Hi I have a 96 jetta, during the winter the radiator started leaking, couple weeks later I changed the radiator and connected hoses back to original. Started up the car and added coolant, but at normal temp coolant keeps bubbling up and overflowing (no heat inside the car). Blower was turned all the way up towards hot, I replaced thermostat and check water pump propelers and observed it... no leaks and everything works. Took out hoses and blow out the system with my compressor, assembled it back and still having the same problem. I recently took vicegrip and clamp the hose thats linking to the upper rad hose going down to the thermostat and I get heat coming through the vents in the car, and everything seems to work properly without any overflow. Does any one know what could be the problem, so I dont have to clamp the hose???

 

You have a lot of air in the system. Open the coolant overflow container and grab that same hose or clamp it and let it run till there are no bubbles showing in the overflow container.

 

clamped it....and was working for abit.. there is constantly bubbles comeing up, and when the engine is reved the coolant starts spitting out, when ever the rad fan's kick in the coolant is sucked in untill the fans stop,and then starts overflowing again... hmm is there any sort of relief valve to let the air out other than the reseviour??? maybe the waterpump housing is no good?? but there is no leaks what could be my other suggestion?

 

I'd say it's the water pump.

 

I went back at it... and did exactly what you said, clamp it etc... put the cap back on and everything seems to be working fine now, without any oveflow and there is heat in the car... thanks alot, I appreciate it...

 

Cool! I always enjoy a happy ending.