I just replaced the thermostat with a 180degree about 2 months ago. Everything has been fine for the last 6 weeks since the change out.

Now as of last week my truck doesn't barely show on the gauge that it warming up, even after an hour straight of driving on the freeway at 75mph. The heater now blows cold only, not even warm air.

Here is the kicker though.....
Since this change in the truck I am getting a noticeable horsepower gain.

Outside temp has been around 45-75 degrees around here this past week.
Engine idle at an off ramp stop light was around 550 after 10 minutes of driving.
Now with this problem it's about 700 rpm at a stop, but smooth idle still...Just doesn't seem to be warming up.

Anyone have any idea what's going on??

Thanks!

 

well when u put in a 180 stat ur adding power the engine is cool enough to produce better compression. now ur cold part... my buddy did the same thing with his chevy in the winter time he puts instillation around his radiator to keep it warm to produce heat. ur problem i have no idea. my Durango only produces heat for 30 seconds then changes to cold. he used to be fine untill bout couple years ago my dad took it down to a mechanic to see if he could to a recharge since then then cold air is abit colder but no more heat... heat just sucks, we tryed redoing the switch that worked for couple months and then it has come back. we could replace the heater core but my farther would rather a shop doing it but that be a bit pricey. ima keep my eye on this post im sure others have experienced the same my friend.

 

Have you bled all of the air from your system? These engines can be a bit tricky to bleed especially if it's the 5.2

 

Defective thermostat, it is staying open.

 

+1

get a new T-stat!

 

sounds like a failed stat (they are designed to fail OPEN)

 

4.7s are tricky. 5.xs are easy. Open rad cap, run till hot, watch stat open and close and add fluid each time level drops until full. Done.

IndyDurango

 

Thanks for the help so far guys.

Update as of this evening.....
Drove around town for about 1/2 an hour, outside temp about 60 degrees.
The gauge went a little past 130 which is the warmest it has got in the last week.
The heater is still blowing strong but is now luke warm air.

I will try to bleed the system as Indy has instructed tomorrow...thanks Indy/All

 

I think your gauge is bad. If you drove it for 30 minutes in 60 degree weather, then engine was a hell of a lot hotter than 130. Even with a open stat, it would have reached temps of 180-205 in that time. Especially on a '98 which does not have an aux fan and tends to overheat, not underheat.

Fill it up and run it as I mentioned then let us know.

IndyD

 

The motor can be tricky and cause (what you would think as an under heating issue) but politically incorrect. I fought this issue for a long time tell I finally tested the output temperature of the antifreeze coming straight out of T-stat with a calibrated thermometer @ 182-185 which was perfect! I figured out that the water making it's way into the motor was so cold that the engine was staying too cold. The thing I also found out later was the instrument cluster gauge was incorrect which was the largest issue. Mine was a 1998 Durango 5.9L.

Next Issue i had was the heater core was plugged and needed replaced. Now my heater NEVER blew hot.


First thing first, measure the hot water coming out of the T-stat neck buy loosing the clamp and pulling the hose up as far as you dare and re-clamping. Then bring the engine up to temp and use a meat thermometer to poke a tiny hole as close as you can to the T-stat neck through the hose. Do this close enough that you can slip the hose back over the T-stat neck and you can clamp on the other side so it wont leak anymore. If you are close to 180 then you heater core is plugged.