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Hey everybody new member here. I have a 2015 Laramie longhorn ecodiesel. I'm having an issue with my heat. I recently had a leaking water pump and I replaced it at about 104k. Truck has 117 now. Every since then, my heat hasn't been working while driving. It works like a champ at idle but as soon as I start driving and I get at a steady speed, the heat goes out and just blows cold air. I've drained and burped the system twice, both times to no avail. First time I was trouble shooting the leak, I put water in the tank to find where it was leaking. I sucked it all out with a shop vac to remove all water. Maybe not the best idea but idk. Anyways, I know how hard it is to get the ecodiesel up to the temperature in order for the thermostat to open to burp. So I drilled a small hole in it to let coolant pass through so air would escape. Even before that, when filling the coolant tank, I left the nipple on the top of the thermostat open untill coolant came out. I highly doubt there's an air bubble in the system since the heat works part of the time and not under load. Could it possibly be the heater control valve messed up? I heard when it screws up you get a CEL? Could I have also messed it up by sucking coolant out with a vacuum? Help needed asap since it's starting to get cold here in Louisiana.
 

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2015 Outdoorsman EcoD CC w/6.4' 4X4
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Help needed asap since it's starting to get cold here in Louisiana.
hahaha cold in Louisiana... it's was 29°F this morning in Michigan, you have what we call Fall weather there..lol
I have to ask because it wasn't mentioned, did you replace the thermostat? and did you use an OEM part?
The three way valve can effect the heat in the cab, if it doesn't work. It does sometimes throw a code if it's not working.
 

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hahaha cold in Louisiana... it's was 29°F this morning in Michigan, you have what we call Fall weather there..lol
I have to ask because it wasn't mentioned, did you replace the thermostat? and did you use an OEM part?
The three way valve can effect the heat in the cab, if it doesn't work. It does sometimes throw a code if it's not working.

lol this is winter for us. Anything below 50 is cold. But no the thermostat is still the original. But it was working previous to drilling a hole in it. After 208 degrees, the upper radiator hose is hot to the touch so I know it's working. I put a hole in it to keep the coolant flowing through the system to try and get all the air bubbles out while the system was open.
 

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lol this is winter for us. Anything below 50 is cold. But no the thermostat is still the original. But it was working previous to drilling a hole in it. After 208 degrees, the upper radiator hose is hot to the touch so I know it's working. I put a hole in it to keep the coolant flowing through the system to try and get all the air bubbles out while the system was open.
Could drilling a hole in the t-stat be the problem??? Just sayin
 

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First thing when filling the cooling system on any engine with egr you should vacuum fill any small air pocket can destroy a egr cooler. Second is test your three way valve it might be damaged internally and passing self check but still not working. Does the transmission warmup quickly even with full cab heat demand?
 

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First thing when filling the cooling system on any engine with egr you should vacuum fill any small air pocket can destroy a egr cooler. Second is test your three way valve it might be damaged internally and passing self check but still not working. Does the transmission warmup quickly even with full cab heat demand?
Now that you mention it, the transmission does take quite awhile to warm up. I never thought that I'd have to vacuum fill the vehicle to remove air from the egr either. Also do you know a good way to test the 3 way valve?
 

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Now that you mention it, the transmission does take quite awhile to warm up. I never thought that I'd have to vacuum fill the vehicle to remove air from the egr either. Also do you know a good way to test the 3 way valve?
If you dont have cab heat and the transmission is taking longer than normal to warm up it could be an air pocket. The cooling system on these is a mess but it works well for the most part. When warm and running feel the hoses at the three way valve and see which feels cold or all feel hot.
 

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If you dont have cab heat and the transmission is taking longer than normal to warm up it could be an air pocket. The cooling system on these is a mess but it works well for the most part. When warm and running feel the hoses at the three way valve and see which feels cold or all feel hot.
Sorry it's been a few days. I was unable to feel for the lines in the cab since I've only been driving my trick to work in the am and back. But I have noticed that the transmission temp is about 30 to 35 degrees cooler than my coolant temp when shown on the dash. Is this normal? If not, I'll investigate that valve further.
 

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I didn't do anything special when filling my coolant system, and never had an issue with air pocket or heating issues.

I did have a no-heat condition once. I researched it and found you can downshift to hold RPM to 3000 and the heat will begin working. I tried it and it worked within 30sec or so of holding RPM to 3k. Must've been a stuck 3way valve or something.
 
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Following... I had same problem last winter. I never found a solution. Nice warm 30f today tho :D
 
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