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How do I flush A/C system om 1991 Lexus LS400 for 134a Converstion?

914lps on Sun June 30, 2013 6:57 PM User is offlineView users profile

Year: 1991
Make: Lexus
Model: LS400
Refrigerant Type: R12
Country of Origin: United States

I am trying to retro fit my Lexus from R12 to 134A. The system is extremely complicated and different in a lot of ways from most other cars. Mostly in the way it is laid out.

We found directions (sort of) on Lexus trade tech site of It gives a short instructions on how to convert. But is not directions so much as telling you the steps to take, but not how to do those steps.

We are trying to figure out the "Best" way to flush the system. On this system it is not so obvious. The compressor does not have a oil reserve on it.

We opened the system. Pulled the compressor to drain it. Removed the receiver (will replace it) . But what is the best way to flush to get as much of the old iol out. I have attached the directions from Lexus. The only difference we are doing is we will not file the system with PAG oil. We will refill with Ester oil.

So anyone know the best way to flush and if so how?

Thank you.

L-AC001-98(1).pdfL-AC001-98(1).pdf  (30 KB)

iceman2555 on Sun June 30, 2013 7:13 PM User is offlineView users profile

Take it apart. Clean each part. Reinstall. Add new lubricant...suggest to us the correct lubricant...PAG/Double End Capped.

Suggestion leave the darn thing a better performing system.

But then I thought we already had this discussion.

The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

HECAT on Mon July 08, 2013 11:26 AM User is offline

I agree it would be easier to just keep it R12.

More info about "how to flush" is in the link in my signature below.


The basic system designs are all the same and some manufacturers make things easier and others make it more challenging. What specific challenges you will face with each specific model is just part of working on cars. Since I do not work on cars daily and definitely do not know this model well; there is no way I can tell you what these challenges will be. However, I can promise you they are there; and it will take some creativity.

Maybe I can be of more assistance with a more specific detailed problem/question?


HECAT: You support the Forum when you consider for your a/c parts.


northernbeach on Tue March 11, 2014 2:13 AM User is offline

Nice post.

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