Flushing evaporator

[eaglefreek]

**Ralph and Rich**
   So, I wasn't necessarily looking for one, but I stumbled on to a brand new Sanden compressor with clutch, not a Chinese reproduction, that has the AMC part number on it, too. I won it for $52 including shipping.  A few years ago after an engine swap, I added R134 to the empty system without flushing it. I did do a trick that Mick posted, where I hooked a vacuum line from the engine and used it to vacuum the system, but I'm sure most of the oil probably stayed in. So I plan to flush the condenser, lines and evap and install a new drier. The lines go in through the firewall so I can't take them off without A LOT of work. Would flushing the evaporator with the lines connected be effective? I would think it would be tough to get all the contaminated oil out. Also, I plan on going back to R12, what all should I replace besides the drier?

[eaglebeek]

Have you found that R134A doesn't provide adequate cooling?

Regarding flushing: I've always done flushing with the hoses attached. It's not practical nor cost-effective to remove the evaporator just for flushing. And you're correct; it's hard to get it all, even if you flush components individually.

In lieu of flushing, it's worked reasonably well for me to charge a system, add the appropriate amount of oil, and then run it for a couple of hours; then valve off the system and drain off the oil out of the compressor. You then refill the compressor with the same amount of oil you drain plus one ounce.

You can use PAG oil with either R-12 or R134A. If you're using mineral oil use it with R-12 only. In either case use viscosity 150 SUS oil.

I've heard of others using engine manifold vacuum to suck out an A/C system. Engine vacuum is not much more than 12 or so inches of mercury vacuum at best. A/C service vacuum pumps can suck a system down to almost nothing...about 28 inches mercury. For an individual doing his/her own A/C it probably isn't worth the $300 or so for a professional vacuum pump. If you have an old refrigerator laying around you can cut out the compressor and make an adequate vacuum pump out of it. I used one so mis-appropriated for quite a while before my employer gave me a surplus unit.

[eaglefreek]

Have you found that R134A doesn't provide adequate cooling?

Yes.


Once I get it back together, I plan on bringing it to a pro to get refilled. I'll probably have to buy the R12 from Craigslist.

[macdude443]

Have you found that R134A doesn't provide adequate cooling?

Yes.


Once I get it back together, I plan on bringing it to a pro to get refilled. I'll probably have to buy the R12 from Craigslist.

You never know.  I called around and found a mom and pop service station that still had R12.  I know where a 30lb container of R12 is sitting and it's for sale.  Not cheap though!  Everyone is shocked at how cold my A/C gets.  My hand cramps up if I hold it in front of the vents too long.

[rollguy]

**Ralph and Rich**
   So, I wasn't necessarily looking for one, but I stumbled on to a brand new Sanden compressor with clutch, not a Chinese reproduction, that has the AMC part number on it, too. I won it for $52 including shipping.  A few years ago after an engine swap, I added R134 to the empty system without flushing it. I did do a trick that Mick posted, where I hooked a vacuum line from the engine and used it to vacuum the system, but I'm sure most of the oil probably stayed in. So I plan to flush the condenser, lines and evap and install a new drier. The lines go in through the firewall so I can't take them off without A LOT of work. Would flushing the evaporator with the lines connected be effective? I would think it would be tough to get all the contaminated oil out. Also, I plan on going back to R12, what all should I replace besides the drier?

The compressor should say on the tag what oil is in it, but it is best to drain the oil and start over for peace of mind.  Remove the drain/fill plug and turn the compressor over so the oil drains out into a container.  Drain the oil out of the head by pointing the ports down.  Once all the oil is drained, do what eaglebeak said.  I agree as well, that flushing the hoses, condenser and evaporator at the same time is best. I use either A/C flush solvent and compressed air, or the flush that is available at auto parts stores in an aerosol can. I also flush both ways.  It is best to use a dry gas (CO2 or Nitrogen) to blow out the system instead of compressed air, but not everyone has dry gas available.   Make sure there is no vapor (solvent or moisture of any kind) is coming out.  Once everything is flushed and blown out, uncap and hook up the drier last.  You need to add the proper amount of oil to the compressor before charging, and the remaining oil during the charge process.  Most compressors will take about 6 oz, and the complete system should take about 8 oz total.  I suggest ester oil if you are planning to run R12, and PAG for 134a....Rich

[eaglefreek]

Thanks. The tag says Suniso 5GS oil. My research says it's a mineral oil. Would you still recommend draining the oil? If I keep the oil that's in it, can I add another type of R12 mineral oil to the system? I have nitrogen at work and planned on using it for the flush. The compressor came today and it looks like a brand new compressor, doesn't appear to be rebuilt and there is no tag that says rebuilt. Unfortunately, it has a different head on it with different fittings. I looks like it's for a Renault or Mazda. The same compressor was used on AMC, Renault and Mazda. No problem, I can get a head gasket kit for $10 and swap heads.
   I don't plan on messing with the A/C for a couple weeks or so. Right now I'm moving my alternator to above the power steering pump. I plan on installing my old compressor under the new one and making it into an air compressor for on board air system for filling tires and using air tools.

[rollguy]

Thanks. The tag says Suniso 5GS oil. My research says it's a mineral oil. Would you still recommend draining the oil? If I keep the oil that's in it, can I add another type of R12 mineral oil to the system? I have nitrogen at work and planned on using it for the flush. The compressor came today and it looks like a brand new compressor, doesn't appear to be rebuilt and there is no tag that says rebuilt. Unfortunately, it has a different head on it with different fittings. I looks like it's for a Renault or Mazda. The same compressor was used on AMC, Renault and Mazda. No problem, I can get a head gasket kit for $10 and swap heads.
   I don't plan on messing with the A/C for a couple weeks or so. Right now I'm moving my alternator to above the power steering pump. I plan on installing my old compressor under the new one and making it into an air compressor for on board air system for filling tires and using air tools.

I would drain the compressor anyway.  I have plenty of heads and gaskets if you can't find one, or don't want to swap the old one. If the head is a rear port head, I would be glad to trade, as that is what I use on my kits.....Rich

[eaglefreek]

Ok, I'll do that. No, it's a UB head I think. It has some kind of O ring setup that looks similar to the GM's. I found a place online that sells the head gasket and spacer gasket for $9.95.

[carnuck]

It's been a couple years since i did a system, but I recall using the synthetic that blends well with either R12 or R134A. It's still pumping cold air too.