Heater Coolant Plumbing...

[Kim Haun]

I finally tried the heater in my RCR GT40 and found the coolant isn't circulating through the heater core the way I have it plumbed. I referenced another GT40 build and plumbed the heater core as illustrated in the attached photo. It seems there isn't sufficient pressure to circulate the coolant..I even disconnected the core outlet tube and left it open and very little coolant pushed through. With both hoses disconnected I could easily blow out what coolant that was in the system out with my breath. Do the fittings need to be angled with the flow to create adequate pressure? What has everyone else done that has had success with this? It is a Vintage Air Gen II system. Thanks!

Kim

.

 

[Randy V]

Angled yes - or you will need to install a circulating pump. I believe that BMW and/or Mercedes makes a pump just for that. I have no part numbers but someone here has done it in the last 10 years...

 

[Ian Anderson]

I finally tried the heater in my RCR GT40 and found the coolant isn't circulating through the heater core the way I have it plumbed. I referenced another GT40 build and plumbed the heater core as illustrated in the attached photo. It seems there isn't sufficient pressure to circulate the coolant..I even disconnected the core outlet tube and left it open and very little coolant pushed through. With both hoses disconnected I could easily blow out what coolant that was in the system out with my breath. Do the fittings need to be angled with the flow to create adequate pressure? What has everyone else done that has had success with this? It is a Vintage Air Gen II system. Thanks!

Kim

.View attachment 120123

Was the coolant actually flowing? Like had the engine run enough for the thermostat to open? If not your test would be invalid.

Ian

 

[Mike Pass]

With the arrangement you have you are relying on the pressure difference across the radiator to drive coolant through the heater. Because the radiator is very free flowing there will be hardly any pressure difference across it. You will need two points in the coolant circuit which have a larger pressure difference.
Cheers
Mike

 

[Chris Kouba]

I sent my heater core return line back through the spine and into the surge/expansion tank. Circulates/heats without issue. This also purges the heater core as well.

My surge/expansion tank was one that I made, so adding it wasn't too big of a stretch, and the reason Mike points out is exactly why I did it.

 

[Kim Haun]

I really appreciate the replies! It all makes sense…I followed another build thread without really thinking it through. I can easily angle the fittings and have them protrude into the coolant stream at the proper angles but I’m wondering if even that will be enough to drive the coolant efficiently through the core. I like the idea of a pump as long as it’s not a large unit and I can install it in-line in the front of the vehicle. Does anyone have information on a pump like this?

 

[Kyle]

Davies Craig DC-9051 Davies Craig Electric Booster Pump Kits | Summit Racing

Free Shipping - Davies Craig Electric Booster Pump Kits with qualifying orders of $109. Shop Water Pumps, Electrical at Summit Racing.

www.summitracing.com

 

[Brian Kissel]

I have used this Bosch until before with good luck. Half the price of the Davies Craig unit. There were wire harnesses available on EBay when I did mine. Not sure if they are still available or not.

Mercedes Heater Recirculation Pump - Bosch 2118350264

Mercedes Heater Recirculation Pump - Bosch 2118350264

www.fcpeuro.com

Regards Brian

 

[Kim Haun]

I have used this Bosch until before with good luck. Half the price of the Davies Craig unit. There were wire harnesses available on EBay when I did mine. Not sure if they are still available or not.

Mercedes Heater Recirculation Pump - Bosch 2118350264

Mercedes Heater Recirculation Pump - Bosch 2118350264

www.fcpeuro.com

Regards Brian

Thanks Brian! That’s perfect… Easy to add to the system. How did you wire it? I’m imagining a relay to the heater valve rheostat to turn it on?
Kim

 

[Steven Lobel]

What is the benefit to doing it this way vs using the heater inlet and outlet on the water pump?

 

[Brian Kissel]

Yes Kim that is how I did it.
Regards Brian

 

[Kim Haun]

What is the benefit to doing it this way vs using the heater inlet and outlet on the water pump?

Two things come to mind. One, there's not a lot of room to run additional hoses to the front of my engine with it being so close to the firewall...hard to service. Two, with everything I've already run thru the center tube, I doubt there's room for two additional hoses of the size we're talking about to get to the engine...less heat in the center tube as well.

Kim

 

[Steven Lobel]

In my GT-R I ran coolant tubes under the center tank and heater hoses up the right side of the frame. Better to not run hot stuff under the tank. I would recommend (next build?) to run only electrics under the tank or make the access panel and do a custom tank with internal pumps. Would be a much cleaner build.

 

[Daniel Lorenz]

Bumping this thread since i am about to plan the plumbing of heater hoses/pipes.
I want to make sure the circuit actually works, but i don't want another pump to force it.
What is my best bet then?
(I run a electrical main circulation pump and no thermostat)

Should i weld in an angled connector in the outlet pipe from the main cooler pipe in the footwell, and returnhose directly to the expansion tank?
Or is there another method that has a more guaranteed success?

 

[Chris Kouba]

I stand by my info in post #5. Heater works well.

 

[Davidmgbv8]

I am glad this came up and I found Chris Kouba's old posts. For a 302. Please correct me as I had planned on pulling the heater inlet hot water out of the tube going to the radiator. The return will go back to the expansion tank. The bottom of the expansion tank goes to the bottom inlet of the water pump. The top pump inlet goes to the small outlet at the thermostat bypass. The Radiator bleed also travels back thru the chassis to the expansion tank.

Now my intake (4bbl dual plane) has a water crossover at the back that join the head passages. I had then planned to bring this forward to a port behind the thermostat. I see there are other recommendations to take this water from the back of the heads to the expansion tank instead. One reason being air bleed in a canted engine. I had intended to pull an air bleed off of the top of the water outlet after the thermostat and have that go to the expansion tank.

 

[Chris Kouba]

Hi David,

I won't proclaim to be an expert but I will say that your plan in the first paragraph is my set up and it has been working well. I arrived at that set up after various discussions as you may have seen on the forum. The challenge with it was fitting all the plumbing in the spine passage, but it is doable with hard lines and foresight. It bled the system well (motor, rad, core, etc...) and I get heat as desired without issue.

I didn't do the bleed from the manifold to the t-stat or expansion tank. Why? Not quite sure at this point. I probably didn't want to go through the process of drilling and tapping the manifold. Seems a little weird at this point given all the other things I felt no hesitation getting into, but at the time I was putting together the motor, it didn't get through my filter. With ~7k miles behind it, I'm not sure it's completely necessary in my rig as the motor isn't noticeably canted, but other chassis vendors may dictate a steeper set up.

If you're going to do it, I'd recommend going manifold tap to the expansion tank, just to make sure the air is truly being pulled out. It might be only a marginal difference, but if you've got to pick somewhere to take it, that's where I'd aim it.

 

[Bill Kearley]

Why a second pump?? Take the hot water from the intake manifold and to the heater core and return to the water pump intake as it has been done for years. Provide an air bleed at the top of the engine and another at the top of the rad. In your photo you won't have any flow to speak of, thus no heat.

 

[Davidmgbv8]

This is the manifold I am using and it comes pre tapped I just have to make the tube to join the two. Now that tube becomes the high point on the manifold so I probably should make a small high point bleed from there to the expansion tank

 

[Chris Kouba]

I think you're close David, but the odds are the front bleed would be addressed with the flow through the t-stat. I would recommend that you plug the forward port and T together the two aft ports and run that line to the expansion tank. Would look like this: