Replacing AC compressor

[Flash66]

Hi Gang,

I bought an New Sanden SD-508 R12 compressor on eBay. I drained the 6oz of R12 oil and filled with 6oz of PAG oil. I'm going to install a new accumulator and tube and vac the system down. After the evac do I need to add another oil charge to the low side, or add a couple of OZ of oil to the accumulator? I was just mainly concerned 6oz wouldn't be enough for the system? Thanks in advance!

-Flash

[Henrik]

Hi Gang,

I bought an New Sanden SD-508 R12 compressor on eBay. I drained the 6oz of R12 oil and filled with 6oz of PAG oil. I'm going to install a new accumulator and tube and vac the system down. After the evac do I need to add another oil charge to the low side, or add a couple of OZ of oil to the accumulator? I was just mainly concerned 6oz wouldn't be enough for the system? Thanks in advance!

-Flash

Since the D's AC systems is of the CCOT type (as opposed to TXV) I would recommend at least 8 oz. The reason being that the accumulator (cold vapor/low velocity/oil pick-up hole in the J tube sitting about 1/2" above the bottom of the accumulator) traps a couple of oz of oil, so - yes - you're on the right track. I put 8 oz in mine.

[NightFlyer]

Hi Gang,

I bought an New Sanden SD-508 R12 compressor on eBay. I drained the 6oz of R12 oil and filled with 6oz of PAG oil. I'm going to install a new accumulator and tube and vac the system down. After the evac do I need to add another oil charge to the low side, or add a couple of OZ of oil to the accumulator? I was just mainly concerned 6oz wouldn't be enough for the system? Thanks in advance!

-Flash

Personally, I wouldn't put PAG into any system or component that previously had mineral oil in it unless you can be absolutely certain that there's no more mineral oil anywhere in the system - that includes in the compressor. As that's nearly impossible to do, even with a thorough and complete gravity drain and system flush, I would not recommend PAG at all unless you're replacing the entire system and starting out with a compressor that was filled with either it or ester.

PAG oil and mineral oil don't play well with each and can gum up the system - what's know as the 'black death' in HVAC circles.

As your compressor previously contained mineral oil, and as your not otherwise replacing the entire system, use ester oil instead and save yourself a future headache - you'll be glad you did :thumbup:

[Flash66]

Yep good point! I'm not going to flush the condenser or evap so I'll use ester instead. Just wondering still if 8oz is enough for the system just adding the oil to the compressor, or should I add a can of oil charge thru the low side when charging along with the oiled compressor?

[NightFlyer]

Yep good point! I'm not going to flush the condenser or evap so I'll use ester instead. Just wondering still if 8oz is enough for the system just adding the oil to the compressor, or should I add a can of oil charge thru the low side when charging along with the oiled compressor?

8oz is total system capacity according to the Sanden manual, and it only needs to initially be added to the compressor via the drain/fill hole - the miscibility of the oil together with the cycling of the refrigerant will carry it to any other places that would benefit system operation. Since you won't be flushing the condenser or evaporator, I'd limit it the 8oz or even assume an 1oz of mineral oil remaining in the other components/hoses that aren't being flushed and only add 7oz initially.

But definitely no more than the 8oz, as you don't want to risk clogging up any of the hoses/pipes or your new orifice tube with oil.

[Flash66]

Perfect! Just what I needed to confirm. Much appreciated NightFlyer!

[Flash66]

Well I decided to flush the system anyway. I'm changing the accumulator and compressor, plus auto zone rented me a flush kit basically free. There's no telling how many cans of cheap R134a with UV, stop leak and oil charge have been added over the years. I figure why not since I'll be right there at the evap, condenser and lines open.

[NightFlyer]

Well I decided to flush the system anyway. I'm changing the accumulator and compressor, plus auto zone rented me a flush kit basically free. There's no telling how many cans of cheap R134a with UV, stop leak and oil charge have been added over the years. I figure why not since I'll be right there at the evap, condenser and lines open.

You might be interested in my step-by-step 'how to':

http://www.dmctoday.com/showthread.php?927-Convert-Your-A-C-System-to-Use-an-Alternative-Refrigerant

[Flash66]

Yup well, that pretty much swayed me against changing the accumulator! Just going to flush it, throw on the new compressor and pull vacuum. I've only got $100 in the new compressor, so I'd rather risk the $100 bucks than replace a busted evaporator! The system worked before I pulled the compressor anyway. It just had a clutch locking up and squealing at times. Really great write-up! Thanks so much for sharing!!

[Bitsyncmaster]

Removing the accumulator or any of the other pipe fittings is not risky if you use two wrenches as designed. Just buy some cheap wrenches and grind or bend them so you can get a good grip onto both pipe fittings. I think I used one wrench through the top access cover and one on the bottom by the wheel. On the condenser (new hose) I had to cut away some of the plastic cover near the radiator to get two wrenches on that one.

I found the pipe fittings were not tight at all on my car. They don't need much torque since it's the O-rings that make the seal.

[DMCMW Dave]

OTOH we see cars often where the threads may as well have been welded together. Go slow and know when to give up.

[Flash66]

Go slow and know when to give up.

This should have been in bold on every page when the repair manuals were reprinted from the originals! Well said Dave. God knows I broke my share of crap on this car. Btw Bitsyncmaster, it took me all day to purchase a 27mm and 32mm wrench. Almost impossible to find even at Harbor Freight. Could come close in SAE but might add to the trouble.

[Farrar]

OTOH we see cars often where the threads may as well have been welded together. Go slow and know when to give up.

I wish the previous owner of my car had known this. I ended up replacing my evaporator because someone decided to fix leaks by going gorilla with the wrenches.

[Flash66]

So we know its very possible to flush with the accumulator as long as the vacuum time is extended to allow the flush agent to boil out of the Accumulator. Seriously, I know it's scientifically possible to use R-152A in an R12 designed system but when I read NighFlyer actually flushed his system with a gallon of lacquer thinner and decided, hey, let me also save a few bucks on freon and charge my system with cans of impure Dust-Off, and has lasted?? I'm really not too worried about it anymore!

To go below Dave's above quote, "When in doubt, if it ain't broke?, flush it!

[NightFlyer]

So we know its very possible to flush with the accumulator as long as the vacuum time is extended to allow the flush agent to boil out of the Accumulator. Seriously, I know it's scientifically possible to use R-152A in an R12 designed system but when I read NighFlyer actually flushed his system with a gallon of lacquer thinner and decided, hey, let me also save a few bucks on freon and charge my system with cans of impure Dust-Off, and has lasted?? I'm really not too worried about it anymore!

To go below Dave's above quote, "When in doubt, if it ain't broke?, flush it!

As a fellow Today member once commented on the forum:

"There is some good information on this forum, but you must always read through a bunch of useless bullshit first. Jeez guys."

http://dmctoday.com/showthread.php?875-Running-a-24V-Diesel-Alternator-On-Your-DeLorean-%28Lou-Did-Not-Create-This-Thread%29&p=17169&viewfull=1#post17169

Thus, for some more A/C info that you may find of interest, see the following posts and skip the bullshit (or you can you read our bullshit if you'd like - we can get pretty funny over on Today :smashfreak:

http://www.dmctoday.com/showthread.php?748-A-C-Work&p=13049&viewfull=1#post13049

http://www.dmctoday.com/showthread.php?748-A-C-Work&p=13187&viewfull=1#post13187

http://www.dmctoday.com/showthread.php?748-A-C-Work&p=13374&viewfull=1#post13374

http://www.dmctoday.com/showthread.php?748-A-C-Work&p=13396&viewfull=1#post13396

http://www.dmctoday.com/showthread.php?748-A-C-Work&p=18227&viewfull=1#post18227

[Flash66]

So I finally had time to get this thing flushed with the accumulator in the system. Managed to pump a gallon of spirits through to finally get nothing but air through. Took a couple of hours. The compressor is freshly oiled with new orings and mounted. Pulled vacuum for 6 hours and of course!, after I close the valves it won't hold vacuum! It bleeds off on the low side in about 60-90 seconds. I've got a complete set of orings and can start changing them but I sure don't want to break that evaporator by not touching the accumulator if at all possible, If there's any chance around it I'd like to go straight to the leak and fix it. I could do the first charge of the clean system with a can of dye, but of course after this shows the leak I'll need to dump the system of freon again. I put 8oz of oil in the compressor so I'm wondering if after doing this how much oil I'll lose? Any advice? What would any of you do in my case? I'm probably just an oring somewhere.

[DMCMW Dave]

I'd charge it with nitrogen. You'll hear the leak. Cheaper than wasting refrigerant. You won't lose any oil.

[NightFlyer]

So I finally had time to get this thing flushed with the accumulator in the system. Managed to pump a gallon of spirits through to finally get nothing but air through. Took a couple of hours. The compressor is freshly oiled with new orings and mounted. Pulled vacuum for 6 hours and of course!, after I close the valves it won't hold vacuum! It bleeds off on the low side in about 60-90 seconds. I've got a complete set of orings and can start changing them but I sure don't want to break that evaporator by not touching the accumulator if at all possible, If there's any chance around it I'd like to go straight to the leak and fix it. I could do the first charge of the clean system with a can of dye, but of course after this shows the leak I'll need to dump the system of freon again. I put 8oz of oil in the compressor so I'm wondering if after doing this how much oil I'll lose? Any advice? What would any of you do in my case? I'm probably just an oring somewhere.

If you don't have access to pure nitrogen, then compressed air (which is 78% nitrogen) is your next best friend for finding leaks, but you'll need to make a custom hose to get the air into the closed system. If you're using a full manifold gauge set, then just purchase an extra hose that you can attach to the manifold where the yellow hose would usually go. Cut the fitting off the other end of that hose and instead, hose clamp an air compressor quick disconnect fitting onto it so that you can hook it up directly to your air compressor hose. If you're not using a full manifold gauge set, then purchase an extra hose that will connect to your service ports, and do the exact same thing. Charge the system with compressed air and look for the leak that way.

As Dave stated, you won't lose any of the oil that you added to the compressor as 1) it's still in the compressor, and 2) with everything connected, it's a closed system and even if the oil is dispersed, you'd only lose an insignificant amount of whatever has accumulated around the source of your leak.

Best luck :thumbup:

[Flash66]

This is one of the main examples why I love being a part of this community. Dave, I guess it's around 9am by you with money to be made on a DeLorean in your shop, and you take time out to help someone in a rut during a repair. I'm publicly saying you're greatly appreciated!

NightFlyer, I have to say you're a damn genius! Thanks guys.

[Henrik]

Personally, I wouldn't put PAG into any system or component that previously had mineral oil in it unless you can be absolutely certain anywhere in the system - ......PAG oil and mineral oil don't play well with each and can gum up the system - what's know as the 'black death' in HVAC circles..... use ester oil instead and save yourself a future headache

I'm sorry Nightflyer but that is incorrect. I personally managed a large program while at Sanden to study this very issue. The results were pusblished in an SAE paper that I co-authored:
http://papers.sae.org/932906/ with two japanese Sanden colleagues.

[NightFlyer]

I'm sorry Nightflyer but that is incorrect. I personally managed a large program while at Sanden to study this very issue. The results were pusblished in an SAE paper that I co-authored:
http://papers.sae.org/932906/ with two japanese Sanden colleagues.

Hey Henrik - any chance that you can post a copy of that paper here so that members could have access to it?

Here's another technical paper that supports your conclusions:

http://papers.sae.org/940599/

The source of my information was an article published in Machinery Lubrication magazine:

http://www.machinerylubrication.com/Read/28867/mix-synthetics-mineral-oils

Specifically, the passage wherein it states:

"Polyalkylene glycol (PAG) bases should not be mixed with any of the others [oils with mineral bases] unless specialized barrier fluids are used to minimize the incompatibility. When PAGs are mixed into other lubricants, you typically will get strong negative reactions (producing sludge and tacky residue) that require extra effort to flush, clean and correct."

While I don't doubt your expertise, experiments, and conclusions, I've personally seen the results of mixing a mineral oil with a PAG (albeit NOT in an A/C system) and it wasn't very pretty - produced a sludgy/tacky residue, just as the article referenced above stated it would. Perhaps the mineral and/or PAG that you're mixing together contains a pre-mix of barrier fluid, thus preventing the kind of problems that are otherwise normally experienced when doing so without such a barrier fluid. It's also possible that the R-134a refrigerant is acting as a barrier fluid - I honestly don't know.

As there are so many different variants of mineral and PAG oils out there, and it's impossible to know exactly what's currently in every system or in the bottle of PAG that one purchases from their local auto parts house, I'd personally feel safer going with ester oil when converting an R-12 system to R-134a, R-152a, or even a 12a product - but that's admittedly just me. Note that the only reason to switch system oil when using a 12a product is for compatibility with any Butyl rubber components that may be present in the system (hoses, o-rings, seals, etc), as 12a (propane/butane/methane/ethane blends) mixed with mineral oil will cause the degradation of such rubber, at least according to 12a manufacturers anyway.

Good info and thanks for the response :thumbup:

[Flash66]

Aside from the chemistry and scientific study's above, for the laymen, my choice was to choose NF's safer method of using ester oil in a R12 system that still utilizes any used components. Flushed thoroughly or not it would be logical to avoid the non-conclusive properties of what's "off the shelf" being mixed in. I for one prefer to avoid costly complications of experimentation unless it's something that's disposable or easily replaced. Which for the DeLorean, and correct me if I'm wrong, I think only the air filter fits that criteria!

[Henrik]

Hey Henrik - any chance that you can post a copy of that paper here so that members could have access to it?

Sure! I pulled out my one hardcopy from 21 years back and scanned it in, so - enjoy!

I can't really speak to the observations you referenced but after my paper was published we conducted additional testing - just to make it more statistically significant - and the results were the same. At that point we published Sanden's R-12 to R134a retrofit procedure that officially blessed PAG + mineral oils in a holy union. Now, all these years later Sanden still shows that procedure on their website: http://www.sanden.com/objects/retro.pdf. So for a company that cranks out a million+ compressors a year, to have said for 20+ years now that the two oils can indeed be mixed we can be sure that everything will be just fine :wink:

30207
30208

[DMCMW Dave]

That's interesting because the lore is that you can't mix them. If it is ok, why is POE (Ester) oil on the market at all? That is generally pushed as being compatible with R134 and residual mineral oil.

I've pulled apart a couple of systems that had apparently had a DIY conversion and the orifice tube appeared to be packed solid with gummy dirt. Not sure what would have done it. The only things I can think of are excessive use of stop leak, or a dessicant bag that exploded.

Reading the Sanden doc it doesn't exactly say that they will mix, but it does seem to imply that the system doesn't have to be antiseptically flushed, just emptied as much as possible.

[Bitsyncmaster]

That's interesting because the lore is that you can't mix them. If it is ok, why is POE (Ester) oil on the market at all? That is generally pushed as being compatible with R134 and residual mineral oil.


I had always read the same. Back when I first converted systems to R134a I always used PAG oil because that is what Sanden recommended with new compressors. My D had been converted before I bought it and it was gummed up with the "black death" stuff. I had to do two or three good flushing of the system before I got the system to work for more than a few months. I always install a new accumulator and orifice tube after a flush and my flush is only done on the evaporator, condenser and hoses.

[Flash66]

For anyone that finds that their AC lines to the accumulator are extremely tight and not worth the risk, my experience is so far doing quite well with a gallon of mineral spirits flushed through the system along with the old accumulator and put under vacuum for 12hrs. I adjusted my LPS for optimum pressure switching, installed a pair of DMC side vent covers and my face got frosty at idle enough to turn the fan speed down on a summer Vegas evening. Quite pleased with the results. I chose mineral spirits over lacquer thinner because I felt it might be milder on the dessicant bags in the system.

[NightFlyer]

Sure! I pulled out my one hardcopy from 21 years back and scanned it in, so - enjoy!

I can't really speak to the observations you referenced but after my paper was published we conducted additional testing - just to make it more statistically significant - and the results were the same. At that point we published Sanden's R-12 to R134a retrofit procedure that officially blessed PAG + mineral oils in a holy union. Now, all these years later Sanden still shows that procedure on their website: http://www.sanden.com/objects/retro.pdf. So for a company that cranks out a million+ compressors a year, to have said for 20+ years now that the two oils can indeed be mixed we can be sure that everything will be just fine :wink:

30207
30208

AWESOME - thanks Henrik! There a lot of good info that paper and it's very well organized :thumbup:

Given what the Dave's have reported from their personal experiences, and from what I've personally seen with my own eyes though, I still have to recommend ester oil for use in any components that were previously exposed to mineral oil, as I honestly think it's the safer choice.

That's not to diminish/discredit your research or Sanden's recommendations in the least, but rather to fully account for all the variations in A/C lubrication products that are currently available and sold on the open market.

[Henrik]

You have to understand the position like a large OE like Sanden was in in the early 90s: If you manufacture compressors that are pre-filled with PAG of which some were going to the assembly lines in Detroit for new vehicles and some were going to the aftermarket for R134a conversions you would end up with confusion in the market: "Hey, I am converting to R134a and Sanden is telling me to flush this brand new compressor filled with PAG and put ester in it instead?" And having two different oils on the assembly line was out of the question. And regardless of all of the recomendations that ester is the preferred oil for R134a conversions: Sanden compressors filled with ester did not pass the durability test specifications!. This made the choice of lubricant easy for Sanden but they did have to prove that PAG would work for conversions (thus the reason for the SAE Papers).

Also, in the early 90s a bunch of lubricant manufacturers rushed to market to prove that their lubricants were compatible with mineral oil. And ester was one of them. There was money to be made. So while Sanden had decided on their official recommendation for retrofit lubricant, that did not prevent others from recommending their lubricants.

So ester works fine, and may be prefered by a lot of people but I do want to emphasize though that ester did not pass Sanden's durability test SES-214 with ester and R134a. I was personally involved in these tests. Our/most cars don't put anywhere near the amount of stress that these computer controlled durability benches put on the compressors. One of the segments of SES-214 for example is 6,000 RPM at 450 PSI discharge pressure and with ON/OFF cycling. This is condition that pretty much doesn't exist (when RPM is high, discharge pressure is always at its lowest and vice versa (except on VW Beetles - I digress)). Testing with PAG passed it. Testing with Ester did not.

I love these discussions. Maybe we all should meet over a beer about these things sometime!

[NightFlyer]

Again, great info Henrik - thanks for sharing :thumbup: