offroadnutz

I am in the midst of converting my 88 4runner with a 3.0 from r12 to r134a. Does anyone know, or know where I can find, the systems oil capacity?

bswarm

Are you draining the compressor, condenser, evaporator, dryer, running a/c solvent through the lines? Or just replacing the service valves?

offroadnutz

I am flushing the entire system of all old oil as it would cause problems with the new refrigerant/oil. I am also replacing the drier and all o-rings.

RJR

When replacing receiver - .4 oz
When replacing condenser - 1.4 oz
When replacing evaporator - 1.4 oz
When replacing compressor - 4.8 oz.

Most of the oil stays in the compressor, thus the different numbers. Since you have to completely flush the system, I'd go with the 4.8 oz number.

scope103

This Technical Service Bulletin http://tms.ccar-greenlink.org/NewsLetter/ac002t98.pdf says the oil needed for the entire system is 100cc (a little less than 3 1/2 ounces). RJR is usually very careful, so he must have a source, but DO consider what Toyota says.

I doubt you will be able to flush anything out of the compressor. And I'm pretty sure you can't flush the Thermal Expansion Valve (TXV). The good news is that Toyota says (in the TSB) that it is okay to mix old (mineral) oil and new (PAG-45) oil. (Yeah, I too had heard that you can never mix the oils. But I never found a reliable source for that rumor.)

I didn't have to face that question; I was replacing the compressor. https://www.yotatech.com/forums/f116...-r134a-284801/ And I replaced the TXV in the process.

It was a lot of work for me to find out "how" to do it; I would be very interested in a careful write-up of how you replaced the refrigerant (and figured out how much to use).

bswarm

There's different conversions, some can get away with just installing R134 service ports and charge the system with R134. Make sure you put a vacuum pump on it before adding refrigerant, it gets the moisture out of the system.

RJR

I got the numbers I posted directly from the FSM. I should have noted that. However, that's for a '94 4runner. According to the TSB that scope references, the 94 4runner needs slightly more (120cc vs 100cc) oil than the earlier models.

offroadnutz

Thanks for the help guys! Much appreciated!

scope103 said (Yeah, I too had heard that you can never mix the oils. But I never found a reliable source for that rumor.)

I remember back in the late 90's early 00's when I worked as a certified mechanic, we had a lot of problems with compressors on some makes/models going bad shortly after the conversions. The problem was traced to mixing of oils. When we started fully flushing the systems the problems stopped for the most part. Of course Im sure formulations have changed since then but I still have that concern in the back of my head :-)
As far as how much refrigerant to use I will just go by the manifold pressures and use the sight glass on the drier. Just like you would do if you were topping a system off.

scope103

Take a look at page 4 of the TSB. They note that leftover mineral oil (from R12) will mix with the new PAG-45, giving the refrigerant a cloudy look that makes the sight glass useless. The TSB goes on to specify that you should put black paint on the sight glass (to prevent the customer from getting fooled)!

So the sight glass might not help you (and if, unlike me, you know how to use the gauges you don't need the sight glass).

I'm all for replacing all the o-rings, flushing the system as far as you can, and stepping up to R134a and PAG-45. But I think you're going to leave a lot of old mineral oil behind in the compressor and TXV. Just do the best you can, and don't be surprised if the sight glass causes problems.

And tell us all how it goes!