Heater Coolant Plumbing...

Davidmgbv8

Supporter
Chris, interesting thought as that could lead to quicker warm up as going to the expansion tanks then recirculates back to the pump so while there is no cooling from that it does circulate the back of the heads still. Since the back crossover on the manifold joins the heads I need then to plug the rear left and just pull off the right to the expansion tank. Both of the front ports can do temp sensor duty, one for the gauge and one for the EFI.

Thanks for your input.
 

Chet Zerlin

Supporter
Hi all,

Like Kim I have hooked up my heater in my RCR40 with two lines coming from the hot and the "cold" hoses from the radiator. Since I live in Naples, Florida chances are very good that I would never have discovered if the heater worked or not since I would never have needed to turn it on!

Nevertheless, it's worth doing things right the first time so I want to see if I can completely understand the issue with the way I (and apparently others) have hooked it up. From what I've read it is a lack of pressure...correct? Is that because the way we've hooked it up basically is a closed loop between both sides of the radiator and removes the engine from that loop?

I'd like to also understand what is being proposed as the right way to hook it up. Should I leave the line to the heater I now have hooked up to the hot side hose of my radiator as is, run a heater hose through the spine back toward the engine (whenever I finally get one of those from Craft...:() and hook it up to the expansion tank and then hook the other end into the heater (where I now have the line pulling from the "cold" hose coming from the radiator)?

I'm not really thrilled with having to introduce another heat source (the heater hose) into the spine and thus into the cockpit. So if instead of running that hose through the spine I wanted to go with an electric pump (as detailed earlier in this thread) where and how would that hook up to my current system?

Thanks for your help!

Chet
 

Chris Kouba

Supporter
Like electricity, water is lazy and will take the path of least resistance. In the OP's pic, there is very little motivation for the heated coolant to divert and flow through the heater core, so it doesn't- resulting in lack of heat.

Your idea of keeping your current heater feed from the hot flow to the rad is a good one, and the most helpful thing would be to run that line back to the expansion tank as proposed. That would result in a parallel path for the coolant to flow back to the expansion tank, giving it a pressure differential which will drive a flow as well as promote bleeding of the system if there is air in it.

In your current system, an electric pump placed somewhere between the feed and the return to the rad lines should do the trick. All you're doing with that is externally motivating the process with the additional pump to drive the flow through the core. Actually, this should also promote the bleeding of entrapped air as well.

Looking at the system as a whole, thermodynamically speaking, you won't be introducing any additional heat source into the spine. There will be an opportunity for more heat transfer, but all the lines I have running through the spine are sleeved and I don't think the margin would be noticeable if you insulated it.

If implemented correctly, either setup should effectively solve the issue.
 

Chet Zerlin

Supporter
Just reporting back that I decided to install an auxiliary water pump for the heater instead of running another heater hose through the spine. The pump I bought came with a rubber isolation bracket that I bolted directly to the floor in front of the firewall. I had wanted to mount it on the firewall itself but there was no way that the hoses would bend that much especially considering that I had to use two 3/4" to 5/8" adapters for the hoses.

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Ian Anderson

Lifetime Supporter
That looks like an interesting set up.
is there a tap to allow/restrict flow so you only get flow when you open the tap and the pump turns?

Reason I ask is that water is lazy and follows the route of least resistance and the resistance to flow through your radiator core may be more that the resistance to flow through your top heater system.

In the worst case the water could come from the engine, through the heater and back to the engine without ever going through the radiator. In so doing it could cause overheating.

This happened in the MGB cars and overheating occurred over the winter as the water never made it through the radiator….but over the summer when the heater was closed off they did not overheat..

Ian
 
Hi Kim, thank you for the question. A lot of forum posts and threads have been started about this issue. As you probably know, the standard heater core plumbing restricts the flow of the coolant. You don't have much choices here, because any modification will mean taking the dash out. There are also issues with the heater core itself, so it might be a good idea to just buy a new one.
 

Brian Kissel

Staff member
Admin
Lifetime Supporter
Steve, Thank You for posting the above information. I was looking at the barbed valve that you listed. When getting ready to order this, I see that it has listed a max temp of 175 deg. Have you run this long enough to see any issues? I have contacted the seller to see if they offer a higher temp version, but as of yet have received no reply. Any info you can supply would be greatly appreciated.

Regards Brian
 
Hello, I have it running over a year with no problems but I do have it installed between the return side of the heater core and return line of the radiator. The temps never reach 175 because of the water temp drop through the core. Steve
 
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