Vehicle is a 1994 f150 4x4 with a 5.8 auto and air. I have a engine temp problem. I can not get it to run above 170.6dg. I have changed the thermostat and put in a new temp sending unit. no change maybe a little cooler if anything.
I put on the snappy scanner and it goes to 77 which calculates to 170,6. I do show a closed loop running which is also confusing as the book reads 185 or up to get that on the engine.
I was wondering if there is a possible connection to a clutch fan being bad causing the engine to run too cool, I never heard of it but thought id ask.
I also contemplate that the thermostat is bad or wrong for that year and model but I thought thermostats were standard, it s a 192dg thermostat. are there special thermostats for this engine and year??
I also put on a new rad cap.
the gauge in the cab reads just over the n a very low position which I would suspect the gauge except the snappy scanner confirms with the low reading.
Last question which is off the wall for sure. the o2 sen . when it is going open then closed loop when it gets as hot as it gets can the o2 have any effect on the engine running to cold? I don't see how but just asking.??
Thanks much for any info
Grumpy

 

You may be more correct than you realize. If the fan clutch is locked up it will be a lot noisier in the engine compartment plus affect engine running temp.
You might try checking the following,
when you start a cool/cold engine the fan blades should start turning fast then quickly slow down to a loping speed. You can hear when the fan is locked because it roars when throttle is increased. If that is the case , fan clutch replacement is required.

 

Thanks Hanky; I tried the fan an found no problems with it so on to the next square; the temp runs from 150 to 170 when it should run in the 185 or above range from my understanding.
Now the snap on scanner reads the 150 170 and the dash gauge reads very low so that seems to mean they agree. Now the open loop starting and cold engine even at the low temp kicks into closed loop as it should. The thermostat is a 192 so how is the temp staying lower ??? and the close loop should not appear til 185??
I unplugged the temp sending unit to see if a signal from it to the gauge caused the scanner to pick up a low temp reading or any bad info. The gauge goes dead and the scanner still reads the temp at 150 170, so where does it get the reading if the temp sensor is unplugged??? Is there another way the computer is reading the engine temp? Maybe another sensor that is bad? that I donk know about??
My apologies for such a crazy situation
Thanks Grumpy

 

You disconnected the wrong sensor. There's one for the dash gauge and one that the computer uses for temperature information.
Get a Motorcraft thermostat and recheck. Aftermarket ones vary greatly in quality.

 

Raski; I am so glad to hear from you. I have been trying to find what and where the sending unit was for the computer to obtain its info. I know the snapon scanner is reading to low temo as the gauge is but disconnecting the temp sending unit don't kill the snap on scanner just the gauge. If you could let me know the part im looking for I would greatly appreciate it.
I will go to ford and get a new thermostat to replace the one I just put in from napa.
Thanks Grumpy

 

You should be aware the system should go into closed loop when the following are reached.
1.Engine temp is 140 degrees and higher
2. When the oxygen sensor reaches a certain temp (around 600 degrees)
3. After a specified period of time has elapsed (PCM)
If the thermostat is defective or questionable and doesn't close as it should the temp will have a hard time going over 140 degrees F. (again depending on ambient temp)
Those of us that have been in the field, many times, have learned the hard way , some, not all, aftermarket "stuff" is not what it should be. OEM usually better.

 

thanks will get a new ford one Monday;
Grumpy

 

Better late than never, Ford 5.8 Lightning truck engine
The coolant temp sensor (ECT) (part # 12A64B) is located screwed into a coolant "tree" that is located.on the front of the intake manifold just above where the thermostat is mounted.

The water temp sensor (part # 10884) is located on the intake manifold, driver's side front,. Also just to the rear of the water temp sensor is the intake air temp sensor (IAT).

Something you can try, When the engine is cold, like setting overnight, the coolant temp sensor, water temp sensor and intake air temp sensor , ALL should read the same temp. Or one or two degrees difference. The one that reads differently from the others is suspect.