Got the van (99 gmc 2500 v8 5.7 150k miles) a couple months ago. Needle always sits a bit low since I got it imo but I wouldn’t know if it was ever different.. is that normal or should needle get closer to 200? Tstat stuck open maybe? Heater works fine..

 

I would do one or both of the following. Seems like something is wrong and it might be the gauge.

1. Use a laser thermometer on the top hose or thermostat housing. Should be around 195* if the stock tstat is installed.

2. You can buy an elm 327 OBD2 module and the Torque app and tap into the temperature sensor and see if it differs from the gauge.

 

Sensor is around 15 bucks and easy to change. If you still get the same reading then you may have a thermostat stuck open or a wrong one may have been put in

 

All right will dig out a thermometer and see what’s up thanks guys

 

But wait I would probably get a cel if my temp sensor was bad..?

 

My temp gauge (2000 3500 5.7) was reading low like yours. I replaced the temp sender (AC Delco 213-820) and also got an OBDII reader which I highly recommend to know that the actual coolant temp is. (At least according to the other temp sensor used by the computer.) With the new temp sender my dial indicator went up to 155F indicated when actual coolant temp was 195F. Ultimately I repositioned the needle on the gauge to match the coolant temp at 195F. One nice thing with the OBDII reader and a connected app is that I can watch the thermostat cycle once the coolant temp reaches 195F. When my thermostat opens the temp drops to around 185F and the cycle keeps repeating.

 

Rule #1 you cant trust any sensor

#2 test it if you can

https://axleaddict.com/auto-repair/C...re-Sensor-Test

 

Just ordered one of those obd2 Bluetooth that show temp, thst should give me a good hint??

If this engine wasn't so dumbly made to just empty the coolant I wouldn't mind just starting to replace stuff but hey... No drain plug on radiator and a fixed clamp on bottom radiator hose really??

 

Rule #3 you not qualified to fix it if you're not a dealer..
. now you are moving into other territory. Mine is obd1 so a computer hookup never interested me. I tackle problems 1x1 so I never have to deal with them again. Last one was my vacuum butterfly valve for heat being stuck and broken. It's now a manual ball valve like kenworth uses.
If you have to replace thermostat drill a small hole in it to get rid of air bubble easier.
But I have to ask.
If the obd2 takes readings from a faulty sensor.....?

 

Nice catch man. Went ahead and bought a thermometer.

pointed at the tstat housing it wouldn’t go above 150 idling forever in hot weather. So I replaced it and the gauge now shows higher (couple notches below 210), I guess that was it. hopefull mpg improves a bit, I was at 14/15 freeway with an empty van stock everything..

side note there was quite a bit of black goo on my radiator cap 🤨