Boiling Coolant in Expansion Tank

[MidLifeCrisis]

Just arrived at Latitude Festival in a sea of smoke from coolant boiling in the expansion tank and pissing out onto the exhaust;
I suspect that the header tank pressure valve may have given up the ghost but am I right? What else could cause this?
I just took the valve off and did a blow/suck test on the valve spigot - I think I can blow & suck but it’s not easy so I might be imaging it?!?! (Do you have to push down on the insides of the valve as you do blow/suck to get it to seal or should it work without this? Ie how do I do test?) (it does quack in one direction if I apply pressure to this inner seal)

(Cheeky request!) Anyone happen to be onsite with a spare?
Anyone got any other investigation ideas?

[itchyfeet]

could also be a leak which meant coolant low and air in system which then means it does not pressurise and boils....or could be a blown head gasket.

let it cool fill up bleed and watch what happens.

[MidLifeCrisis]

Thanks - we were in crawling traffic trying to get onsite; engine temp was up a bit but not surprising given crawling traffic; then went up even more and noticed coolant bubbling out of expansion tank;
Obviously at Festival so limited in what I can do - but will try refill and restart and see what happens - is there anything I should be looking for to help rule out things?

[937carrera]

Did you notice what the temperature gauge said - any warning lights ?

I would do as itchy says, but leave the pressure cap off at first. It shouldn't be spilling coolant all over the place on tickover, if it is then that'll be indicating the HG has gone.

Post back once the cool / refil is done & we can chip in with further diagnostic help

Instructions here : http://www.brick-yard.co.uk/forum/bleed ... 29710.html

edited as I just spotted it isn't a WBX

[MidLifeCrisis]

Cheers - temp gauge was on the way up and got flashing red light (but didn’t get flashing light until the very end when stuff was already obviously going wrong);
Header tank is about an inch below full; Expansion tank only has about an inch in it (but not surprising given way it was pissing out)

[itchyfeet]

doesn't sound like you lot much then, might just be a duff cap, is it a VW cap or a Blau one or some cheap crap off ebay

https://www.brickwerks.co.uk/brickwerks ... ch/Header/" onclick="window.open(this.href);return false;

[R0B]

You do carry a spare cap, don't you?

[Mocki]

Firstly let us establish where the coolant was coming from to get on the zorst .....

The top up tank ( the one behind and accessible from the numberplate flap) has three vent holes at the very top, often not noticed unless the tank is not fitted. If it gets over full it vents coolant out of there , straight onto the silencer guard.

If you were not getting the red flashing light of over temp , and the gauge was not at the hot end , you could just have a dogey cap on the headertank. Don’t panic yet !

[itchyfeet]

You do carry a spare cap, don't you?

I do yes.

[MidLifeCrisis]

You do carry a spare cap, don't you?

I do yes.

I did - got a different van - not transferred over yet (obviously!!)

Coolant coming from expansion tank (the one behind the number plate flap) and pouring onto exhaust

[937carrera]

You do carry a spare cap, don't you?

I do yes.

He carries more spares than Brickwerks

Midlifecrisis - how are you doing on the tests, or has that been abandoned for festival activities for the evening ?

[R0B]

I am sure you do Itchy. I was asking midlife

I do yes.

[MidLifeCrisis]

Appreciate all the advice.

Just topped everything back up - and started up; at idle with dalek cap off there was no coolant bursting out of the top of the tank (which I have taken as a good sign?!?)
It’s a little difficult to rev the t*ts off it to get it up to temp as I am surrounded by other vans and folks trying to enjoy the festival; but I am hoping that this is just a knackered dalek cap; it’s a Blau by the looks of it (so not a crappy eBay special) but I guess they all go eventually;
Think we will try to call out the friendly GreenFlag folks to help out - but not sure if I can pre-empt them to bring a spare?!?

[937carrera]

That's a good sign, but not definitive.

Next step is to replace the cap and just let it idle to get up to temperature. I doubt there's a big air lock to worry about.

Watch out for bubbling in the header tank or coolant overflowing from the expansion tank.

The alternate test is to whip the plugs out and get someone to spin the engine over while you watch for water coming out of a spark plug hole

Can you get a cap locally - might not be perfect quality but should get you home

[itchyfeet]

The alternate test is to whip the plugs out and get someone to spin the engine over while you watch for water coming out of a spark plug hole

Any significant amount of water in the cylinder would come out the exhaust and stop the cylinder firing so it would run on 3