Heater blow cold air and car overheat

Hi all. My z3 1.9 1999 heater blow cold air and also engine overheat when drive slow or in traffic. There is no coolent leak and i bled the system already.

Either you have no coolant or your thermostat is stuck shut

Thanks for reply. Coolent is full I have checked few times. If there is thermostat problem how do i fix that ? I am wondering if the water pump is working or not

It's hard to say. I would replace te thermastate and thermastate housing before replacing the water pump. Reason being it's cheaper. While the vehicle is running and at operating temp try squeezing your radiator hoses. If they they are super stiff you have built up psi. They should be squeezable while the vehicle is running and at normal operating temp. If not. Thermastate is stuck closed.

Thanks for help. I will try that

If you decide to replace the thermostat, strongly consider replacing the water pump. Make sure you get one with a metal impeller....(see photo of 'new" pump with composite impeller). This is what caused my car to overheat after replacing the entire cooling system.

Does the car have the original cooling system? If yes or unknown, I'd replace every component of that 12+ year old cooling system. The component quality of our cooling systems are, ahh, sketchy.

See
http://www.318ti.org/forum/showthrea...hlight=cooling
http://www.318ti.org/forum/showthread.php?t=18066