Coolant Temperature

[franklin2]

Every ford vehicle I've owned the oil pressure read perfectly at the 50% mark

Want to know why? Starting in the late 80's, Ford did away with the oil pressure sensor. A real oil pressure sensor is a large metal can screwed into the oil pressure port. In the late 80's they kept the gauge in the dash, but on the cluster circuit board they installed a resistor in the circuit. They then got rid of the oil pressure sensor and installed a oil pressure switch. The ones like on a idiot light dash board. Below 5lbs oil pressure the light comes on. Above 5 lbs the light is off. But in the case of the later Fords, the pressure switch completes the circuit if there is no pressure, and makes the gauge go to zero. Above 5 lbs pressure the circuit goes through the resistor making the oil pressure gauge read 50%. Great system isn't it? How much engineering did it take to come up with that?

 

[JohnG]

I remember back in the early 90s when the Miata came out it had a true oil pressure gauge minus the numbers. Forums and dealerships we constantly getting questions from people worried about wrong oil, engine health, etc. simply because the pressure looked “too low” at idle.
Rumor at the time was we Americans just couldn’t get past the fact that it wasn’t like the temp gauge showing “middle is normal”. When you started the engine cold, pressure at was near “the middle” and got “worse” as it got hot.
A few years later the car also got the on/off gauge.

 

[rusty ol ranger]

Want to know why? Starting in the late 80's, Ford did away with the oil pressure sensor. A real oil pressure sensor is a large metal can screwed into the oil pressure port. In the late 80's they kept the gauge in the dash, but on the cluster circuit board they installed a resistor in the circuit. They then got rid of the oil pressure sensor and installed a oil pressure switch. The ones like on a idiot light dash board. Below 5lbs oil pressure the light comes on. Above 5 lbs the light is off. But in the case of the later Fords, the pressure switch completes the circuit if there is no pressure, and makes the gauge go to zero. Above 5 lbs pressure the circuit goes through the resistor making the oil pressure gauge read 50%. Great system isn't it? How much engineering did it take to come up with that?

I heard they switched because customers were bitching about the oil pressure needle moving throughout the RPM range.

So instead of explaining to said customer thats how oil pressure works they just came up with what they came up with

 

[Josh51]

Here's my follow up. I changed the temp sender, put in a new motorcraft 192 degree thermostat, did an oil change and changed the air charge sensor. The needle still sat at the top of the normal line but sometimes a bit below.
I bought a bosch mechanical gauge. I just drove 20 miles on streets and the temp ran around 190 most of the time. Once I stopped and turned the truck off it went up to 200 but never above. Let me know what you guys think

 

[Josh51]

Another quick follow up. I just did my 2nd fill up after changing the air charge sensor, thermostat, etc and I went from mid high 12/low13mpg to 15mpg now. The air charge sensor was extremely beat up, not sure if that was the culprit.

Curious, at what temperature reading should I start to worry?

 

[RonD]

Where is the ACT(IAT) sensor on your 1986?

Upper intake or Air Filter box?

These use 5volts same as ECT sensor, and have almost the same temp vs voltage return
Seen here: https://www.grandmarq.net/oldfuelinjection/images/temperature.gif

ECT seen here: https://slideplayer.com/slide/15540...+sensor+temperature+versus+voltage+curve..jpg

IF air temp sensor is on the intake then 2 times outside temp would be expected on warmed up engine, so if outside temp was 60degF then air temp inside the intake would be 120degF

IF its on the air cleaner box then should be closer to outside temp


O2 sensor needs to be changed every 12 years or 100k miles, only sensor that wears out on a regular time or mileage scale
Its the main sensor for MPG

 

[rusty ol ranger]

Where is the ACT(IAT) sensor on your 1986?

Upper intake or Air Filter box?

These use 5volts same as ECT sensor, and have almost the same temp vs voltage return
Seen here: https://www.grandmarq.net/oldfuelinjection/images/temperature.gif

ECT seen here: https://slideplayer.com/slide/15540...+sensor+temperature+versus+voltage+curve..jpg

IF air temp sensor is on the intake then 2 times outside temp would be expected on warmed up engine, so if outside temp was 60degF then air temp inside the intake would be 120degF

IF its on the air cleaner box then should be closer to outside temp


O2 sensor needs to be changed every 12 years or 100k miles, only sensor that wears out on a regular time or mileage scale
Its the main sensor for MPG

On a 2.9 the IAT is in the upper plenium.


@Josh51
Those temps seem fine.

You got a gauge issue.

I wouldnt get worried untill 210-215. Temps will always spike a bit after shutdown just because the coolant quits flowing.

 

[franklin2]

Curious, at what temperature reading should I start to worry?

Hot day, using the truck hard, start worrying and slowing down around 230 degrees. That is why a real gauge with numbers is nice to have.

 

[Josh51]

Thanks you guys. Yes, the sensor is on the passenger side of the intake manifold

 

[svtcards]

For a while now my coolant temperature reads at the very top of the Normal line when warmed up (see pic). I changed the temp sender unit out and it reads the same. Is this ok? I own a temperature gun, where could I take a temp on the engine to see if it's in a ok range? What is an ok range? Thanks

I just changed my sender on my recently purchased bronco ii and it barely goes up into the cold area. I wonder if my New sender is messed up also? And it does go to hot when grounded and stays cold or under when disconnected as well.

 

[rusty ol ranger]

I just changed my sender on my recently purchased bronco ii and it barely goes up into the cold area. I wonder if my New sender is messed up also? And it does go to hot when grounded and stays cold or under when disconnected as well.

Thermostat stuck?

 

[franklin2]

Go ahead and start spending a bunch of money and time replacing parts looking at what a lousy Ford instrument cluster temperature gauge tells you. I hate Ford gauges. I use aftermarket gauges. At least get a infrared thermometer from harbor freight to check the engine temp before replacing parts.

 

[rusty ol ranger]

Go ahead and start spending a bunch of money and time replacing parts looking at what a lousy Ford instrument cluster temperature gauge tells you. I hate Ford gauges. I use aftermarket gauges. At least get a infrared thermometer from harbor freight to check the engine temp before replacing parts.

He said when he grounds it it goes all the way to H...which means gauge and wiring ia fine. Hes replaced the sender. Its not heating up.

 

[RonD]

Yes, the test for "thermostat stuck open" is to start cold engine, and open the hood
Feel the heater hoses and feel the upper rad hose, all cold of course

Wait 2 or 3 min, feel them again
Heater hoses should be warming up
Upper rad hose should still be COLD
If upper rad hose is warming up then thermostat is not stopping flow to radiator, which is the whole point of a thermostat

So either its stuck open or otherwise not blocking the flow to radiator

 

[franklin2]

He said when he grounds it it goes all the way to H...which means gauge and wiring ia fine. Hes replaced the sender. Its not heating up.

Still watching that crappy factory gauge, even if it's working and has a new (made in China)sending unit. I don't trust them.