Cooling System (again...)

[nigelj77]

While working on something totally different at the weekend I noticed the hose from the top of the radiator was sucked flat, one of the others was also looking a bit deformed, the blue expansion bottle cap has always been a nightmare to remove (needs pipe grips or stilsons), does this sound like it's not working properly and not allowing the pressure to equalise when the engine cools back down?

[shake n bake]

Sounds like the pipe that is deformed needs replacing to start with and the cap as well, when you put the cap on I assume you're only just pinching it up?

[nigelj77]

It had sucked one hose doen just about flat and another one was starting to collapse, maybe I need to look at these then.

I only put the cap on hand tight yes but there is no hand capable of taking it back off after a bit of use, always have to use the stilsons.

[Sardonicus]

That's either a failed expansion cap or the swirl pot to expansion bottle pipe is blocked (not venting) check the little nipples on each aluminium pot they are prone to corrosion thus restricting if when squeezing the top or bottom rad hose you dont see/hear the coolant moving in the expansion pot you have found your problem got nothing to do with how tight the ex cap is

[TVR Beaver]

Also check your cap… when you look on the underside, there should be two valves.. one to let pressure out at a pre-determined level .. but also one to let air back in as it cools. A lot of aftermarket ones don’t have the second valve letting air back in.. result when cold.. a pressure in the system that’s less than atmospheric (partial vacuum).. and it could be this that’s collapsing your pipes… (I’m assuming when hot and running they are okay?)….

[Adrian@]

IF you are forcing on a cap..make sure that it the right cap. there are two different threaded version of blue cap.
Adrian@

[davettf2]

Peeps
New blue cap for my '99' chim £4.84 from euro car parts, no contest! (bought last month)

regards
dave

[nigelj77]

Cheers for the replies folks, new cap ordered from the dealer (more than the £5 one from eurpoarts....) so will check hoses and tanks are clear and if so give the cap a try.

Will have to get the diff back in it first though.....

[cureton]

Adrian, could you shed some more light on this? I bought two blue caps from local Volkswagen dealer, after showing him the original one. Took a while to figure out which model they are from but gave me two new caps looking exactly the same as mine even showing the same code numbers. And indeed, threads are different, won't fit. So which is the one with the correct thread, any article numbers? Thanks in advance!