2 X new rad cap wont hold when hot

[jonnydico]

Hey guys, 92 VP V6, flushed the coolant and fitted with a new rad cap (CPC) saw that it was leaking when hot and got another one (orignally bought the wrong one (110kpa) and now have 135 on there). Cap is tight and seems to go on fine, but when the system is pressurized and hot there is leaking coolant out from the cap, coolant is not being deposited in overflow, just a small leak out the cap. all lines clean and new water pump and thermostat installed. Is ther something i am missing that is causing the chronic rad cap leak? overpressure? need a O ring in there? the car is not overheating, run about 2/3.

[pow3rslave]

hard to say for sure, but it could be some damage or warping to the mouth of the radiator where the cap fits.
i had a cracked header tank (plastic bits on the sides of the radiator, one had the radiator cap on it) so i guess it wouldn't be a stretch for a crack to have occured higher up, round the cap area.

[jas98]

where the cap goes there aint and crap stopping the cap from sealing properly? maye old gasket/oring...otherwise it may be that radiator or **** brand caps...but i have that brand and its all good on mine

[jonnydico]

ya mate, cleaned out the neck and the pipes seems to seal tight, might go for a new band of rad cap or try fitting a pastic washer in there,

[Morton]

Sounds like the neck of the radiator may be a little stretched I know I have a brand new cap on my radiator, and I still get splatters of coolant all over my airbox after a spirited drive

[centy]

mate check that the overflow tube seals and has a clamp on it not just pushed on.
mate 2/3 on the temp gauge is high.
the only way mine gets anywere near that is going up to the lookout when the radiator fan plays up. Did not get that hot towing a big trailer.
I would look at getting some of the radiator flush that removes sludge and crap from your cooling system and clean it out.
My radiator has always had coolant and the bottom 6 or so fins are blocked so yours is most likley the same.

[jonnydico]

thanks again guys, going to try a flush with treatment and see if that cleans it up, prob needed to be done as I didnt use a treatment on original flush because it was extrememly dirty

[jonnydico]

conclusion: neck on rad warped and CPC rad caps did not make seal, bought TVC cap from Repco, it has a different type of top seal (looks like rubber compared to the copper of the CPC). TVC seems to sit tighter, no leaks!!!!!
thanks again

[jas98]

conclusion: neck on rad warped and CPC rad caps did not make seal, bought TVC cap from Repco, it has a different type of top seal (looks like rubber compared to the copper of the CPC). TVC seems to sit tighter, no leaks!!!!!
thanks again

glad you got it sorted...just keep an eye on it but it should be fine