2500 Radiator Pressure Cap

[Mr Tiger]

Hi,

Should the pressure cap for the radiator header tank on a (Vixen) 2500 have a vacuum valve / vent ? I've been paying closer attention to the cooling system on mine since changing the water pump. The top radiator hose has a tendency to collapse when the system cools down.

If it's supposed to have the vacuum valve, will this suck coolant from the overflow bottle back into the header tank as things cool?

Also, does anyone know what the correct pressure cap for this car is? The one on mine is old and I can't make out any markings.

Thanks,

Chris

[plasticpig72]

On my cars i have rad cap with vacuum valve so when cooling down coolant is sucked back into circuit from expansion tank. Works well
Alan

[RCK974X]

Original Triumph 6 pot caps were vacuum types (with non-pressurised overflow tank) and were 14lbs as I remember....

[plasticpig72]

On my 3000S and on my 3000M they have Expansion Tanks which i keep half full.
But on my Lotus Elan there is a 2 way pressure cap on the Rad and a non pressurised Expansion Bottle which i keep half full.
Both systems work very well.
The cooling system just needs a possible way for the coolant to expand then when cooling return to keep circuit full
Alan

[Mr Tiger]

Thanks both,

It looks like the 6 cylinder Triumphs either had a 7 psi or 13 psi cap originally but it's not all that clear.

I've contacted Fahler who sell polished stainless caps. They state all of theirs have the return valve. I've just ordered three - 7, 10 and 13 psi. Hopefully one of them will suit.

Chris

[280i]

Are you trying to return your car to stock? If yes I can send you a picture of what the upper tank looks like (cylinder looking thing) A line comes off that to a bottle on the fender.

[Mr Tiger]

280i said:

Are you trying to return your car to stock? If yes I can send you a picture of what the upper tank looks like (cylinder looking thing) A line comes off that to a bottle on the fender.

Hi,
Thanks for your offer. I'm not looking to return the header tank to stock. Having said that, if anyone has a spare original one they don't require I'd happily buy it.

The previous owner made the tank that's on mine.



The new Fahler caps arrived this morning. The old cap that's currently on the car has a noticably weaker spring than the weakest of the ones I've just bought. Presumably the old one is rated at 4 lbs.

I'll probably start the car up with a new 7 lb cap (if it stops raining) and see if it behaves.

Chris

Edited by Mr Tiger on Friday 2nd June 12:34

[280i]

From the look of it that set up should work fine. That tank is similar to the original (original is smaller). good luck