fiesta mk4 radiator cap

[j77drs]

can anyone tell me why i would hear a hissing sound from cap ?

it seems there is a valve of somekind at the top which is where the sound was coming from

the cap is not leaking in anyway

the car is a 1997 fiesta endura e engine

 

[Mursal]

Is it a red Fiesta?

Only kidding !!

Yes the cap has 2 valves. One lets pressure out if it goes above +0.5bar (approximately). The other Valve allows air in (or coolant depending on the position of the cap) as the engine cools down after a run.

So I'd say everything is fine, if you are still worried just call into your local garage (small ones are best) for a quick check.

 

[j77drs]

YEP - ITS RED

SOUNDS LIKE ALL IS OK WITH THE CAP, I JUST HADNT HEARD THIS BEFORE

 

[Peter.N.]

If its only hissing when the engine is cooling down - that's normal, if its hissing all the time your head gasket is leaking.

Peter

 

[j77drs]

not hissing all the time

i just replaced the coolent and had it running to temperature to make sure the fan was cutting in, when i turned the engine off is when i heard the hissing,

I checked the next day under normal driving and no sound at all

 

[Peter.N.]

As long as you are not loosing colant I wouldn't worry about it.

Peter