A/C quits after car heats up.

[mytrplseven]

On my '04 RX 330, the A/C shuts down (compressor not engaged) after the engine get above normal operating temp. Recharged it, full service, fans running, new cabin filter and initially it's very cold. When engine sits at idle for very long, engine temp goes to just below red mark before fans go to high speed. This also happens with A/C selected off. Engine will also cool off quickly with rpm increased and car moving. Is there a connection between the engine heat and the A/C shutting down? Since I recently bought the car with no history, and it's got just over 100k, I'm wondering if the timing belt is slipping on the water pump and at higher rpm there's enough friction on the shaft to make it work more efficiently.

[lenore]

First the temp should not be going to just below red.  You have either a bad thermostat or a air bubble in the cooling system.  I would address that first. 

[mytrplseven]

Is there a bleeder port in the cooling system to purge the air from the system? This is my first Lexus. If that's not the problem, I'm planning on replacing the water pump with the timing belt soon. I appreciate your response. I was curious if higher than normal engine temp would cause the A/C  to shut down.

[lenore]

two things, on My RX400h radiator there was a small hex head cap on the top radiator hose area.  Also under the engine cover the radiator cap on the left side of the radiator.

First the temp should not be going to just below red.  You have either a bad thermostat or a air bubble in the cooling system.  I would address that first. 

[2005_RX330]

I've seen a similar behavior on a '94 Cad.  The engine wasn't cooling right (the thermo was bad, it turned out) and when the engine temp exceeded a threshold the AC would stop working.  I assumed, but did not determine, that the ECU simply shut down the AC in order to aid in engine cooling (e.g., to prevent the AC condenser from pre-heating the airflow through the radiator).

Fixing the engine cooling problem "fixed" the AC "problem".