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Best oil for GM R4, and is my quantity OK...

mckpaul on Thu October 04, 2007 5:48 PM User is offlineView users profile

Year: 1984
Make: Chevy
Model: C-10 1/2 ton
Engine Size: 305
Refrigerant Type: R-134
Country of Origin: United States

Just joined, this is my first post. Been looking and reading. Lots of great info here!
I'm not an AC tech, but been working on my own cars for 30 years. Have a decent working knowledge of AC systems.

I'm about to re-do my AC on my 84 Chevy truck, it has an R4 compressor. Had the truck for 4 years, never worked, don't know the history, and there's no charge in it now.
I have a replacement accumulator rated for R-134, a new oriface tube, a new cycling switch for R-134, new O-rings, and will buy a new compressor, don't want to take a chance on the old one. I plan to flush the condenser and evaporator and any other tubing or hoses with miniral spirits or paint thinner. I have looked all over the net and found info about how much oil to use, a little vague, but have found that the R4 compressor needs 6oz of oil, not sure it that's for the compressor or the entire system. The sticker on the compressor also says 6 oz.

I found an AC Delco document (05D-J-114) that tells me instead to drain the oil from the compressor and basically put back 2.5 oz of oil if less than that was drained out, or match the amount drained out if it's more. Then, assuming all the other parts were flushes and are completely dry, add 1 oz of oil to the condenser, 1.5 oz to the evaporator, and 1 oz or 2 oz to the accumulator or more depending on how much I drained out of the old one. So now I'm thinking there should be about 6 to 7 oz of oil for the entire system. By the way, new accumulators don't come with any oil in them do they?

Other than quantity, oil still remains as the biggest question as to what type, PAG or Ester oil. I found HUGE write ups about pros and cons for each, which leads me to believe I can use either. On one hand, no matter how much I flush, I'm sure there will be some R-12 and mineral residue left in the system, and the AC Delco document specifically states "There are NO ESTER lubricants approved..." (however this report was written in 2005). I read where some compressors depend on a foaming effect of the oil for proper lubrication, and ester doesn't foam like the mineral oil did. But at the same time, it doesn't look like PAG oil will be happy in the long run if put in a system where R-12 and mineral oil EVER were. And everything I read says the R4 prefers 150 viscosity oil, and Ester oil is 100 viscosity, but seems to be the preferred oil...AAAARRRGGG!!!

I have no idea what oil will come in the new compressor (not sure if I'll go new or reman., but will be an over the counter auto parts store unit) I did see an artical that stated origina OEM R4 compressores from the 80's were not candidates for R134 retrofit because of the valves, but Factory Air (brand) replacements were. I assume any compressor I buy might come with PAG oil instead of mineral since R-12 isn't really getting used any more? I'm guessing it should state somewhere what it has in it? Being a new (or reman.) compressor as opposed to one that's been running on the car, should I replace the amount that came in it with the same amount? I've also read after I determine the final amount, that I should pump some new oil thru it to flush all the old oil out, then empty and refill it with the proper amount. If if comes with PAG and I chose to go with PAG in the system, should I assume it has the proper amount in it, or should I empty it to see how much is in it to make sure?

I have a handle on flushing, replacing all needed parts, vacuuming and charging and all that, but for a completely flushed system with a new accumulator and compressor, I just want to get the oil amount correct, and the kind of oil that will be the lesser of the two evils for my retrofit. Incidently, I read the thread about using DEC PAG oil if PAG is used.

Any input you guys have to offer would be greatly appreciated!

Thanks - Paul

Edited: Thu October 04, 2007 at 6:02 PM by mckpaul

Chick on Thu October 04, 2007 6:31 PM User is offlineView users profile

Use 7 to 8 ounce oil in a clean system with the R4.. That said, you are right, there are pros and cons as to which oil to use. I can say this, if using PAG, only use "douyble end capped" PAG 150 with the R4, if using ester, only use a "quality" ester like BVA Auto 100. I use it all the time in R4's with NO problems. But PAG, be sure it's onlyt double end capped as shown on that link. Check out their link for conversion items, Nylog assembly lube, O ring kits, and most of all, A new R4 remans are not recommended with R4 comprtessors..Hope this helps..
Also, add about three ounces of oil to the compressor, the rest in the accumulator so the compressor isn't oil starved while charging. I use the "Ford" blue O tube with retrofits, you can use that or the GM white. Check out the vac/charge procedures on the tips and FAQ page of this forum, and there is a lot more info there for you to browse..

Email: Chick


Freedoms just another word for nothing left to lose

Chick on Thu October 04, 2007 6:51 PM User is offlineView users profile

PS: If using one of the four seiziens brands of compressors, factory air, everco, murry or four seziens, (All the same company) better off just leaving it as is...Just "my opinion" but those are only sutible for boat anchors...

Email: Chick


Freedoms just another word for nothing left to lose

mckpaul on Thu October 04, 2007 10:09 PM User is offlineView users profile

Thanks for the response Chick.

Have a couple of compressor questions. I don't have a switch of any kind on my existing compressor. I found a site that showed artistic back views (not photos) for identification purposes. On the switch version drawing for the R4, it looked like it had three ports or openings all together, and the non-switch drawing had two ports. This one is like mine, I have only the two hoses/lines connected together on the little header and no third hole or port or switch on the compressor. The only wires on the compressor are the ones on the clutch. So I'm assuming mine is considerd the non-switch type. Is this what they are referring to as "O-ring ports" and "Switch ports"? Guess the answer is obvious, just asking to make sure.

Now, I still have to buy and add a high pressure cutoff switch. I was thinking about adding the "T" fitting kit to the high pressure port, but it's location in the line that it's in is down on the truck frame on the passenger side, and the compressor is on the driver side. I could route the wires up to the low pressure switch on the accumulator and just series it in there. But do new compressors have a place on them where I could mount a high pressure switch directly to the compressor? Or if I do that will it turn into a weird situation trying to get the right switch and I'd be better off just going with the "T" kit? I just noticed on the link to ackits that you provided that they mentioned "direct mount high pressure switch port", even on the O-ring port model. Sure would make a neater installation there at the compressor as far as wiring it in.

As for the four Four Season brands, I suspected some of those companies were the same when I was researching cycling switches and some of the numbers cross referenced each other. That's good to know. Other than those four brands, I'm seeing Ready Aire and Visteon out there, and of course the ones there at ackits, and I'm sure there's others out there. Any particular brand, or should I say manufacturer, that may be better or more reliable than the Four Seasons?

Edited: Thu October 04, 2007 at 10:10 PM by mckpaul

mk378 on Thu October 04, 2007 10:57 PM User is offline

If you have a pressure of zero there's almost certainly a leak somewhere. First thing try putting an ounce or two of R134a in (just to build some pressure) and see if it stays. Do not run the compressor. If it leaks out, determine where. Often the compressor shaft seal is leaky, so you're going to replace that anyway.

mckpaul on Fri October 05, 2007 9:30 AM User is offlineView users profile

A possible leak is a concern. When I got the turck, the motor had been changed out, and from looking at how sloppy the workmanship was on that, I just assumed whoever changed out the motor let the freon out. Later, I changed the motor out again, and I bent and cracked an aluminum AC line, but luckily it's on the accumulator and will get replaced with the new accumulator. So the system has been closed up but uncharged for at least 4 years. I'm really not 100% sure if the evaporator or condenser coils are leak free, but at this point I'm going to assume they are OK and flush them out. With all new O-rings and other parts replaced, I guess the truth will come out when I pull a vacuum.

If it weren't for the bent and cracked aluminum line on the old existing accumulator though, I definitely would take your advice on shooting a little R134 in there to look for leaks. But with the present state of the system, I know there's leaks, all of which will get corrected (I hope) with the flush and re-assembly.

Thanks for the response and the tip!

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