Thermostat question

[Andrew Fort]

My truck ('90 F350) temp gauge used to sit right between "O" and "R" on the temp gauge. The truck had to sit for a while while I was fixing it and now it doesn't even hit the "N". I'm thinking my thermostat is stuck open. It'll be a few weeks before I have a chance to replace it. Would any damage occur in that time?

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[nostrokes]

No nothing is going to happen, it'll just be running cool.

Just for kicks, let it warm up and feel how hot the upper hose gets. It may not actually be your t-stat but a crappy gauge. The stock gauges are nothing more than moving idiot lights and never work right to begin with.

 

[icanfixall]

You are going to be ok driving it this way. As already posted.The stock dash gauges are nothing to depend on. Install and after market gauge and report back what you find. Also NEVER use any thermostat other than the original MOTORCRAFT thermostat. They are the ONLY one that works. they are 192 degrees begins to open and fully open at 212 degrees.

 

[Kevo1288]

You are going to be ok driving it this way. As already posted.The stock dash gauges are nothing to depend on. Install and after market gauge and report back what you find. Also NEVER use any thermostat other than the original MOTORCRAFT thermostat. They are the ONLY one that works. they are 192 degrees begins to open and fully open at 212 degrees.

The motorcraft one I got is part number RT1049... there was another one but I couldn't remember the part number of the other motorcraft one.

 

[Oledirtypearl86]

The stock gauges are useless I have a 86 with a 6.9 a few years ago the wife and I are on a 1300 mile trip and on i15 in Utah and she tells me the gauge is pegged past the l So we pull over and I grab the super duper temp gun start shooting temps nothing is even close to hot we stop at the closest Napa grab a set of gauges I take 30 min to hook up the temp gauge and the truck never even came close to 225 the rest of the trip pulling a trailer with a skid steer tied to it

 

[IDIBRONCO]

Since you're in Missouri, it will be easy to tell at this time of year. When I first got my current 85 F250, the thermostat was stuck open by a piece of debris wedged in it. It had to be in the 50's before anything that resembled heat came out of the HVAC system, the heater hoses were both barley lukewarm to the touch, and the fast idle never kicked off. If don't have any of these symptoms, then it's just your gauge or sender.

 

[Andrew Fort]

I'm guessing it's just the gauge. The truck had warm air blowing in about 5minutes earlier and it's in the 40s tonight.

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[icanfixall]

Sometimes the over temp light on the dash comes on telling us ... Sorry its too late to save your engine now... Well the switch in the front of the drivers side head is the over temp dash light and gauge switch.Its normally open till the coolant temp reaches 242 degrees. Then it will close and cause the dash gauge to peg telling you theres trouble ahead. When they fail this switch randomly closes and sets you to worry.Easy test is to remove the wire to it and ground it to metal. Do this on a cold engine to verify this. Grounding the wire will cause the dash gauge to peg. So if you ever see the dash gauge peg but feel the engine is ok just remove the wire from the big fat switch and see if the dash gauge goes normal again.