I’m having to daily my 1991 C1500 while switching out some vehicles. This was intended as a project truck so it really hasn’t been gone through as well as I would like up to this point.
It has a TBI 350 that is overcooling to the point that I’m getting lukewarm air from the heater at best. All of these TBI trucks I’ve owned up to this point, the gauge sits just below/to the left of the 210* mark. This truck is sitting around 150*-170*, and although I haven’t thrown the scanner on to verify, I’m definitely getting poor fuel mileage from the truck from it being stuck in open loop, so I feel that the gauge is correct.
I replaced the thermostat twice with 195* units - once because the gasket was leaking, and again because I thought the first one had possibly stuck open. Both are quality parts. I have also drilled a small (1/16”) hole to eliminate the possibility of air bubbles stuck under the thermostat.
I drained the block to install a new block heater. Used new 50/50 coolant. Upper radiator hose feels warm and has pressure after a drive. I have verified that the blend doors and actuators are working, and even physically removed the actuators and manually operated the doors. I’ve blocked off half of the radiator with cardboard since it’s been cold lately (-10*F), which made a very small improvement.
Radiator appears to have been replaced in the past, water pump looks much more recent. Heater core cooling lines are hooked up as factory (rear intake/upper radiator). Fan clutch seems to be working properly, not seized, spins for a few rotations when engine is shut down. Hell, even the fan shroud has a large gap on one side from unrepaired previous accident damage, and the engine still will not come up to operating temp. I have not used a temp gun on any of the hoses yet. Timing was set recently and is correct (0* with wire disconnected).
I‘m about out of ideas aside from removing the radiator and running only the heater core. Even that may not be enough!
It has a TBI 350 that is overcooling to the point that I’m getting lukewarm air from the heater at best. All of these TBI trucks I’ve owned up to this point, the gauge sits just below/to the left of the 210* mark. This truck is sitting around 150*-170*, and although I haven’t thrown the scanner on to verify, I’m definitely getting poor fuel mileage from the truck from it being stuck in open loop, so I feel that the gauge is correct.
I replaced the thermostat twice with 195* units - once because the gasket was leaking, and again because I thought the first one had possibly stuck open. Both are quality parts. I have also drilled a small (1/16”) hole to eliminate the possibility of air bubbles stuck under the thermostat.
I drained the block to install a new block heater. Used new 50/50 coolant. Upper radiator hose feels warm and has pressure after a drive. I have verified that the blend doors and actuators are working, and even physically removed the actuators and manually operated the doors. I’ve blocked off half of the radiator with cardboard since it’s been cold lately (-10*F), which made a very small improvement.
Radiator appears to have been replaced in the past, water pump looks much more recent. Heater core cooling lines are hooked up as factory (rear intake/upper radiator). Fan clutch seems to be working properly, not seized, spins for a few rotations when engine is shut down. Hell, even the fan shroud has a large gap on one side from unrepaired previous accident damage, and the engine still will not come up to operating temp. I have not used a temp gun on any of the hoses yet. Timing was set recently and is correct (0* with wire disconnected).
I‘m about out of ideas aside from removing the radiator and running only the heater core. Even that may not be enough!