D5 (D5244T to 2005) Cooling system pressure

[shiningliao]

Originally Posted by buster1950

I,v recently sold my beloved S60 D5 (52) & bought an S80 D5 (53) I have a build up of pressure in the cooling system that is still there when cold. Could it be Headgasket or does anyone know of another problem it could be ? It does not have a thermostat at present as the old one was not working, It does not overheat and runs and idles perfectly (not lumpy) Help anyone ?????

I have exactly the same problem after I flushed out the coolant. I don't know if I have this problem before or not...

I have tried everyhting I could to get rid of possible air lock. No luck. This includes all the tips in this Volvo forum and Haynes V70&S80 manul.

Could this be worst case which is cracked head? maybe, maybe not. I decide to find out, not to sell the car immediately.

So, I put the car to the Independent Garage. Ask them to get ride of possible air lock in the coolant system. Paid some ££££ and ask garage how did he get rid of air lock? He said he need to remove pipe from time to time and refill slowly...etc. But the next morning my D5 engine still have the same problem. Lots of pressure in the cooling system that will push the coolant out the expansion tank.

After spending all day on internet for the car cooling system design. I have a good level of knowledge and decide to go to Volvo dealer and challenge them... (because they done a pressure test before and told me that the gasket is okay, no sign of problem.)

The Volvo engineer told me:
If head cracked, or gasket is broken. It might add the extra pressure to the cooling system. However, it should release the pressure next morning as well. The air come from the cracked head should release air back after engine stopped. The leak should be bi-directional....

For my case, he believes it's simply an air lock.

I challenge him again that a trustworthy (to me) independent garage had remove all the air lock but the sympton still there.

Volvo engineer suggest me to run (stationary) the car without coolant expansion tank cap on and turn the heater on until engine is hot and radiator fan cut in.

I think this is a good ida! With all the cooling sytem knowlege I got, I believe this could get rid of air lock easily. (The pressure is the cooling system is to make coolant boiling point 20 degree higher which means better cooling effect, with heater on and radiator fan cut in, this means the whole cooling sytem is open and water pump will push coolant around, include air as well. Thus, get rid of air lock.)

So I did it. Guess what?

No more air pressure in the cooling system next morning!

Therefore, in my case, it is simply an air lock problem. The trustworthy independent garage isn't that trustworthy.

Whoever read this post in the future, don't panic when you have such problem. Make sure you don't have simple problem like air lock in the system first. And don't completely trust one single garage or dealer. After all, the job will down to one single mechanic who might be a rookie...