Heat Cold At Highway Speeds - Dodge Durango Forum
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post #1 of 35 Old 01-21-2010, 12:57 PM Thread Starter
zidane
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Heat Cold At Highway Speeds

Hey guys,

I;ve been looking all over the place for an answer to this, but it seems people have the opposite problem where the heat is cold/ luke warm at idle/low speed and gets better at high speed. When making my commute back home from Long Island (about 7 hour ride) my heat just started blowing cold air at about 75 mph. I rode home frozen to the steering wheel the rest of the way and replaced the thermostat. Backflushed the heater core, before winter hit, but the problem still developed. I have tried blocking the radiator off, pipe insulation around the heater hoses. Nothing really seems to fix it or improve the quality of the heat. I have to drive it around for about 30-40 minutes for it to blow luke warm heat at city speeds. Any ideas? I wanted to get opinions before I take it to the shop and shell out cash for a new heater core or something. Thanks in advance for your help.

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post #2 of 35 Old 01-21-2010, 01:15 PM
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what degree thermo did you put in it?

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post #3 of 35 Old 01-21-2010, 04:06 PM Thread Starter
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195. Up to the point in my trip where the heat stopped working you could watch the temp fluctuate to the temp the t state would open then the temp would drop, then suddenly the temp drooped and stayed low, like 160 or so, so I thought the t stat was stuck open. Didn't seem to fix the problem though.

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post #4 of 35 Old 01-21-2010, 05:12 PM
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sounds like the heater core is leaking mine was doing the same thing never ended up in the cab though it was draining through the drain hole in the heater box do you smell coolant at all with the heat on?
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post #5 of 35 Old 01-21-2010, 07:21 PM
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Sounds like a bad radiator cap and it's releasing the pressure in your cooling system too early.
post #6 of 35 Old 01-21-2010, 07:56 PM
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my 98 was a 4 banger, and it did it to me sometimes. i just figured it was the simple fact that at 10 degrees outside and 75 mph, that little 4 cyl didnt make enough heat to keep the coolant system temp up high enough for adequate heat. basically the cooling system was just too efficient in super cold temps.

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post #7 of 35 Old 01-21-2010, 10:34 PM Thread Starter
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I was concerned about the heater core, but I haven't been losing any coolant, the level as been constant in the radiator and in the overflow reservoir. I'm liking the radiator cap idea, since its just a tad cheaper than the heater core. I've been watching the passenger floor mat for wetness but nothing there either. I'll give the radiator cap a shot, it's never been replaced. Thanks for the advice, I'll report back after.

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post #8 of 35 Old 01-21-2010, 11:09 PM
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Sounds like maybe your blend door isn't working properly. Either a broken vacuum line or just a bad solenoid for the door.

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post #9 of 35 Old 01-21-2010, 11:43 PM
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Originally Posted by hskrRT View Post
Sounds like maybe your blend door isn't working properly. Either a broken vacuum line or just a bad solenoid for the door.
Guess you didn't read post #3.
post #10 of 35 Old 01-22-2010, 01:00 AM
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Quote:
Originally Posted by bwdakrt View Post
Guess you didn't read post #3.
Okay??? He changed his t-stat and it didn't fix it.

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post #11 of 35 Old 01-22-2010, 01:08 AM
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Okay??? He changed his t-stat and it didn't fix it.
195. Up to the point in my trip where the heat stopped working you could watch the temp fluctuate to the temp the t state would open then the temp would drop, then suddenly the temp drooped and stayed low, like 160 or so, so I thought the t stat was stuck open. Didn't seem to fix the problem though.

Since when does a blend door cause the temp to fluctuate?
post #12 of 35 Old 01-22-2010, 03:57 AM
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Quote:
Originally Posted by bwdakrt View Post
195. Up to the point in my trip where the heat stopped working you could watch the temp fluctuate to the temp the t state would open then the temp would drop, then suddenly the temp drooped and stayed low, like 160 or so, so I thought the t stat was stuck open. Didn't seem to fix the problem though.

Since when does a blend door cause the temp to fluctuate?
So how does your radiator cap theory fit in here?? You didn't see me jump on your case about that shit, why did you feel the need to post your BS about my suggestion?

zidane, what was the outside temp when it was doing this? And have you changed the t-stat since it started?? Your post was a little confusing. My heater doesn't work all that great when driving down the road, but sit still in a drive through and it warms up as the coolant in the radiator warms up more than when driving and forcing cold air through it. If I stop and pop the hood right after a drive in the 30 degree or colder temps we've been having, my bottom radiator hose is cold, and my heater hoses are cool enough to hold on to.

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post #13 of 35 Old 01-22-2010, 05:38 AM
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Quote:
Originally Posted by hskrRT View Post
My heater doesn't work all that great when driving down the road, but sit still in a drive through and it warms up as the coolant in the radiator warms up more than when driving and forcing cold air through it. If I stop and pop the hood right after a drive in the 30 degree or colder temps we've been having, my bottom radiator hose is cold, and my heater hoses are cool enough to hold on to.
My trucks seems to be the opposite. I get great heat when moving and next to nothing when idling.

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post #14 of 35 Old 01-22-2010, 05:46 AM
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Quote:
Originally Posted by dave2003 View Post
My trucks seems to be the opposite. I get great heat when moving and next to nothing when idling.
thats your water pump impeller fins bein shot. i had the same problem on a friends yota a while back. took the pump out, the fins looked like a saw blade cause they were corroded right off. your coolant isnt circulating because your moving, its circulating because your at a higher engine rpm, making up for the worn out blades.

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post #15 of 35 Old 01-22-2010, 06:15 AM
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Quote:
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thats your water pump impeller fins bein shot. i had the same problem on a friends yota a while back. took the pump out, the fins looked like a saw blade cause they were corroded right off. your coolant isnt circulating because your moving, its circulating because your at a higher engine rpm, making up for the worn out blades.
That sucks! I hope its not the case. I changed out my water pump about 35k miles ago. If it is then it is a relatively cheap and easy fix.

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