Cooling system issues

[Mitch]

Right.. a week ago tonight, i noticed the Miami's temp gauge go up to around 100 degrees, had a look at the next day and found the thermostat to be stuck, replaced with a new one and new antifreeze, all bled up etc, was all fine until Sunday morning, when on the way to work the heater went cold, all of the coolant was coming out of the overflow for some reason, got it to work, looked over it again, replaced rad cap just in case, bled it up again, drove home 50 miles with no problems, done another 50 odd miles since then too, no problems, until it chucked it all out again this afternoon.

I have already done, thermostat, rad cap, put the hose pipe in rad and other pipes, all of which don't seem blocked. Basically it seems to be pressurizing but only from the bottom rad pipe, the top pipe doesn't get pressurized at all if that makes sense? all of the pipes all warm too, heater is good, and runs at a constant 80 degrees, until the water decides to fall out, any ideas/ help appreciated.

[Anton]

Sounds like HG

[Mitch]

Forgot to say i put a sniffer on it too, which didn't show up anything, testing fluid stayed blue, obvs doesn't rule out the gasket though, just strange how there is no pattern to when it overflows.

[mikey b]

Have you ever change water pump have had the newer type water pumps with plastic impellers fall of or it may be a air lock some were

[Mitch]

Have you ever change water pump have had the newer type water pumps with plastic impellers fall of or it may be a air lock some were

Never have changed, there is a receipt saying it had been done in 2011, about 20k ago, im 99% sure its bled correctly, if there was an airlock surely it would be a constant issue? not 100 miles apart?

[mikey b]

Not to sure really bit strange that the bottom hose is pressuring and the top not

[Mitch]

yeah, its pretty confusing