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Does coolant flow thru heater always?

4K views 19 replies 14 participants last post by  Richard 
#1 ·
Still dealing with over-heating issues with my 70 Chevelle. Won't go thru in detail the list of things we have done to try and fix this but after new upgraded aluminum radiator, new electric fans and bigger alternator, upgraded water pump, flushing, re-flushing, new tsat, new gauges, timing changes, new belts, hoses, etc. it is still overheating. One thing we did do when putting in new radiator was to disconnect heater hoses (don't need a heater here in Hawaii). My question here is, do you think reconnecting heater would help with cooling problems? Thinking that the heater core acts like another small radiator, but does the coolant flow thru the heater core if the heater isn't turned on? Do you think it's worth it to reconnect heater and would I need to have heater running to make that difference?

Thanks, Ben.
 
#2 ·
Its those details that you left out that will create the next 10 posts of questions. What temp is your engine reaching at both idle and cruise? What is the temp setting of your thermostat?

While the late 67 and before cars had coolant flowing all the time, I believe that the 68 and up had a heater control valve that turned the flow off if the heater was off or the a/c was on.
 
#4 ·
I believe you only had a heater control valve (1970) if the car had AC. Get yourself an infrared temperature gun, then you can easily rule out things. and get the true temperature the motor is running at.
 
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#5 ·
I have the gun and have been working on a recommended list of things to do to get the temps down from this site for quite some time now. Hence the new, larger radiator, etc. That's why I didn't include all the details because I'm working thru list. But was curious about the one step we did of unhooking the heater and if anyone knew if that would make any difference.
 
#7 ·
I agree with Dean that it would help cool down some if your heater was on and running, but this is not the reason you are overheating.

It is not going to matter if you have the heater core hooked up or not in order to solve why your car is running hot.
 
#9 ·
Pics of what is in front of the Rad Core/Grill side
and what it ,looks like on the Engine side
 
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#10 ·
This should help to show you your answer...

https://www.chevellestuff.net/tech/cooling.htm

...if the heater core is connected it is always circulating coolant so the added volume of coolant should help keep the temp down somewhat.But unless the heater is blowing air it doesn't really make a big difference.I know there were times when my Buick would run hot I had to run the heat on high to get to a place where I could cool it down.
 
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#11 ·
Ben,

I also have a 496, it’s in a ‘71 car so the radiator support & radiator flow is the same as yours.

I have no overheating issues, here’s what I have:

-Griffin aluminum radiator (25 + years old), twin 1.25" tubes
-CVR 55 GPM electric water pump
-Delay relay keeps the pump running for 90 seconds after engine shut down
-Large coolant expansion (overflow) tank
-15 PSI radiator cap
-Robert Shaw high flow 180 degree thermostat
-No heater connections
-No thermostat (intake manifold) by-pass hose
-1/8" holes drilled in the thermostat to allow warm-up by-pass
-Dual high flow electric fans
-Fans come on half speed at 170 degrees, full speed at 190 degrees
-Automatic transmission and engine oil have separate external plate style coolers
-60% water, 40% coolant mix

Sitting in traffic on a 90 + degree day, my 600 HP engine runs around 200 degrees. I haven’t yet used the air conditioning.

It’s important to keep in mind that at idle engine speeds, the stock water pump and fan is hardly moving any coolant or air.

About the coolant: The higher percentage of water you have in the system, the better it absorbs and releases heat. Only use Prestone un-mixed and use supermarket distilled water. Ben, as you’re in Hawaii, you may only need like 10% water in your system.

It’s also important to use high flow fans. Most aftermarket electric fans have pretty a low CFM rating. I’ve been using high flow fans from a 1986 Toyota Camry V6 station wagon-and they work great. Half for looks and half for more airflow, I’m upgrading to a pair of Perma Cool 19114 fans which flow a ridiculous 2,950 CFM each, I’m making a proper aluminum shroud for them.
 

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#14 ·
Ben,



It’s important to keep in mind that at idle engine speeds, the stock water pump and fan is hardly moving any coolant or air.

About the coolant: The higher percentage of water you have in the system, the better it absorbs and releases heat. Only use Prestone un-mixed and use supermarket distilled water. Ben, as you’re in Hawaii, you may only need like 10% water in your system.

It’s also important to use high flow fans. Most aftermarket electric fans have pretty a low CFM rating. I’ve been using high flow fans from a 1986 Toyota Camry V6 station wagon-and they work great. Half for looks and half for more airflow, I’m upgrading to a pair of Perma Cool 19114 fans which flow a ridiculous 2,950 CFM each, I’m making a proper aluminum shroud for them.
Paul,I'm sure you meant to say 10% coolant, right ? Too much coolant is a definate no-no as you probably already know
 
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#17 ·
Having also driven my 1970 in Hawaii for many years, I can say having the heater connected will not help with cooling the engine. It is correct on the A/C equipped cars, one heater hose had a vacuum-controlled shutoff valve that would stop coolant flow to the heater core unless the control slider was moved to provide heat. During warm periods, no coolant would move through the heater.
At what water temp will the electric fans turn on? Are the fans the puller type between the radiator and engine? How many CFM provided by the fans? Too little airflow through the radiator will cause overheating.
Retarded ignition timing and the use of ported, not manifold, vacuum to the ignition advance unit can produce extra heat.
Long tube headers radiate a lot of heat in the engine compartment. Perhaps consider coated headers or a header wrap to reduce underhood temps.
 
#18 ·
Dive into some of the other probable issues. What heads are on the motor, what head gasket did you use? How much timing are you running at idle and cruise? How is the carb tuned?

As for cooling system, nothing beats an OEM 7 blade fan, Hayden HD Thermal clutch and factory shroud. Ran this setup on my 540" with a dual core (two 1-1/4" core) alum radiator, factory AC condenser and trans cooler, all stacked up one in front of the other, overheating was a non issue.
 
#19 ·
Had a '65 Pontiac started running hot/overheat on highway. After chasing many of the "usual suspects" it turned out to be the vacuum canister on distributor had stopped working; replaced it and temps came right back to normal...a $10 part AFTER swapping numerous higher dollar parts.

Let us know if you find problem.

Bob
 
#20 ·
what is hot is it boiling water out the radiator cap overflow or just the gauge temperature put a recovery tank on it and then it will not run out on the ground and go back in the rad. when it cools down just my thought
 
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