Pressure in the coolant bottle

[johncroz]

My sons coolant bottle cap keeps blowing off with high pressure the bottles been replaced recently by his mate any ideas thanks

[declan]

@johncroz happened to me so I cable tied the lid down with good results

[declan]

@johncroz however this can be a sign of head gasket failure and some other pretty serious stuff so I don't reccomeny doing what I did but each to there own

[Calum]

It's going to be head gasket.

Quick way to test is see if there is any oil in your radiator.

[johncroz]

Cheers for the advice

[declan]

@johncroz turned out my head wasn't tight so I think that was my problem but I still keep the tie on just in case

[Calum]

@declan That's not really a good idea.

When pressure is addded to the cooling system, it WILL find a way out. Since liquids require immense pressure to compress, the easiest option is for the liquid to move to a different location.

A nice plastic cap is ideal escape mechanism, requiring little force to actuate.

If however it can't escape via there, it will just find an alternate route. Like the thermostat housing.

I had this on my Starlet when I bought it. The Fcking bodge jobbers simply removed the thermostat to stop water leaking through there.

But water was leaking through there for a reason, the head gasket was blown.

Consequently the coolant just leaked out the overflow bottle. And by the looks of it, the coolant had been doing this for some great length of time!

So let coolant blow out the bottle, rather that than through the radiator core.

But better still, fix the problem.

[declan]

@Calum I'm pretty sure mines all good mate

[Jens Eskildsen]

An overfilled overflow bottle can also do this.

[Calum]

@Jens-Eskildsen If the bottle is overfilled, it SHOULD just leak out the overflow hose.

But so long as the pressure is gradual. If it gets a surge it will rupture the cap.