Coolant Temperature

[John 69 Camaro]

Hi,

I have a 383 Stroker with 10.5:1 compression ratio, Dart PRO 1 Aluminum Head 64cc, GM Serpentine System, Northern Alumium Radiator with an electric Fan, a Solid Lifter Comp Cam with a .555 Lift & 262 @ .050 Duration, and an Edelbrock 3500 Pro-Flo Multi-Point Programmable EFI.

I am running a 195 Thermostat and I have the EFI Coolant Sensor installed in the intake next to the thermostat housing and a mechanical Sport Comp Temperature Gauge Sensor installed in the head between #1 & 3 cylinders. The Sport Comp Gauge indicates an operating temperature between 195 & 205 degrees; however, the EFI sensor is reading between 165 & 175 degrees. I checked the temperature at the thermostat housing & intake with a temperature gun and it read 175 degrees.

I haven't experienced any cooling issues; however, I can't figure out how the thermostat would open if the temperature at the housing is only 175 degrees. The upper radiator hose is noticeably hotter than the lower radiator hose, so I figure the flow is going from the water pump into the block & heads and back through the intake past the thermostat into the upper part of the radiator and cooled through the radiator and out the lower hose into the water pump. What am I missing here! Any help would be appreciated.

Thanks, John

[gmachinz]

Your readings all are normal. Your head reading is always going to be higher than your intake reading because the combustion chamber process is going to elevate the localized coolant temperature. Your t-stat is rated at 195 because that is the temperature at which full flow happens meaning a wide open t-stat. They don't just pop open at 195, they gradually begin to open as the pressure begins to work against the spring. So it's safe to assume that it takes about 15-20 degrees from the time the stat begins to creep open to when it's wide open.

[John 69 Camaro]

Thanks for the info. My concern is that my Pro-Flo EFI needs to get to a temperature of 177 for the Closed Loop to engage and I can't seem to get that temperature at the intake. I don't want to go to a higher thermostat if I don't have to, so I'm thinking of moving the EFI temperatur sensor from the intake to the top of the water pump. If my memory serves me correctly the temperature gun took a reading of 185 at the top of the water pump. John

[gmachinz]

Running too cool is a much better problem than the alternative! lol-I seen what you mean about the closed loop coolant reading-Are you running a water bypass? If so, try adding a take-off pressure port like -6AN to -6AN with an 1/8" pipe thread for a temp. sensor for the computer. This way, it'll read the outlet temp. of the rear coolant passage-that should get you a warm enough reading for closed loop. -Jabin

[another69]

Make sure you are taking your temp readings from a dull surface. Shiny metal and chrome will give you erratic readings. A flat black surface seems to be perfect. I'm assuming you're using an infared gun.

[John 69 Camaro]

Thanks Jabin.

I'm not sure what you mean by a Water By Pass. I probably am not because there is nothing between the water pump and the Engine/Radiator. Do you know where I can get information regarding the purpose of a Water By Pass?

The weird thing about this stuff is when I took the car for a ride today the EFI temperature was between 177-189, while the temperature at the head was 195-205. I have no explanation why I finally got a higher reading from the EFI sensor because in the past the most I could get was 175 and the head temperature was the same as today. Does this make any sense to you?

John

I did use a Infrared Gun and I did notice a lower temperature reading when I checked the temperature on the chrome thermostat housing. I also checked it today and the IR gun read the same as the EFI sensor when I positioned it below the sensor on the intake. John