89 Ford F350 Weird Issue

uncle

Observer
Lately when I drive my truck, 7.3 idi, and the truck warms up and I get to Hwy speed, the Engine light comes on and the Temp gauge pegs out.
If I back off the throttle, ht elight goes out and the gauge returns to normal within a second. I touch the accelerator and Light and pegged gauge.

Any ideas? Part of me thinks feedback from alternator or am I too out there with this?

Brian
 

mr_ed

Toolbag
I had an 87 idi for a while, and it did have some weird electrical idiosyncrasies to it. However, I'm far from a pro on them.

Oilburners.net was always a godsend for me in those times.


Sent while on the toilet using Tapatalk
 

Rot Box

Explorer
Assuming it's the factory gauge.. replace it with an aftermarket unit as soon as you can. The fitting is on the front of the driver side head just in front of the valve cover and 1/4 npt if I remember right. The factory temp gauges in our trucks are notoriously unreliable and inaccurate.

X2 on oilburners.net :cool:
 

k9lestat

Expedition Leader
In no expert either but sounds like z thermo stat , water pump or you system flush because sludge.

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uncle

Observer
Back in the Spring, I replaces the waterpump and factory thermostat and had the radiator boiled out as I knocked a hole in it. New Fleet Gourd with anti cavitation.

It seems to be rpm based.
 

Madbaddad

New member
Lower radiator hose collapse ?

Sometimes the lower radiator hose will get soft and collapse under the suction created by the water pump at highway speeds.

Something to check out.
 

Rot Box

Explorer
Here's a pic of the sensor location (hopefully your engine is cleaner than mine! lol). I'm holding the old sensor and sorta pointing at the new one. I'm using a $12 Equus gauge that I bought from auto zone six years ago and it's still working great. Simple install and it came with an assortment of fittings as well. I would recommend pipe thread sealant and not teflon tape like I used..

Anyway anytime the coolant temp gauge spikes or the oil pressure gauge drops the check engine light will come on. Depending on barometric pressure, moon phase, throttle position or number of passengers the stock gauge can spike and turn the CEL on. Another advantage of the aftermarket gauge is knowing exactly what temp the engine is running at. The C-[NORMAL]-H is useless and the coolant temp can be well over 240º without going into the red zone :Wow1:

IMG_4080_zps6v39aalz.jpg
 

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