coolant system burp process - blower fan off?

[NissanMaxima]

Hi all;

Am I correct that after a coolant change during the burp process, that it is better to actually have the blower fan off or perhaps on low (but not on max) to eliminate air? With the blower on high, the thermostat will be slow to open and therefore prevent or at best minimize flow through the radiator where you want it to go to burp the air. Last month when I changed my coolant, I had the blower on max and it probably took an hour+ to burp the coolant. I later realized it probably would have been better to have the blower actually off. With the heater temp on high, that should still force flow through the heater core but also heat up the block quicker and thereby open the thermostat sooner and in turn, burp the air faster.

 

[KGMtech]

The blower speed has no effect on the coolant flow, only the temperature setting on the HVAC system could influence flow through the heater core. Some cooling systems have full flow through the heater core regardless of the cabin heat settings.

 

[WyrTwister]

Also , check for a bleed / burp fitting , such as in the photo , in the tstat housing ( where the threaded plug is ) .

 

[NissanMaxima]

I know the flow is probably the same, but if the fan is on high, aren't you bleeding off more heat from the engine block via cooling of forced air over the heater core, therefore keeping the block cooler and delaying full opening of the thermostat?

 

[NissanMaxima]

Thanks, no bleeder for burping on my Maxima, but I am aware of those.

 

[Dave9]

Yes, turn the heat up so if there is any valve on the heater core, it is flowing coolant through it, and set the fan on lowest setting, or even off if you can determine this setting still opens your heater core valve.

Some thermostats have a check valve to help burp them. Some old timers drill a tiny hole to make their own permanent valve, which does make the vehicle take a little longer to get up to a closed loop fuel efficient state as well as heat the cabin or defrost the windshield in winter. I wouldn't do it unless your engine is notorious for being hard to burp.

 

[NissanMaxima]

Originally Posted by Dave9
Yes, turn the heat up so if there is any valve on the heater core, it is flowing coolant through it, and set the fan on lowest setting, or even off if you can determine this setting still opens your heater core valve.


Thanks Dave. I guess I should be able to determine if heater core valve is open with fan off if I feel any heat emanating from vents, etc. Good test for cold day I guess.

 

[Mad_Hatter]

Have you considered placing your car on ramps or jack stands during bleeding? Air will always travel to the highest point. If you don't have ramps or jack stands, find an incline somewhere close by, park, let things cool, then open up the radiator cap and run the engine until it gets hot to open up the thermostat. Also try squeezing the upper radiator hose a few times.

 

[eljefino]

I like the way you think. I have a hill by my house which I point my cars up, then nail the gas in low gear to try and slosh more bubbles out.

Only my Mercedes and Volvo, IIRC, had heater control valves that isolated or connected the heater core. Rest of the fleet had constant flow.