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Flushing GM R134a system

nlt99 on Sat July 17, 2010 1:37 PM User is offline

Year: 2003
Make: Buick
Model: Rendezvous
Engine Size: 3.4L
Refrigerant Type: R134a
Ambient Temp: 92
Pressure Low: 18
Pressure High: 360
Country of Origin: United States

At idle, the pressures are normal, but when I raise the RPM, the low-side pressure drops pretty low and the high-side pressure goes way up. Both fans are running at high-speed and the condenser is clean on the outside. The condenser appears to be factory-original, not one of the smaller aftermarket condensers I've seen. I have evacuated and recharged the system with specified weight of R134a which helped the high-side pressure stay lower, but didn't affect the low-side pressure. The cooling appears to be LESS after doing that which makes me suspect it was possibly overcharged with R134a before to compensate for whatever other problem exists.

I'd like to flush the system to eliminate possible overcharge of oil. I also plan to replace the TXV and drier afterward. My questions are:

- What solvent should I use to flush with?
- Can I flush the cross-flow condenser?

The condenser has many thin, flat tubes going horizontally between round vertical tubes (about 1" dia) at each end. The drier is attached to the bottom end of the driver-side vertical tube.

If I hang the condenser vertically with the inlet and outlet at the bottom, will that sufficiently drain the oil?

Do you have any other suggestions?

Thank you! Nick

TRB on Sat July 17, 2010 5:12 PM User is offlineView users profile

Read Hecat's tech paper on flushing. It should pretty much cover that area if you decide to flush your system.

Hecat Flushing link.


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