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Discussion Starter · #1 ·
This may seem like a silly question but: What is the proper way to flush the cooling system on an OBS 4.3 V6?

My OBS chilton manual say to remove the lower radiator hose and pour water into filler. It just flows directly thru the side tank and out. They probably cut and pasted the procedure from and older model from before serpentine belts.

My NBS manual says to remove the upper hose to drain coolant while filling thru the upper hose port on the radiator. That doesn't work either.

This should be simple.:mad:
 

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I don't know about proper, but your second way is sort of the way Ive always done it. take the upper hose off, point it at the ground and I fill with a garden hose into the radiator filler cap until only clear water comes out the upper hose.

turn the heater on too, if it's off some kind of valve prevents coolant flow to the heater core so it retains all the old shit still inside it.

you do have to let it run for a bit so the thermostat will open before anything comes out the upper hose.

And someone pointed out to me the last time I posted about this: my method could be dangerous to your engine if the engine is hot when you start this. (cold water from hose flowing into hot engine.) if its cold when you start this process it shouldnt ever get hot enough or have cold enough water going to it for there to be a problem
 

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By proper method, I guess just I mean one that works. Neither of the two I mentioned seemed to clean out the block.

Your point about the cold water and a hot motor is a good one.

I started by draining a cold motor, refilled it and ran it long enough that heat was blowing in the cab. The thermostat should have been open.

Since the water pump on the serpentine trucks rotates reverse direction from the v-belt systems, if figured the procedures may have changed.
 
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