Heater core flow direction?
- Thread starter Bonnewagon
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I should have tried that on my 88 when I had it, the heat was horrible, multiple heater core changes. I may try that on my Dakota🤔. My 70S has very good heat but I am adding a restriction to the inlet at the intake, those years heater cores balloon and leak if non restricted flow is used at high rpm.
Fast flow is not so good. That is why not having a thermostat can overheat the engine. If the coolant passes through too fast, there is not enough time to release the heat. Even race cars use a restriction washer to slow the flow so it can be effective.
Your engine will increase heat output if it runs at a higher RPM. Where does it go? To the coolant. Your coolant system MUST be able to remove as much or more heat generated from the combustion process or you will overheat. I wonder how many high flow water pumps have been sold, and those high flow Robertshaw thermostats are in use today? Why did they bother selling them if you needed to slow the flow?
If you're familiar with Q dot equation, higher mass flow rates mean greater heat transfer. Q dot is for heat transfer over a unit of time, or rate of heat transfer. It's a math thing. Doesn't take into account every nuance of a moving car as the Q dot changes depending on conditions, but in general, the faster the water and air flow through and around the radiator/heater core, the faster it cools the fluid. Otherwise, why blow on a piece of hot food before giving it to a small child when, by your thinking, more heat should be released because it's not moving? Why does an overheating radiator usually start to cool down when the car starts to move and get up to speed? (Hint, that's what the old TVS system would do on a 69 442, for example. The TVS sensed the engine temp getting too hot, and bypassed the ported vacuum to the distributor vacuum advance and put it directly to the intake manifold, increasing timing, thus RPM went up speeding up both the water pump and fan, and HOPEFULLY, the coolant temperatures came back down. When they did, the TVS "reset" and the vacuum advance was swapped back to ported vacuum again. )
And think of this- where does the coolant go in a closed loop? If you slow it down through the radiator, where's the coolant in the block go at higher RPM? Oh, it doesn't. Meaning coolant temps RISE and potential hot spots develop and engine failure could more easily occur. How does the coolant system work then?
I used to think the same thing you did, but a nuclear plant steam generator engineer I used to work with set me straight on that point with nucleate boiling thrown in for good measure, etc. I don't understand all of it, but that part was driven home. And he mathematically proved it. No offense, but I'm going to take his word over someone who doesn't design bazillion dollar heat exchangers for a living.
But you can believe whatever you want, that's the beauty of free exchange of ideas.
If you're familiar with Q dot equation, higher mass flow rates mean greater heat transfer. Q dot is for heat transfer over a unit of time, or rate of heat transfer. It's a math thing. Doesn't take into account every nuance of a moving car as the Q dot changes depending on conditions, but in general, the faster the water and air flow through and around the radiator/heater core, the faster it cools the fluid. Otherwise, why blow on a piece of hot food before giving it to a small child when, by your thinking, more heat should be released because it's not moving? Why does an overheating radiator usually start to cool down when the car starts to move and get up to speed? (Hint, that's what the old TVS system would do on a 69 442, for example. The TVS sensed the engine temp getting too hot, and bypassed the ported vacuum to the distributor vacuum advance and put it directly to the intake manifold, increasing timing, thus RPM went up speeding up both the water pump and fan, and HOPEFULLY, the coolant temperatures came back down. When they did, the TVS "reset" and the vacuum advance was swapped back to ported vacuum again. )
And think of this- where does the coolant go in a closed loop? If you slow it down through the radiator, where's the coolant in the block go at higher RPM? Oh, it doesn't. Meaning coolant temps RISE and potential hot spots develop and engine failure could more easily occur. How does the coolant system work then?
I used to think the same thing you did, but a nuclear plant steam generator engineer I used to work with set me straight on that point with nucleate boiling thrown in for good measure, etc. I don't understand all of it, but that part was driven home. And he mathematically proved it. No offense, but I'm going to take his word over someone who doesn't design bazillion dollar heat exchangers for a living.
But you can believe whatever you want, that's the beauty of free exchange of ideas.
It is a way to back flush it run for a while and then swap it back. it just pushes/flushes all the crud that built up inside the unit.
I believe the newer cars may have a problem with this flow tho.
I believe the newer cars may have a problem with this flow tho.
I learned this lesson back in the mid 90s. Young and dumb, pulled the thermostat on my 455. Hiway driving the engine temps slowly kept rising. I was about to pull the heads then an old geezer told me to up the thermostat back in to slow the water down. Problem solved.
Its been a few yrs I have watched vent temps but if iirc to be worth a shitt around here in below freezing temps vent temps need to be in the 160-180 range. Long time ago my 81 cutlass blew the heater core on my way home. Needed heat and didnt have a replacemnt. I didnt have a working ac so I ran the heater hoses to the evaporator. That was some serious heat. Thought the vents would melt.
I'll leave this here and then I'm out. It's a listing of tech tips from some folks who are considered experts in the field. It can't be any more fact-based. These guys live/breathe coolant systems. According to them, no matter what you've "heard", slowing down coolant flow in your system is a bad idea.
A car is not like an industrial cooling system. It is limited by design and function to what works best in varying situations. That is where it differs. Airflow is limited by the radiator, fan, grille, and outside airflow from the car's movement. The heater fan speed is limited to the blower motor and heater core design limits coolant flow. I agree that if coolant speed and airflow were constantly increased simultaneously then the cooling capacity would also increase. But they are not. The car's design limitations prevent that. I am reminded of a 1967 Firebird parts car that had a 400HO motor and a manual transmission. It had manual steering and the single fan belt ran the alternator and water pump. The pulley on the water pump was HUGE, the largest I had ever seen. What that did was slow down the flow so the radiator could handle the heat of the HO motor. I have used that same huge pulley to cure overheating in several of my Firebirds. But I also agree this is going nowhere. Later.
I fought cooling my 403 in my 88 Cutlass. The under drive crank pulley definitely made it run hotter. Cavitation is probably part of reason for Pontiac for using the larger water pump pulley. Olds used a better closed Impeller pump to move more water, more smoothly and a larger crank pulley on the heavy duty cooling option. Pulling the thermostat didn't make it run hotter, cooler if anything. It basically overheated the same way, towing my 16 foot fiberglass boat in hot weather, the 3 core aluminum Champion radiator was just too small. Honestly, adding the GN rad surround made the biggest difference in cooling on my 88, it should have been the first mod I did, probably dropped temps by 30 degrees. Just my 3 cents, inflation and all.
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