[rickschabener]

Hi All,

68 Firebird convertible:
Is there any reason why I shouldn't block off (install a valve) on one of my heater hoses to stop coolant from going through my heater core?

I know all the foams on my heater box are shot, and I get warm-to-hot air from my interior ducted vents even with controls set to Off.

I know that the coolant path goes from the water pump, through the heater core, and back to the rear of the motor. Is that coolant flow through that nipple at the rear of the motor necesary for engine cooling, or can that flow be stopped without affecting engine cooling?

My car is black on black, and I never put the roof up. Driving in southern Virginia is hot and humid enough without having heater core heat flowing over me also.

So, can I put a valve on one of those hoses and keep it closed off for 9 months out of the year?

I'm thinking I would install a 12v valve on a switch under my dash so I could open it near the end of my rides just to let "new" coolant flow through it, to fend off electrolysis from coolant just sitting there stagnant.

Thanks in advance.

[b-man]

Close it off, it won't make any difference in engine cooling.

Some folks simply plug off both heater feeds on the engine and don't use a heater.

[Blued and Painted]

Coolant flows the other way. From head to heater core to suction side of water pump. Note how the heater hose nipple at the pump is just above the lower hose. So you would install a heater control valve between the cylinder head nipple and heater core.

Many cars of the day had vacuum or cable operated heater control valves.
Vacuum operated valves default to open. Applying vacuum would close the valve.
Cable operated used a simple lever on the valve too open and close coolant flow.
If you installed a valve with a lever, you could open the hood and switch to open for seasonal change. I think its a good idea.
No, it should not create an overheat condition. Actually, more coolant will be forced through the radiator instead of simply bypassing back to the water pump.
Heater control valves are fairly generic. Just be sure the connections on the new valve match the hose size. I believe it's 5/8 hose on the head to heater core side.

[Longs]

When my heater core started leaking, I bypassed it by removing the hose that connects to the water pump from the core, then removed the hose from the head to the core, and connected the outlet at the head back to the long hose to the pump.

Maybe it makes no difference, but since coolant was supposed to flow from the outlet at the head, I didn't want to create a "dead spot" by just blocking it off.

[XLR8STEVE]

My Vintage Air in my 68 convt came with an elecric block off valve. Works great. No change in cooling but I did have to make sure I burped out the air from the core when I first installed the system.

[Goatracer1]

The factory used shut off valves on some of the AC cars so go for it.

[rickschabener]

Thanks for the responses guys.

I wanted to find a valve that was small, and black, so it wouldn’t stand out. Napa Online showed a bunch of them that I thought I could make work, so I went to the store to look at one. It was nice and small, but very flimsy and thin.

A lot of places had the same universal, T-handle, screw-in post, heater valve. I didn’t want that one because the interior passage, block-off hole on it is very small. I do use my heat on cool days, and when I do want heat, I want all of my heat; not a luke warm heat that I believe that tiny opening would give me due to the very restricted coolant flow through it.

So I went with my standby plan: A plumbing valve from a home improvement store. They had two choices for me in 1/2” quarter turn valves. The interior diameter of the one I chose is noticeably larger than the other, and real close to the ID of the 5/8” nipples they have, which fit the 5/8” hose that I was going to splice into. This is an oil/water/gas valve, rated to 600 psi, and 400* F.

As I mentioned, I didn’t want this valve to stand out. My engine compartment is very stock appearing. So, I painted it black, and cut the handle down to a smaller size.









I drove the car the next two days with the valve open to burp any air out of the coolant.

On the third day I closed the valve and drove it again. I was disappointed that I still had (maybe almost) as much hot air blowing out those AC vents as I did before. And, both heater hoses were as hot to the touch as they were when I had the valve wide open.

So, the next day, I took a vise-grip I have that has a big flat tip on it and clamped off the other heater hose. It wasn't as hot of a day as it had been for the past 2 weeks, but I still had more hot air blowing through the vents than I think I should have. The heater hoses felt cooler, but still rather hot. But, I'm going to assume that's just a factor of coolant heat transferring "through" the valve; and also heat from the engine compartment itself transferring to the hoses.

Before I went and bought an adapter to completely bypass the heater core, I decided to find out why I had so much airflow through those vents. The airflow changes with vehicle speed. I found the vacuum hose that feeds vacuum to the interior HVAC control panel disconnected at the vacuum storage canister in the fender, by the brake booster. I used my pump to pull a vacuum on that hose and saw that the vacuum controlled door in my cowl did work (and close). I fixed and connected that hose to the canister and went back out.

This was the next day, and it was again, a slightly cooler day. The door in the cowl was now closed and the airflow was drastically reduced. The small amount of air that was blowing through was much, much, much cooler; but not as cool as the air outside the car. However, I don't know if the air there was ever as cool as the outside air. That may just be a factor from some heat transferring from the engine compartment into the cowl. Or, it may be due to all of my HVAC Box seals being 48 years old.

Right now, I am nuch happier that I no longer have a lot of hot air blowing through those AC vents during the summer. I am anxious for another very hot day (like it was when I started this project) to see just how much it was changed. When we get a few more hot days, I will also completely bypass the heater core and see if that makes any difference.

Thanks again for all your responses.

[Goatracer1]

Some of the MOPARs use a heater valve that not only shuts off the water to the heater core but by passes the core sending the water back to the engine. Might be adaptable.