Hey Yotatech,

Vehicle is a 1991 Toyota Pickup 4x4 with 3.0L and manual transmission.

I am in the process of a 3VZE rebuild and wanted to tackle the A/C that never really worked during my ownership of the Pickup. I've been tearing apart the A/C system while following the Toyota FSM and plan on replacing everything except for the high pressure tubes, compressor, amplifier, and maybe the dual pressure switch. As I was taking apart the expansion valve, I found these hard plastic like spherical clumps in the liquid side tube. What could have caused this? PAG oil solidifying when mixed with mineral oil? Also, I'm not sure if this is normal, but when I shake the receiver, it makes a rattle sound—possibly more spherical clumps in it?

I plan on running PAG 46 with dye and R134a when everything is back together. I'll run PAG 46 through the compressor by hand to clear out the old stuff. As for the high pressure tubes, I was thinking of running an oil degreaser through it, rinsing it with water and then clearing it out with an air hose. Would that be safe for the tubes or should I use an A/C solvent?

Also, anyone recommend a method to test the dual pressure switch when it's disconnected from the system?

So some backstory: I had a neighborhood mechanic retrofit my A/C to R134a because the R12 leaked out. This was probably back in 2012-2013 so my memory is fuzzy on his process and what oil he used. I believe the system held vacuum for over an hour so he poured oil with dye into it and added refrigerant. The compressor kicked on and cold air finally started flowing out the vents. I finally had cold A/C! Unfortunately it only lasted a month before it started blowing hot again. I took it back to him and he told me something may be wrong with the expansion valve when he looked at his gauges. I never pressed him further as I only paid him in refrigerant cans.




Possible mineral/PAG oil contamination?


More pictures:

A/C Compressor turns smoothly and has great resistance when blocking the low-side port. No signs of metal shavings in the oil. Magnetic clutch engages when energized and spins with the pulley.
Inside top of compressor

What came out of the compressor. Fortunately, no metal shavings.



High Pressure side expansion valve with goop and some spherical clumps in it.

Orange oil in some parts of the A/C system?

Thanks, Yotatech!

 

Nice pictures.

I found this reference https://www.machinerylubrication.com...20gooey%20mess. on the mixing of PAG and mineral oil, but they were specifically referring to water-soluble polyglycols. (I don't know if PAG 46 is water or oil soluble.) I don't know what could cause hard spherical bits.

I'd avoid using water to flush any part of the A/C system. You might be able to blow it out of lines and then get it adequately dry laying in the sun on a very dry day, but items like the condensor or evaporator are going to retain some of whatever you put in. Vacuuming the system is able to remove some water, not because you can hit a perfect vacuum (where the water would all instantly vaporize), but because at the low pressure you can hit the water will evaporate more quickly. It would still take a lot of pumping to get any significant amount of water out. A/C flush isn't that expensive, and with its higher vapor pressure should be easier to vacuum out.

A new receiver shouldn't rattle, but it's mostly activate carbon granules so I wouldn't be surprised if a used one had something loose in it.

Keep us posted.

 

Dessicant granules that have escaped from defective receiver/dryer????

 

Thanks for the reference. I'll be flushing out the tubes then; I just ordered an A/C flush kit on Amazon. Also millball pointed out that the hard bits can be desiccants from the receiver. I'm going to cut into the receiver to confirm this.

By the way, I read your post about your compressor replacement and it gave me the courage to finally tackle my A/C! Thank you!

I just google desiccant and I think you're on to something. I'm going to cut up the receiver to see if that rattling is broken up desiccant.

 

So I took the grinder with cutting wheel to the receiver and found this inside. Looks like the desiccant broke apart and clogged up the expansion valve. Any idea why this would happen?

I do recall the neighborhood mechanic did not replace the receiver. I thought that was odd since I've heard every time the A/C system is exposed to air, you must replace the receiver. I even had one on hand and asked him to replace it, but he assured me it wasn't necessary. I should have been more persuasive.


Cut open receiver. Looks like the desiccant escaped and clogged the expansion valve.

I ordered a replacement Denso Receiver 478-0107.

 

There should be some sort of mesh that holds the dessicant.

Sometimes the dessicant is held in some sort of bag; other times there is screening at the refrigerant entrance and exit points.

Sometimes both. Belt and suspenders, I guess.

Is your dryer a genuine factory part??

 

It's screening on both sides. The side towards the expansion valve failed and the center pipe has a few bits of desiccant in there. It states it's a Denso 047810-9010 which doesn't seem to be in production so I don't know if it's genuine or not.

Original Denso 047810-9010 Receiver.



Input Screening

Failed Output Screening

 

sorry for your troubles ... but great info here .
thanks for the thread !

 

My AC failed on my '94 after I had it converted to R134a by a local AC shop. This was 2 years ago. it made it less than a year before it stopped working. Took it back to them and they looked it over then called me up and said the receiver dryer had failed. Said the filter/screen inside had blown out, and that they didn't know why. They replaced it, charged me another like $300, and now here I am with it still leaking down once every 8 months or so.

Fortunately now that it's R134a, I can just keep refilling it. Even got a can of refrigerant with oil in it to toss in there so it doesn't frag the compressor, cause I sure as hell won't be taking it to a "professional" with prices/service like that. Thought about replacing every last part of the AC system just to start fresh, but that's an assload of work and money, plus you can't get half of the lines anymore, so might as well just keep adding refrigerant & oil every year.

 

Sounds like I had the same exact failure as you except the desiccant broke out in mine. Did they replace the receiver dryer with retrofit? The new receiver dryer I installed looks a lot like the original. Hopefully these things aren't prone to failure.

I just finished reassembling my A/C and it's held perfect vacuum for over two hours. I replaced everything except for the liquid tubes as those are too expensive. I used an A/C flush kit to clean them out. For the A/C components, I used UAC low and high pressure hoses, UAC condenser, Four Seasons evaporator, Denso expansion valve, dual pressure switch, thermistor and receiver drier. ​​​​​​​The condenser and evaporator piping were bent all wrong and made it difficult to install so I don't recommend those companies. The UAC hoses are good, though. If your OEM evaporator and condenser are not broken, clean it out with A/C solvent and reuse it. It is quite a bit of work and I imagine it would be even tougher to do if you have to work around an engine, but definitely worth it. .



I bent it as close to OEM as I could. Four Seasons evaporator on the left, OEM right.

Success! It's held perfect vacuum for over two hours.
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