305 Vortec Running Cold

Airspeed-Alive · October 14, 2009

Hey guys,

I'm a bit paranoid. I have a 97 Chev C1500. Ever since I bought it, the temperature stabilizes at around 70 degrees Celsius (160 F). The bottom of the gauge shows 40, then 70 half way up and then 100 right at the top middle.

All the trucks that I used to drive would stabilize just under the 100 mark.

I threw a new thermostat in (AC Delco) yesterday, and the temperature rests at the same spot!

Would this be a temperature sensor thing, or am I just being too picky here?

kuhl_530 · October 14, 2009

What temperature thermostat did you buy?

rodram · October 14, 2009

... there are two temperature sensors on these 97 Vortec engines

... the one beside the thermostat gives signal to the PCM (not the temperature gage)

... the other one provides the signal to the dash temp gage

... when the engine is hot you could check the resistance across the pins on the one near the thermostat and cross reference the temperature to see if the two sensors are telling the same temperature

... 70C does sound a little low, and 100C sounds more typical... depending on which thermostat you put in

txab · October 15, 2009

What temperature thermostat did you buy?

+1 Check the installed thermostat temp. Maybe the previous owner wanted it to run cooler

HDChuck01 · October 25, 2009

From my experience with the 305, they are designed to run hotter than yours is. I would go with at least a 190 degree stat (farenheight)

Airspeed-Alive · November 2, 2009

Thanks guys. I honestly don't know what temp thermostat I threw in. Just went to my normal parts guy (Napa) and he gave one for me to throw in. Looks like I'll be going somewhere else and finding another one.

I also forgot to mention that I'm getting a lot of black residue on my tailpipe. I'm thinking the temp is the source here. Truck runs great though.

txab · November 2, 2009

195 degree is OE stat. I'd double check the part number to ensure the installed replacement is the correct part. If it is a 195 then your sending unit or gauge is bad. You're probably running a bit rich since you may not be getting out of open loop on the ecm controls.