Temp Problems

[sport883]

2002 B3000 3.0 fresh rebuild with 150 miles on it so far. Within the past two days, I have noticed that my temp guage isn't going to to the operating range but staying right around the second white line after the "C". Drove to work this morning which is always at operating temp by the time I get there; still right around the second line. Five minutes later trying to troubleshoot. Turned the key to to ON and temp guage went to the normal operating temp. I then started the truck and the guage slowly went back down. Am I right on thinking a sensor has gone bad?

[McCormack]

One way to find out for sure = replace the sensor.

[sport883]

Originally Posted by McCormack

One way to find out for sure = replace the sensor.

Thank You,

For a obvious solution, however last time I checked and I do check everday, money doesn't grow on trees.

Anyone else have any possible ideas?

[Rearanger]

Originally Posted by sport883

Turned the key to to ON and temp guage went to the normal operating temp. I then started the truck and the guage slowly went back down. Am I right on thinking a sensor has gone bad?

Should be the same as my 2003. Gauge/sensor remembers last temp setting. If at operating temp when key off then gauge stays at operating temp, or whatever temp the engine was when turned off (assuming operating gauge & sensor). If you let the truck sit with engine off it cools (of course), but first it heats up from heat soak then cools, and when you turn ignition to on or run the gauge then reads present temp until the temp changes. if you turned it on just after heat soak it's possible the engine was hotter than when turned off.

It could be you have a malfunctioning stat keeping the engine too cool. You'd have to measure the actual engine temp either with thermometer, or more safely with infrared temp gun on the stat housing or upper rad hose.

Gauge check would be to ground the temp sender and gauge should go to upper limit with key on engine off. Unfortunately replacing the gauge sender is the best way to verify sender - if you suspect it. They're relatively cheap - I believe.

[McCormack]

Originally Posted by sport883

Thank You,

For a obvious solution, however last time I checked and I do check everday, money doesn't grow on trees.

Anyone else have any possible ideas?

Ouch, sorry I offended you with an obvious answer. Per rearanger's suggestion in his post, temp sending units aren't all that expensive, and they commonly go bad on 3.0 Rangers, so that's why I recommended changing yours out, especially seeing as you already just sunk a bunch of money-tree money into a rebuilt motor already. My bad.

I know that multimeters also don't grow on trees so I doubt that you'd have one, but if you're able to borrow a meter from someone you can test the temp sending unit by measuring between the sending unit's connector terminal and ground:
Full cold = 75 ohms
Full hot = 10 ohms.

Thermometers and pans also don't grow on trees so you probably don't have those items either, but if you can borrow a pan and a thermometer from your mom you can put your thermostat and the thermometer in a pan full of water on the stove and heat it up and see if the thermostat opens at it's rated temperature, although if it were me I'd get a second job and just buy a new thermostat and swap it in to eliminate that as a possible source of your temperature problems.

Hope that stuff wasn't too obvious for ya.