Key On Engine Off = soaring temp (1 Viewer)

[grrlscout89FJ62]

The other day, I had to wait in the parking lot, so I just let it idle for a while. Then the waiting got longer and longer, so I cut the engine off, and just turned the key on, so I could listen to the radio.

But then I noticed the temp needle going up at an alarming pace. It was about to peg, when I decided to start the engine back up. The needle immediately started to drift back down to its normal range.

Any idea what could cause that? Is it anything I should worry about?

 

[BwardeAZ]

Only need to worry if it doesn't go back down once it starts back up. It may rise a little at idle lights, stuck in traffic.
It is normal.

 

[KLF]

Common problem with the FJ62, mine did it several times.

The little voltage regulator contact behind the fuel gauge is dirty. You have to pull the gauge cluster out and clean the contact. Consider replacing the gauge, as sometimes cleaning the contact doesn't fix the problem.

 

[weak-link]

heat sink= normal

 

[High Desert]

It's normal..when you shut it off the coolant stopped circulating the system just stops and the hot block will heat the water for a while before the whole block et all starts to cool..

will happen with any water cooled engine. not just old iron..

 

[zuluzeugma]

Totally normal. Coolant stops moving. no heat transfer = high temp

 

[grrlscout89FJ62]

Common problem with the FJ62, mine did it several times.

The little voltage regulator contact behind the fuel gauge is dirty. You have to pull the gauge cluster out and clean the contact. Consider replacing the gauge, as sometimes cleaning the contact doesn't fix the problem.

I don't understand how that would effect the temperature, but would this also explain why the voltage needle bobs up and down along with the turn signal when it's on, and why the needle dips down when I use the power windows?

 

[weak-link]

I don't understand how that would effect the temperature, but would this also explain why the voltage needle bobs up and down along with the turn signal when it's on, and why the needle dips down when I use the power windows?

They all do that. at least my three cruisers do

 

[grrlscout89FJ62]

mkay I'm not worried. Thanks y'all.

Now, the super sluggish acceleration is my only remaining concern.

 

[Lance Lucas]

I don't understand how that would effect the temperature, but would this also explain why the voltage needle bobs up and down along with the turn signal when it's on, and why the needle dips down when I use the power windows?

That problem is more likely explained by the somewhat weak charging and electrical systems.

 

[tonkota]

I'm going out on a limb and say its normal. Just a guess though after reading the previous posts...

 

[RockDoc]

mkay I'm not worried. Thanks y'all.

Now, the super sluggish acceleration is my only remaining concern.

What have you done tune-wise lately? Fresh air and fuel filters can make a big difference. Cap and rotor. Some have their air hose between the throttle body and the air flow meter crack. An out of adjustment kick-down cable can affect performance,......... How is your milage?

If it is a real issue, maybe you could start a new thread.

 

[jonheld]

I'll throw one out that says no, it really shouldn't do that. In 16 years of ownership my 3FE has only done that once. I was fully loaded with the AC on running 36" Swampers with high ambient temps. After a 2 hr highway run I had stopped for fuel and the temp needle started to climb above normal. Nowhere near the red, just above normal. I would consider that heat soak.

What you describe is not what I would consider normal at all. I would do what KLF said as a first step. Make sure the gauge is reading correctly, then look into your cooling system.

 

[D'Animal]

X - 2

heat sink= normal

 

[Marc311]

I agree that it is not "normal" in the sense that new cruisers did not do this and most do not. However, I also agree that it may not be as bad as it looks since many older cruisers do, but still don't have overheating problems.

The sensor is just a resistor and it may be getting finicky. Since it immediately goes back to normal when you start the engine, I would presume the temp is not actually soaring when the key is off or cooling once it is turned on. When the key is in the "on" position, it is using the battery, not the alternator. So the system may not be getting a full 12+ volts if there is a charging/battery issue. That lower voltage is probably effecting the guage reading.

My $.02

 

[Cruiserdrew]

Totally normal. If I am cruising on the highway, pull off and shut down, if I turn on the key within 10 minutes, it will show the temp near the red. As soon as I restart, it drifts back to normal. Over all my truck runs cool, so what you are experiencing is heat sink. Trucks can get semi hot just idling, leading to the same heat sink issue if the motor is immediatly turned off. Just make sure you fan clutch is still locking up tight when really hot.

The fuel gauge voltage regulator is a real but separate issue.

I agree that it is not "normal" in the sense that new cruisers did not do this and most do not. However, I also agree that it may not be as bad as it looks since many older cruisers do, but still don't have overheating problems.

New Cruisers starting with the 80 series don't do this because of the engineering of the temp gauge. It has a dead spot in the center of the gauge that does not vary from 1/2 until it's overheated. It's more like an idiot light than a gauge. So under conditions of heat sink, which still exist, the temp still reads normal, because it is.

 

[Landpimp]

110% correct.......all mine up to 1990 do this(its normal), 91+ do not.

Totally normal. If I am cruising on the highway, pull off and shut down, if I turn on the key within 10 minutes, it will show the temp near the red. As soon as I restart, it drifts back to normal. Over all my truck runs cool, so what you are experiencing is heat sink. Trucks can get semi hot just idling, leading to the same heat sink issue if the motor is immediatly turned off. Just make sure you fan clutch is still locking up tight when really hot.

The fuel gauge voltage regulator is a real but separate issue.




New Cruisers starting with the 80 series don't do this because of the engineering of the temp gauge. It has a dead spot in the center of the gauge that does not vary from 1/2 until it's overheated. It's more like an idiot light than a gauge. So under conditions of heat sink, which still exist, the temp still reads normal, because it is.

 

[mtb_rider]

Now, the super sluggish acceleration is my only remaining concern.

This is normal as well. This is common with all F motors, and we all have to deal with it.

 

[brett76]

grrl theres no water circulating with the motor off. temp goes up for a bit after long idle

 

[cruiser88]

Slap a aftermarket somewhere inside and call it a day.

And if you do and it goes over 210 or 220 you have issues....