I have a 92 F-150 2wd 5.0L that will not get up to normal operating temperature. It takes about 20-30 minutes to warm up and blows hot air. The check engine light comes on after about 5 minutes of driving. Even when I drive it for 45 minutes to over an hour the needle on the temperature gauge never goes into the normal operating temperature range but the heat does work. I have replaced the thermostat and know that it is closing and is not stuck open. I even tested the old thermostat in boiling water and it was opening and closing correctly. I don't know where to start to fix this problem any suggestions would be greatly appreciated.

 

Did this start before or after the new T stat. What was the temp rating on the new T stat?

 

maybe the water temp probe has gone bad? Happened on my jetta a while back, caused the thing to run like crap because the computer couldn't get a proper read. just a stab in the dark. Hope you figure it out!

 

Before and after and 195 degress

 

The factory gauges are well known to give less than accurate readings. If you have a good thermostat, then you either have a bad temperature sensor or the gauge itself may not be accurate. For peace of mind install an aftermarket temperature gauge if you are worried about it.

BTW..the gauge temperature sensor is not the same one that sends the engine coolant temperature (ECT) to the PCM.

I also suggest you check to see what codes are triggering the Check Engine Light.

 

Have to agree w / the above post from rla2005

 

Is the EGR disconnected in any way? mine got cut out and since then the temperature stays quite low... also, don't believe in the stock gauges, they're little more than idiot lights.

 

Its more than just the gauge not working, like i said it takes way to long to heat up and the pressure in the radiator doesn't seem right to me. Does anyone know where the DLC is on this truck and where I can find an older OBD reader that will work

 

DLC?

I assume you mean the port to check for error codes? Ford Fuel Injection » How To Run a Self-Test

Or purchase one of these: Amazon.com: Equus 3145 Ford Digital Code Reader

 

Hmmm,
water/antifreeze level-ratio,
water pump/radiator/block condition...

Start it up with a thermometer in the rad opening. (Digital would be great...) Leave heater controls off. See what it does.

How's the cooling fan?

 

sorry if this is a duplicate.
My 92 straight 6 runs perfectly for this discussion.

It got real cold the other night so I drained and added antifreeze to the radiator.

I let it idle so the t.stat would open and run the solution thru the block.

20 min later , the top hose was still cold.
I got out the laser temp gauge and the head by the tstat had a hard time going over 170.
I'd say it took 1/2 hr for the top rad hose to get warm and then hot like it should.
Head temp finally hit 180F.
Coolant level perfect but I can hear fluid pouring thru the heater core.

I'll try to bleed the air out somehow tomorrow.
Everything is working but it sure seems overly efficient at cooling and cold blooded for sure.

 

It should Be a good mix 50/50 of coolant
Thanks for the link this video was also helpful

YouTube - How To Run A Self-Check On Fords 198?-1995

I'm not sure if I'm reading the codes right but I'm pretty sure it's saying 11 for the KOEO reading which is good and explains why the check engine light doesn't come on right away but I'm pretty sure it's telling me 33 for the CM reading which says that the EGR valve is not opening so thats where I'll start next. Thanks for all the help