Hissing Noise

[PETER G]

Passat 2003 1.9 tdi
After driving usually 20 miles+ when I get out of the car I can hear a hissing noise it appears to come from the very back of the engine compartment / bulkhead on the drivers side. Any help or advice would be greatly appreciated.

[snapdragon]

Probably just refrigerant hissing through the pipes and valves as it settles down and equilibrates?

[808]

Does it happen when the aircon is turned off? I had the same thing happen with my motor. It dosnt happen if aircon is turned on economy or turned off. Havnt had any problems because off it and its happened since i bought the car.

[Izalman]

Its the Aircon system pressure equalising when the engine driven compressor stops when you switch the engine off. Best thing for the system is to turn it to ECON about 1 mile from your destination, this will turn off the compressor and ensure all gas / oil is in the correct place when you do switch off the engine & no hissing...
(I do aircon for a living..)

[MalcQV]

As already mentioned the A/C.

[scotty33]

Another possibility is a vacuum leak, the vacuum system includes the servo and control pipework for the turbo boost control and EGR control

[PETER G]

Another possibility is a vacuum leak, the vacuum system includes the servo and control pipework for the turbo boost control and EGR control

I have also noticed that the car does not seem quite so gutsy, as I had it remapped a couple of years ago. All was fine at first but now dont seen to get the same performance. I have fitted a new MAF, temp sensor and recently injector loom, any suggestions would be appreciated.