2004 4.7 tundra temp gauge reads high

Radiator blew recently, after replacing it truck starts and runs fine but the temp gauge reads 90% hot immediately after starting a cold engine. Took out the thermostat, no effect, replaced coolant temp sensor, nothing. Looks like there is a second sensor (or sender?) next to coolant temp sensor, possibly for gauge... hoping its not water pump.

 

You’re correct, one sensor tells ECU what temp is and the other is for idiot guage. Not that we are idiots but you know what I mean.

In any case, do you feel you burped it good after radiator replacement and do you feel you clocked the thermostat properly.

 

Believe I have the air out of the radiator, haven't replaced the thermostat, the most suspicious symptom is the instant gauge rise on starting the cold engine, maybe two seconds

 

Agree that is suspicious without even asking you to define cold. Within 2 seconds, it's practically impossible on a cold eng.

Just to make sure, do you feel you changed the actual water temp sensor ?

I too have an 04, so yours should be same....
W 3(grey connector) Water Temp. Sender....for idiot gauge
E 2(black connector) Engine Coolant Temp. Sensor....input to ECM




You could double check proper sensor resistance by unplugging and with a volt ohm meter, if you have VOM.
Ideally having an OBDII meter could verify what actual temp the ECU is seeing. Perhaps you have a bad water temp guage on Combination Meter/Instrument Cluster.
Won't say impossible but will say highly unlikely it's actually 200+ deg 2 seconds after engine start on a cold engine.

 

I had this happen to me once after working on the instrument cluster. (along with some other gauges going haywire)

Finally traced it down to a single bent pin on a connector, it was a ground wire.

100% though its electrical and not actually overheating so don't bother messing with your coolant more.

 

Thank you both for your thoughts and time. I have replaced both the sensor and sender and thermostat, still running up 3/4 to 90% to the H, maybe three seconds after having been off several hours in 70 degree ambient. I also find it hard to believe it's getting that hot that fast, but I'm insecure about runnning if it really is. Still worried about water pump, if I can find my infrared gun I'll check the block temp.

 

Also I'll go out and plug in the OBDII

 

It's not getting that hot that fast. Not physically possible, even with no water pump.

Remember, halfway up the gauge, 'normal' represents 180º of temp....you don't need a temp gun to tell you your block isn't that hot.

And yes, I wouldn't run it a long time with no temp gauge.

 

So you replaced the gauge sensor and the ECU sensor at this point? Beware the cheap gauge sensors they could make your gauge act wonky.

Part numbers
Appropriately labeled in the pictures.