'68 Cooling System Problem

bchampion

Member
Jun 7, 2004
113
0
17
51
Lafayette, LA
So let's start at the beginning. Back in December I noticed a crack in my intake manifold where my temp sender screws in so time for a new intake manifold. Drained coolant and replaced intake manifold (like 4th time doing this) and while I was at it, swapped in a Cold Case aluminum radiator along with their 16" electric fan & shroud. Swap was fairly easy as was the wiring for the setup. Purchased a new thermostat housing with fitting for the electric fan temp switch. Thermostat is installed correctly and I tested it out in a pot of boiling water to make sure it opened, thermostat good. Tested all of my connectivity with my multi-meter, all good. Tested hot wires to make sure they were getting 12V w/key in the run position, all good, 12v solid on the multi-meter. Tested ground, good ground. Tested fan w/direct hook up to 12V source, fan good. Pressure tested system, held pressure w/no issues. Started car up, let it get up to 190°, which is where the fan is supposed to turn on, nothing. My temp gauge kept going up, up, and up. Turned car off to let it cool down. Took off radiator cap and started car again. Watched it get up to 190°F and same results. When I got to 190°, that's when the thermostat should open fully and electric fan kick it. Did not notice any sort for coolant flow through the radiator w/car running and temp gauge reading 200°. I let the temp get up to 225° then turned off the car again. The radiator is only warm to the touch and when I drained some coolant, it was outside ambient temperature (~80°). It seems as if the water pump is not pushing the coolant through the block, out the thermostat, and back into the radiator. Water pump is not leaking or making any noises, and I know when they go, they do one or the other or both. I'm at a total loss here.

1968 Fastback, 289 w/mild cam & T5, factory AC
 
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bchampion

Member
Jun 7, 2004
113
0
17
51
Lafayette, LA
Issue ended up being the temp senders I was trying. They had the wrong Ohm range for my NVU gauge. Found the right one and no it tracks my mechanical gauge to the T.