Fuel and Temperature Guages gone Wild!

[3rdmdqm]

I was having issues with my guages. The fuel guage would wildly jerk back and forth across the dial occassionally. Then my temperature guage started to run hot, then when it hit about 220 it started jumping back and forth like someone was flicking it. Once it cooled down it was fine again. Then the other day while driving, it pegged itself out at 240 and wouldn't return. Obviously scared the crap out of me, stopped truck to check for overheating. Truck was not overheating. Got home and let truck cool completely down, dead cold. Turned the power lever back on and temperature guage is still pegged at 240.

Started checking wires and found the wire that comes out of the temperature sending unit going back to the firewall had a very small chaffe area which depending on the trucks vibration would contact the hot engine block, really heat up and ground itself out. Once I moved all of the wires completely away from touching the engine block, the guages work fine now. I'll be replacing the wires shortly.

Just some FYI, even those wires that look ok at first glance need some close inspection.

 

[AceHigh]

Good troubleshooting, and it is great when the repair costs $0.00.

 

[3rdmdqm]

I consider myself lucky in this case. Had the temperature guage not stayed pegged at 240 after the truck was dead cold I propbably would have started replacing the temperature sending unit first and then likely the guage after that when the sending unit didn't work. And you're right, the no cost repair was a definite bonus!

 

[3rdmdqm]

Should I be concerned now? Everything was going fine after the guage repair. Yesterday while driving the guage crept back up to about 240 and I started smelling antifreeze. Pulled over and noticed the stop cock on the radiator was open and coolant had been leaking out. Was able to get home and refill (wasn't completely empty but it was really really hot. In fact smoke was coming out of a small small hole in the slobber draft tube that looked like it used to have a plug in it so I know the engine was getting really hot. Refilled (water was acting like a volcano while adding cool water spitting all over the place until it cooled down and making these god awful noises inside the radiator), no leaks, test drove. Now under light driving conditions, going about 30-40 mph on level ground etc she runs at around 180-190 degrees. Once I get to highway speeds (50 mph and over) for long stretches or have to traverse hills and do a lot of shifting etc, she runs at about 220 degrees. Is this normal? Shouldn't it stay around 190-200 all of the time? If I stop and let it idle, within about 5 minutes the temperature comes back down to between 160-180 degrees. Before the overheat she ran at 200 degrees no matter what the operating conditions were.

 

[FormerNewMVGuy]

Putting cold liquid in a hot engine is just BAD! It is a very good way to crack things, Like the block or heads....
With that being said my trucks never go over 200 degrees, But there are others on here who have had similar running temps.

 

[glcaines]

My deuce runs at at 180 - 190 100% of the time once warmed up, regardless of speed, duration of trip or load. I've never had it run over 190. I did have a problem a few weeks ago when I lost the ground, but this was an easy fix.