Refurbish 91’ Toyota AC system or patch it?

Cars 30 years old since everything is that age and you didn't pin point the leak get so uv dye and a uv flash lite install a 1/4 oz and recharge system run it for a few days start looking for the leak/ leaks. Can even be leaking for the compressor shaft seal.
 
Toyota sells the O-rings for the block and pipe joints. It’s a doable job. Many of those joints use a 10mm bolt to hold them. the pipe flare joints use a 20-something mm wrench. The hard lines and hoses are NLA, so if one is cracked, a local guy will have to fix them. They are made out of aluminum. Any competent hydraulics shop can crimp and braze new AC hoses.

Now the heat exchangers and dryer, unless Denso still makes them you’ll have to deal with Chineseium there. It’s always a good practice to install a new dryer with a fresh fill of PAG/POE oil for R-134a unless you live close to the Mexican border and can venture into TJ/Nogales or south of the Rio Grande for R-12.
I was thinking based off your post. Perhaps I can take an inventory of parts still available for this vehicle, via online. If most OEM parts are available, swapping ac components can’t be that complicated, can it? This vehicle is my camping van, so I am in no rush at all to get it finished. If I am not dealing with the recharging and aluminum piping, it isn’t too complicated, it seems.
 
I was thinking based off your post. Perhaps I can take an inventory of parts still available for this vehicle, via online. If most OEM parts are available, swapping ac components can’t be that complicated, can it? This vehicle is my camping van, so I am in no rush at all to get it finished. If I am not dealing with the recharging and aluminum piping, it isn’t too complicated, it seems.
When I tinkered with a 1991 Lexus LS400, I was shocked Denso still stocked a new dryer and TXV for it. All the O-rings were stocked(common parts) and Toyota said R-134a was OK for use with the right oil(official procedure was to run the system to recover oil, recover the existing R-12, change O-rings and add a prescribed amount of PAG oil to the system, the old mineral oil will settle at the dryer AFAIK). If you’re starting from an empty system, the hard part is getting most of the old mineral oil out with a flush. Too much oil is as bad as too little.

Ester oil(NOT PAO) is the way to go. If you can drain the compressor and EVAP/condenser to see how much oil is in there, even better.

and it looks like Denso still sells the evap/condenser, compressor, TXV and drier for your Previa. The O-rings can also be had on the aftermarket, as green HNBR ones. Toyota sells the black ones. The OEM R-12 ones were red nitrile.
 
Instead of just asking here, which is good.
In addition, I would also check Youtube on how to replace AC equipment in a car.
There are also specialized AC forums that you can read and ask questions.
This will determine if the task is something you want to do or have a shop to do it for you.

The most difficult part is to find the leak.
It requires a sniffer tool or you can put dye in the system and again use a UV light to see the leak.
If it is behind the dash, then you have to figure out on how to access it without pulling the whole dash out.
 
If it is behind the dash, then you have to figure out on how to access it without pulling the whole dash out.
Every Japanese car of that era the evaporator is in a separate box which can be taken out through the space left by removing the glove compartment. No major disassembly is required.
 
You need to understand and heed the clean air act, and understand what you can and can’t legally do.

Assuming it’s evacuated (legally or leaked out), it’s not rocket science. It’s piping and tubing.

Once you get it truly leak free (tested by vacuum and pressure), you can fill yourself.

If you’re having issues, filling with a propane/butane mix (Envirosafe) may be worthwhile for “off road” use in testing performance. That system was r-12 originally, and the AC in those vans never were that cold. Lots of glass and not a ton of capacity. So if you aren’t going to go the 607/609 route and put r-12 in, you will lose capacity. Learn about a proper retrofit.
 
For those of you that missed it, he said that it has been converted to R134 years ago.

The system can be fixed as long as parts can still be found which it sounds like they can be. You definitely need gauges and a vacuum pump at the minimum and a can tap if using 12 oz cans to refill with.

I've kept the AC in my 92 Cavalier working up until recently when I discovered that I have a leak somewhere since my compressor wouldn't come on and I only had about 10 psi of pressure on both sides. I still have a partial 50lb tank of R12 so I've kept using that in this car.

This is a good auto AC forum where I learned a lot about AC repair. You can also ask questions and there are a lot of knowledgeable people in the forum.

 
For those of you that missed it, he said that it has been converted to R134 years ago.

The system can be fixed as long as parts can still be found which it sounds like they can be. You definitely need gauges and a vacuum pump at the minimum and a can tap if using 12 oz cans to refill with.

I've kept the AC in my 92 Cavalier working up until recently when I discovered that I have a leak somewhere since my compressor wouldn't come on and I only had about 10 psi of pressure on both sides. I still have a partial 50lb tank of R12 so I've kept using that in this car.

This is a good auto AC forum where I learned a lot about AC repair. You can also ask questions and there are a lot of knowledgeable people in the forum.


Just because it was done doesn’t mean it was the right thing to do. Retrofits don’t have the physics in their favor, especially if as noted, it was only four o rings and an oil change. Generally at least some pressure switches should be changed too, if not the condense...

Unless a substantially larger and different condenser was installed, the performance of retrofits is generally poor m smaller cars can get away (I had a 134a retrofit in a bmw for about 10 years and 100k thst I was pleased with), but the physics just isn’t there. As someone with around 225k miles of experience in a previa, and maintaining it, the van is great. The AC, meh.

R-12 has also come down in cost as demand has subsided. I keep my Mercedes cars on 12 because it runs so much better. I have retrofit them before, it works, not great. This is the chance, with OP conspidering a quality refurbishment, to use the right materials and do it right... Granted, in Detroit, the climate may be more amenable to a retrofit than someplace warmer or more humid.
 
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I retrofitted another 92 Cavalier I own to R134 and it cooled just about as good as the R12 car does. I also used the same condenser. It just depends on the system and you are right, some don't retrofit that well.

The OP mentioned his was done per a Toyota service bulletin so maybe it was done correctly and it worked effectively.

I still have several cans of R12 that I had before buying the tank of it plus I have my 609 certificate so that I can buy it from places that require the certificate.
 
In an attempt to stay as neutral as possible, I'll add my .02 for the OP:

Given the age and obscurity of the vehicle, certain small parts may be hard to find. However, an o-ring is an o-ring and if you can find stock specs it's not too hard to source replacements.

If you're serious about the project, just cut to the chase and replace everything. Condenser, compressor, drier, seals, maybe even switches. Evap core is a must, since you said your sniffer picked up on a leak near the dash. After doing all that, you shouldn't have any issue converting to 134A. I'd also, personally, block off the rear AC. If you use the van for camping while it's stationary with only you and maybe one other person in the rear, the main AC will be plenty. Less complexity, less likelihood of a leak.

If you aren't comfortable or can't evac and charge the system yourself, just factor that into the cost. Have the system evacuated, take it home and perform the work, then take it back to be vacuum checked and charged properly. Easy peasy
 
A/C work won't destroy your engine if you don't tighten a bolt correctly.
OP was talking the need for specialized equipment. If someone doesn't know how to properly torque a bolt, maybe they shouldn't pursue it in the first place.
 
Yes.
Hours and hours of mechanical swaps, followed by a skilled/equipment vacuum check and fill.
If it fails vacuum (low $) back to work!
The swaps could not pay for themselves, but easy to do.
You need to look at every hard/soft line (seals at each end, damage in between), every component (same), and don't forget compressor body can leak too.
The rear stuff probably tees off (welded tubes), may be worse to exclude.
 
I retrofitted another 92 Cavalier I own to R134 and it cooled just about as good as the R12 car does. I also used the same condenser. It just depends on the system and you are right, some don't retrofit that well.

The OP mentioned his was done per a Toyota service bulletin so maybe it was done correctly and it worked effectively.

I still have several cans of R12 that I had before buying the tank of it plus I have my 609 certificate so that I can buy it from places that require the certificate.

Violent agreement :)

Spent many years an miles driving and working on a previa. Small ac, even with rear blower, lots of glass, big windshield that’s pretty flat.

Great van, ok AC.
 
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I have decided to attempt patching the AC. I did a thorough check of the AC lines. I reasoned that flare lines metal on metal sealed connections can be left alone. It turns out a lot of the connections were flare metal to metal connections. It was easy to distinguish flare type connections from the other type - O-ring.
Any connection that didn’t have two nuts for two adjustable wrenches were o-ring connections. These, I have disassembled and will replace with new R134a rings. I will also replace the drier/receiver. I am hoping this will slow down the leaking to tolerable levels. I don’t need perfection, just not refilling every year. I am also going to replace a few seals on the compressor.
The compressor spun remarkably smooth. No play on the clutch and cam. Very good condition for 200k miles.
 

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So you took it all apart without looking for the leak first...

The fittings with two wrenches will have an o-ring inside. Metal on metal flares were phased out in the 1970s.
 
Oh, great. Thanks for the info. Perhaps I will get those disconnected as well. There aren't that many more that need replacing.
 
Leaks don't go away, it only grow bigger eventually. If it was my van I would bring it to a shop to check for leak, then replace the bad part and then convert the needed o-rings and parts and fill with R134a. It may not be as efficient but I wouldn't throw away a van just because the AC isn't efficient. It may be good enough for one's climate but not for another, it doesn't matter if the owner is happy with the result.

My leak happens on a hard hose between compressor and condenser, a pinhole leak, at 150k. It works fine after my mechanic replaced it and then charge the system up again, and is still fine 12 years later at 270k miles.
 
For those of you that missed it, he said that it has been converted to R134 years ago.

The system can be fixed as long as parts can still be found which it sounds like they can be. You definitely need gauges and a vacuum pump at the minimum and a can tap if using 12 oz cans to refill with.

I've kept the AC in my 92 Cavalier working up until recently when I discovered that I have a leak somewhere since my compressor wouldn't come on and I only had about 10 psi of pressure on both sides. I still have a partial 50lb tank of R12 so I've kept using that in this car.

This is a good auto AC forum where I learned a lot about AC repair. You can also ask questions and there are a lot of knowledgeable people in the forum.

Thanks- much appreciated
 
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