Weird cooling problem T16 2.0 GT 3S-GE

[Borg]

Hi, I have lately a weird cooling problem. When I drive 50 in the 4th gear, the engine suddenly gets hot. I can feel it coming by the air of the heater. suddenly cold air is comming from the heater, and about 10 seconds later the engine starts to get hot. Then I switch of the engine and start again, I can see the temp immediately cooling down to normal.

I have replaced the thermostat without luck. Still got the problem...

Is it possible that the rotorblade of the waterpump is sometimes loose? Is it a lot of work to replace the pump?

The system is not leaking coolant

[RedMist]

The cooling system has trapped air in it. The airs simply cavatating your water pump. You may need to bleed it from the highest coolant point, or if its something like the MR2 there is a process to bleeding the system.

[Borg]

I shall try if I can find similair points to bleed the system. http://www.lovehorsepower.com/MR2_Docs/mr2_bleeding_cooling_system.htm

But, the weather is to cold at the moment to work on my Celica (-1degree celcius in Holland )

I only can't understand how this air is gotten into the system. I didn't work on my Celica for 6 months.