I recently got my fourth Ranger a 1999 3.0 manual with 83K. I see the temp gauge will only move from the C line to the first line of the arc. This makes me very nervous as I've had a couple radiators blow before and toast the head gasket in minutes. Anyway I'm hoping someone has seen this same issue or can advise on where I should start.
Thanks in advance.

 

First thing would be to replace thermostat, someone may have put in a 160 or 180degF t-stat, 190-195degF is spec

Every few years Ford changed the gauges, so "only move from the C line to the first line of the arc" is only usable to someone with exactly the same gauge
Try 1/4, 1/3, 1/2, ect.....as description
Between Cold and Hot would be 1/2 way and an estimate is good enough from that, and no "letters", Ford also like to put N O R M A L on their gauge faces, and they are spaced differently over the years

With 192degF thermostat temp gauge usually runs just below 1/2 after warm up, and then will go just above 1/2 when climbing a long grade or pulling a trailer, Ford usually had 200degF as 1/2
3/4 is bottom end of over heating so reduce the engine load and pull over, but don't shut off engine if temp gauge starts to drop, raise idle a bit to get more coolant circulation until temp gets lower, then you can shut it off.
When you shut off a hot engine all circulation of coolant stops, so the hottest areas, the heads, have no way to bleed off heat, so get supper hot, and that blows head gaskets and cracks heads
Obviously if a hose or radiator blows all coolant is lost so shut off engine ASAP

 

I'll replace the thermostat and report back. In the meantime here's a pic showing the movement I described. My needle sits in the same place at operating temp as in the pic. Starts at the C and only moves to the first line.
Thanks for the fast response I appreciate your time.

 

That about an 1/8, so gauge IS getting a signal from Temp Sender on the engine, but coolant is not getting hot enough
1/8 is probably about 120-140degF, feel upper rad hose to confirm low temp, if you can hold you hand on the hose then gauge/sender are accurate, it its HOT then could be sender is failing

Fuel injected engines have TWO temp devices on the engine
ECT sensor, for computer only
Temp Sender, for gauge only

 

Still haven't had time to change the thermostat but I did feel the top hose and it was HOT. Hand on maybe 1-2 seconds. So maybe I shouldn't change the thermostat but should change the sender? I saw somewhere but can't find it again... which one is the gauge sender? Could someone remind me?
Thanks

 

It is at the top front of engine, screwed into a metal "elbow" with hex shape

This elbow often rusts and leaks so be careful with it

SENDER has just one wire attached, it is Grounded thru its metal threads and metal engine parts, so don't use TAPE on the threads, or leave a few bare threads for the grounding
Sender should have Red/white stripe wire, it runs on 12volts, if you ground this wire, with key on, temp gauge should go to HOT, all the way up, that tests the wire and gauge

Sensor has two wires and runs on 5volts from computer.

So these are totally different units, not at all interchangeable, make sure you get a SENDER, not a sensor, from the parts store

Sender should have a cylinder shaped end that is immersed in coolant: https://www.obd-codes.com/faq/images/ect-sensor.jpg
Sensor has a Cone shaped end: https://www.2carpros.com/forum/autom...p_Sensor_1.jpg

 

Yes the parts store will give you the wrong one. Best to look up the correct part numbers before you go and have them ready.