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Why the Cooling Bypass on 318LM thermostat?

I

iflyboeing

Member
Raw water cooled 318LM has a cooling bypass in the thermostat housing. The 1970 TSB re-routed the bypass to the manifolds. So, how can the engine ever reach normal operating temp? Regardless of thermostat position (opened or closed) the water is being discharged overboard.
 
Right Jeff. Point is, that when the thermostat is closed, the bypass is open and the water is discharged overboard. When the thermostat is open, the water exits the thermostat and is also discharged overboard. So.....Why have a thermostat at all if the water is being discharged overboard regardless of it's position? BTW, it is the big barrel type thermostat. Housing has two outlets.
 
Then the small hose that comes off the top of the thermostat housing should be plumbed back into the engine side of the pump with a tee fitting so that it creates a loop, allowing the engine to warm up faster, then when the thermostat opens, it will close of the by-pass & dump the heated water through the larger hose out into the risers. At least..thats how mine works, they warm up fast & never run over 150 deg. The rear outlet of the pump is plumbed into the tranny cooler, then split to feed each manifold.
 
Pete31. Correct description about the "loop" The tee fitting you describe was called the "sweet potato" by Chrysler. Thing is that a 1970 TSB eliminated the sweet potato and changed the plumbing to dumping the "small hose" (which is the bypass) overboard through the risers. This was done to correct overheating problems.
 
They must have changed their minds later on, mine are 71's , I wonder if prior to 1970 they ran the screw in type thermostats ?, I know they had problems with them. Eliminating the "loop" might be why your engines never reach operating temp
 
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