No cab heat

[Dodgeguy44]

2010 2500 5.7 4x4. I have replaced a plugged heater core, repaired a blend door actuator, replaced the water pump, flushed the system, and refilled and bled the air out as best I could. Now I cannot keep constant heat in the cab. I took off the heater hoses at the engine and used a pump to push air out of the heater core then pinched off the lines when full and refilled the engine with coolant then took off the hose pinchers and had heat for about 10 minutes and cold again. Both heater lines are hot. So I tee'd in to the heater return line and ran a hose up above the rad, then pinched off between the tee and the engine. Started the truck and I get a small trickle of coolant out of my added hose. Seems the pump is not pushing the coolant to the heater core.

 

[Dean2]

Brand new water pumps have been known to be defective. That said, have you checked the thermostat before deciding you new pump is the issue. Second thing to check, have you got the heater in and out lines the right way around? Final thought, if your heater control valve is not opening and allowing hot water to get to the core you get a trickle on the outlet side, which seems more likely to me than the new pump.

2015 Ram truck 3 way coolant valve removal and replacement

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[jws123]

Ahh yess heater core season yours is a 2010 so age is right After you confirm no air in coolant system and tsat/water pump is good. You will need to replace the heater core the oem 4th gen cores love to clog up I have never been able to un clog one have done about 10 of them so far and another one coming in its really not that bad of a job.

 

[Jeepwalker]

Well at this point, how about tee-ing into your heater core 'supply' line and double check the flow when the engine is warm (not under pressure though). If flow is low, then you probably have a flow issue. what can happen under certain conditions with some water pumps where the impeller tolerances are on the 'loose' side, is as the impeller heats up it expands (from the heat) and can slip where it's pressed on the shaft. If/when that occurs, it won't pump. But while cool, it can shrink down and pump fine. It's rare, but possible. Certainly worth a check.

Is there a spring in your lower heater hose? It's not 'sucking in' under acceleration, is it?

If you rule out flow issues, go back and look at your blend door motor you replaced. Was it a Mopar blend door motor, or the cheapest unit on the first boat out of asia??

,

 

[Dodgeguy44]

As I mentioned in my post all of the parts have been replaced including the thermostat. The only other factor I did not mention is when I started this project I found a jelly like substance in the coolant collecting around the rad cap and thermostat. That was the reason for replacing the heater core and flushing the system but through all of this nothing has changed as far as cab heat. In the shop I get it to work good then test drive it about 2 miles and it goes cold.

 

[Dean2]

Did you look at the heater control switch/coolant valve? The lack of coolant flow from the heater core out line still makes me suspect that.

 

[turkeybird56]

YUP, sounds like a HCV. Wish I had one in MY 2019 DT truck instead of remodeled Blend Door BS.

 

[Dodgeguy44]

These trucks do not have a heater control valve only blend air doors and they are working.

 

[Dean2]

Okay, then my take is you still need to figure out why the flow through the heater core is so low. Pull the inlet hose and see if you have good flow. If you don't is that hose plugged up. If you do, then what is stopping it from going through the heater core. It really is a pretty simple system. The frustrating part is so much of it can be tough to get at. Makes for pretty high frustration level if you have to keep getting into it. I feel for you.

 

[turkeybird56]

These trucks do not have a heater control valve only blend air doors and they are working.

BOIRD absolutely HATES BS redesigned Blend Door System. HCV was just so much better, efficient, and easy to troubleshoot IMHO (very humble).

 

[Dodgeguy44]

I agree. There was nothing wrong with a valve in the system but here we are.
There is only a trickle of coolant returning from the heater core as I tested. I’m just not sure why that is. Good flow across the rad when the thermostat opens so why not into the heater core. I had both lines that run to the core off of the engine side and it flows good both ways with a garden hose attached. So for some reason the water pump won’t push it up the hoses.

 

[turkeybird56]

Not being there, Internet Guessnosis, but if the hoses are clear, and no restrictions and the water pump not pushing: then there may be a blockage at the point of the water pump to the outlet hose, something wrong with the impellers, or maybe just a bad water pump. As long as the thermostat is opening and coolant being released.

Did U try this: Hoses off core: Take a garden hose with a small nozzle and put right into the opening of the core inlet and see if under pressure the water runs through the core and comes out the outlet. If it does, then water pump/pressure (T stat issue). If not, then U still have a core issue.

All IMHO...

 

[GTyankee]

My thoughts, for what is worth

If the water pump is pumping, shouldn't you see water moving in the radiator ?

If you have a giant AIR bubble,
looking at the top face of the water pump, at the highest point, you should see a plumbing plug.
When the engine is COLD, remove that plug, add water to the radiator, until nothing but coolant comes out.
IF, you can't remove that plug, look to the right about 6 inches, there is a hose & a sensor, with the cold engine, the sensor can be removed to purge the air.

The other thing that can be checked with the proper scan tool, is the controls in the center stack.
running a scan on that part of the system, actually bypasses the buttons & knobs & electronically works the Actuators & Doors

 

[GTyankee]

This is the type of scanner that i was referring to

HOW TO TEST HEATER AC BLEND DOOR ACTUATOR on Most Cars

HOW TO TEST HEATER AC BLEND DOOR ACTUATOR on Most CarsIn this video we will explain how to test blend door actuator on a car. You may have multiple blend doo...

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snap on test

Quick Tip: Chrysler HVAC Test

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[gofishn]

Hoses that attach to heater core show good flow, throughout, when attached to core only?
If so, then blockage is from T-stat to where the heater hoses attach to engine.

Radiator shows good flow when T-stat is open?
If so, then water pump is functioning properly.
Definitely with enough enough pressure to push a bunch of coolant, through those big **** hoses, so those little heater core hoses should not be a problem for that pump.

Remove T-stat, hook up a garden hose, with low pressure and see how much flow ya got from t-stat hose connection to wher the heater core hose attaches.

Get some RMI-25 and run it so you can clear all that gunkiness out of your system. clean it up by cleaning out yoru overflow, often until you no longer need to clean upo your overflow because it never gets gunked up.

Report back with updates adn what ended up working.

 

[Marshall]

On a long drive , what is the motor temp like? normal?
wonder if a cold air door is open?
If you put the heater on recycle, would that shut the cold air door?
I have not worked on these newer ones, but if you have no water flow, door don't matter.
Bad hose that is separated inside and blocking heater flow??? but I think you said they where changed.

 

[Atcer2018]

Ahh yess heater core season yours is a 2010 so age is right After you confirm no air in coolant system and tsat/water pump is good. You will need to replace the heater core the oem 4th gen cores love to clog up I have never been able to un clog one have done about 10 of them so far and another one coming in its really not that bad of a job.

A man who has done ten heater cores probably knows the answer to my question. On a 4th gen, is the recirculation door mechanism/unit removable without pulling the dash? I can pull my upper glove box and see the white accordion, half circular door and the actuator connected to it. The actuator works but the splined hub the actuator fits into on the actual door itself is cracked and missing half the plastic. The splined hub is part of the recirculation door so i’m assuming the door which comes as a unit needs to come out for repair but I don’t see how it’s removable without pulling the dash.

 

[jws123]

A man who has done ten heater cores probably knows the answer to my question. On a 4th gen, is the recirculation door mechanism/unit removable without pulling the dash? I can pull my upper glove box and see the white accordion, half circular door and the actuator connected to it. The actuator works but the splined hub the actuator fits into on the actual door itself is cracked and missing half the plastic. The splined hub is part of the recirculation door so i’m assuming the door which comes as a unit needs to come out for repair but I don’t see how it’s removable without pulling the dash.

You might be able to get it out never had to replace any blend doors on a 4th gen only heater cores so I always have dash out. Blend door issues not as common as the older rams at least the recirculation door is not rly that important you could jam it open or closed its normally open most of the time any ways.

 

[Atcer2018]

You might be able to get it out never had to replace any blend doors on a 4th gen only heater cores so I always have dash out. Blend door issues not as common as the older rams at least the recirculation door is not rly that important you could jam it open or closed its normally open most of the time any ways.

Thank you. It’s jammed closed now and will stay that way if the dash needs to come out to replace it. I’ll wait till the heater core needs to be replaced LOL

 

[jws123]

Thank you. It’s jammed closed now and will stay that way if the dash needs to come out to replace it. I’ll wait till the heater core needs to be replaced LOL

makes sense ahahah.