my truck always runs at 190-weather winter or summer.. the past couple of days on the way to work in the morning i noticed 194 degrees on my gauge. so i opened up two of the winter flaps on the winter front (always left the inter cooler flap opened) no difference. on the way home tonight i hit the throttle hard at 40 mph up to 70mph hour and the temp gauge spiked at 200 degrees but dropped back down to normal-190 as soon as i backed off. like i said my truck runs steady at 190-always. the coolant has 40,000 miles on her and at that time the radiator cap and thermostat was replaced. the water pump was replaced 25,000 miles ago. i turned the a/c on and off this morning and i could here the click of the fan clutch engaging. any ideas what to look at or replace first?

 

Mines been doing the same exact thing. Since my truck was new I have only heard the fan engage a half dozen times. Can you really hear them engage at an idle when the a/c turns on?

 

yes i can hear it click. changed the coolant, radiator cap, t stat and coolant temp sensor. truck still doing same thing. always ran at 190 degrees.

 

RJM, I just got online to post my problem, and saw yours - what timing!

Traditionally, my truck always ran around the 190-195 range (hard to tell exactly where the needle is pointing on my gauge), but always the same, regardless of time of year. In heavy stop and go traffic and when towing heavy, my temp has run up around 200 maybe a hair higher, but otherwise the same. About 10k miles ago my temps started fluctuating...running up to around 200, and then almost as if the tstat opened, and the temp goes quickly soaring down to 190ish or below even.

Fast forward to this week- crazy things are happening - yesterday and today the truck's gauge went up WAY too fast..its 25f and it was sitting all day...within a copule miles the gauge is up to 200 and today even went to 225+, before all of a sudden shooting wayyyy down to barely warm. My initial thoughts were perhaps the thermostat or coolant temp sensor. Are these easy to replace? I will do some searching unless someone has a quick link. I even wondered today if perhaps something is stuck in the coolant passages, and one little section gets really hot before bursting through.. There's no way the engine could truly be getting that hot that quickly in these temps...and the fact that when I turn the heat on I only get mildly warm air would seem to support that.

Does anyone have a suggestion? It sounds like several of us have the a simliar problem, although mine is in the worst stage apparently!

 

i bought a new t stat and coolant temp sensor from cummins. total for both was 45.00 bucks. it takes a total of five minutes to change both. but it did not help my fluctuating of my temps

 

Darnit - because I ordered both of those last night.

I was reading in the dodge service manual, and there were several choices for possible problems with our engine if the coolant was either too hot, too cold, or fluctuating/swinging. In both of my cases (hot/swinging) (and no, I'm not doing any hot swinging, ), air in the cooling system was listed. As soon as I read that, it occurs to me that almost every time I take my air intake in/out to service the filter, I knock off the little black coolant hose up there near the top of the radiator that's in the way. Perhaps those few seconds that thing is disconnected introduced enough air to cause the problem? That almost would make sense too, because just this week it has started doing totally crazy things like spiking up high, and I just changed the air filter out last week.. It says the fix for air in the system is to drain and refill according to procedure. I am considering doing a full drain/refill when replacing the thermo/cts, just to kill three birds..however as silly as it sounds, i'm struggling trying to figure out how to catch/keep 7+ gals of clean coolant. May have to use two buckets and see if my minnnows all die next fishing trip..haha


Sorry it's unformatted, but below is a copy/paste from the service manual for our trucks.

 

CONDITION POSSIBLE CAUSES CORRECTION
TEMPERATURE GAUGE READS
HIGH. COOLANT MAY OR MAY
NOT BE LEAKING FROM
SYSTEMNOTE:
Information on dash cluster is
displayed based on broadcast data
from ECM. DTC will be set for
engine sensor circuit concern.
1. Vehicle overloaded, high ambient
(outside) temperatures with A/C
turned on, stop and go driving or
prolonged operation at idle speeds.
1. Temporary condition, repair not
required. Notify customer of vehicle
operation instructions located in
Owners Manual.
2. Temperature gauge not
functioning correctly.
2. Check cluster (Refer to 8 -
ELECTRICAL/INSTRUMENT
CLUSTER - DIAGNOSIS AND
TESTING)
3. Air trapped in cooling system 3. Drain cooling system (Refer to 7 -
COOLING - STANDARD
PROCEDURE) and refill (Refer to 7
- COOLING - STANDARD
PROCEDURE)
4. Radiator cap faulty. 4. Replace radiator cap.
5. Plugged A/C or radiator cooling
fins.
5. Clean all debris away from A/C
and radiator cooling fins.
6. Coolant mixture incorrect. 6. Drain cooling system (Refer to 7 -
COOLING - STANDARD
PROCEDURE) refill with correct
mixture (Refer to 7 - COOLING -
STANDARD PROCEDURE).
7. Thermostat stuck shut. 7. Inspect and test thermostat.
Replace thermostat if necessary.
8. Bug screen or winter front being
used.
8. Remove bug screen or winter
front.
9. Electronically controlled viscous
fan drive not operating properly.
9. Check viscous fan (Refer to 7 -
COOLING/ENGINE/FAN DRIVE
VISCOUS CLUTCH - DIAGNOSIS
AND TESTING)
10. Cylinder head gasket leaking. 10. Check for leaking head gaskets
(Refer to 7 - COOLING -
DIAGNOSIS AND TESTING).
11. Heater core leaking. 11. Replace heater core.
12. Cooling system hoses leaking. 12. Tighten clamps or Replace
hoses.
13. Brakes dragging. 13. Check brakes. (Refer to 5 -
BRAKES/HYDRAULIC/
MECHANICAL - DIAGNOSIS AND
TESTING)
14. Accessory drive belt. 14. Inspect. Replace as necessary.
15. Water Pump. 15. Inspect and

 

CONDITION POSSIBLE CAUSES CORRECTION
TEMPERATURE GAUGE READING
INCONSISTENT (ERRATIC,
CYCLES OR FLUCTUATES)NOTE:
Information on dash cluster is
displayed based on broadcast data
from ECM. DTC will be set for
engine sensor circuit concern.
1. Heavy duty cooling system,
extreme cold ambient (outside)
temperature or heater blower motor
in high position.
1. None. System operating normally.
2. Temperature gauge or sensor
defective.
2. Check cluster or engine coolant
temp sensor (Refer to 8 -
ELECTRICAL/INSTRUMENT
CLUSTER - DIAGNOSIS AND
TESTING)
3. Temporary heavy usage or load. 3. None. Normal condition.
4. Air trapped in cooling system. 4. Fill cooling system (Refer to 7 -
COOLING - STANDARD
PROCEDURE).
5. Water pump 5. Replace water pump.
6. Air leak on suction side of water
pump.
6. Check for leak. (Refer to 7 -
COOLING - DIAGNOSIS AND
TESTING)

 

been a couple of days watching coolant temps. temps have been in the low to mid 30's during the days. truck will get up to operating temp of 190- but mostly drops to around 185 when driving at 60mph. odd- never did this before.

 

Do you have a different gauge than I do? HOw are you differentiating 185 and 190?

This may sound like a stupid question- but when you are changing out the thermostat, it says to drain coolant out of the engine until it's below the level of the thermostat. How does one know/monitor the level to determine this?

 

changed my t stat when i drained out all the coolant. i have the edge juice/attitude combo. gives me my reading

 

before you go and drain out the coolant park facing up on a steep incline, and let the engine idle a bit, rev it up a bit to force any air bubbles out of the engine and into the radiator. Once the air bubbles are out that should do the trick.

 

Mine did that right before the pump completely failed. Bearing/seal gone. No prior warning drips. Temps just started fluctuating wildly, and then it puked all the fluid out in the parking where I stopped after I shut it off.

 

kokalit- are you talking about the water pump? Perhaps it's time for a new one of those too.

 

Well, I finally got a break in the weather and schedule and got a chance to go look at the truck up close. Wow! My overflow reservoir is bone dry as far as the eye can see down. Laying under the truck reveals orange drips. Do we assume my water pump has gone?