Coolant issues?
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Coolant issues?
Took the beast out for a run the other day to get it nice and warm for the emissions test. When it warms up at idle the temp gauge needle usually sits right in the middle, but when I started driving the coolant temp dropped almost all the way to C. I know that coolant flows more rapidly as you drive, but I’ve never experienced such a dramatic change. I’ve got a newish radiator, a new thermostat, and a new sending unit. Should I be concerned? How can I fix this?
1993 F250 4x4 5spd 7.5
1993 F250 4x4 5spd 7.5
Lead Driver
Joined: Jul 2017
Posts: 9,606
Likes: 1,175
From: San Jose, CA
With a new thermostat the first thing I'd suspect is the new part. Rather than anything dire happening with the engine itself.
It's not something to actually be concerned about in a Danger Will Robinson kind of way. But it's certainly worth figuring out what it is so that it does not mask any future problems.
That said, I would wait for it to happen a second time too. Don't base a lot of digging and scratching on a single happening. If it's consistent and repeatable, start digging.
Maybe measure the temps with an infrared thermometer when it's acting normal so you have a baseline. Then start carrying the thermometer with you and if it does it again, check all the same places.
This lets you know if it's the gauge, or if the engine is actually cooling down.
It's a start anyway.
Of course, at this time of year you could test it by the heater output too! If the gauge goes to cold, but the heater stays hot, that might tell you something. Then again, maybe not since these gauges are hardly more than glorified lights. As long as it's within the normal range you really don't have any idea what the actual temperature is. Unfortunately...
Good luck. Hopefully it was a fluke. One time only...
Paul
It's not something to actually be concerned about in a Danger Will Robinson kind of way. But it's certainly worth figuring out what it is so that it does not mask any future problems.
That said, I would wait for it to happen a second time too. Don't base a lot of digging and scratching on a single happening. If it's consistent and repeatable, start digging.
Maybe measure the temps with an infrared thermometer when it's acting normal so you have a baseline. Then start carrying the thermometer with you and if it does it again, check all the same places.
This lets you know if it's the gauge, or if the engine is actually cooling down.
It's a start anyway.
Of course, at this time of year you could test it by the heater output too! If the gauge goes to cold, but the heater stays hot, that might tell you something. Then again, maybe not since these gauges are hardly more than glorified lights. As long as it's within the normal range you really don't have any idea what the actual temperature is. Unfortunately...
Good luck. Hopefully it was a fluke. One time only...
Paul
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I ran the heater when the gauge was at C and there was plenty of hot air. Does that indicate a bad gauge? I registers normal temp when it’s idling the way it should, but drops when I start driving.
Cargo Master
Joined: Jan 2004
Posts: 3,118
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From: South Dakota
I would replace the thermostat again. Personally I won't use anything but Ford or Stant. Your fan clutch must be engaging at just the correct time if the temperature gauge stops rising at idle when your temperature gauge goes half way up. The reason it cools down when you drive is the speed of the truck pushes air through the radiator. The reason the heater still works when the temperature goes down is the coolant is still at maybe 140 degrees.
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