Coolant Leaks Until Minimum and System Shuts Off. Leak Stops. Ideas!?

pha3z on Fri July 15, 2011 11:54 PM

I'm really confused.

I thought I had a bad a/c pump on my car, so I replaced it. I had a local shop with a nice a/c machine charge it to 1.14 lbs. Its a Toyota Corolla and the spec calls for 1.14 lbs max and 1.01 lbs min. I got back on the road and within 10 minutes, it lost charge and stopped working. I went back two days later and they told me there was 0.98 lbs in it. The new guy claimed that the old guy probably didn't charge it right. I was skeptical but I let him charge it up again to 1.14. I got on the road again and within 10 minutes it loses charge and stops again!! I go back again and they drain it and the machine says it reclaimed 0.98 lbs again!!!

So in a nutshell the behavior is this:
Charge the system to max.
Run the a/c for 10 minutes and it loses charge.
Check the coolant and find that its just barely below the minimum threshold for the pressure switch to come on.

So why would the coolant be leaking with the pump on but then stop leaking when the system kicks off?

Am I crazy or has anyone else seen this behavior?

mk378 on Sat July 16, 2011 12:00 AM

It is not possible to recover 100% of a refrigerant charge because some of it gets absorbed in the oil, and also the recovery machine can't pull down to a full vacuum.

Even if you really did have only 0.98 lbs, the pressure switch will be on, and you'd likely get considerable cooling. If your compressor doesn't run at all in that condition, something else is wrong. A very common reason for running for a while then stopping is that the clutch gap is too wide. It can happen on a new compressor too.

Edited: Sat July 16, 2011 at 12:02 AM by mk378

pha3z on Sat July 16, 2011 12:31 AM

mk378: Thanks for the response!

I looked up clutch gap on google and found this article verifying what you are saying:
http://www.springerpop.net/F350/air_gap.html

I'm rather annoyed now because I had them drain out what refridgerant was in there until I could take a further look at the problem. But it sounds like I can't easily verify this problem on my car unless I go back and have coolant put in again.

I suppose I can at least measure the clutch gap. I just can't observe the on and off behavior without coolant in the system. Would I need to get a Chilton's or other manual specific to my Corolla to find out what the clutch gap distance out to be?

Edited: Sat July 16, 2011 at 12:40 AM by pha3z

mk378 on Sat July 16, 2011 9:50 AM

With the engine OFF, unplug compressor and jump clutch coil to the battery +. Clutch should pull in. Nothing turns of course since the engine is off. Walk away for about 15 minutes to let the coil heat up. Then disconnect the jumper and reconnect it see if the clutch will pull in again.

Dougflas on Sat July 16, 2011 3:18 PM

you can measure the gap with a business card. Crude but works.

pha3z on Sat July 16, 2011 5:19 PM