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-   -   Runs hot with A/C on. (

J C Smith 07-24-2013 10:25 AM

Runs hot with A/C on.
Hello all, I have an '05 1500, 3.7l engine. The temp guage usually reads right on the center mark in hot and cold weather, around town or on the highway. With the A/C on around town pointer reads 1/2 way between 1/2 and 3/4. But on the highway pointer quickly reaches top mark ( black line in what I would call normal range ) . Then it climbs toward the red, when warning on dash comes on saying check guages (duh), and stop engine. I've never let it overheat to the point of spewing coolant. Engine also stumbles when warnings come on. I've got new thermostat, bottom hose, and Mopar 5 yr coolant. Have not installed them yet pending complete diagnosis. Then I started thinking fan clutch might be going bad. Also NO coolant leaks.

Is there a way to check fan clutch? I appreciate any input .Thanks in advance.

Warlock III 07-24-2013 02:43 PM

That's a good question. I don't know of any technical way to check it. I usually feel it for resistance.

You might consider installing an electric fan/conversion to eliminate the clutch as a problem and reduce some drag on the engine.

J C Smith 07-25-2013 01:19 AM

still runnin' hot
Warlock, thanks for the response. The clutch does have resistance and no apparent leakage. I can't believe this truck has a 1 row radiator. I do like the electric fan idea tho. Chris

J C Smith 07-29-2013 01:20 PM

still runnin' hot
86 views and 1 response ( much thanks Warlock ). I'm bummin' here people. I'm a " certified shadetree mechanic ", but I need help with this one. Hopefully I can return the favor. Must not be enough V6 enthusiasts here. If fuel wasn't such a rip off scam, I'd love to have a V8, which probably gets better mileage than the 3.7.

Hopefully one of you pro mechanics (no disrepect here either) can help me diagnose this. Thanks everyone.

Simple guy 07-29-2013 03:11 PM

have you tried cleaning out the fins? squirt a hose from the inside.. other than that maybe corrosion on the inside of the radiator. Might be worth it to take it to a radiator shop to be rodded if you can see any signs of corrosion from the cap.

A coolant system is fairly simple. Fan, Radiator, heater core, pump, thermostat, coolant passages, hoses, temp sensors and the cap. just check off each part of the system and rule it out. process of elimination. it's how the pros do it. Diagnostic trees.

Edit: almost forgot the most important part- The coolant.

deanhinsley1963 07-29-2013 05:27 PM

I would probably change the thermostat refill with straight water and see how it does. Check everything shroud,fan and blades,bottom hose for sucking together. If the thermastat fixes the problem then put your anti-freze in and your good to go. If it does'nt then I would be suspecting the water pump. I have heard of a few going out. I dont think its your fan. They will heat up idling and around town,not going down the road,unless pulling heavy with a/c on.

Simple guy 07-29-2013 08:19 PM


Originally Posted by deanhinsley1963 (Post 1162477)
If it does'nt then I would be suspecting the water pump. I have heard of a few going out.

I replaced a water pump on a 04 5.7 hemi little over a year ago. Wonder if it's about the life expectancy of the pumps?

RogerRamJet 07-30-2013 12:53 AM

Best way to check the fan clutch is to get a heat gun and heat it up to 200+ degrees. Then you can test the resistance in the fan.

J C Smith 07-30-2013 10:30 AM

running hot with A/C on
Thanks fellas, I sure appreciate the input.

Simple guy, the fins are clean. I haven't looked inside yet. The coolant in expansion tank looks brand new. Speaking of coolant , the Mopar stuff isn't cheap. I've learned alot about coolant recently. It does get confusing.

deanhinsley1963,good idea with plain water. I did get a fail safe thermostat that stays open if overheating occurs.

RogerRamJet, that's a great idea with the heat gun.

I'll let y'all know the outcome. Thanks again, Chris

wchnu 08-08-2013 06:14 AM

Hope that works. I had to replace the radiator in another truck I have to fix this problem.

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