Xantia - Hiss sound long after parking the car

[lancia58]

Hi

The car is not fitted with hydractive suspension. The temperature in summer time most of the time will not raise over 30 Celsius and on top of it , it happens also at the winter. The hiss comes from the engine area and it is accompanied with a click sound that is typical to a relay or a valve

Zohar

[myglaren]

Could it be the purge cannister activating randomly?

[lancia58]

Is the purge cannister valve is powred when the car is parking i.e. when the car key is not in the ignition switch ?

Thanks
Zohar

[myglaren]

Well, that is the question - perhaps it is being activated when it should not be due to some fault in the electronics.

[Mandrake]

If by purge cannister valve you mean the valve that goes from the charcoal cannister to the intake manifold then no - that should never operate when the engine is stopped.

The whole reason for the cannister is to capture petrol vapours from the tank and store them rather than letting them escape - operating the purge valve when the engine is not running to suck the vapours in and burn them would just allow them to escape.

So if it's the purge solenoid operating after the engine has been off for 8 hours it can only be due to a fault. The purge solenoid would only cause a click though, unless there was a lot of pressure in the tank there wouldn't be a hiss.

So the fuel pump priming is still the main suspect as it would both click and hiss (the flow of fuel) and is able to run when the key is off - but it also shouldn't be operating that long after the key is off unless there is a fault.

To be honest if the car and engine are working fine I wouldn't be worrying about it.

[lancia58]

Hi

Is there any temperature sensor that is used by the ECU to "know" is priming is needed ?

Thank
Zohar