Strange engine temp problem...

[BrianDye]

So today, I got out of orientation for my new job, and picked my girlfriend up, we had some errands to run. It was about 75 degrees and the sun was blaring down, so it felt closer to 90 outside.

I was out in my Explorer waiting in the parkinglot (Blacktop), and had the AC on. It was a little over 25 minutes or so, and my temp stayed consistant. I switch my ultragauge screen to show my coolant temp, just to keep an eye on it. A warning came up, and it was the 210 temp warning, it was saying that it was 210.2

She was walking out, so I pulled back up to the door, thinking that getting some airflow and being off the blacktop would cool it down a bit, but it didnt.

I looked down, and saw the gauge steadily moving up, about 2 degrees every couple seconds, it got up to like 228-232 before I quickly shut it off. I turned the key on about 5 minutes later and turned the air off, it was down to about 220. I checked the engine bay, under the Explorer, and didnt see any signs of leakage, or blown lines etc.

We started driving, AC off and it got back down to normal temp pretty quickly, (~190), so I turned the AC on and a few miles later noticed the temperature was still dropping.

Now while driving with the AC on, it stays at like 158-160.
AC on:

And with the AC off, it drops a bit more.

Im letting it cool down right now before I open the radiator cap, but im guessing maybe my thermostat is stuck open? It NEVER used to fluctuate, AC on or off, it would always stay right below the middle.

Im really hoping no damage was done letting it get that hot, (I turned the motor off within seconds of noticing that it was climbing, plus I was sitting still so there was no load).

A: Where it normally is no matter what. AC on, heat on, off, running for 2 hours, always sits right here, only fluctuates a matter of a couple degrees.

B: How high it got up to today right as I shut it off.


Any idears?


Edit: I am going todo a coolant flush tonight or tomorrow, its been about a year now, I hate to say its been that long, but im sure that could use fresh fluid.

And might I add, this is the first "problem" shes given me in almost a year now besides a couple minor things. Cant express my love enough for this Explorer!

 

[1996BLKBauer]

I am not sure if this helps at all, but on my Ex, it ALWAYS stay right at the "A" mark you put on there. Mine some times fluctuates during times of excessive load, such as going up a hill, but it never has gotten as high as you "B". I know you mentioned the thermostat, you might as well replace it with a good quality one, and possible you rad cap. It is crazy what these 2 small things not working right can do.

 

[BrianDye]

Yea, mines always stayed there, before and after the new thermostat (Back when I replaced it), but after it "overheated" today it slowly ran cooler and cooler until it stayed right around the line running cold.

It runs great, fires right up, doesnt drive any different, and its not throwing any codes

 

[BrianDye]

Checked the coolant, it was a bit low, so I topped off, but still nothing. Its actually running a bit cooler now, I let it run with the AC on for about 10 minutes and drove a mile or two and it stayed right at about 148-150.

Im really leaning towards the thermostat being stuck open, maybe its some kind of failsafe, so im gonna go get a new one and some fresh coolant and flush it tomorrow morning after work.

 

[FU MONSTER]

i had the same problem. my thermostat was indeed stuck open.$10 at auto zone and problem fixed. worth a shot.

 

[2000StreetRod]

fail open thermostat

I remember reading a post some time ago to always purchase a thermostat that fails open instead of closed. It could prevent the head gaskets from blowing out. I've never investigated further but it sounds like a good idea.

I did a quick internet search and learned that the Motorad fail safe thermostats have a tendency to lock open when slightly overheated.

 

[BrianDye]

So the culprit was like 2000streetrod said, it was stuck open.

And I bought new coolant/thermostat/gasket to flush the system and that turned into a 4 hour job. I dropped the lower bolt and it fell into the depths of hell so we had to make a trip to the hardware store to find a matching short bolt. After that, flushed the BROWN crap out, and finally just took her for a spin. All was well.


Can someone confirm normal operating temps though? It's a bit chilly outside and with the heat or ac cranked, it was fluctuating between about 189-195.7 said my ultra gauge. My dash gauge stayed put in the middle, as usual.

 

[vroomzoomboom]

make sure you dont have any air trapped in your system as well. you might need to burp it a few times, or run it for a bit with the cap part way on if you understand what i am saying.

 

[jremington59]

So the culprit was like 2000streetrod said, it was stuck open.

And I bought new coolant/thermostat/gasket to flush the system and that turned into a 4 hour job. I dropped the lower bolt and it fell into the depths of hell so we had to make a trip to the hardware store to find a matching short bolt. After that, flushed the BROWN crap out, and finally just took her for a spin. All was well.


Can someone confirm normal operating temps though? It's a bit chilly outside and with the heat or ac cranked, it was fluctuating between about 189-195.7 said my ultra gauge. My dash gauge stayed put in the middle, as usual.

Did you put in a 190 degree thermostat?

 

[1996BLKBauer]

make sure you dont have any air trapped in your system as well. you might need to burp it a few times, or run it for a bit with the cap part way on if you understand what i am saying.

Yea, for sure do this, after I burped mine I was about 1/4 of a gallon, closer to a half lower on coolant.

 

[BrianDye]

Did you put in a 190 degree thermostat?

Autozone only had 160 and 195's (I got the 195)

make sure you dont have any air trapped in your system as well. you might need to burp it a few times, or run it for a bit with the cap part way on if you understand what i am saying.

Yea I know exactly what you mean, I've burped it a few times, only added probably a quart so I'll burp it again in the morning before work.

But I'm assuming that much fluctuation isn't normal then?



Thanks for the tips though guys.

 

[jremington59]

I think fluctuating between 189 and 195 would be normal. It's opening at 195 like it should.

 

[BrianDye]

Yea when it opens it quickly drops to about 188-189