A/c Refrigerant Loop Repair '90 Ls400

[ericcohen]

My mom has a 1990 LS400, with about 175,000 miles. She’s owned the car since it was new, but it recently developed a number of problems. One of these problems is that the AC stopped working about 6 months ago. The compressor is not locked, but I had the system leak tested at Car Cool (Casselberry, FL) and was told that refrigerant is rapidly leaking from the compressor and from the evaporator. They recommended replacing the compressor, evaporator, expansion valve, receiver/dryer, soft plumbed lines, and o-rings. The estimate was about $2k, so I’m going to do the job myself, but I have a few questions.

- Compressor: I believe the compressor is leaking from the front seal. My understanding is that a rebuild kit can be purchased from Toyota. Has anyone gone this route? What were the results? As it stands, I intend to purchase a rebuilt compressor. A number of threads recommend Pace Compressors ($350+$25 for the filter) or Techchoice. However, I found cheaper ($275) rebuilds with a longer warranty (1 year vs. 90 days) from ebay seller air_parts. Anyone here have any experience with compressors from this seller? Seems to have good feedback on ebay.

- Evaporator: Car Cool claims they detected a leak in the evaporator (I assume they checked at the drainage hose). Seems more likely to be an o-ring issue to me, as I don’t really see what would cause the evaporator itself to fail, but other threads seem to indicate this actually is a fairly common problem with this car. I’m planning to replace with the plate and fin unit from techchoice ($120). Does anyone know if the original evaporator is a plate and fin type or a serpentine type?

- EPR: I’m not sure why this vehicle has an EPR, as it only has a single evaporator, but I’m guessing it’s probably a good idea to replace this while the system is open. Any advice for or against this? I’m also planning to install a new expansion valve.

- Oil: I am unclear on the oil fill procedure. According to L752 pg. 18, “When replacing a compressor, remember that a new or remanufactured compressor usually has enough oil to fill the entire system. Therefore, you must compensate (add/remove) lubricant for the proper system amount.” Since I am not replacing the condenser, this seems to imply that I will need to either remove 45cc of oil from the new compressor (AC-14) or drain the condenser of oil. Can someone please explain how to do this?

- Pressure switch: Should this also be replaced while I’m doing all of this other work?

- Soft plumbing: I would like to replace all soft plumbed lines in the system. Can I get these somewhere other than Lexus? What about the Schrader valves?

- R-134 conversion: I’m not trying restart the religious war here, but I’m leaning towards sticking with R-12. However, I notice that Toyota puts out a conversion kit. Does anyone have any experience with systems converted with this kit?

- Tools: I have a vacuum pump from my laser building days, and ordered a manifold gauge set with hoses. The refrigerant has been removed already. Are there any other specialized tools required?

As an aside, in addition to the dead AC, this car was belching white smoke on start and eating power steering fluid. My mom brought the car to Jimmy Bryan Lexus in Winter Park, FL, and they gave her an estimate of over $10,000 (supposed cracked block and new power steering system). I ended up replacing the air control valve for about $100, which fixed both problems. So watch out for those guys at Jimmy Bryan.

Thanks for any assistance or advice with any of the above, and for making it through this really long post.

- Eric

PS I’ve read all the other threads on this issue I could find, and linked the the ones that seemed most relevant:

http://us.lexusownersclub.com/forums/index...790&hl=r134

http://us.lexusownersclub.com/forums/index...=r134&st=15

http://us.lexusownersclub.com/forums/index...c=20493&hl=

http://us.lexusownersclub.com/forums/index...c=20088&hl=

http://us.lexusownersclub.com/forums/index...c=12359&hl=

http://us.lexusownersclub.com/forums/index...c=10139&hl=

http://us.lexusownersclub.com/forums/index...ic=6931&hl=

[Threadcutter]

eric

As an aside, in addition to the dead AC, this car was belching white smoke on start and eating power steering fluid. My mom brought the car to Jimmy Bryan Lexus in Winter Park, FL, and they gave her an estimate of over $10,000 (supposed cracked block and new power steering system). I ended up replacing the air control valve for about $100, which fixed both problems. So watch out for those guys at Jimmy Bryan.

Wow!.......

Jeez! I think that's a new one on most of us here!.....Cracked block(?).....Yeah, I'm on my 3rd one........ ;)

Clean the screen/filter on the steering rack solenoid, THEN you'll have it all taken care of........

[LScott400]

- Compressor: Compressors normally develop leaks at the shaft seal. If the seal is simply worn a rebuild would do the trick. However, if there is wear on the shaft (we're talking thousandths of an inch) then it would have to be replaced also. Assuming the compressor is original, a replacement compressor would seem to make more sense.

- Evaporator: Evaporators can develop leaks both externally and internally. Poor air flow (debris) and plugged condensate drains cause oxidation and result in a leak. More often moisture in the refrigerant creates an acid which eats through the evaporator. It pools and eats through the bottom which is why the leak is often detected at the condensate drain.

- Oil: I don't have the specs, but each component of the A/C will trap a quantity of refrigerant oil. Somewhere there are specs on the amount of oil to add to each component replaced. Ideally, the condensor would be removed and purged of any oil and debris, then refilled.

- Pressure switch: Depending on the cost, I would not likely replace this unless I determined it was malfunctioning.

- Tools: The performance of the vacuum pump will be critical. A pump that only pulls 28.3" of vacuum will require that the ambient temperature of the system must be ~93F degrees or higher to boil out the water. A unit that pulls 29.7" only requires the ambient temperature of the system need be ~35F degrees or higher. The longer you let the pump run, the more likely you will remove all of the moisture. When complete, allow the system to sit with the vacuum pulled on it for a half hour to check for leaks. Assuming no leakage in the manifold gauge set, a loss of vacuum will let you know you still have work to do.

Moisture is invariably introduced into the system any time refrigerant is added or when all of the refrigerant escapes. The receiver/drier has a dessicant bag in it to capture residual amounts of moisture, but its capacity is limited. That is why the drier needs to be replaced whenever components are replaced. Directing a heat gun or lamp at the drier during the vacuum process will help the dessicant give up moisture trapped there.

Hopefully, someone else will have answers for your other questions. Have fun!

[ericcohen]

Thanks for the info. As for the evaporator, I had been thinking of mechanical damage, but now that you mention it, it certainly seems plausible that the cause is moisture contamination. Assuming this is the case, it seems that all the other parts such as the condensor and lines may be suffering from similar corrosion problems, although they are not -yet- leaking. I'm wondering if this type of problem affects the evaporator more than other parts of the system due to the phase change from aerosol liquid to gas on the inner tube walls of the evaporator?

The specs for the oil quantity are contained in the shop manuals, which I downloaded from Toyota. It's just not real clear on how to remove the oil from the condensor. Would compressed air do the job?

Threadcutter, to be accurate, Jimmy Bryan apparently changed their name to Lexus of Orlando a few years ago, but it's the same place. And yes, I was as shocked as you were when my mom called to tell me about the estimate. A Toyota engine, particularly the 1UZFE, is just getting broken in around 170k ;). Anyway, that's not the first time Lexus has tried to rip my mom off.

- Eric

- Compressor: Compressors normally develop leaks at the shaft seal. If the seal is simply worn a rebuild would do the trick. However, if there is wear on the shaft (we're talking thousandths of an inch) then it would have to be replaced also. Assuming the compressor is original, a replacement compressor would seem to make more sense.

- Evaporator: Evaporators can develop leaks both externally and internally. Poor air flow (debris) and plugged condensate drains cause oxidation and result in a leak. More often moisture in the refrigerant creates an acid which eats through the evaporator. It pools and eats through the bottom which is why the leak is often detected at the condensate drain.

- Oil: I don't have the specs, but each component of the A/C will trap a quantity of refrigerant oil. Somewhere there are specs on the amount of oil to add to each component replaced. Ideally, the condensor would be removed and purged of any oil and debris, then refilled.

- Pressure switch: Depending on the cost, I would not likely replace this unless I determined it was malfunctioning.

- Tools: The performance of the vacuum pump will be critical. A pump that only pulls 28.3" of vacuum will require that the ambient temperature of the system must be ~93F degrees or higher to boil out the water. A unit that pulls 29.7" only requires the ambient temperature of the system need be ~35F degrees or higher. The longer you let the pump run, the more likely you will remove all of the moisture. When complete, allow the system to sit with the vacuum pulled on it for a half hour to check for leaks. Assuming no leakage in the manifold gauge set, a loss of vacuum will let you know you still have work to do.

Moisture is invariably introduced into the system any time refrigerant is added or when all of the refrigerant escapes. The receiver/drier has a dessicant bag in it to capture residual amounts of moisture, but its capacity is limited. That is why the drier needs to be replaced whenever components are replaced. Directing a heat gun or lamp at the drier during the vacuum process will help the dessicant give up moisture trapped there.

Hopefully, someone else will have answers for your other questions. Have fun!

[LScott400]

The evaporator is the lowest point in the system so the hydrochloric acid formed by R-12 in contact with water collects in the bottom.