Thermostat Temp being weird

[Arissett]

This is now the third post in relation to my thermostat. I replaced it again and this time I can tell it’s functioning correctly however bleeding the air out of the system posed a humongous challenge last night. Upon connecting the no spill funnel to the radiator I filled the radiator up until it started to come up through the funnel. Started the truck and it didn’t get sucked down at all. Maybe 10 minutes went by and nothing. I know air is in the system because I no longer have heat. The coolant level in the funnel didn’t rise yet at all until it did and spilled everywhere lol. This was on me I was in the truck making sure the gauge didn’t spike. The other issue I have is as the gauge was rising in the truck my scanner was telling me the temperature was dropping. I don’t know how this is possible. Feeling the coolant and the engine you can very much feel it warming up steadily. The number got to around 130 and dropped to 90 while the truck was running. However the gauge was basically sitting in the middle at this point. I’m assuming this is due to air in the system or something like that. My questions are is there anything I can do better to bleed the air out of my system and if the temperature number issue isn’t linked to the air being still stuck in there what could it be? Btw I have a 1999 Explorer 5.0L V8.

 

[Turdle]

First thing, raise front of truck so radiator cap is higher than firewall heater hoses. Switch HVAC control to floor, temp to 90 or max heat. Start engine with front end raised. The air should move to the radiator in minutes.

Edit. Also, have someone watch the heater coolant control valve while you switch from ac cold to floor hot and back. The valve should move when switched.

 

[Pete Deering]

You can also purchase a coolant vacuum bleed tool.

 

[Motorhogman]

"First thing, raise front of truck so radiator cap is higher than firewall heater hoses. "

Exactly how I did my 2000 Sport when I changed the radiator a while back. Ran it up on ramps. It burped up all the air in no time at all.

 

[Mr. Alligator]

^^^ yep.

And you do not need a special tool.

Best to lean it up hill, but if you pay attention you can also do this on level ground.

Good luck.