1978 F150

A good analog temp probe installed in the cooling jacket through any number of orifices Ford drilled and tapped into the block/heads will generally produce good results.

Can you be a little more specific?

Harbor Freight. $20.00 US.

Infrared Laser Thermometer

Item #93984

Dont you mean, 124.16 Yuan ?

Unless it's boiling over and steams coming out I wouldn't worry about the engine temperature. Replace the sensor. It's a relatively inexspensive part. If that does not do it the thermostat could be bad. Running cool the cause was usually it's stuck open. With a cool engine open the radiator cap. Start the engine if you notice the coolant is circulating rapidly. The thermostat is stuck open. If it's not circulating rapidly wait until it does thens when you need a temperature gage. To tell if it regulating the temperaure properly.

You might need one of these...

http://www.autopartswarehouse.com/sku/Motorcraft/Coolant_Temperature_Sensor/MISW2328.html

that would be the replacement...... and if it accessible, only about 2 minute job to replace.

• Place a smoker kipper (Google it) on the engine, and see how long it takes the neighbourhood cats to arrive?
• Drop water on it and see if it turns to steam?
• Grab hold of it and see how long it takes blisters to appear?

The possibilities are endless!

As an extension of your answer, I offer this. Most people can hold onto something up till about 150 degrees F. And water will boil at 212 F. at sea level. Those two things should tell you how hot your engine is.

Is the temp gauge the only one not reading? If so, the issue is isolated to the temp gauge. If others are out, then look for a common power feed, or common ground.

The factory gauge was powered from the key, to a voltage reducer, to the gauge, and finally out to the sensor, searching for a ground. This ground was temperature variable, causing the gauge to move relative to coolant temperature.

One more tip for the OP, if the temp sensor came out of, or was designed for a vehicle with an overheat indicator light, it will be opeck.n between the wire connector, and the threaded part of it. In that case it will always show cold till it reaches the overheat temp. Then it will change to almost 0 resistance. Good lu

Smoked kippers are yummy with saltine crackers and grey poupon mustard.

Sssssssssssshhhhhhhhhhhhhhhh! Don't tell Del!!!!

You have generally 3 main possible error sources, though engine management systems can also cause such problems, some modern cars even have "controlled" thermostats, where the MMU opens and closes it with a tiny motor, not directly by water temperature....:-

1) Electric fan never switching off - never seen that one personally - but very easy to check.

2) Thermostat jammed open, this can even be due to the fact that it was wrongly installed, years before maybe, and eventually the little "bobble" got caught in the mouth opening. Place in boiling water to release and to check operation. If OK (as mine was on my then Volvo) simply replace with the "bobble" at the bottom, in my case that was 180° (angle) to how the idiot mechanic had put it in....Or replace it if is staying open all the time.....

Some have a simple mechanism to hold it open IF THE ENGINE HAS OVERHEATED, WATER MISSING FOR EXAMPLE, TO DEMONSTRATE THAT THE THERMOSTAT WAS NOT THE REASON....

3) Sender for the thermometer is defective, already covered in some detail by others.

I personally like the idea of buying a cheap IR remote thermometer that some here have mentioned to read the temp off the motor block.

Such a unit can be a good addition to any household/workshop, one simply needs a reason to buy it, now you have that!!!

Remember that with some engines, not only will a cool engine increase fuel consumption, but it may even increase oil dilution and or wear on the engine, so it does need to be fixed.

Best of luck..You should be able to fix it yourself!!

when you put your finger on the top of the rad and it hurts is a cheap way otherwise laser thermal temp guns are quite cheap

My money is on your thermostat stuck open. Especially with an older vehicle. It's located where top hose from radiator meets the intake manifold--two bolts hold the bell-shaped housing onto the manifold. A new one will cost you maybe $10. Scrape the old gasket remains clean. Use gasket shellac/cement--and install the thermostat correctly. Eyeball the old one--if it's stuck open, you will see space through which water can flow. If it's closed, check by immersing in a pot of boiling water. If it opens (it's a subtle thing) as the water approaches boiling temperature, then it's working.

You don't mention if there has been a deviation from the normal temperature indication. The gauge is merely an indicator and may be reading correctly. Did you replace the wire from the gauge to the sensor? This wire is calibrated for a specific length and type of wire (usually Iron and Constantine).

If this is an OEM gauge, wire, and sensor, there have been may responses regarding stuck thermostat. If you installed an aftermarket temperature gauge, you may have placed the thermocouple sensor on the radiator output (cool side) or in the fan airstream (also cool).

Look at the exhaust pipe to see if it is carbonized. A cool engine will be rich in carbon.

Aslo one other item. There are at times a voltage regulator on the back of the dash. If this is faulty it will give you a false reading. If it's changing rapidly from cool to hot and visa versa, this could be the issue. I had a '88 T Bird that drove me crazy. replaced everything including recore of the radiator. Turns out this $50 item on the back of the dash panel was all I needed to correct the problem. Never had a heat problem again... wonder why that was.

OK, this thread seems to be going nowhere. Your factory gauge setup has been calibrated at the factory The marks on the gauge correspond to an exact ohm reading on the temperature sensor. For the cold line, the hot line, and possibly a their line in the middle, there is a published ohm reading the sensor should be at. The fi find it. Let me know.ne people at Ford have this information. Auto parts stores MAY have this information. And I have this information. It is located in my storage unit, and will retrieve it if you can not.