mr.t3
+1y
98% under hood new. Engine, head, weber carb, header, radiator, all motor parts, water pump, all hoses... (Only fan clutch and heater core not brand new)
I removed all factory vacuum junk and have 4-5 electrical connectors hanging right now that were from the factory carb.
-- Truck idles perfect, runs cool at 1/4 temp for hours parked. Turn on heater while parked temp goes up to 1/2. Turn on lights temp bumps just a smidge.
-- Drives with no heat on..... Runs cool no issues. Turn on heater while driving, 10 seconds later it red lines temp and pops radiator 13lb cap....
-- Bypass heater core and runs much hotter at 3/4 temp
I'm baffled!
Things I have checked:
- timing and advance
- water pump and thermostat check (even though they are new)
- heater core for clogged (flows fine and has heat)
- bypass heater core (truck runs much hotter at 3/4 temp when bypassed?!?!)
- pulled everything apart and verified that all water jackets and hoses were passing water on block, head, intake and everything.
- burped air out for 20+ minutes (with truck level)
- checked photos of all block/head/head gasket jackets being there and lining up as they should
- watched coolant flow in radiator at idle while parked. Minimal until revved up.... Flow Much better with heater core bypassed.
I removed the dash tonight and got the heater core out.... Going to change it out for a new one to eliminate that possibility.....
Any ideas, advice or help greatly appreciated!!