Coolant gauge problems

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Sep 24, 2017 | 07:30 PM

GuyinWy

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Coolant gauge problems

Alright, I'm looking for some help with my gauges. Truck is a 97 F-250 HD with a 5.8 and automatic transmission.

For some time I've noticed my factory 'gauge' reading near the top end of normal. I've checked the cooling system with an IR thermometer and it's not overheating. As part of my truck rebuild I've replaced the entire cooling system, new water pump, thermostat, radiator, fan hub, heater core and all the hoses.

I installed a VDO brand electric coolant gauge, I tapped the thermostat housing and installed the sending unit there and wired everything up. After a 5 minute drive at 30 mph my factory gauge is reading at the end of normal and my VDO gauge is reading 230-240*. When I check the cooling system with the IR thermometer it's showing 154 * at the thermostat housing. It seems like a gauge/ sender problem but seems strange that it happened to both gauges. Any ideas?

Sep 24, 2017 | 07:44 PM

88n94

Cargo Master

Joined: Jan 2004

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From: South Dakota

Are you sure your IR thermometer is accurate? I would check it with a pot of boiling water, Shine it at the boiling water and the outside of the pot.

Sep 24, 2017 | 11:55 PM

jtmalott

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Joined: Apr 2013

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From: Fort Wayne, IN

I'm here to tell you, the IR readings are a joke. I have used a lot of them and the only thing they do is give you decent measurements of what's hotter than what, not really relative to other guages with precision. Check the resistance of both of your guage sending units. I would trust those over IR any day. With all of these things being changed, I suspect you have air somewhere in the system causing airlock. Rev that sucker at the throttle body with the cap off cold and watch the coolant level at the radiator header. Add until full and put the cap on. If problem continues, and you feel heat on the downstream side of the fan, I would try changing the clutch fan, maybe it's not engaging.

Did you put the fan shroud back on? What is ambient temperature? Do you have ac, and is it running?

Sep 25, 2017 | 08:13 AM

GuyinWy

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Everything is

Sep 25, 2017 | 08:16 AM

GuyinWy

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Everything is assembled and full, I've put around 250 miles on the truck hauling tractors and it shows no sign of actually overheating. Has AC but not using it, high yesterday was 46.