Coolant temp rises when ignition off.

[Boobylinks]

My dashboard panel coolant temperature needle indicator (original equipment) slowly rises nearly all the way to the "H" after I shut off the ignition at the end of the day. The needle swings back to the middle of the normal range if I immediately turn the key to accessory or restart the ignition. Is this normal for the needle to behave this way?

p.s. -- The needle never strayed from normal while driving after sufficient warm up time. I haven't driven this truck in nearly three years so I've still yet to get re-aquainted with my trucks quirks.

 

[icanfixall]

This question has not come up before. What I can state is that my 89 doesn't do this. Maybe others will chime in with what their trucks do. Also the stock dash gauge isn't really what you should be looking at for temp. These dash gauges were never very good especially the oil pressure gauge...

 

[82F100SWB]

Where does the guage sit before you turn the key on? I have seen some that sit on the hot end of things, while sitting at dead cold with no power fed to it is the norm.

 

[Boobylinks]

The engine's been off for about an hour (engine now dead cold) and the needle sits now in the normal range. Turning the ignition on (just now) and firing the engine, the needle goes back down to "C". Was this just the engine's "heat soak" causing the needle towards "H" after shutting down a warmed up engine?

 

[Boobylinks]

This question has not come up before. What I can state is that my 89 doesn't do this. Maybe others will chime in with what their trucks do. Also the stock dash gauge isn't really what you should be looking at for temp. These dash gauges were never very good especially the oil pressure gauge...

I'll start a new thread on the oil pressure guage since I have issues there too.

 

[icanfixall]

No, the heat soak will not show up untill you add power to the switch. Probably what you are seeing is just needle creep. It means nothing if the gauge isn't getting any power so it can "read" anything.

 

[sle2115]

The engine's been off for about an hour (engine now dead cold) and the needle sits now in the normal range. Turning the ignition on (just now) and firing the engine, the needle goes back down to "C". Was this just the engine's "heat soak" causing the needle towards "H" after shutting down a warmed up engine?

No, don't think so, if that were the case, everyone's would be doing it. I think you are probably experiencing electrical issues, probably a bad ground in the dash or chassis to engine (the negative cables from the batteries go to the engine block, then to the frame and cab via cables. I haven't read the oil pressure gauge post, but if you are having problems with it, I would definetely think it is ground or voltage. There is also a known issue with the voltage regulator for the gauges. As for the gauges, I would get a good set of gauges in there. The stock gages are basically idiot lights with a needle and are not accurate. When I had ground issues, my fuel gauge was crazy like that, temp and oil would all do weird stuff, often going to max even with the engine off and cold. The safe bet is to install a quality set of gauges. I used the pillar for a later model truck on mine, just had to cut the bottom of it off. I have digital VDO's on the pillar and they tell me what is actually going on, but any quality gauge will work.

 

[Diesel JD]

Hey I notiice sometimes on my mechanical gauge, if its quite warm willgo up after I cut off the engine. I think it heats up because just the fact of the coolant circulating does a lot to keep the engine cool. On the other hand, you really need some real gauges. I don't trust those factory gauges.

 

[Boobylinks]

I'll start a new thread on the oil pressure guage since I have issues there too.

I've started this thread to address oil pressure issues I have.
http://www.oilburners.net/forums/showthread.php?t=15295

 

[sle2115]

Hey I notiice sometimes on my mechanical gauge, if its quite warm willgo up after I cut off the engine. I think it heats up because just the fact of the coolant circulating does a lot to keep the engine cool. On the other hand, you really need some real gauges. I don't trust those factory gauges.

Yes, that is true JD, a mechanical gauge reads rather there is voltage or not. You can heat the water in your engine by lighting a fire under it, with no batteries and your mechanical gauge will measure it. A mechanical gauge is just a thermometer, the tube running in carries alcohol mix and the gage just measures the pressure of it as it expands. The in dash gauge is electrical though and once the switch is cut, it should "turn off".

 

[icanfixall]

The water pumps circulate 70 gallons per minute of coolant. When it stops the hot metal will run up the coolant temp just a little.