire from the battery to the fans through a relay which is energized by the compressor coil. Seems to work OK except for the fuse blowing. The 2 fans are only supposed to draw 21 amps.

I'm wondering if I should replace the pop-off valve with an overpressure switch to cut the compressor instead. Does anyone know of an appropriate part? The pop-off seems to go at about 600 psi.

Edwin