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coolant system burp process - blower fan off? #5112278 05/22/19 11:03 AM
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NissanMaxima Offline OP
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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.

Re: coolant system burp process - blower fan off? [Re: NissanMaxima] #5112291 05/22/19 11:18 AM
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KGMtech Offline
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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.


2017.5 Nissan Rogue SV FWD
2013 Nissan Maxima SV
2009 Ford Flex SEL FWD
1984 Yamaha XJ750RL
Re: coolant system burp process - blower fan off? [Re: NissanMaxima] #5112317 05/22/19 11:44 AM
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WyrTwister Offline
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[Linked Image]

[Linked Image]

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


Wyr
God bless
Re: coolant system burp process - blower fan off? [Re: NissanMaxima] #5112318 05/22/19 11:45 AM
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NissanMaxima Offline OP
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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?

Re: coolant system burp process - blower fan off? [Re: WyrTwister] #5112320 05/22/19 11:46 AM
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NissanMaxima Offline OP
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Thanks, no bleeder for burping on my Maxima, but I am aware of those.

Re: coolant system burp process - blower fan off? [Re: NissanMaxima] #5112326 05/22/19 11:52 AM
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Dave9 Offline
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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.

Re: coolant system burp process - blower fan off? [Re: Dave9] #5112351 05/22/19 12:18 PM
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NissanMaxima Offline OP
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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.

Re: coolant system burp process - blower fan off? [Re: NissanMaxima] #5112430 05/22/19 01:52 PM
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Mad_Hatter Offline
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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.

Last edited by Mad_Hatter; 05/22/19 01:56 PM.
Re: coolant system burp process - blower fan off? [Re: NissanMaxima] #5112540 05/22/19 03:44 PM
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eljefino Offline
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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.

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