My heater blows luke warm air most of the time now and im wondering if it might have something to do with me changing the thermostat. Truck runs same heat but colder heater now. Burped the system with truck jacked up. Could air be in the heater core somehow? and if so how do i get it out
88 pickup 22re

 

Verify the valve on the firewall moves freely with the lever, and the cable is still attached to the valve.

The surefire way to purge the air is with the right tool. lisel makes a large funnel that attaches in place of the radiator cap.

Start with a cold engine, remove the radiator cap, raise the front end so that the radiator cap opening is higher than the heater hoses on the firewall, set the heater valve(s) to hot, start the engine and let it idle till the thermostat opens and you see flow across the radiator. Then keep the radiator full as needed while it purges air..

Lots easier with the special funnel, or at least less stressful.

 

I would also check and see if the hoses are hot after the truck is running for awhile and you know it is warmed up. If hot water is flowing thru the core, then the heat is not getting transferred from the core to the cab. Could be build up inside the heater core or the core can be full of dust not allowing the heat to transfer.

Does your truck have AC or not? I have seen a truck that did not have the AC and the dirt goes straight from the blower to the heater core and fill the fins full of dust, there by not allowing heat to transfer.

 

Does not have ac will check for dust and try burping it again

 

*I had the similar issue with my 85 and 83 turned out that before I bought them the trucks were sitting out in fields [Rural living] and pak-rats had nested up inside air ducts, the various types of debris clogged everything. I took dash and venting apart cleaned it out , solved problem.
If burp,n the system doesn't change it ....might want to look into this .