Doing the plenum upgrade and on each side of the thermostat housing there are two little sensors and I broke one of them off. What was it?

 

Pics will help!!!

 

would most likely be your temperature sensor/senders.. yours is a '97, so I would guess you need them both.. the one that goes to your PCM is crucial for proper operation timing/ fuel trim.. the other is a convenience and for you to see where the temperature is (your dash in other words)

 

If you are standing in the front of your truck looking at the engine bay - if it is on the right side it is the Temp sensor, if it is on the left side it is the temp sending unit.

 

the little white spot you see to the left of the thermostat housing

 

I've heard of those being flipped before.. I'm thinking a better way of telling is by the wires.. IIRC one is a one wire, the other a two wire.. I can't go look because mine is a later model with just one duel purpose sensor/sender..

Mebbe somebody will know which one is which- two wire for sensor, one for sender, or flip it around the other way.. Either way, that's what it is..

BigBird- look at your wiring harness and determine if it is either the one wire or two wire- and replace whichever.

 

Thats the one that runs the gauge. Should only have one wire going to it.

 

I broke that exact same one. It was brittle and didn't take much to break it. I bought a new one from autozone and put everything back together correctly. I started my truck up and it overheated. I couldn't figure out why, and I took everything apart again to inspect and found out the new temperature sensor from autozone was longer and blocked my coolant flow. Make sure when you put the new one in that it doesn't block the coolant passage.

Good Luck!