Does this sound like a clogged heater core?

[nlambert182]

2018 Ram 2500

On my way into work the other morning I turned the heat on for the first time since buying the truck. On my other Rams the heat would melt you within 10 minutes. I noticed that my heat wasn't blowing as hot as my other trucks had all the way into work. The air was downright chilly.

Came home and checked the coolant level and all was fine. The coolant is really clean and looks like it was changed recently. The way this truck was maintained, I don't doubt it. It looks to be the correct coolant as well.

Yesterday afternoon I got the truck to operating temp (it's averaging 190-195 degrees) and then checked the blend door actuators and all were cycling as they should be. I stuck an infrared thermometer on each vent.

Pass window - 123 degrees
Pass center vent - 122 degrees
Driver center vent - 87 degrees
Driver window vent - 86 degrees

I hit both of the heater core hoses with the thermometer and both were reading within 6 degrees of each other.

The only thing I can think of is a partially clogged heater core. I have 2 gallons of the Mopar coolant on the way. What's the success rate of flushing the heater core? I'm going to give it a shot this evening and try to get some heat back to the driver side. Any tips that I need to know before I knock this out? As an aside, I am going to flush with a standard garden hose and if needed I can turn down the regulator on my air compressor and send some lower pressure air through it as well.

 

[mtnrider]

Most likely a clogged heater core, extremly common on these trucks. But also keep in mind it takes a long time for a diesel to heat up. Blend door problems were a 3rd gen issue, pretty rare to happen on a 4th gen

Here is by far the best way to flush it but be aware it will likely come back. You may have to do it several times and I also recommend a good coolant system drain/flush to try and get any junk out of the system (I disconnected the heater core when I did this to not flush more crap into it)

Flushing A Heater Core

Come along with Eric O. at the SMA shop as we diagnose and repair this 2013 Ram 3500 Cummins that came in with a complaint of no heat out of the dash vents. ...

youtu.be

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[nlambert182]

Yea it normally takes my trucks about 10 miles to heat up. Both of my other Cummins would have heat by the time I reached a certain point on my ride into work. This one made it the 25 miles to work (after warming up in the driveway) and still didn't have heat.

I'm going to give this a try and if necessary and if/when it comes back I'll likely do a full on coolant flush as well. I guess I got lucky in that none of my other 4th gens ever suffered with this issue. Has anyone had any success using any flushing chemicals or just a straight water flush? I've seen mixed reviews both ways.

 

[mtnrider]

I've tried CLR but to be honest just using that air assist gun in the video works the best. I also try to do it while it's warm but you have to be careful not to burn yourself obviously. I've also put boiling water down the hose and let it sit in the core and then flush and repeat to break up any possible gunk. I usually don't get a lot of stuff out of it, just some small particles but it always gets it going again.
I've been limping mine along for a couple years now, but did a good coolant flush about 6 months ago so hoping it does better from here on out, I really really don't want to pull the dash!

 

[RamDiver]

Pass window - 123 degrees
Pass center vent - 122 degrees
Driver center vent - 87 degrees
Driver window vent - 86 degrees

This difference from the passenger to drive side sounds excessive. It makes me wonder if one of the blend doors isn't fully opened or closed.

How long was your travel?

I'll check mine later this morning and report.

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[mtnrider]

This difference from the passenger to drive side sounds excessive. It makes me wonder if one of the blend doors isn't fully opened or closed.

How long was your travel?

I'll check mine later this morning and report.

.

Typical of a clogged heat core. It's because of the way the air blows across the core and were it's routed. The driver side air tends to blow across the lower part of the core (which is typically clogged) and the passenger side air is blowing more across the top of the core (less clogged).

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[nlambert182]

This difference from the passenger to drive side sounds excessive. It makes me wonder if one of the blend doors isn't fully opened or closed.

How long was your travel?

I'll check mine later this morning and report.

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25 miles one way. I let it warm up a bit in the driveway before I left. I was at 120 degrees coolant temp when I left home. It was at 190 within 10 miles. I'm assuming heater core as well. The doors are opening and closing as they should. I believe the heat difference is common with heater core issues from what I've been reading. I think mtnrider is spot on with what I've been seeing.

I'm going to try to slip away from work a little early today and attempt a flush. I did test our Armada heat and it's putting out 150 degrees across all the vents. I would assume that mine should be in that ballpark. I know the others in my sig would melt you to the point that I couldn't run the heat for very long.

I'm not going to have enough time to pick up the air assist gun so I'm going to have to use what I have to try and get this done for now but if I can get the heat back in the cab through this winter I'll work on a more detailed flush in the spring. If it comes to the point of heater core replacement in the future, I'll send it to the shop. I don't have the time or the desire to spend an entire weekend removing my dash.

 

[mtnrider]

nlambert, I just sent you a message. You still in Huntsville? I'm actually heading up there today.

 

[nlambert182]

I appreciate the offer! That's the great thing about this forum!

 

[Hanover Fiste]

My 2005 had the exact symptoms you have; hot on passenger side, cool on driver side.

I disconnected the hoses at the water pump and used a garden hose to flush the core both ways (reverse and forward).

The water pressure at my house is ~90 PSI, and most will say it's too high for the core; however, I let the hose go "full throttle" for a couple of 10-second bursts while doing the flush.

I really didn't see anything come out of the core, but nevertheless, my heat is working normally again. I also installed new heater hoses just in case.

 

[nlambert182]

I'm likely going to flush at the pump as well, just due to the restrictive access at the firewall. Hopefully a good 10-15 minutes of flushing both directions will shake loose whatever is causing the problems. I'm going to guess casting sand but curious to see what (if anything) shows up in the bucket.

 

[GTyankee]

The water only goes in & out of the HVAC Heater box

Fresh Air enters the cab above the upper glove compartment, that door can be closed & the air inside of the cab keeps passing over the heater core & gets warmer.

After the air passes through the BLEND DOOR & the Heater Core, it then passes through the first MODE DOOR & continues on through the 2nd MODE DOOR

If i am not mistaken, the first mode door moves the air flow to either the passenger or drivers vents or through both sides

The 2nd mode doors moves the air to the defrost vents or floor vents

I have a feeling that something is going on with that First Mode Door & most of the Heat is going to the Passenger side.


I watch a video, where the guy turned his HVAC Fan on Low
Then he pushed in knob on the Left & held it for 10 seconds, then he released it & held it again for 10 more seconds. The knob has a Light in it, it comes on when you are done.
Supposedly, that synchronizes all of the actuators
That makes the air flow better

2016 Ram Truck 1500/2500/3500 | Manual Climate Controls

This video will show you how to use your climate control system.

www.youtube.com

 

[LeeD]

I used to have to flush the heater core on my daughter’s Nitro every fall. Same issues as yours.

 

[nlambert182]

The water only goes in & out of the HVAC Heater box

Fresh Air enters the cab above the upper glove compartment, that door can be closed & the air inside of the cab keeps passing over the heater core & gets warmer.

After the air passes through the BLEND DOOR & the Heater Core, it then passes through the first MODE DOOR & continues on through the 2nd MODE DOOR

If i am not mistaken, the first mode door moves the air flow to either the passenger or drivers vents or through both sides

The 2nd mode doors moves the air to the defrost vents or floor vents

I have a feeling that something is going on with that First Mode Door & most of the Heat is going to the Passenger side.


I watch a video, where the guy turned his HVAC Fan on Low
Then he pushed in knob on the Left & held it for 10 seconds, then he released it & held it again for 10 more seconds. The knob has a Light in it, it comes on when you are done.
Supposedly, that synchronizes all of the actuators
That makes the air flow better

2016 Ram Truck 1500/2500/3500 | Manual Climate Controls

This video will show you how to use your climate control system.

www.youtube.com

I did see a video like that and I did attempt it, but all of my climate controls are touch screen and I never could get them to do it.

Luckily the amount of air coming from each side is roughly the same. I can't feel a difference in airflow. I was able to watch the other motors and they did "seem" to be functioning as intended. Nothing was bound up and as best I could tell they were fully opening and closing.

But I did flush and the heat has returned (thankfully). I wasn't completely sure at first because the water that flushed through came out clear. However, once I finished it was a pretty noticeable difference as soon as the truck was up to temp.

Pre-Flush:
Pass window - 123 degrees
Pass center vent - 122 degrees
Driver center vent - 87 degrees
Driver window vent - 86 degrees

Post-Flush:
Pass window - 151 degrees
Pass center vent - 150 degrees
Driver center vent - 144 degrees
Driver window vent - 143 degrees

I'm sure I'll have to do it again in the future until I do a full on flush, but it was a simple process. I appreciate the help and a shout out to @mtnrider for offering up his assistance.

 

[greg mayrhofer]

Trapped air can also cause this problem, after changing the coolant or flushing, use a funnel that can burb the air out when pouring in the new mixture of the proper coolant,, and air trap in the coolant system can cause other problems as well , had this problem your experiencing on another dodge ram i owned, and burping was the fix

 

[Dbrewton]

I had same issue. I flushed with water hose and refilled with coolant. Lasted a few weeks, but getting noticeable cooler again. Will have to flush again.

 

[Joseph Godvin]

1/2 plugged core, they changed design years ago, old style were a continuous loop and could be back flushed, new style looks like a small radiator, back flushing doesn't work anymore....you have to replace core. been there too many times !!!

 

[nlambert182]

Seemed to work just fine for me?

 

[Thomas Scott]

I had that problem and it was three way valve had code but cleared it and it seemed to work but not alot of heat changed valve and had all kind of heat

 

[Thomas Scott]

Check 3way valve more water going to transmission cooler than heater change mine and heat now works fine