2000 4x2 ext cab with a 3.L

Bought the truck about 2 or 3 weeks ago, scrap yard couldn’t or wouldn’t give me any info about the truck or than as is. when I drove it home I noticed that the temp gauge wasn’t working got home parked the truck and waited for it to cool down. The next morning I pop the radiator cap and saw there was no fluid. Thought to myself ok that’s why the gauge didn’t work. Went and grabbed 4 gallons tried to throw in 2g but only took 1 1/2. Fried it up and drove around town and out to a friends house. Noticed that the gauge still wasn’t working waited about an hour for the truck to cool down. We both looked at the truck and noticed no coolant. so to make a long story short heres what we did and still don’t know or understand.

Replaced thermostat, replaced the two sensors on the water pump filled it back up drove it around again and once again no coolant. Did a compression test on all six cyc they all came out within standards low 130s, checked the radiator drain plug (check) and checked and changed the oil twice just in case ( No chocolate milk )

I have it parked for now until this mystery is solved

 

Welcome to the forum

The one with the red/white wire is for the dash temp gauge, a 12volt sender, not a 5volt sensor
Pull off the connector, put a jumper wire on the red/white wire and other end of jumper on battery negative or a good ground
Turn on the key/engine off
Temp gauge should go up to HOT, that means the wire and gauge are OK, if not then wire issue, can be gauge but usually not
If there is just the 1 red/white wire on the connector, so no black ground wire, then you should not tape the threads on the sender as that's its ground

Remove both heater hoses at the firewall
Fill radiator with water or coolant until BOTH hoses have water coming out
Put hoses back on
Air is out of the system

leave rad cap off
Start engine
Let it idle
There might be a burp of water that overflows the cap opening just on start up, but that's it
If Water continues to overflow you have a blow head gasket or cracked head, period, no other option

If water level stays the same put cap back on
Turn Climate control in the cab to Defrost
Feel the heater hoses and upper rad hose
After a few minutes the heater hoses should be warming up, upper rad hose should still be cold, thermostat is working, not leaking

 

Well tomorrow is my Monday so I’ll have to give it a try next Wednesday Thursday and I’ll let you know thanks

 

Have ya done a pressure test on the radiator where the pressure cap is?

 

No I sure haven’t, I’ll be trying these ideas on Wednesday that’s when I get back home

 

Ended up being a blown HG.

 

Bummer

 

And the compressions matched (low 130's) 2 months ago? Coolant must be running out somewhere; you'd've seen steam.
Truck had a hot lunch. Odo?