Even after changing my thermostat flushing the cooling system it doesn't want to move of of cold. Is there a wire loose somewhere or is there any other sensor that plays a role in moving this gauge. Idle is perfect. Exhaust is a little stinky.

88 351w auto

 

Check the coolant sensor on the intake manifold. It shoud be near the front driver's side. You can pull the wire off to test the gauge. Short it to ground and the gauge should swing to oneside or the other (I don't remember which). Unshort it and it should move to the otherside.

The gauge in my Bronco actually went bad on me. It would read full hot all the intermittantly.

 

Could a faulty coolant sensor be sending wrong or no signals to the computer resulting in a bad exhaust. I ask because as I mentioned my idle is really even no missing but my exhaust is smelly but is not white or black. The bronco had been sitting for awhile and when started had white smoke but that burned off after driving it awhile and running fuel cleaner through it.

 

Yes there is a coolant temp. sensor that feeds the computer with that information. It is NOT the same one that drives your temp guage. The one for the computer (in my experience) is a two wire sensor in a fitting immediately above the thermostat housing. the one for the temp guage will be a single wire sensor in the location Adelyser mentioned. (information based on my experience with my 92 XLT 302). Sensor location may vary from year to year and for different engine types. I would imagine the 351 considering its similarity to the 302 would have sensors in the same locations.

 

my dad had an 88 f150 and every morining the temp guage would stay on cold and he would smack the top of the dash and it would work. maybe its a loose wire

 

its possible that it could be the thermostat. it may have gotten stuck open. I know in my bronco, the gauge doesn't move off cold since i took the thermostat out.... normally the thermostat say its a 180* one cycles to keep the temp in the system at a pretty constant 180*... just some food for thought. larry

 

What temp thermostat did you use? If you did not use the right one, its 195 I think, then your gauge is probably fine and the truck is actually running that cold.

 

I used this because the lower the temp on the stat the better cooling will be in the summer? I'm in southern california and there is no winter here. last week it was up to 90 for a couple of days. My gauge is stuck on cold as if the car was turned off. I picked up a borg warner coolant temp sensor tonight will put it in the morning but that really is for my milage and exhuast. Any ideas?

 

Kudos to adelyser!! I was having the same problem with my temp gauge on my 74 F100and was wondering how to check it. When I shorted out the wire going to the temp sender, it made the gauge go up to and peg out on the Hot side. Thanks for the help!!

Andy

 

I'm having this same problem. I just replaced the temp sensor directly under the throttle body. My dash gauge still is in-op. I noticed this was the two wire gauge... maybe i replaced the wrong one? It's '96 351.

Any thoughts?

 

I replaced the temperature sensor on my 91 f150 302, and no luck. It is a small 1" socket size three prong attachment that runs to through the wiring loom to the main junction on the drivers side, inside fender the well, from.there it goes into the computer and through the firewall to the internal temp gauge. Tested continuity from the temperature sensor to the junction at the fender well, but from there I have no clue. I think it is a wire grounded somewhere, as I know the sensor is good and otherwise, I am asking for any input. Thanks, Jim
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1991 Ford F150 302/5.0 A40D with 93,000 unmolested miles... Stock.

 

When replacing temp senders do not use teflon tape to seal the threads. Can insulate it from ground which is normally needed.

 

I checked to ensure that Teflon or other medium wasn't used. Also, I stand corrected it is a two prong plug, not three as I previously posted. Even though the parts guys gave me the wrong one in the first place (plastic) I obtained the correct part and ensured that it had a positive connection. Still stuck at cold on the bottom. Thanks for the help GFW1985. Any more suggestions on where to start?

 

The sending unit for the temperature gauge is NOT the ECT (Engine Coolant Temperature) sensor mounted in the water neck. The sending unit for the gauge is a small single-wire resistive unit in the lower intake manifold near the front (because there is a coolant crossover passage in it).

Replacing the ECT sensor will have zero effect on the gauge because it is in no way attached to the gauge.

 

I've tried replacing both with no luck... got upset and installed mechanical water temp gauge