2018 ram 2500 6.4 heat issue

[samsdad02]

Mines factory 203 rated thermostat according to dealer that’s the highest rated one for mine

Huh. I could be wrong about the temp. Doesn't seem to matter with the range it has. My v10 ford is 192* and stays within 2* either way, so it's weird to me the range it runs.

 

[Lb30]

Huh. I could be wrong about the temp. Doesn't seem to matter with the range it has. My v10 ford is 192* and stays within 2* either way, so it's weird to me the range it runs.

Yea I figure I’ll end up having to have the dealer just tear the dash out of it I’ve tried everything that I know of without tearing the entire dash out with it and still can’t find the problem, sadly it’s been that way since I got it last year and the dealer I bought I from said it was normal for those trucks which I know it’s not they just didn’t want to fix it under the 30 day warranty

 

[RamCares]

Hello, @Lb30!

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[Lb30]

Update: heater core needs replaced dealer wants $3500 to replace it

 

[Deleted member 47449]

Just back flushed our 2016 PW with a Lisle water and air heater core flush tool. Was 120F at the vent. Now 144F at the same vent. Temp stick is in Celsius. Outside temperature was in the 60's before and after, not 90F as displayed. Just the sun was shining onto the driver's mirror thermometer.

When you back flushed did you use air pressure too?

 

[mwalsh9152]

I just flushed the heater core in my 21 6.4 this weekend. The far left vent was cold, not lukewarm while the passenger side was hot. I used a 110v pump to circulate, and added air from a cobbled together Y fitting. I got a good amount of crap out, and the heat is great now. I'm trying to figure out the best way to filter the coolant, then I will flush again and put the filter in.

 

[Trash Panda]

I just flushed the heater core in my 21 6.4 this weekend. The far left vent was cold, not lukewarm while the passenger side was hot. I used a 110v pump to circulate, and added air from a cobbled together Y fitting. I got a good amount of crap out, and the heat is great now. I'm trying to figure out the best way to filter the coolant, then I will flush again and put the filter in.View attachment 92763

I’d just get two birds stoned at once, and drain all the existing coolant out, and flush out the block & radiator.

Start with fresh coolant after

 

[Vamphry2000]

I had the same issue on my 2014 2500 6.4L stated 2 years after buying the truck new. When I flushed the core I got a ton of sand and other partials. When asking around was told this era of trucks had a poor designed heater core that was sand cast and there were a ton of issues with them. Even if a bit of sand was left inside it would clog the narrow passages for the coolant. Had my core and blender doors replaced in early 2026 and everything has resolved.

 

[Lb30]

I had the same issue on my 2014 2500 6.4L stated 2 years after buying the truck new. When I flushed the core I got a ton of sand and other partials. When asking around was told this era of trucks had a poor designed heater core that was sand cast and there were a ton of issues with them. Even if a bit of sand was left inside it would clog the narrow passages for the coolant. Had my core and blender doors replaced in early 2026 and everything has resolved.

I flushed mine to many times to count never had anything come out of it even with using clr a few times and compressed air and even let it sit overnight with vinegar in the core over night and never got anything out of the core