Expansion tank cap leak....

[Rob S]

I've had the "low coolant" symbol come up for a split second tonight coming home, mostly upon either strong acceleration or cornering, and upon checking, have seen that the cap has a pool of coolant around it, and that it does nt sit flush. To be clear, it is not cross threaded, nor twisted, it's just when fully on, the flat flange that fills the void recess in the expansion tank that the cap screws down into, sits at an angle.
Are these caps supposed to do this, is seems to be square on the tank itself when screwed down, just the flat dish section sits up.
The rest of the coolant system seems ok, just leaking a little fluid.
Does anyone know if the expansion tank/cap suffer age related maladies, or if it's just one of those things (Or, heaven forbid, the sign off something more serious)?
Thanks
Rob
PS I'll be replacing it anyway, just in case, just want to know if it needs the whole expansion tank or just the cap.

[cameron]

Hi Rob

Start with the cap itself :B_thumb:

Less than £10 delivered ( £9.18 ) for a new one :D

http://www.partsforvolvosonline.com/product_info.php?products_id=4737

[Rob S]

Just seen GSF do them for £4.60 odd, I'll get one in the morning. Thanks Cameron!

[Johnny5]

Mine does the same! small pool of coolant around the cap, time for a new one me thinks ;)

[Rob S]

Bought one yesterday, so far so good.
Also got a nearly new tank coming from Baba on here, along with hoses.
After my steamed and boiled Subaru, I am not taking chances.

[My T5]

I had exactly the same problem too,so i purchased a new cap and it made no difference!!. I also get a hissing noise which is only noticeable when the engines switched and the bonnets up??
However i have noticed that if you push on the top of the cap it stops?So maybe its the resevoir that been distorted due to heat or age?
I also a bubbling noise from the same place,is this cos its not a sealed system and i have air in there or is there a bigger problem? Sorry to hijack your thread dude!

[Rob S]

Update,
the old inner face old the cap had become soft and was capable of being pushed in and away from the seal.
On the expansion tank I've now notices the very small plastic outlet that feeds the small pipe that goes to the thermostat (I guess) has a crack in it and thats where it's leaking from. So I was right asking baba for the expansion tank after all!
Hope it's just old age and not the system over pressurising.......