LT35 coolant system

[viking power]

I have a long running problem with the coolant system on a 99 LT 35 2.5L engine. Could anyone explain the role and purpose of the small vacumn value in the lower radiator line?

Many Thanks

[dxrob]

The valve ensures the coolant is circulated adequately onto the pump further down the line, and onto the heat exchanger, for heating.
If it was'nt there, or not working properly, you would have probs with lack of heat on blowers, and overheating on the engine, as the complete circuit needs to be operated to a certain pressure

[viking power]

Thanks rob, worthy of further investigation then. The vehicle over heats on any form of hill in high gear, I need to be reving the **** of it in lower gears to help it stay within acceptable (anything less than steam escaping) levels.

One thing i have noticed when it overheats is an apparent 'air lock' in the short length of pipe between the lower radiator inlet and the 'T' junction in the pipe work leading up to it. The other side of this 'T' joint going to the thermostat in the engine and the 3rd arm of the T going to this vacuum valve.

When it overheats all the other pipes are hot except this short length! Any further thoughts on this or on testing the operation of the valve would be most welcome