Coolant guage sits under cold but warms up .

[Cypress65]

I've recently had my engine swapped and now have my truck back and the only thing I notice is that my coolant gauge sits under C but when the truck warms up its only goes up about a quarter above it. Just curious if this is a issue? Ive just swapped out the thermostat,sender and sensor. With no luck. I grounded the sender wire and it shoots to H. Maybe im just over worrying? Any input would be great.

 

[RonD]

Welcome to the forum

2003 Ranger with a 2.3l, 3.0l or 4.0l engine?

If grounding the SENDER wire, red/white wire, gets gauge to go to HOT then that wire is OK
If sender has two wires, a black/white wire, then repeat test but use that 2nd black/white wire as the Ground, because thats what it is, if gauge doesn't go to HOT again then that black/white wire has a bad ground connection

If sender only has 1 wire then Senders threads to the metal of the engine is its Ground, so DO NOT use tape or sealant on the lower threads or you get a weak or no ground and so incorrect gauge reading

If wires test OK then new sender is bad or new thermostat is the wrong one or bad

Rangers all use a 190-195degF thermostat(since the early 1980's), except the 2001, and up, 2.3l which uses a lower radiator hose thermostat rated at 180degF

The gauge is calibrated for 210degF at 1/2 way point, so just below 1/2 would be correct needle position after 5 to 8min of driving time to full warm up
Also check the heater air, it should be HOT after full warm up, 190degF, not Luke warm, if not then its for sure a thermostat issue, not a gauge issue

 

[Cypress65]

Ok so it blows hot. The sender is only 1 wire.the truck its a 03 3.0 v6. The thermostat that was in there was a 180. I swapped to a 195 or 192 .

 

[RonD]

So you may have gotten the wrong sender or its threads are not making a good contact to engine metal
Ford has used the same senders since the 1960s

OHM Chart here: https://www.vintage-mustang.com/attachments/temperature-sender-values-jpg.312146/

If you want to test sender

 

[Cypress65]

I have swapped what was in there sender and sensor to Motorcraft parts. I'm assuming all is left is to try to ground it send see if it works right . Appreciate the help!

 

[RonD]

Sender is 12volt device
Sensor is 5volt device

You can use OHM Meter from sender post to ground with cold engine, 100 ohms or so
And then after warm up, 35 ohms or so

 

[Cypress65]

I haven't gotten around to test it yet but I think I'm just going go leave it alone it seems to work I suppose.

 

[RonD]

That represents about 185-190degF on the gauge so correct after full warm up, 5 to 8 min of driving

 

[Cypress65]

Guess I was over worrying about it being past cold in that case. Appreciate the help.

 

[BiggSherm1988]

So mine sits at this level but occasionally on a cold day I will get a fault that says "P0128 Coolant thermostat- coolant temperature below thermostat regulating temperature." I have never figured it out but all summer I didn't have it pop up. now that its fall I have started to get it popping up on cold days.

I haven't tried grounding the temp sender though. It definitely blows HOT air too. I kinda thought maybe its because its freaken cold here in Germany and its just cooling down the coolant too much. I have no idea. I usually just stop and clear the code or clear it when I get to work.

 

[Cypress65]

Yeah that makes sense. No code here but it's the end if summer with it still being 80 plus here so no reason for it. I just Saud screw it. It goes up to half after a few mins so whatever I guess lol