how accurate is the coolant temp gauge?

thedave · Sep 1, 2009

The temerature sending unit on the 91 4.0 ranger I picked up a few days ago was trashed, would barely get to the N on normal. I replaced it with a new sending unit and now it is reading very high. After flushing the coolant and changing out the thermostat for a new 195 degree one it sits on A and will climb to about 1/8" past L before dropping back to A. I have tested it so far at idle and at speeds up to about 30 mph, have not had a chance to hit the highway.

I should have access to a thermal temp gauge tomorrow but I'm trying to find out if I do have a problem or the new sending unit is simply reading high.

ForOffRoadDriving · Sep 1, 2009

mine has always read very cold on the temp scale, but when i put a real temp gauge in it always runs around 190-210

locovaca · Sep 1, 2009

Working properly they're as accurate as they are on any other FoMoCo product as almost all of them of that vintage us the same sender. Mine was always cold until I stuck in a new sender and from that point on it was "accurate"- meaning it stayed in the normal range when it was normal and you could see when the thermostat opened up when first starting out

calypso93 · Sep 5, 2009

This was in response to a slightly different question, but may have something for yours in it---

"I used a non contact thermometer (IR) aimed at the t'stat housing, just about where the upper hose connects. It read from 185-210 while the dash gauge read between "N" and "O". Getting an idea of the actual coolant temp may help in finding the real problem.
An even better tool is a thermal imaging camera. Found a few cooling system problems with one. Lucky we have a bunch at work. Check with some of your fire department friends. They may have access as well."

thedave · Sep 5, 2009

calypso93 said:
This was in response to a slightly different question, but may have something for yours in it---

"I used a non contact thermometer (IR) aimed at the t'stat housing, just about where the upper hose connects. It read from 185-210 while the dash gauge read between "N" and "O". Getting an idea of the actual coolant temp may help in finding the real problem.
An even better tool is a thermal imaging camera. Found a few cooling system problems with one. Lucky we have a bunch at work. Check with some of your fire department friends. They may have access as well."

Yeah I never updated this, I put a infrared thermometer to the thermostar housing and at the A in normal is right around 195 degrees. I guess te sending unit I put inreads high which is odd but it doesn't waver too much from the A so I can live with it.

how accurate is the coolant temp gauge?

thedave

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ForOffRoadDriving

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locovaca

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calypso93

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thedave

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