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Ah ha .... Thnx Codge and please pardon my terminology! So what I meant to say was ....

Are you saying that coolant is coming from the expansion bottle under pressure? And if so, how full was the expansion bottle when cold?

If you start out with the expansion bottle level at MAX, then the coolant has little room to expand and will quickly accommodate your engine bay. Also, the halfway reference will tell you if you are using/losing coolant as well. The level drops and the coolant is sucked back into the system as it cools.

Yes, the expansion tank was filled to MAX when I flushed and filled the system, at cold.

After driving, the expansion tank was more than overflowing, and even when it had cooled down, was quite high. I emptied some out, and drove home

I get the "tap" light come on a fair few times, I assumed I had a poor connection, but now think it is due to air getting into the system, like you say, any air at the top of the rad will make that come on.

I fitted a new rad cap, same pressure rating, and the problem remained. I will check the coolant level again, and maybe mark up the expansion tank so I get a better idea of exactly how much I am loosing...


thanks for all your input so far guys, it's much appreciated

If the expansion bottle overflows this says either the rad cap is very weak or more likely you are getting air into the cooling system, either by seal fail, or gasket fail somewhere. Somewhere the air/exhaust gases can be pushed into the cooling system under pressure.

The reason the expansion bottle is then to high i.e. above 'full' when cold, is that once air gets in the radiator top it is compressible/expandable and the coolant cannot suck back into the rad. Instead the air simply changes it's pressure/volume to match the temperature as it cools.

Perhaps this has been said above, sorry if it has, but thats my take on it. Just my two pennerth.

Hope it's helpful and an easy fix.

Thoughts from the hotel shower ın Istanbul.........What a poser......ÇÇÇÇÇÇÇÇğğğğğğğğ:

The car could be boılıng for other reasons. Wrong spark plugs (I use BR8 ET for 12A street use). Then there is the tımıng......why should ıt be wrong though? Is the vacuum system OK?
What about a clogged radıator? Faulty fan coolıng? EtcŞ Etc.

Codge

I will check the spark plugs, can't remember what they are...

Otherwise, the car runs fine, pulls really well, still lovely, apart from a few puddles

Another one.....this from the missus......dooh, I forgot this:

The thermostat is well worth checking for opening in a pan of boiling water. Again sorry if this is mentioned above.

Dave.