hissing from expansion cap??

[grey_clio]

Hi guys, After a run I opened bonnet to check a few things and noticed a slight hissing noise from my expansion cap, Im guessing the seal is knackered, I know these are dead cheap but I have one or two questions, Could this be a reason for coolant level going slowly down? Also could the thermostat be a reason for the coolant level going slowly down??

Thanks in advance for any input

 

[bing_17]

The system must be pressurised, thats how it stops the coolant boiling over at 100 Oc If youve got a leak then get it sorted asap. And depending on how much of a leak your talking, over a period of time the water level would drop because its allowing the water vapour to get away, this would take a LONG time though so doubt its your problem.

As for the stat, i dont understand why you think this would cause you to lose water? its in a sealed housing in your coolant system.. so why would that cause a problem?

 

[Mark One]

You should never over tighten those caps. They are not designed to hold a lot of pressure. You'd rather you lost water out the cap on the motorway than out of a hose.

I've heard of people loosing water out of the cap and then pissing in the system to top it back up to get them home.
As long as it's nearly water, it'll do the trick.

 

[grey_clio]

Not sure of my problem then, ill change the cap anyway to be safe. The radiator is fairly new as in 3 or 4 months old and hoses all seem fine. Recently had cambelt & waterpump changed, coolant seems to go down 1cm over a couple of days, not sure how much the mechanic refilled after the waterpump change though as he only asked me to supply 2 litres.

CONFUSED

 

[Mark One]

right well It sounds like your headgasket has gone and your rad fan doesent kick in properly.
Get any funny smelling thick white smokey steam out the exhaust? any oil in your water (will float to the top)?

 

[grey_clio]

right well It sounds like your headgasket has gone and your rad fan doesent kick in properly.
Get any funny smelling thick white smokey steam out the exhaust? any oil in your water (will float to the top)?

Rad fan kicks in ok and temp never ever goes up high. No smoke or steam from exhaust and no visable oil in water

More confused lol

 

[grey_clio]

bump

 

[AndyT23]

White creamy emulsion in your oil filler cap?

 

[grey_clio]

White creamy emulsion in your oil filler cap?

none whatsoever, looks perfect there

 

[grey_clio]

Any ideas guys??

 

[matty w]

my valver kept pressurising the water system and it was the headgasket,it blew a hole in the rad in the end

 

[grey_clio]

hmm so car was fked then???

 

[bing_17]

Sure its not still air locked?

 

[grey_clio]

Yeah I thought that so today I started up with cap off, heaters on max and ran for a bit to try and get rid of any air. Then topped up to required level. Hopefuly this will make a difference. Any other ideas??

 

[matty w]

soon as mine got warm the water would bubble but had no other headgasket signs,the water gallery's where been pressurised

 

[grey_clio]

what preventable action should I take, keep topped up??

 

[grey_clio]

the water gallery's where been pressurised

what do you mean??

 

[grey_clio]

Surley I would have other symptoms if the headgasket was on its way out??

If not should I replace it now before anything worse happens??

 

[grey_clio]

bump

just bought a new cap