Temp guage all over the place?

[ap3x]

94 B4000 5 speed 115k ish miles. Normal spot on my guage has always been 1/4 the way up. Now that its cold, it seems that when I climb a big hill or accelerate hard, the guage goes to almost half, then when I'm crusing it just comes back down in a few seconds. Am I looking at a sticky thermostat here? Maybe a poor ground for the guage? Or could it be the fan isn't kicking on when it should? (that happened to my rx7)

 

[Big Jim M]

Sounds completely NORMAL from here..
Big JIm

 

[ap3x]

Well I just drove it to work and back and paid more attention to it. Turns out, it goes back and forth slowly between 1/4 and 1/2 no matter what (sitting at a stop sign, cruising at 35, 55, climbing hills, accelerating hard, etc.) I'm not overly worried since its not getting anywhere near overheating, but if it's something serious like a water pump, I don't want to let it go.

 

[sholzy]

That's just the effects of your t-stat opening and closing slightly to keep a constant temp and the water pump pumping fluid through your system faster when you speed up.

 

[Big Jim M]

You don't sqy where you are... when the thermostat opens it allows the cold coolant to come into the engine from the bottom... Then when that colder coolant hits the thermostat the thing closes till the coolant heats up to operating temperature.
Depending on how far north you are that cool coolant might just be -20* which would take a while to heat up.
The test would be to put her on the hiway for a few miles to see if the gauge finds a sweet spot to rest at.
Big JIm

 

[ap3x]

I'm in a chicago suburb. It's probably 20 degrees ish and the truck stays in the garage overnight. Even cruising at 55 on the highway with a warm engine for a good 5 miles, it's constantly moving slowly back and forth.

 

[sholzy]

I'm in a chicago suburb. It's probably 20 degrees ish and the truck stays in the garage overnight. Even cruising at 55 on the highway with a warm engine for a good 5 miles, it's constantly moving slowly back and forth.

Just this morning, with the temp about 28*, mine was still looking for it's "normal" spot on the gauge after 5 miles. By the time I got to work (10 miles away) it finally evened out.

 

[AllanD]

Erratic movement of the guage is often a grounding issue.

Check all the grounds but use special care to make sure the braided strap that runs between the cack side of the driver's side cylinder head and the mounting stud for the wiper motor is clean and tight. at both ends.

AD

 

[backroad101]

Erratic movement of the guage is often a grounding issue.

Check all the grounds but use special care to make sure the braided strap that runs between the cack side of the driver's side cylinder head and the mounting stud for the wiper motor is clean and tight. at both ends.

AD

do you mean check the grounds for the the gauge itself? If so, where is it grounded?

.

 

[ap3x]

I'm going to assume any and all grounds I can find that are temp related