2014 4.0L Overheats at idle? Kinda?

Truck got to 232F just over a month ago. Was warming it up, and forgot about it with the AC full blast. Outside air temp was ~90F

Tonight, over a month later, I'm testing it while the weather is cooler (65F). Let it idle at 185 for 15m and there's no budge. Then I let the AC run full blast for 15m and it got up to 190F right at the 15m mark.

So I let it idle in drive and after 10 minutes it's up to 210F. Didn't want to go further and as soon as I dropped it back into park the coolant temps dropped.

Which is strange because the first time it over heated, it was in park. Just hotter outside.

My coolant levels are 1cm below where I filled it to (full) when I changed the thermostat and coolant w/ OEM stuff 11.5k miles ago. Currently at 87k.

I just did an oil change at 87k and there's zero sign of milkyness. Don't ask, I got the truck at 67k. Eventually I'll get it back to normal service intervals.

I'm thinking I must have just let it idle for REALLLYYY long the first time? Just don't do it again? Doesn't really seem broken, and it never overheats on me driving it to and from work in the summer heat of the day up and down the mountain. Even at really long stoplights no overheating or sitting in parking lots for a few minutes no overheating.

 

You're getting no airflow through the radiator and your water pump is just turning at idle speed. I don't see an issue.

 

Clean the radiator fins. Have you ever changed the coolant, it’s due at 100k miles. How’s the serpentine belt.

I crawl, in 4low, 80-90 degree days, 30-45 minute slow trails waiting for everybody to clear obstacles w AC running. The transmission temps hit low 200’s, the water temp stays 190 ish.

 

Check behind the radiator, i know some people who got dirt/mud at the bottom blocking some air flow, causing high transmission and coolant temperature. I know the fan always turn with the engine (serpentine belt) but there some oil/liquid inside who "move" when engine is hot to "engage" the fan. I don't know how to check that but maybe your fan don't spin enough for the heat generated at idle. In heavy traffic my engine never go over 192F.

 

Check and see if the cooling fan spins too easily by hand when it’s warm. If so, the fan clutch is going bad.

It’s also possible your radiator is plugged in places. You can use an IR thermometer to look for cold spots when it’s warmed up. I think this is less likely, but worth checking if the fan clutch seems to be OK.

 

The viscous clutch fan has it's own "tell" that indicates whether it's working or not: When you first start the engine the fan should always make a lot of noise/roar indicating it is fully engaged. Unless you just parked and shut it down on a 90+ degree day to get gas, it should quiet way down and make virtually no noise within 10 seconds or so as it disengages and returns to idle speed. It will do this even in the winter when it's 10 degrees out. I don't know the exact science on how they work; centrifugal force and mystery viscous fluid that gets thicker when hot or some such magic. The ideal situation is a clutch fan -and- an electric fan working together... especially with A/C added to the mix. I have had several vehicles with them and never had one fail.

 

I’m thinking fan clutch too. You should be able to turn it by hand but it shouldn’t free wheel like an alternator.

Like others suggested, check if the radiator is clogged with dirt or mud. Someone once showed me if you take the radiator out & blast it with water back to front a bunch of dirt comes out, then it cools much better. Now they make a special hose attachment thing so you don’t need to remove it.

 

Watch this concerning the fan clutch, it might help
https://youtu.be/vgWJN4EEl-U

 

https://www.youtube.com/watch?v=UwM4OqsLek4

I had this video in my history, very good explanation. Yes the fan should make noise and calm down if working proprely, good catch i didn't think of that.

 

So I finally got around to checking this out, the fan clutch spins much much easier when fully warmed up. There’s a lot of resistance when cold, and it will almost free wheel when warm but there’s obviously some resistance and I wouldn’t consider it free wheeling. Hard to explain with words. I tested the head gasket just for shits n giggles and there’s no sign of any leak using the color changing fluid. The thermostat was replaced with OEM less than 20k miles ago, along with a full coolant drain (drained both blocks too) and fill using OEM coolant following FSM procedures. Radiator looks pretty clean from the front and back, but I’ll try back flushing it.

 

OP. have you done any mudding or water crossings?

My 2013 with 145k miles all original coolant parts (sans coolant change at 100k miles) will sit in 115deg temps ac blasting idle and crawling along without issue of overheating, 1k lbs in the bed and towing 2klbs of shit. I doubt it your fan clutch (though it is possible). More than likely some fresh coolant (make sure its burped properly - park your truck nose high on a steep incline, start cold rad cap off and wait for flow - add as needed) and a good radiator fin cleaning and you wont have any issues.

 

Nope no mudding or water crossings here. But idk what the previous owner did. I will burp it again I suppose since it hasn’t been done since the problem started, but that is how I filled the coolant. Maybe looks can be deceiving, so I’ll run water through my radiator from the back and see what comes out. But it looks sparkly clean.

 

Yeah, id pull the grill off (so you can get hose nossle up in there from the front as well). Hose DAFUQ outta the various radiators, the do again a few times ~ 15 min apart to try and break up any debris, you could even get some coil cleaning spray

https://www.homedepot.com/p/AC-Safe-Air-Conditioner-Foaming-Coil-Cleaner-AC-921/206740351

to help the process.


As far as coolant. Did you or the previous owner replace coolant? I wonder if they put in full coolant and didnt dilute it properly to 50/50?

 

I replaced the coolant. OEM comes pre diluted.

 

Hmm. OK. yeah. Park the truck nose high and let cool off, pull rad cap and see what coolant level looks like in the rad, could just be air in the system.

 

Okay I’ll do that will report back if it worked

 

Spray the radiator with a hose when it's idling and see if the temp drops on the scan tool. If yes suspect a bad fan clutch and/or bad radiator.

 

Not normal.

my truck can idle all day in 100 degree plus weather. I had the same issue as you and I changed the fan clutch, water pump and radiator and it doesn’t overheat anymore.

 

I had same issue with mine. Changed fan clutch. While the fan and clutch were removed, I took the hose to the backside of the radiator. I removed soo much dirt from both the radiator and A/C coil. I spent a good 45 minutes to an hour just spraying out the dirt. I probably had very little airflow thru the radiator based on how much dirt came out.

 

The issue was weeds blocking the radiator. Looks can be deceiving. Thanks everyone!