Dumping Coolant

[bullfist]

Recently when idling after being driven, my car has taken to dumping a quantity of coolant through the expansion-bottle filler valve (this is coolant and not steam). Car is ok and just needs re-topping up next time it's used.

 

Upset the MOT examiner last friday when he had it at high-revs for some time (emissions test) and it peed all over the floor (didn't he have an unlucky Friday 13th).

 

Obviously cooling needs to be improved - faster fan turn-on reaction.

 

But what is the mechanism that is causing this? Is there air in the system? It could be sucking air back from the air-pocket at the top of the expansion bottle.

 

Over the last year I have failed to successfully add in a heater, thereby changing/re-routing some of the secondary coolant pipe-work. Before adding the heater, I never really had this problem - i.e. once it had happened, it never did it again, I assumed I was just venting any trapped air in the system.

 

Initially I need a quick fix, so any (constructive) comments welcome.

 

Car is a Superspec

 

Cheers,

-Steve

[philshelton]

Is it possible that you have too much water in and pressure is getting to high as not enough room to expand?

[fry61]

As Phil, says Steve, probably too much water, see what happens if NOT topped up -- keep an eye on the lower level in the expansion bottle -- it may remain the same at cold.

[alanrichey]

Had exactly the same in my Superspec. And Bob is right, I was overfilling it. I had been advised to fill it until the bleed valve on the tube that runs across the top of the engine started spouting. Once I ignored that advice and stopped topping it up and just accepted the expansion bottle is empty when the engine is cold, the problem went away. That's assuming it doesn't overheat ?

[kevin the chicken]

A bigger expansion bottle would probably tell you if there was a problem. I have been experiencing something similar in that if I fill the header tank up too much then the next time I check the level it has gone down but there are no leaks visible. It stays at this lower level and I have come to the conclusion that the expansion of the coolant is more than the capacity of the overflow bottle so it overflows, then the rest is drawn back when the car cools. I would like my header tank to have a slightly higher level due to its low mounting point (no space) so I will probably fit a slightly bigger overflow bottle at some stage

[fry61]

Maybe could prove your theory Kevin by just connecting another bottle to existing over-flow, will catch & suck once more.