My volvo v40 2002 is for some reason losing coolant fast, 100km and the whole coolant tank is emty. I preasure tested the system and the pressure didnt drop. My oil is good colour. And when I have it running for about 3-5min the temp guage shows that its overheathing however when i check the coolant it full, then I start the engine again and it goes to the working temperature it was before it overheated.
Summary: It overheats alot and uses alot of coolant, system holds preasure, and oil is good colour.

There is also a wierd clicking and banging noise coming from the engine, this noise came afther I instaled a new alternator. Cant figure out where in the engine room the noise comes from.

Enny help will be greatly appreciated.

 

if there's no visible exterior leaking then there's two choices - 1) check the heater core ie feel around the floor by the pedals and passenger footwell etc. If you smell a sweet aroma when starting off that's a clue 2) its going into the engine - cracked cylinder head or head gasket. The fact you are seeing odd temp readings suggest either a head problem or a thermostat/temp sensor.

 

Thanks for the reply, I going to change the temp sensor and see if that fixes the problem.
Today I noticed a long line of coolant on the ground when i drove in 1gear. So I opened the hood and It looks like the coolant came out of the coolant tank.