At work we have an 04 LLY. I have been looking at the radiator and surge tank arrangement and scratching my head. How does the radiator and the top of the engine get full if you were to drain and refill the coolant? With the top hose off the radiator, which is normally a vent, going to the bottom of the surge tank rather than the top which is what I usually see, I can't understand how the top third of the radiator or even the area of the thermostats would not be trapped full of air when refilling.

Birken

I believe there are bleeder screws on the engine in specific locations to remove the trapped air.

Do a search in reference to coolant flush in the LB7 forum.Draining is done by the petcock on the radiator and refilled through the reservoir tank.The system creates a vacuum and will draw from the tank.

Bleeding the air is done by holding RPM's allowing coolant to circulate pushing the air through the system.

Exactly. There is a bleeder bolt on the t-stat housing to purge air from the system. Mac is correct it is filled via then draws from the expansion/surge tank upon refill.

Also the cap is a relief cap which is the vent source you are looking for.

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