Hello, I had purchased my first deisel last February, it's a 1991 7.3 F-250 4X4 automatic Lariat with 87500 miles on it.
The temp gauge seems very sensitve to road conditions (goes up as soon as it's working harder, comes down just as quick) but it never reaches the normal mark usually reading just above the lowest point even on very hot days. Gas milage is good (21+ MPG on HWY), power is good.
Is this normal for a deisel?

Side note: when I purchased the truck I had a mechanic change all fluids but he forgot to change radiator fluid and the next night the fluids froze and came out (luckily I had the engine plugged in so no engine damage).

thanks for any advice, Gary

 

my dad has had 4 ford diesels, i have 1, and my brother also has 1.

i've never seen the temp guage on a diesel even on the normal letters.

 

Factory temp guages are known junk,you need an after market guage to tell what the temp really is. 21+mpg is excellent fuel milage. Make sure you add the sca's to the coolant to avoid cavatation,if you dont know what cavatation is do a search here on it,it is serious sh$t,and i mean ser$$$$$$s.BTW,Welcome to the forum

 

garyct,
Welcome to FTE and the IDI diesel forum.

 

21 mpg is definetely a good fuel milage for this truck, especially considering it is an automatic which typically do worse than the standard trucks. I have had my 93 F250 up to 19.5 mpg HWY which include going up and down BC mountains climbing from sea-level to 4,000 ft.

Go with a aftermarket temperature gauge, the factory dash gauges have a tendency to die slowly and show lower and lower temps over time. The factory gauges in the dash work on the old resistance principal yet their internal resistance goes up as they age which translate into a lower and lower reading as they age. Changing the temperature sending unit might help bring things back a little; however you would be off best to install an aftermarket gauge.

To test if your gauge in your dash has completely failed pull the sensor wire off the sending unit on the engine and attach a wire to ground to the signal wire you pulled off the sending unit. This should send the needle on the temperature gauge in the dash to HIGH temp with the ignition is on.

Seb.....

 

My temp gauge works the same way... Quite reliably even... Is there any warning toward the engine overheating then?