Luke warm drivers side but hot passenger

[Tbot191]

Hello, I have a 2010 2500 5.7. I just replaced the heater core flushed the system before reconnecting the heater core hoses I had hot heat from both sides for about a week now I only have hot heat on the passenger side and it gets Luke warm on the drivers side. I have the single climate control and can't for the life of me figure out what happened.
Does anybody else have this problem? If so did you fix the issue?
Thanks in advance for those who could help me out!

 

[markabby]

is the air flow the same on both sides?

 

[nlambert182]

Sounds like air in the cooling system. Something is blocking the heater core if you only have heat on the passenger side. Try bleeding the cooling system again. There could be a large air pocket trapped in the core.

Otherwise, if you're not getting the same airflow from both sides it may be a blend door actuator issue. Doesn't matter if you have the single climate control, it still has blend doors.

 

[Wild one]

Hello, I have a 2010 2500 5.7. I just replaced the heater core flushed the system before reconnecting the heater core hoses I had hot heat from both sides for about a week now I only have hot heat on the passenger side and it gets Luke warm on the drivers side. I have the single climate control and can't for the life of me figure out what happened.
Does anybody else have this problem? If so did you fix the issue?
Thanks in advance for those who could help me out!

Time for a heater core.The heater core is basically split into 2 sections,one side feeds hot air to the pass side,the other side feeds hot air to the drivers side.

 

[nlambert182]

Time for a heater core.The heater core is basically split into 2 sections,one side feeds hot air to the pass side,the other side feeds hot air to the drivers side.

He just replaced the heater core. I think it has an air pocket that's blocking the flow on one side myself.

 

[Wild one]

He just replaced the heater core. I think it has an air pocket that's blocking the flow on one side myself.

I totally missed that fact,what you get for just skimming a post.You're probably right about an air pocket

 

[markabby]

Sounds like air in the cooling system. Something is blocking the heater core if you only have heat on the passenger side. Try bleeding the cooling system again. There could be a large air pocket trapped in the core.

Otherwise, if you're not getting the same airflow from both sides it may be a blend door actuator issue. Doesn't matter if you have the single climate control, it still has blend doors.

my guess is the blend door as you stated.

 

[nlambert182]

my guess is the blend door ass you stated.

Why?

Not saying you're wrong, but it's much more common to be a heater core/coolant flow issue based on the OP's description.

If it were a lack of airflow from the driverside vents I would lean more towards blend door.

But.. since he's getting airflow from those vents (just at the wrong temp), AND he just replaced the core I am leaning heavily towards either a blockage or an air pocket that is preventing coolant flow.

I'd definitely try bleeding the system really well first. Much easier to do than trying to fool with blend doors. Plus... it costs nothing to bleed it again. The last time I had to bleed mine for almost 30 minutes to remove all the air.

 

[Tbot191]

Is there a good bleeding method? I also replaced the water pump and t-stat before tackling the heater core. I did also notice there is a little less air flow through the driver side vents. After I replaced the heater core I had full heat on both sides which I thought was weird that now a week later it's doing this. I'm genuinely confused as to what's happening lol.
Oh I also should add that I couldn't get the bleeder screw to remove.

 

[Docwagon1776]

my guess is the blend door ass you stated.

How would the blend door effect the temp out of one vent but not the other? Doesn't the blend door just control the ratio of ambient air to HVAC air?

 

[mdc1990zr1]

Is there a good bleeding method? I also replaced the water pump and t-stat before tackling the heater core. I did also notice there is a little less air flow through the driver side vents. After I replaced the heater core I had full heat on both sides which I thought was weird that now a week later it's doing this. I'm genuinely confused as to what's happening lol.
Oh I also should add that I couldn't get the bleeder screw to remove.

I just bled my 2016. Parked it facing downhill and drained. Closed the drain and filled best as can. Started truck and turned facing uphill, stopped and filled to top. Started truck and let idle till thermostat opened. Filled some more and shut off. Filled overflow tank. Checked next few mornings and added very little till one morning it was still full with no head space. Didn't need to play with the bleeder on the water pump. Nice and easy with OEM coolant and distilled water and verified with a refractometer. Old school way still works in 2024.

 

[GTyankee]

The BLEND Door, is just to the LEFT of the A/C Fan

It is only 1 door, 1 actuator on a single system



this is a DUAL Controls system
notice Up & Down arrows on both sides
2 blend doors & an actuator for each door




The single door system lifts up & drops down

I may be wrong, but i think lifted up, the Air Flow passes over the Heated Coils



Then the Air goes to the 2 MODE Doors
those 2 doors direct the air to the different VENTS

the Mode doors are directly below the radio & A/C control knobs

floor & top of dash

& i believe drivers & passenger side vents


found this

Temperature Blend Air Door Actuators: The temperature blend air door actuator controls the temperature of the air flowing from the vents by mixing hot and cold air from the heater core and the evaporator.

Mode Door Actuators: The mode door actuator controls what vents have air flow, i.e. floor, panel or front, defrost, or any combination of those.

Recirculation Door Actuators: The recirculation door actuator controls the intake of air into the system, either bringing outside air in or using inside air in recirculation.

 

[markabby]

he never mentioned how much air flow is coming out of each side: is it equal? is one side pushing more air? wouldn't that be a tell-tale sign?

 

[nlambert182]

he never mentioned how much air flow is coming out of each side: is it equal? is one side pushing more air? wouldn't that be a tell-tale sign?

First general rule of troubleshooting. If you just repaired a problem in the system and shortly after a different problem occurs that interacts with that system.... backtrack and verify that your previous work isn't the cause. Changing the water pump, t-stat, and heater core at the same time allowed everything to get filled with air.

OP - don't worry about trying to open the bleeder screw above the water pump. Fill up the truck with coolant, remove the reservoir cap, set the heat to high, point the nose of the truck up, and let the truck run for 20-30 minutes and gravity bleed. I'd bet after the thermostat opens you'll start seeing some air bubbles.

If you have a thermometer, stick it in the vents and monitor temps. You'll likely see them start to climb once the air is out. You should see a few degrees lower temp on the driverside by the window than you see at the passenger side by the window. The air has further to travel from the core and has a little more time to cool down.

It's highly unlikely that a blend door/actuator problem occurred right after. Not impossible, but highly unlikely.

 

[Tbot191]

Okay I will definitely start with bleeding the system again, seeing as that's a great place to start. Also it does seem like there is a little less air flow through the drivers side but not a significant amount that is causing concern for a blend door, while I had the dash out I did check all the door and actuators and all seemed to be in pretty good shape, no obstructions when I put back together and don't hear any noises when I move the doors with the controls, I have a borascope that I'm going to feed into the vents to hopefully see the blend doors move.

 

[nlambert182]

You may see slightly less airflow from the driverside anyhow for the same reason as the temp variance. The blower motor sits on the passenger side so the air has further to travel. It should lose some velocity by the time it makes it over there.

 

[Gary Hill22]

What happens when the AC is running? My belief is that the Driver side is colder than the passenger side.
This is an issue with the TWO blend doors (one for passenger side, one for driver side) One is opening properly, one is not.
Since both sided were hot in the beginning, the ONLY culprit is the blend doors not operating the same. Forget all the Bleeding advice.
Been there.

 

[Marshall]

standard heater, just has one blend door, I believe, not 2.

 

[nlambert182]

What happens when the AC is running? My belief is that the Driver side is colder than the passenger side.
This is an issue with the TWO blend doors (one for passenger side, one for driver side) One is opening properly, one is not.
Since both sided were hot in the beginning, the ONLY culprit is the blend doors not operating the same. Forget all the Bleeding advice.
Been there.

Sorry, but this is incorrect.

It is a well known common problem that the heater cores clog on these trucks and provide the exact symptoms that the OP described. Just as with a clog... if coolant cannot pass through the heater core for any reason you will get no heat on the driverside first. If there is a large air pocket/air bubble preventing proper coolant flow that is what will happen.

While it's not impossible to have a blend door problem, it is highly unlikely given that the OP just opened the cooling system up during the install of new components. Common sense should say to go back and check your work. If there wasn't an issue prior to doing this work, there shouldn't be one now with new parts. If there is.... well.... Bob's your uncle. It's 99% of the time something you touched.

 

[LeeD]

If bleeding the system again doesn’t work you should flush out the new heater core. With all the work you’ve done it might have stirred up some junk and blocked the core.