2002 2.3l ford ranger engine temp spike

[TimDaniel]

Hello, trying to solve a problem with temp gauge spikes. My son has had most of the issues at college so i don't have all the first hand experiences so i traded my truck for his so i could figure it out. So I run the truck on the hwy for an hour or so and suddenly the temp gauge spikes to all the way hot. I turn on the heat full blast and the needle returns to normal. I drive 10 more minutes and the needle spikes again. Drive 5 more minutes and needle goes back to normal. Have been fighting this problem for a year now. coolant reservoir stays full. No steam. engine despite gauge does not seem overly hot. Water pump changed, two thermostat changes. vehicle towed twice when son was driving. mechanic serviced twice. Wetter water added. hydro carbon test negative. Mechanics baffled. 1st mechanic was ford dealership ex mechanic called friends in the buis and reported ford is aware of this problem and do not offer a solution. Second mechanic made sure to burp air out of system on second thermostat change in 6 months. I have found exact same problem on other forums and replacing temp sensor does not correct problem. Getting super tired of throwing darts and money at this issue. Any advice would be great. Thanks

 

[Dirtman]

There are technically 2 temp gauges and senders. One goes directly to the pcm and the other directly to the gauge cluster. The one to the gauge is a sender, the one to the pcm is a sensor.

If you have access to a scan tool you can bring up the live data from the sensor (pcm side) and see if the pcm sensor data matches what you see on the gauge. If it doesn't, then the sending unit is bad. If they both read hot you know it's truly a cooling system issue.

Also you didnt mention checking the fans. There are 2, electric and clutch fan. With the engine cold the clutch fan should spin somewhat freely. Then run the engine up to temp and shut it down, the fan should be hard to spin now. If not the clutch is failing. As for the electric fan, start the truck and turn on the AC and then just visually make sure its moving.

 

[TimDaniel]

Bit the bullet and decided to change both the heat sensors anyway. 50 bucks in parts and we will see what the labor is. More darts. Guy at the parts store suggested taking the truck to the ford dealership and getting the computer swiped as this might be a false signal from a problem we corrected with earlier work.

There are technically 2 temp gauges and senders. One goes directly to the pcm and the other directly to the gauge cluster. The one to the gauge is a sender, the one to the pcm is a sensor.

If you have access to a scan tool you can bring up the live data from the sensor (pcm side) and see if the pcm sensor data matches what you see on the gauge. If it doesn't, then the sending unit is bad. If they both read hot you know it's truly a cooling system issue.

Also you didnt mention checking the fans. There are 2, electric and clutch fan. With the engine cold the clutch fan should spin somewhat freely. Then run the engine up to temp and shut it down, the fan should be hard to spin now. If not the clutch is failing. As for the electric fan, start the truck and turn on the AC and then just visually make sure its moving.

Thank you for the info, I will pass it onto the mechanic who now has the truck and the new sensor and the new sender.