Do Cerb expansion caps fail?
Discussion
They have a valve in to release at a certain pressure, maybe an airlock?
Run it up to temp at idle with the fans on hot to see if anything happens again, theyre a mk1 golf item iirc, i have had one let go before but that was during a very bad bleed up after changing all the hoses and coolant pipes!
Run it up to temp at idle with the fans on hot to see if anything happens again, theyre a mk1 golf item iirc, i have had one let go before but that was during a very bad bleed up after changing all the hoses and coolant pipes!
Make sure the cap is on properly! I failed to do so once and got steam coming out when I'd stopped, only caused by me not putting the cap on straight when I'd checked the fluid level. Now when refitting the cap, I turn it the wrong way until I hear a 'click' then turn the right way and tighten 
I actually did one again yesterday:
1.Jack up the front of the car and chock up at around a foot, open bleed nipples on water rails.
2.Remove plug on rad and fill from here as well as the expansion tank, it will take 12 litres.
3.Drop the car down and run with cap off until water comes out of bleeders, close these.
4.Continue to run until fans kick in with hot blower running, fit cap and allow to settle to temp, obviously checking for leaks throughout.
5.Top up if necessary.
Other people may do it differently but after a bad experience last time i did it exactly like this yesterday and it was perfect.
HTH
1.Jack up the front of the car and chock up at around a foot, open bleed nipples on water rails.
2.Remove plug on rad and fill from here as well as the expansion tank, it will take 12 litres.
3.Drop the car down and run with cap off until water comes out of bleeders, close these.
4.Continue to run until fans kick in with hot blower running, fit cap and allow to settle to temp, obviously checking for leaks throughout.
5.Top up if necessary.
Other people may do it differently but after a bad experience last time i did it exactly like this yesterday and it was perfect.
HTH
knight said:
Make sure the cap is on properly! I failed to do so once and got steam coming out when I'd stopped, only caused by me not putting the cap on straight when I'd checked the fluid level. Now when refitting the cap, I turn it the wrong way until I hear a 'click' then turn the right way and tighten
Hmmm, I did take it off yesterday, I wonder....Onzlouk said:
I actually did one again yesterday:
1.Jack up the front of the car and chock up at around a foot, open bleed nipples on water rails.
2.Remove plug on rad and fill from here as well as the expansion tank, it will take 12 litres.
3.Drop the car down and run with cap off until water comes out of bleeders, close these.
4.Continue to run until fans kick in with hot blower running, fit cap and allow to settle to temp, obviously checking for leaks throughout.
5.Top up if necessary.
Other people may do it differently but after a bad experience last time i did it exactly like this yesterday and it was perfect.
HTH
Thanks, will print that off 1.Jack up the front of the car and chock up at around a foot, open bleed nipples on water rails.
2.Remove plug on rad and fill from here as well as the expansion tank, it will take 12 litres.
3.Drop the car down and run with cap off until water comes out of bleeders, close these.
4.Continue to run until fans kick in with hot blower running, fit cap and allow to settle to temp, obviously checking for leaks throughout.
5.Top up if necessary.
Other people may do it differently but after a bad experience last time i did it exactly like this yesterday and it was perfect.
HTH
Most odd - new cap sorted and fitted, the old one and the bottle have been miss-threaded badly in the past, presumably mega tight was the only way to get it to seal previously.
So...
Topped up the fluid, the temp goes up, fans come on, temp goes down, all good.
But...
Every so often I see a tiny wisp of steam, I can't see where it's coming from and it's driving me mad! I can't see any fluid pooling anywhere from where I filled it that could be spilling onto something hot but there was some fluid on the underbody by the expansion tank.
This is getting annoying...
So...
Topped up the fluid, the temp goes up, fans come on, temp goes down, all good.
But...
Every so often I see a tiny wisp of steam, I can't see where it's coming from and it's driving me mad! I can't see any fluid pooling anywhere from where I filled it that could be spilling onto something hot but there was some fluid on the underbody by the expansion tank.
This is getting annoying...
Theres some heat shield material around the hoses/cables and between the body/exhaust manifolds down under the expansion tank, if this is wet it will 'dry' by the heat generated from the manifolds, this could cause the whisps of steam.......of course though, your headgasket could always be gone....
Onzlouk said:
Theres some heat shield material around the hoses/cables and between the body/exhaust manifolds down under the expansion tank, if this is wet it will 'dry' by the heat generated from the manifolds, this could cause the whisps of steam.......of course though, your headgasket could always be gone....
No bubbles in the coolant, no white in the oil - don't even mention the head gaskets!! Perhaps it's some damp then, will keep a very close eye on things.
I had the same problem recently, came back from a run out, steam suddenly came from under the bonnet - panic. Having left the Cerb out this winter under 2ft snow and -10deg temp I thought the bottle or Y piece may have split although it looked like the steam was coming from the blue bottle top. Anyway the problem turned out to be the hose clip for the hose connected to the bottom of the expansion bottle, just nipped it up and fingers crossed its been okay since. I think the hose was softening when the water temperature raised and leaking.
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