Lude Generation

Go a problem temp gauge stays at half, flushed the complete system and backwashed a lot of jobby came out all running clear replaced thermostat and heat switch filled with water and got all air out of system, when engine gets to temp expansion bottle boils over what is going on please help

The expansion bottle much have the correct fluid level in when the engine is stone cold .
Did you do that?

Have you replaced the rad cap?

I had the same a couple of weeks ago and traced a leak to the bottom of the iacv - fixed the leak and coolant has been fine since then. Ive seen quite a few leaks in the small cooolant pipes from iacv or fitv - some of them only show under pressure and as its in the engine bay it evaporates quickly so difficult to spot.

The engine was hot but expansion bottle wasn't fingers crossed and no I haven't replaced rad cap I'll check that tomorrow thanks for the information God I'm stupid

try bleeding it again and then check for any leaks
most of these pipes will never have been replaced and so are probably about 20 years old

Found small 5 pence piece size plastic mushrooms shape in the radiator and looks like it has broken off radiator cap so it is not sealing so needs new cap thanx peeps

It was the rad cap