Engine coolant temperature issue

[Matt D]

I own a 2018 RAM 1500 Big Horn 5.7 Hemi with just over 40k miles. Recently I got an engine overheating message and saw that the engine coolant temp had risen to over 250 degrees. After 2 or 3 seconds it began to drop back down to normal operating temps, 200 - 210, and ran there for several minutes. I started watching the temp closely and after several minutes of normal city driving, it started to rise again. In a matter of 5 seconds, then temp ran up to 250, engine overheating message, then 2 seconds later cooled back down. It did this several times. I replaced the thermostat, filled the coolant and it seemed to run fine for a few days. Then yesterday the temp jumped up again, engine overheating message, temp goes back down. Any ideas??? I'm thinking maybe a sensor going bad? I can't imagine engine coolant changing temp that quickly.

 

[Wild one]

I own a 2018 RAM 1500 Big Horn 5.7 Hemi with just over 40k miles. Recently I got an engine overheating message and saw that the engine coolant temp had risen to over 250 degrees. After 2 or 3 seconds it began to drop back down to normal operating temps, 200 - 210, and ran there for several minutes. I started watching the temp closely and after several minutes of normal city driving, it started to rise again. In a matter of 5 seconds, then temp ran up to 250, engine overheating message, then 2 seconds later cooled back down. It did this several times. I replaced the thermostat, filled the coolant and it seemed to run fine for a few days. Then yesterday the temp jumped up again, engine overheating message, temp goes back down. Any ideas??? I'm thinking maybe a sensor going bad? I can't imagine engine coolant changing temp that quickly.

I wouldn't rule out a bad thermostat.Just because the thermostat is new,doesn't mean it's any good.The odds of getting a dud "new" thermostat these days are higher then getting a good one. I've had several bad new thermostats lately,they'll work good for a week or two,and then start sticking,and causing the same issues as you're experiencing

 

[crash68]

You could temporarily unplug the AGS to rule out if that's causing the temperature spiking. You'll probably get a CEL but it can be replaced and something easy to check before replacing parts.
Also it could be the fan clutch that sticking on engaging.

 

[Sherman Bird]

I own a 2018 RAM 1500 Big Horn 5.7 Hemi with just over 40k miles. Recently I got an engine overheating message and saw that the engine coolant temp had risen to over 250 degrees. After 2 or 3 seconds it began to drop back down to normal operating temps, 200 - 210, and ran there for several minutes. I started watching the temp closely and after several minutes of normal city driving, it started to rise again. In a matter of 5 seconds, then temp ran up to 250, engine overheating message, then 2 seconds later cooled back down. It did this several times. I replaced the thermostat, filled the coolant and it seemed to run fine for a few days. Then yesterday the temp jumped up again, engine overheating message, temp goes back down. Any ideas??? I'm thinking maybe a sensor going bad? I can't imagine engine coolant changing temp that quickly.

Late last year, I bought a 2002 S-Blazer, 2WD, 4.3Liter with 4L60E auto transmission.... it had sat for 5 years+. The white paint turned green from the trees. Brakes were locked up, and the vehicle had died the "Death of 1000 Cuts" in that the prior owner let every little thing go to the point that, collectively, the car wasn't worth fixing. I got it for a very good price. After spending several weeks on and off in spare time fixing rear hatch operation to dome lights, and windshield washer among many many things, the water pump began to leak right after I'd replaced the t-stat, cap, and hoses, and flushed the cooling system, installing GM original Dex-Cool. I replaced the water pump, factory fan clutch, and had to settle for aftermarket pump and fan blade because the General doesn't support those parts anymore. (The original plastic fan had many micro cracks).

During this past few months with over 100 degree temps and record heat indices, the fan roared VERY loud pretty much constantly during operation. The Temps ran at 205 to 220. Interestingly, with full factory gauges, the temp gauge was right at halfway at 210, and only slightly higher at 220. Kind of scary, but they do that to ensure lower emissions!

 

[Matt D]

Just a little update, and a new wrinkle... cylinder misfire... it's still under the power train warranty so I took it to the dealership. Told them about the misfire and the overheating issue. They started with the cylinder and found coolant in it. Not sure it is the cause of the overheating but it is not good. They are taking it apart to find the cause and extent of the damage. With the recent strikes, it will be interesting to see how long it takes to get parts to fix it, I know someone who has had his F-150 sitting at a dealership in pieces for over a month waiting for parts.

I will update when I have new information, which will hopefully not be too long...

 

[Yardbird]

Cracked head, leaking head gasket, ect...will cause your exact symptoms.

 

[Matt D]

Final update, turns out it was a torn head gasket. They found coolant in cylinder 2. New head gasket, seals, coolant flush, oil change (all covered under warranty)... runs like a champ again and doesn't overheat. I'm a little concerned about a torn head gasket at only 40k miles, but it is what it is. Still love my RAM.

 

[FullForceRam]

Final update, turns out it was a torn head gasket. They found coolant in cylinder 2. New head gasket, seals, coolant flush, oil change (all covered under warranty)... runs like a champ again and doesn't overheat. I'm a little concerned about a torn head gasket at only 40k miles, but it is what it is. Still love my RAM.

hmm, that is a little concerning with only 40k, but glad that fixed the issue.