Percolation? Heat soak? Don't drive during summer??

69_340_GTS said
Somehow that makes no sense to me. Maybe on an Chevy S-10 the function is different. You do not need the heater core on an A-body to cool the engine. Plugged-up, disconnected, bypassed, working, leaking, or missing... it isn't meant to cool the engine.

dartfreak75 said
No it doesnt cool the engine your right. But if its stopped up its limited the flow of coolant and slowing the flow down in other words coolant is going in but not coming out. Therefore it's not pumping thru the block as efficiently. By bypassing it your removing the amount of area the coolant flows. Your absolutely correct you dont need it that's why I said bypass it. It may not be the problem but it is a free test that couldnt hurt to try.

Some more contemporary designs use the heater core as the recirculation loop in the coolant system. If I remember right, that's how my old FWD dodges were setup and the HC could definitely cause some headache with the cooling.

On these cars, the water is supplied from the thermostat area and returend back to the water input of the water pump - just like the bypass hose. If a person isn't running the bypass hose then the HC circuit serves that function (which just helps normalize operating temperature to prevent large temp swings as the thermostat operates). With the bypass hooked up, the HC is just 'along for the ride' and not offering any function to the system.

Now, I have seen a gunked up HC cause coolant temp problems after the system was drained because not all of the air would come back out of the HC. Caused hot spots, lack of cooling system pressure, and spikes in operating temperature. Bypassing the HC fixed the issue in those cases.

In Doc's case, I agree with the notion that the HC won't just cause a high operating temp. Lack of airflow from the fan, or another of todays aftermarket thermostats not fully opening until well beyond it's rated temp. It's too bad the thermostat diameter is larger than the 'other' brands which makes it tough to source a quality high-flow stat w/o an expensive adapter.