Engine temperature gauge reading consistently cold

Tiny
TRENTDUPE
  • MEMBER
  • 2001 FORD RANGER
  • 4.0L
  • V6
  • 4WD
  • AUTOMATIC
  • 100,000 MILES
I noticed my truck was running very cold. The heater works fine, but the engine temperature only ever gets up to about 1/4 hot at the highest. I replaced the engine temperature sensor above the thermostat but that didn't fix the problem. I noticed that when I changed my coolant and was trying to get air out of the system, once I topped off the radiator no more fluid got sucked in from the radiator even though it was running for 15-20 minutes. The temperature gauge was still reading cold. I'm wondering if maybe the thermostat is stuck open? I don't know what else to try and don't want to do any damage to the truck. Please let me know if you have any suggestions? Thanks!
Saturday, May 2nd, 2020 AT 5:22 PM

5 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,108 POSTS
Hi,

Is the heater working now? I ask because if there is air in the system, that is the first place you will notice an issue. Also, is the heater putting out hot air?

Now, chances are you are correct regarding the thermostat. Since it was showing 1/4 of the way on the temperature gauge, that indicates it is working. So, the next step is the thermostat. Here are general directions for thermostat replacement:

https://www.2carpros.com/articles/replace-thermostat

Here are directions specific to your vehicle. The attached pics correlate with the directions.

____________________________________________________

2001 Ford Truck Ranger 4WD V6-4.0L VIN E
Procedures
Vehicle Engine, Cooling and Exhaust Cooling System Thermostat Service and Repair Procedures
PROCEDURES
Thermostat

Removal and Installation

1. Drain the engine cooling system.

2. Remove the air cleaner outlet tube.

3. Remove the generator wiring harness bracket nut and position the wiring harness aside.

pic 1

4. Disconnect the upper radiator hose.

pic 2

5. Remove the bolts, water outlet adapter, and thermostat.
- Inspect the O-ring seal, install a new O-ring seal if necessary.

pic 3

6. To install, reverse the removal procedure.

_________________________

Let me know if this helps or if you have other questions.

Take care,
Joe
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Saturday, May 2nd, 2020 AT 7:04 PM
Tiny
TRENTDUPE
  • MEMBER
  • 3 POSTS
The heater is working and putting out hot air. I'm wondering if I should also replace the second sensor behind the thermostat housing. I'm hoping that swapping out the old thermostat will fix the problem completely. Thanks for getting back to me, I really appreciate your input!
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Saturday, May 2nd, 2020 AT 7:40 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,108 POSTS
Hi,

There are two coolant temperature sensors on this engine. One is for the gauge and the other is for the computer. I attached a pic. Let me know if that is the one you replaced.

Joe
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Saturday, May 2nd, 2020 AT 9:50 PM
Tiny
TRENTDUPE
  • MEMBER
  • 3 POSTS
Hi Joe! Looking at the engine from the front of the car I replaced the sensor further to the right on the drivers side. If that picture is the same orientation I would say I replaced the one not highlighted, I believe it was the one to the gauge but I could be wrong.
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Sunday, May 3rd, 2020 AT 7:01 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,108 POSTS
Hi,

The pic is from the front. I believe you replaced the wrong sensor. Do you still have the one you removed? I would switch it with the new on on the truck and then put the new one in the place indicated above.

Let me know.
Joe
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Sunday, May 3rd, 2020 AT 8:00 PM

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