A hiss

Post by **Onne** » Fri Jan 26, 2007 6:20 pm

I have travelled down to Cornwall, and I now have some problems with the engine.

There is a hiss at idle, and number 2 doesn't seem to do anything, there is no difference if I pull the plug.

We have changed the head gasket today, but that didn't make a difference.

What else can it be?

Am I right in guessing a burnt valve? I had a look, and number two exhaust was black underneath.

Post by **rayofleamington** » Fri Jan 26, 2007 7:38 pm

Time for a compression test then - let me know if you want to borrow one.
A valve being 'black' (sooty) just means that cylinder is not running correctly. this can be valve, rings or even electrics/plug.

If it is a valvve you often find rough running and/or missfiring and/or low power at low revs which seems not to be present at high revs. A leaky valve makes less impact at high revs.
I had a Fiesta once where the valve seat had dissappeared completely where you could push the valve right up into the port

and it ran fine at motorway sppeds (but failed the MOT check due to unburnt Hydrocarbons in the exhaust - as it should have done)

Post by **Onne** » Sat Jan 27, 2007 7:14 pm

Cheers for that Ray.

It turned out to be a burnt exhaust valve

Post by **bmcecosse** » Sun Jan 28, 2007 4:49 pm

I would assume when you changed the gasket - you would inspect the valves anyway!!