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samert111 · 12-06-2022, 02:26 PM

Does it run cooler and stay steady temp with the heat control on hot but without the fan running?
If so it needs the heater circuit open as a bypass loop to keep constant flow of coolant past the sending unit
I just went thru this on my 68 with the vintage air and 350 CI. Temp would climb up to 240 then bounce back down to 200 then back up again repeatedly. Once I turned the temp control to hot it would drop to 185 and stay there all day.
I tried everything including drilling holes in the stat, burping the system repeatedly but no luck.
I ended up adding a bypass loop from the unused coolant port in the intake to the unused port on top of the water pump and problem solved.
I can't explain why it works but it does.

12-06-2022, 02:26 PM	#17
samert111 Registered User Join Date: Jul 2022 Location: Rockford, Mi Posts: 79	Re: Another Overheating Mystery Does it run cooler and stay steady temp with the heat control on hot but without the fan running? If so it needs the heater circuit open as a bypass loop to keep constant flow of coolant past the sending unit I just went thru this on my 68 with the vintage air and 350 CI. Temp would climb up to 240 then bounce back down to 200 then back up again repeatedly. Once I turned the temp control to hot it would drop to 185 and stay there all day. I tried everything including drilling holes in the stat, burping the system repeatedly but no luck. I ended up adding a bypass loop from the unused coolant port in the intake to the unused port on top of the water pump and problem solved. I can't explain why it works but it does.