quote:Originally posted by JFB #05177:
would not using the heater hose connection as a bypass. looping outlet back to inlet.
the heater loop does create a bypass. lack of any flow path during warm-up causes a dead head condition of the cooling system, the water pump is working against the closed thermostat & there's no coolant flow. the heads will generate hot spots until the T-stat opens, further aggravating a backwards head gasket situation
the only other thing I can think of is if there's a piece of cylinder block material floating around loose in the water jacket back there where the critical coolant passage is in the rear of the passenger side. when a block gets machined for a sleeve, many times there's not enough thickness of the cast cylinder & the machining operation (boring) opens up a window into the water jacket. when the material gets that thin that it's gonna window through, the material deflects & avoids the cutter. that remnant of the missing cylinder bore area will be paper thin & fall out, into the water jacket or it may even hang on by a thread for a time & let loose whenever it wants. if this engine had been sitting for a long time I'd say rust scale could be the culprit but in this multi sleeve build it might be a wafer of cast iron from the boring operation blocking that rear passage