Question about Engine Temp's...

[DennisG01]

I don't think I'm having a problem, but this is just something I was wondering about:

Whether I am towing, or not (although obviously it happens more when towing), my engine temps are almost always constantly fluctuating. It goes from about 190* up to about 205* then the fan kicks on and it comes back down. Is this normal for this constant fluctuation?

[john8662]

Normal pulling, sounds like fan clutch. The factory fan clutch engages a bit late.

The KD clutch is a great unit, but only works on waterpumps with the 4 bolt flange, not the screw on type.

[Hubert]

Are thermostats OE?

From the factory they are 180F and 195F I think. At least they are offset not sure of temps I think. Just maybe the 180F is stuck partially closed?

Mine doesn't really fluctuate much at least not quickly. It does run warmer with stop and go traffic and hot ambient temps. But once it settles it doesn't fluctuate unless load or outside temps change or traffic jam.

[DennisG01]

Yes, normal pulling (6,000lbs). By the way, the low temp is probably closer to 185* than 190*.

OE Stats? Don't know. I've had the truck for 3 years and have not replaced them. I guess it would be a good idea to replace them? At least as a preventitive maintenance thing, anyway. I'll order a set from JK right now.

[Hubert]

Dang after reading what John said I don't know.

If (1) thermostat is partially stuck I am not sure the radiator would get warm enough to engage clutch fan unless coolant in engine is getting really hot. Then by the time the coolant starts circulating its so hot it heats the radiator up with surge of really hot coolant. I thought the O.E. fan clutch did not engage until 210-215???

I have seen a few thermostats stick open and closed. And obviously if stuck closed it gets hot in a hurry.

Assuming water pump is good and radiator clean I am inclined to think stuck thermostat.

Is in cab heat output really toasty?

[Patrick m.]

one thing i did several years ago was remove the fan shroud and wash "back" through the radiator and condensor to clean out the years of debris that collects there.
I did this after reading about others having much sucess.
My symptoms were similar to yours, temp fluctuation, but no overheating

[DennisG01]

Heat output is good - never noticed a problem there.

That's a good idea about cleaning the radiator - I'll check into that, too. That makes me think of something else: I bought the truck with a plastic Lund bug screen (hard plastic with little holes in it) that snaps onto the factory grill. Maybe that's not letting enough air through? I like it because it keeps bugs out, but maybe I should take it off and see what happens?

I ordered (2) 195* stats from JK.

[rameye]

Dennis I'll second the cleaning of the radiator... I removed mine and gave it a thorough douching with my power washer. I was amazed at the crap that kept coming. Also do the oil cooler and A/C condenser with the rad out of the way.

I had the same conditions flucuation up and down replace thermostats, clutch and fan upgrade. Wish I had pulled the radiator first.

Enjoy

[Hubert]

Yeah I am starting to think radiator too. Sorry to mislead with thermostat theory. Having (2) thermostats has always made me wonder which opens and closes first and if it affects other one.

It could possibly be the lower temp one is not opening fully. But if it was stuck closed it should act like you only have one at the hotter temp and truck would just run to the next temp. thermostat.

It more sounds like your radiator is getting hot and the fan (or air flow) is more so controlling cooling temp swings.

I've cleaned my radiator stack and was also amazed at crap stuck in fins. Use a heat exchanger cleaning agent. They usually foam and lift stuff out of fins. Also note the grill opening is not all that big for these trucks I would take a close look at any grill accessories, winches, aftermarket bumper, or other that affects air through stack.

[DennisG01]

i'm going to replace the stats, anyway (since I don't know how old they are). Can you clean the radiator without disconnecting anything or draining the anitfreeze? I guessing I can take out the fan shroud, but anything else?

[Warren96]

I did mine without draining anything.It's realy a decision you should make based on how hard you work (any towing involved?) yours.I will be taking my shroud off at the start of summer every year after seeing all the leaves it tried to swallow.I would bet mine was packed half way up from the bottom between the radiator and the oil coolers! I used a shop vac for the leaves and a garden hose for the mud. Keep us posted! Good luck!