98 Nissan Quest Heater Issue ?

[GolfVenture]

I have a 98 Nissan Quest, bought new with 200k now.

 

Recently drove 800 miles in a day.

 

The heater gage would vary from lowest normal to mid normal and the heat varied with it, through out the 800 mile trip, But mostly stayed on the very low normal mark on the gage.

 

I installed a new thermostat with a radiator flush and new anti freeze.

 

Also new transmission filter and fluid.

 

The heater gage now works normal all the time, but the temp initially get hot but then cools down, then gets hot, then cools down. It seems like if I do not change the heat vent setting from defrost to floor vent to dash vent the hot air most of the time stays on hot.

 

But when I change the vent settings is when the hot to cold variation occurs the most.

 

Any Suggestions?

[Venturous Randy]

Are you absolutely sure it is full of antifreeze? It sounds like you are low on coolant.

RandyA

[Flyinfool]

Or have an air pocket stuck in the cooling system somewhere.

[GolfVenture]

Or have an air pocket stuck in the cooling system somewhere.

 

It must have been an air pocket for it seemed to have gotten better with more use.

[MidlifeVenture]

I have a Nissan that to fill the coolant you need to get the front end as high as possible IE: Front tires on ramps or steep hill. remove radiator cap run with heat on and keep filling till all bubbles come out. If there is a bubble in the system at low RPM the heat from the vents gets cold.

[wrenchrob]

I have found with them that they are famous for getting air pockets in them. I will put a vacuum on the system to get the air out