Hissing sound after the engine has been turned off?

[BoxheadTim]

Went to see a very early Elise S1 on the weekend. Mostly liked it but there were a couple of odd things I noticed about it.

One - the most worrying in my mind - was that when we turned off the engine there was a faint hissing sound from the engine bay. A bit like air escaping from a tyre. Guess it might have just been the cooling system depressurising?

Didn't find any evidence of mayo, coolant looked clean and all that...

[Gad-Westy]

Almost certainly just the pressurised cooling system venting via the spring loaded coolant cap. Mine does this when its very hot, however I do know that the expansion tank has a slight split in it and is being replaced tomorrow. I wouldn't let that stop you buying the car.

ETA Meant to add that if you have any concern about HGF on a potential purchase, a hydrocarbon or compression test wouldn't cost much and would put your mind at rest.

Edited by Gad-Westy on Monday 3rd August 15:18

[rdodger]

My VVC does that. It comes from the plenum.

[BoxheadTim]

OK. I assume that this wouldn't be anything to be worried about then?

[lee111s]

Make sure the lid on the expansion tank is on tight!

[955sp3]

could be a curved ball, but are you sure the hissing wasnt coming from your fuel filler cap, they do that sometimes (pressurised system) and can sound like its coming from the engine

[Skaffen]

On mine I occasionally get hissing that's down to pressure build up in the fuel tank (which someone else has mentioned) - easy to check if it's that as opening the cap to release the pressure in the tank would stop the noise .

[chris7676]

Some funny suggestions. I think it's quite normal and more to do with intake than other things mentioned. Oh hold on, what is it's air escaping through the head gasket ?

[dwilkie]

Bit of threadomancy here, but I guess this sort of topic is always relevant...

If it has an induction kit fitted it's almost certainly that - my track car does that for about 5 seconds after you switch it off - worried the hell out of me for ages at first! It just vents air back through the ram pipe and out the filter.