Heater blowing barely warm air.

[04Z71w]

The heater on my z71 blows barely warm air yet the engine operating at normal temperature. There's no loss in coolant, all the heater hoses look good and there's no loss in coolant or signs of coolant leaking or burning off. Came across a few articles saying it could be the thermostat....could it be the thermostat even though it warms up to normal operating Temps?

FYI it's been a little chilly the last 2 weeks so not as hot as it was during the late summer in Texas. But in later summer the engine temp is normal when driving but when I come to a stop light or low speeds the needle creeps past 210 goes but never in the danger range. When I start driving the temp goes to normal. Now that it's cold it doesn't really do that but foes move up a little bit. When I changed the water pump a months ago I didn't change the thermostat. Previous owner said he already changed it but not the pump. I'm guessing possibly it could be the thermostat and the idiot didn't change it judging by all the sloppy modifications he did to it.
Yes the radiator has had a flush and running correct coolant. Possibly thermostat??

 

[OR VietVet]

Things to check: Make sure the radiator air path has no restrictions that can cause the temp to be higher in warmer temps, change the damn thermostat-every time the water pump is done, heater core may be partially blocked, get a temp gun and see if heater hoses show the same temp-indicating a clear heater core and yet you still may have a blend door/actuator problem. Several threads and you tube videos about checking for that. Those actuators will go bad eventually, guaranteed.

 

[corvette744]

Agree with mo VietVet but no temp gun needed to verify core isn't plugged just grab each hose both should be same temp hot

 

[04Z71w]

Things to check: Make sure the radiator air path has no restrictions that can cause the temp to be higher in warmer temps, change the damn thermostat-every time the water pump is done, heater core may be partially blocked, get a temp gun and see if heater hoses show the same temp-indicating a clear heater core and yet you still may have a blend door/actuator problem. Several threads and you tube videos about checking for that. Those actuators will go bad eventually, guaranteed.

Will do-Thanks!. Will report back.

 

[04Z71w]

I know the radiator is getting enough Flow. Checked that after I changed the water pump. I'll check the hoses tomorrow when it's warmer and replace the thermostat.

 

[Fless]

Don't count on the cluster gauge being accurate until it can be verified. Check the coolant temp with a scan tool, see what the ECT sensor is reporting. Compare that to your thermostat's rated temp. The thermostat should be the OE temp (187°), not 180° or 160°.

Has the radiator been changed from stock or OE? Some replacements are missing a restrictor in the output to the surge tank, and that can cause overcooling or overheating.

If all that looks good, check the actuators as @MO VietVet recommended. A Tech 2 or similar makes it easy to verify operation, to see what's commanded vs. what position is actual.

 

[OR VietVet]

Forgot about a partial restriction with a hose clamp on the hose from reservoir to radiator. May need to do that if radiator has been changed, like @Fless said. Good call.

 

[04Z71w]

Don't count on the cluster gauge being accurate until it can be verified. Check the coolant temp with a scan tool, see what the ECT sensor is reporting. Compare that to your thermostat's rated temp. The thermostat should be the OE temp (187°), not 180° or 160°.

Has the radiator been changed from stock or OE? Some replacements are missing a restrictor in the output to the surge tank, and that can cause overcooling or overheating.

If all that looks good, check the actuators as @MO VietVet recommended. A Tech 2 or similar makes it easy to verify operation, to see what's commanded vs. what position is actual.

I'm not sure about the radiator how knew it is or where it came from....oem or not. It has 277k miles but the radiator looks damn good for an 04 so assuming it got changed down the road some where.

I'll check everything you and go from there after replacing the DAMN thermostat ,hahaha, like @mo Viet VET said.

So last night when it was 62 degrees out I'm the driver through the temp pushed itself past 210 I wanna say about 220 maybe but went down so something ain't right again.

 

[04Z71w]

I'll send a picture of the radiator and find the part number. I can find the brand that way.

 

[OR VietVet]

First thing is do the thermostat and you can experiment with the hose from the reservoir to the radiator. Put a hose clamp around it and then squeeze it down just a bit but still allow flow. If the radiator has been changed that could help with the problem. But still don't disregard the chance of the blend door actuators causing flow problem with the air from blower.

By the way, always and I mean always, change the damn thermostat with any water pump replacement, no matter the vehicle.