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heat issue driving me nuts

6K views 14 replies 6 participants last post by  Dennyboy 
#1 ·
I know this may have been all ready covered. But I have my truck to the mechanic three times. The heater core was leaking so I had it replaced. I got the truck back barely had heat. Changed the thermostat. (195 degrees) Still luke warm at best. Temperature right at or around 210. Not overheating or running cold. Both the feed and return from the heater core are burning hot to the touch. Mechanic says control for heat is working fine. This is really driving me nuts. Winter coming and no one can get my heat back. Please any help would be appreciated. Especially before I start tearing into my mechanic.
 
#4 ·
seems this is a fairly common issue - mine is having the same problem.

going to start the investigation tonight on the heater hoses, etc...

So, if anyone has any input or has gotten theirs fixed, I would dearly like to know.

Thanks
 
#7 ·
Mine ended up being a dirty heater core. I flushed it, backflushed several times, topped off the rad with water, ran it with full heat for 10 mins etc....I did this about 4 times total. The heater now works like a champ. I put a cooking thermometer in the driver's side vent. With the heat on full speed and all hot, the temp got to ~140* at idle. Give it a try if you haven't already. Hope this helps.

BTW, I disconnected the heater line at the w/p and flushed/backflushed thru the hose then the w/p fitting, all with the radiator cap off. I did this several times (about 4) until clean water was being flushed out everytime. It takes time but it well worth it and FREE too!
 
#9 ·
so when I got home tonight, I started looking around in the engine bay... didnt realize it but I had grabbed the radiator hose... and it wasnt uncomfortably hot like I would have expected.

I then grabbed one of the heater hoses and it was cooler than the radiator hose... the other heater hose was about the same temp as the radiator hose.

does that sound like a stuck-open thermostat to anyone else? cause it sure does to me.

and I would expect one of the heater hoses to be cooler than the other after its gone through the heater core, so that seems somewhat normal to me (or at least expected, especially if the thermostat is wide open.

The one tidbit thats also important to note is that I either my temp sending unit or the gauge is bad, because since I picked up the truck a couple of months ago, the temp gauge has never shown a temp.

Also, switching from hot to cold and back I can definitely feel the difference in the temp... but that really doesnt mean much I dont think, does it?

thoughts?
 
#10 ·
The hoses for the heater core might feel the same temp to the human touch. Lets address the engine temp first. What do the upper and lower hoses feel like as the engine warms up? Hot water from engine flows into the radiator via the TOP hose. The BOTTOM hose feeds the engine with cooled water. During the first few cycles of the t-stat, you should notice a differenct in temp by touching them. If you cannot, or do not have the experience, use a cooking thermometer and keep it in the top of the radiator (DO NOT REMOVE THE CAP ONCE IT'S WARMED UP). After the engine has reached it's full operating temp, you should see a reading ~ 180*-220*. I see you live in Wa State. The ambient temp is probably ~60* where you are so your temp might be a little lower but not much if the truck is sitting still. Did you take a baseline temp reading from your vents? This will help determine if you have done something that has effected the temp reaching the cab. I am in Sunny Fl (don't use heat that often) so let me know how things unfold. I can check my truck to use as a comparison for you without freezing my ARSE off!
 
#11 · (Edited)
no problem, I will check tonight when I get home.

I do know that after a 5 mile drive through town, on an engine that was already warm from a previous drive, hitting a couple stop lights and a couple stop signs, that the TOP radiator hose was not uncomfortable to touch... which seems odd to me as this is the hose that should be the hottest coming out of the engine.

I have not taken the time to get a reading on the temp coming out of the vents, at low after the 5-mile trip, the temp out the vents is luke-warm, nowhere near 140*.

also, the heater hose on the left of the engine was warmer than the hose on the right side of the engine (while facing the front of the truck), slightly... (could have been mentally cooler versus actually - I will check that tonight too) though neither were uncomfortably warm, definitely neither were warmer than the radiator hose.

yeah, its raining like mad and is 54* outside today... so while I am not excited about heading out to check, I need heat in the truck.

Oh, one other small note, the longer I drive the truck, the warmer the heater gets - again, it seems like its just not getting hot and my darn water-temp gauge is either bad or the engine is just never getting hot enough to register on the gauge (which starts at 130)
 
#12 ·
OK, I've checked the following on my truck which is basically a stock 5.9. With the heat on hi and full hot setting I get:

- Both heater core hoses are too hot to keep touching for more than a couple of seconds. The passenger side (goes to intake) is noticably hotter than driver side (goes to w/p).
- Upper Rad hose is hot but can keep my hands on it, lower is noticably cooler.
- Rad water temp taken at the rad neck with a cooking thermometer is ~170*
- The guage in the cab shows just under 1/2 and partially covering the "2" in 210.

It is starting to sound like a stuck t-stat from what you are describing. I would compare against what I found on my truck and if you find cooler temps (vent air, hoses, guage, water temp at rad neck) then I would suggest something cheap like replacing the t-stat and going from there. Who knows, the stat might not be in there (like the old Chevy's in So Fla). Let me know if I can make any more checks for you. I've been to your location and you NEED heat!

Troy
 
#13 ·
I finally had a chance to work on the Ram yesterday. thinking that it was a thermostat issue, thats what I went after first. Sure enough, the T-stat was a failsafe and had been stuck open.

I replaced it with another failsafe (I prefer them to fail open versus fail closed) and like magic, the temp gauge started working (though it didnt get very high, just to the line over 130* - but most importantly, the heater got nice and hot while at full-speed.

Thanks for all the input/help everyone... I appreciate it!

 
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