Aircon pump knocking

[LimSlip]

A few days ago whilst driving my 2013 Swift Sport there was suddenly a loud screeching from the engine bay which lasted a few seconds then stopped. I assumed one of the aux belts must be a little loose, and maybe some water from the river-like roads had hit the belt and started it slipping. However I checked when I got home and the belts where both tight and intact.

When I started the car yesterday I heard a loud regular knocking noise which a bit of investigation showed was coming from the aircon pump, the knock can be felt through the pump by touching it with the engine running. It sounds a little like the machine gun noise a starter motor can make with a flat battery. Opening the magnetic clutch by switching off the aircon makes the noise disappear.

Since the clutch appears to be working fine, and makes no noise when disengaged is it reasonable to assume that the original belt screeching was due to the pump itself locking up, and now it has freed off but with something damaged internally? The car has less then 50k on it and having an aircon pump fail like this is new to me, what could cause such a failure?

[Penelope Stopit]

If the aircon system has leaked and the lubricant left the pump.............???????????????????

Anything could happen

[cuprabob]

Penelope Stopit said:

If the aircon system has leaked and the lubricant left the pump.............???????????????????

Anything could happen

I believe in most systems if the pressure drops below a certain value, the pump will be disabled.

[Penelope Stopit]

Has leaked

Good point all the same

Pump will kick out before the system runs dry

Edited by Penelope Stopit on Saturday 28th December 16:14

[LimSlip]

The aircon was working perfectly prior to this so I doubt it was low on gas, unless you mean it's run low before I owned the car. I've put about 30k on the car in my ownership.

I was hoping this could be caused by the clutch so didn't have to get the system evacuated and refilled to change the pump, but I can't think how the clutch could only make a noise when engaged. If the clutch bearing was bad it seems like it would be making a noise when not engaged.

Found an almost new looking pump that allegedly has only 10k miles on it so will get it swapped over.

[LimSlip]

Forgot to post back on this, fitted the low mileage compressor, a new evaporator and a new expansion valve and flushed the condenser and pipes out with the proper flushing solvent and it's all working lovely again after a re-gas (and re-oil).

I took the old compressor apart and was surprised to find it was a scroll compressor like a G-Lader supercharger. It was pretty much destroyed, something (I think a steel ring that stops the scroll rotating) had got behind the reciprocating part of the compressor and push it forward into the end plate, destroying the edges of the scroll. The oil in it was a lovely silvery grey.