Isolate heater core in summer
 

Anyone use valves in their heater hoses to manually isolate the heater core in summer? Curious if it makes a worthwhile difference. 65 GTO, non-ac car.

I was wondering that myself as the 64 Corvette I am working on they used them on both lines -as well as made a spaghetti bowl of heater and A/C hoses that is butt ugly!

Why for summertime do you not just use a union to jump it out instead of spending far more money on a control valve?

And yes it makes a difference as that’s why ac cars have control valves, a ton of difference , no.

i meant something like this:

https://www.amazon.com/Joywayus-Auto...Y2hfYXRm&psc=1

Nope never done that and we drive the cars in 100+ temps. Plus it's butt ugly. I'd gasp if I opened my hood to that and then quickly close it before anyone else saw that mess :D

the day that valve is the ugliest thing under my hood, i will kneel down and thank the heavens.

At 20 bucks this is a far cheaper and far less unsightly solution.

If you jack up the ass end of the car 8” when installing these you will not even spill any coolant.

I think one gets more heat through the floor boards from the headers than hot water circulating through the heater core. Plus running the heater on high can help cool the engine down if you get caught in a traffic jam and the temperature starts creeping up.... That's what summer time cruising is all about. Sweeting like crazy with the heat on high, windows down and showing off the Burger King drive thru rough idle camshaft.

I pinch my heater core line in summer. And notice it helps the engine cool a little better. Not recirculating hot coolant from head back to water pump.

Prior owner of my 66 made this contraption - a 3/4 to 5/8 reducer would have been so much easier…

I haven't used this yet 5/8 barbed 1/4 turn ball valve from Lowes or Homie'D

LOL I knew I could count on you to find the humor in that :thumbup:

I've used stuff like that. You can buy smallish valves like that with 1/2" female pipe threads. I buy the barb fittings from a parts store.

Yes, it does work.

I work on school buses. They all have heater valves, and all are common hardware ball valves. Older models had gate valves.

Some of the older buses only used one valve. It did its job. I just didn't trust one valve on my car...

is it better to bypass or block it entirely?

.. or you could just set your heater control valve to the coolest setting limiting coolant flowing through the heater core, but I guess that would be too easy.

Didn't GM-Pontiac have 1 vacuum-pot controlled heater valve, like in 69-70 cars?

Yes my 1970 Van Nuys Formula had a vacuum operated heater control valve, pretty sure only time it was open was when heat was selected they liked to freeze up as in not operate and they would leak coolant as well, i took mine off for the leak when i got the car in the 90's

does a non-AC car even have one?

Just put the valves inline, in the heater hoses. Circulate the coolant to bleed the air out, with the valves open. Then just turn them off in the summer.

I recently put one of these on the 3/4 line of my new engine:
https://www.amazon.com/gp/product/B09MQ1J55W/

It seems to be working fine with the flow to the heater core turned off for the summer.

Do you notice a difference?

They added the heater control valve to A-bodies in 69 correct? An actual water valve. On 68's there is no valve, just the air control to stop air flow through the heater core. But yes you still have a hot heater core sitting on the passenger side of the firewall.

Yea, i tuned the duct valve controls for best closure to assure the heat was isolated. ( btw a simple task but i failed at that ).

The real inetrest is to isolate the heater core on 95-97 Towncars because the AC control "malfunctions and blows hot heat while on AC. A digital reset will make AC cold again but some cars keep faulting. Design problem.

been there and done that, running the heater to cool the car down ... good times!

i'm just trying to figure out if there is any benefit to letting the coolant circulate back into the hose by using a bypass instead of "deadheading" the coolant in the hose?

Not really. I just didn't want my heater core being hot in the summer.

Yeah, heater core blocking doesn't provide much help, better off insulating the floorboard and firewall. By blocking some of the radiant heat from other sources (than the box) overall you will get a better improvement.

You could insulate the box too, but it really isn't going to help much, not enough to make any kind of noticeable difference anyway.

After driving a while, put your hand on the box, the floor, and the firewall, can see where most of the heat is coming from.

In my bird, I removed the tar paper one time when I did a carpet and driving to the beach one time the side of my sneaker melted to the tunnel. And that was just from removing the tar paper.

Dynaliner (or the like) is not expensive compared to the Dynamat.

You can wrap a section of the exhaust too, but not only is it a pain and cost, it can hold moisture and rot the pipe.


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Food for thought
 

Drivers side goes out the front and through the radiator to be cooled.

Drinkers side recirculates back to the water pump and doesn't get cooled.

Yeah the back of the head hose goes to the heater core, the one from the core goes to the water pump.

So the one that goes to the water pump mixes with cooled coolant and goes back thru the engine. Has little to no effect on engine cooling.

But the added capacity of coolant the heater core supplies does have an impact on overall cooling. How much of an impact is debatable.

As previously mentioned, it does help 'burp' the system tho, along with the cover to intake passage. That is a positive effect, no doubt there.

I removed the vacuum valve on my 71 A-body AC car and it had no noticeable effect on cooling or heating. I now have a Vintage Air setup, which comes with a valve (electric), and did install it as directions outline, but if it ever fails I will omit it. I get 31-32 degrees at the vent.

I got that car with like 68k original miles on it, and the AC blowed so cold, you couldn't run it on high on the highway without freezing you out of the car. Without the valve, it might have made a 2 -3 degrees difference, if that. You could see your breath on a 100 degree day. I don't remember what vent temps were, but it was cold.

I drove that car without AC for a number of years, replaced a part here and there trying to get it to work, and finally gave up and got the VA setup. Drove it with no valve that whole time. Think my problem was a combo of a compressor failure, and 2 dead replacement compressors, with the addition of a failing vacuum control panel. And yes, ran a filter after the original compressor burnout.


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Damn, Mike - 31-32 degrees? The lowest I recorded on the bird was 36.

Yes, all '64-72 GTO's used a similar vacuum actuated heater control valve to adjust the flow of hot coolant through the heater core. The only difference was the manner in which it connected to the heater core and the orientation of the vacuum connection. They will fully shut off the flow of coolant through the heater core if functioning properly.

I have a factory air conditioned 1964 Le Mans and there’s no valve of any kind on the hoses going into the heater core. The same on ones with a standard heater, no such vacuum actuated heater control valve.

Maybe later years but not 1964.

Here is the AC Delco replacement part for 1964 GTO ... if you can modulate the heater temp, then there must be a control valve.

https://www.carparts.com/details/Pon...ll%20-%20Parts

All cable controlled on 1964 GTOs no vacuum, there’s simply a metal elbow on the intake manifold for the heater hose connection. Heater temp is modulated by a cable operated flapper door in the heater box.

1965 GTO did go to vacuum controls.

I’ve never seen a vacuum valve like the one pictured on any of the ‘64s I’ve owned.

It’s listed as a big Pontiac ‘63 and ‘64 piece as well as a ‘63 -‘64 Tempest part so I think their application listings aren’t completely accurate.

that heater valve doesn't look right at all most of them i have seen on cars like ours did not screw into anything they have a bracket attaching it to the heater a/c box and the heater hose slips on both ends.. i still have one in a parts box saw it a few weeks ago

had to get into the parts box for another reason saw the valve took a pic.. 1970 Van Nuys 400 Formula With A/C

I installed this one. I intended to play around with the flow to optimize. But haven't touched it.

https://forums.maxperformanceinc.com...1&d=1720784770

Blocking heater core will provide much help as no circulation to core means no heat to the core , may get a bit warm but not hot.

I don't believe this is accurate. 68 A-bodies had no device to control flow of coolant through the core, they had a vacuum operated flap that controlled AIR flow through the core. The coolant flow through the core was 100% all the time. In 68 the hoses from the engine go straight to the heater core and back again, no interruptions. In 69 a coolant flow control valve was added in-line on a hose to the core, this valve DID control coolant flow through the core.

my 66 Grand Prix w/ac start leaking heater core today. can I disconnect the heater hoses from the core and connect them together temporary fix till I can replace core? thanks Allan
also does any one know the over process of how the core comes our, it is not covered in my chassis manual.

I can’t help you with the removal but you can certainly bypass the heater core - just get yourself a 3/4 to 5/8 adapter

I82much, one thing you can do, if you ever take the heater box out, is to clean the old foam off the air blend door(this door moves when you adjust the heat slider) and replace with new foam. This helps the door seal better when your HVAC control is at full cold.

I will say that it’s not a very fun job since you have to take the fenderwell out and a bunch of butyl ribbon seal on both sides of the the firewall.

I have a shutoff in the inlet to the heater core on my TA And I notice a little cooler engine temps in the heat of the summer for sure. No hot coolant just bypassing back into the pump.

Are you saying it runs cooler when you shut off flow to the heater core?

I have seen this same thing, reason being pump pressure is being reduced on one bank of the motor to feed the core.

PSI in the heater core is the same as the rest of the system on the engine side of the t-stat.


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Let me rephrase, PSI will not exceed the PSI of the system on the engine side of the T-stat.

Flow is only restricted at times, if it has a cutoff valve.



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Yup, I noticed a few deg cooler. 7-10 maybe. And my elec fans take longer to cycle in stop and go traffic

Pressure isn't being reduced, it's static throughout the whole system. But flow is greater in the pass head when running through the heater core. BUT, if not extracting any heat in the heater core, then the hot coolant just recirc's back to the pump inlet. Thus actually heating up, the incoming coolant from the radiator.
Hotter inlet coolant temp, will require hotter outlet coolant temp to open T stat more and flow more through the rad to counter act the heater core line heating.