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.

 

[04Z71w]

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.

Haha well I hope the it's the damn thermostat and nothing under the dash. Watched videos of that mess with the heater core and what not and yikes. At that point I can go without heat!

 

[04Z71w]

Are these damn things coolant specific? Can't remember what I used but I think it was autozone brand 50/50 mix

 

[OR VietVet]

Dex-Cool or whatever is available that is still Dex Cool. No matter what brand and yes, mix it 50/50.

 

[04Z71w]

Dex-Cool or whatever is available that is still Dex Cool. No matter what brand and yes, mix it 50/50.

Well crap it wasn't dex cool. Generic autozone antifreeze 50/50 no dex cool labeled on the jug. Live and learn. I'll be draining that damn stuff out today too.

 

[OR VietVet]

The other coolant will work but will not protect the system as well. At 277k miles it may be no big deal if your plans are to trade in or sell the rig in the future but if plan to keep and protect the cooling system, then yes, drain and fill with Dex Cool.

 

[04Z71w]

The other coolant will work but will not protect the system as well. At 277k miles it may be no big deal if your plans are to trade in or sell the rig in the future but if plan to keep and protect the cooling system, then yes, drain and fill with Dex Cool.

I'm keeping it for as long as possible...soon as I can get my lift fixed it's going to get torn down. Got everything for the front suspension, Steering, brakes, heads. Gaskets and all the other stuff that goes a long with it. Just need to decide on what to do with the headliner. Might go custom with a different fabric and color

 

[OR VietVet]

I would do a compression test first to see if the lower end of that engine is in good enough shape to do heads. Low compression could be a valve problem or rings. Do a wet test if low and if stays the same, the valves are suspect. If compression comes up, the rings are the problem.

 

[04Z71w]

Well both heater hoses are hot as hell! I didn't did it by touch and damn it feels to hot on both. Doing a temp gun test today. I haven't bought a tech 2 yet but plan to this week. To busy finishing up some house projects while I'm off work. Didn't find a part number on the radiator but looks to be a newer one versus what would come on it. May just pinch the line for a restriction and see what they does. Luckily it blows just enough warm-ish air right now.

Think this is a head gasket leak?..oil build up right behind the thermostat housing upfront of the head.

 

[04Z71w]

I would do a compression test first to see if the lower end of that engine is in good enough shape to do heads. Low compression could be a valve problem or rings. Do a wet test if low and if stays the same, the valves are suspect. If compression comes up, the rings are the problem.

I've already decided to rebuild the engine. My plan is it buy en existing pull out 5.3 and rebuild it while I milk what I can out of the current one. Probably a stock rebuild with worked over heads, mild cam and if I cam long tube headers...I just need to work on cats due to emissions here. Good running 400hp 5.3 is enough for me. Hell 380hp or 350 would work.

 

[OR VietVet]

Look under the oil fill cap and see if shows a milky buildup and check oil dipstick for same. Doubt it is head gasket related but may be. The other possibilities are more likely. Did the thermostat get done yet and let us know what happens after that. Maybe you already did but have not back tracked thru thread.