Valve behind the coolant bleeding bolt

[superdesi]

I have been noticing a hissing sound around my engine and today I found it. There is a valve looking thing with 2 vacuum hoses attached to it about 30 degrees left and sort of back behind the coolant bleeding bolt. Does anyone know what that thing is. It is bolted on and it seems that the plastic part of the unit broke and is hissing. When I cover the broken off part with my finger, the idle seems to go down. So I am asssuming that it is some important part that I should take care of.

I will try to take a photo and post. Thanks.

[A20A1]

it's a thermo valve or thermowax valve... usually the valve will close or open depending on the temperature of the coolant... I'm guessing that when the valve is open the car operates cold start and raises the idle. So when you closed the valve manually the idle dropped as if the engine had warmed up. It really depends on the operation of the valve though... some simply bleed vacuum while others direct vacuum somewhere for a specific use at certain coolant temps.

[superdesi]

Thanks. Is it expensive to replace? There are more vacuum hoses on this car than any other car I have ever owned or worked on.