Heater Hose Routing Issues

Anyone out there using this layout for their heater hose routing? I've got a T-fitting in the coolant line coming into the radiator (right side of the picture) going into the heater core, then back out into another T-fitting that joins the flow out of the radiator and back to the water pump.

The result has been an intermittent heater that takes a very long time to warm up (long past when the coolant temp gets to 180 degrees) when it does decide to work at all. Yesterday, I got the car up to operating temperature and felt the smaller lines coming off the T-fittings into and out of the heater core -- both were very hot. But when I went to the other side of the bulkhead fittings, the lines (the two on the left side of the second picture) were cold to the touch all the way from the bulkhead to and from the heater core.

What I'm trying to figure out is if this is a result of air trapped in the heater core (a distinct possibility) or that these T-fittings don't allow the opportunity for coolant to properly circulate throughout the heater core. I can understand that on the high pressure side (coming out of the engine), the flow would easily make its way through the smaller diameter hose into the heater core, but it doesn't seem clear that returning from the heater core, the coolant flow would necessarily join the flow back to the water pump. I could see that being a"loop" of stagnant coolant. If so, would it help to have an angled fitting in place of one or both T-fittings so that the flow of return coolant out of the heater core would join the stream rushing back to the water pump at less than 90° angle?

Does anyone have experience with this set up?
 

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Chris Kouba

Supporter
Hey Pash-

You didn't show me (and I didn't think to look in) the footwell when I was over... Try elevating your lines under the dash. Get them up and pointed directly to and from the HVAC unit. Any air trapped in those lines will not want to head downhill before being pushed up to and through the heater core. By elevating them, you'll let any trapped air run up and into the heater core and then hopefully have enough pressure differential to head down the return and back to the water pump intake and expansion tank.

Once the air has been truly bled from the lines, they can lie back on the floor again as the line will stay purged of air. Until then, make it as easy as possible for the bubbles to migrate to your expansion tank.
 

Randy V

Moderator-Admin
Staff member
Admin
Lifetime Supporter
I used angled fittings with a tube that protruded into the flow Of coolant. I sold the car before I had a chance to test it, but reports were that the heater worked okay. I be BMW makes a recirculating pump for the heater in one or more of their cars, but I’ve long since list my reference material.. Certainly there’s info here that could be found via search.
Attached a couple of pics that may help.
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Pash

You have 2 points against you with that setup.

1- I'm assuming you have the thermostat on the engine in the OEM location. This will mean zero fluid flow until the engine is fully up to temp and the t-stat opens.

2- At the point your heater is connected, there isn't a huge pressure differential (unless you're screaming at 4000 RPM+) to make the hot water prefer to flow through the heater, so the bulk of the hot water will instead go through the radiator ignoring your heater.

Solutions-

Most effective would be if you can add a hose from the engine from the OEM heater outlet (top of intake manifold or engine side of T-stat) to the hot side of the heater box

Second option will still require engine to be fully up to temp, but will provide much more flow when it is, add an auxiliary pump.
https://www.ebay.com/itm/350953539290 Many of the German OEMs used this to get heat from the engine when it is not running to operate the heater in aux mode.
 

Ken Roberts

Supporter
I would first address the t-fitting issue. Very little coolant will flow to the heater core with your current 90 degree fitting. Change it as shown in the drawing. The coolant will then be forced to flow in the appropriate direction.

image.jpg
 
Thanks, L! Very helpful. Chris Kouba took a look at the car last weekend and I believe suggested something similar.

To be clear, for option #1, are you talking about running a line all the way from the engine to the bulkhead fitting in front that leads INTO the heater core and leaving the outlet from the heater core plumbed as-is? If so, where exactly on the engine to I tap this line into? You mention the "OEM heater outlet" -- is this a port on the water pump?

Separately, I've got VERY little space in the spine between the two 1.5" coolant lines, A/C refrigerant lines, and brake lines and associated heat shielding wrapped around them. What's the skinniest aluminum hose I could get away with trying to shove through there that would provide adequate flow through the heater core? I believe the existing hoses are 5/8" -- would a 1/2" stainless steel tubing running the length of the spine be too restrictive?
 
I would first address the t-fitting issue. Very little coolant will flow to the heater core with your current 90 degree fitting. Change it as shown in the drawing. The coolant will then be forced to flow in the appropriate direction.

View attachment 133012
Thank you, Ken! I can't seem to find a fitting like the one you described -- it needs to have 1.5" diameter on the "fat" ends and 5/8 for the skinny pipe. The only one I can find that's 1.5" has a 1" Y-pipe.

Know of a good source for these fittings that may offer a better selection than what I can find online?
 
I would first address the t-fitting issue. Very little coolant will flow to the heater core with your current 90 degree fitting. Change it as shown in the drawing. The coolant will then be forced to flow in the appropriate direction.

View attachment 133012
Ken - One more thing that just occurred to me. The way you have drawn the "Y-fitting" makes sense because there is that "scoop" portion that channels the flow into the smaller pipe. I believe the ones that exist simply have the Y-splitting off in the same manner as the T-fitting I am currently using with no portion of the side pipe sticking into the primary flow. In that case, would it be any better than a T-fitting in diverting the high pressure main flow into the side channel?
 
Thanks, L! Very helpful. Chris Kouba took a look at the car last weekend and I believe suggested something similar.

To be clear, for option #1, are you talking about running a line all the way from the engine to the bulkhead fitting in front that leads INTO the heater core and leaving the outlet from the heater core plumbed as-is? If so, where exactly on the engine to I tap this line into? You mention the "OEM heater outlet" -- is this a port on the water pump?

Separately, I've got VERY little space in the spine between the two 1.5" coolant lines, A/C refrigerant lines, and brake lines and associated heat shielding wrapped around them. What's the skinniest aluminum hose I could get away with trying to shove through there that would provide adequate flow through the heater core? I believe the existing hoses are 5/8" -- would a 1/2" stainless steel tubing running the length of the spine be too restrictive?


1/2" stainless would work, and better than waiting for the thermostat to open. At the engine, there should be a port on the intake manifold in the same passage that is common to the back side of the T-stat. The water pump connections are all inlets, so unless you run 2 pipes, don't use that. The top of the manifold is high pressure and max temp spot, and the best possible place to supply the heater from. I understand how valuable the real estate in spine is, so this may not be doable.

I'm guessing the intermittent heating you're seeing is as the T-stat opens and closes. The hot water at the radiator only flows when the t stat is open, and unless you're beating on it or it's real hot, that's only intermittent.

Will it give some warmth? Yes, but as you see, sub optimal. Maybe fine for your race car, but totally unacceptable for and OEM. Where in that spectrum you target is up to you.

I know it's a big PITA, but the 2 large tubes, and then 3 smaller (ac and one heater supply) worked out fine in mine.

Another hack could be add a 1/8"- 3/16" hole in the thermostat so there is always at least a trickle of hot water. It'll increase warm up time, but if you add the small electric pump, it'll keep you from back flowing the radiator when the T-stat is closed and putting cooled water in the heater core.
 

Ken Roberts

Supporter
I’ve never seen the fittings I have drawn commercially available. If you are handy then you could cut the parts to fit then take to a welder. A wye fitting would be better than the current t-fitting but introducing a new bend in the main 1.5” tube would slightly hurt flow.
 
So before I go tapping into the wrong place on the intake manifold, I took these two photos to clarify which port i should connect to the inlet side of the heater core. I'm thinking Brian is talking about the one I have circled in red in the closeup photo of the water neck/thermostat housing.

But I wanted to make sure it wasn't one of the two plugged ports in the other picture (circled in green and red). Hopefully it's not the one right next to/under the distributor because there is no getting to that one. This is a Ford 302 (Dart Block). Would the right port be 3/8NPT thread?

Thanks everyone!
 

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OK, I can see now that the fat red circle is around an intake manifold mounting bolt. The hole that Brian is talking about (just above and left of the red circle) seems to be the one I'm using for the coolant temp sensor. If I swap that for the heater supply, is there somewhere else I can take coolant temp reading? I've got a separate sender on the other side of the intake manifold that triggers the electric fans. Am I all out of coolant ports?

How about the 90 degree rubber hose connecting the T-stat to the water pump? What's the purpose of that and can I tap into either side of that and plug off the other?
 
On the SBF in my Cobra, I ran out of coolant ports as well. If you want accuracy, don't use the port at the rear of the intake/engine (if there's even one there) as it will always read cooler than the actual coolant temp due to being outside the normal coolant flow. I tried it and that's what I found out. The port on front of intake near distributor is where Ford originally put the heater hose coolant outlet. There's a special 90 degree fitting with an extended pickup tube that Ford used for this. I'm not sure why the extended pickup but they most likely did it for a reason.

I added a coolant port in the upper radiator hose for the temp sensor for cooling fan. You can buy one of these or easily make one by welding a bung on the right sized tube. The readings are accurate, especially if located close to the engine. Mine is probably 12" from engine and has worked fine for 15+ years now.
 
The extended pickup was to keep from getting air in the heater where it would recirculate to the pump intake, then again back to the heater. Truth is it will bit by bit make it to the Tstat and the radiator.

If you tee the temp sensor and heater supply, it can make the temp gauge a little laggy when the heater isn't on.

The plug in the other pic is likely a vacuum port.

Teeing the Tsat bypass hose is a good place if there isn't another port on the front. You could use a barbed TEE and straight tubes instead of the OEM elbowed rubber hose. Play with the orientation to make it as pretty as possible.
 
Great feedback -- very helpful! Will try to stuff a 5/8 aluminum tube through what little room is left in the spine and move my temp sender into the T-stat bypass line. Thanks everyone for the great advice!

I'll be using aluminum tubing that comes in a big coil and when I cut it to length the ends will just be smooth and without the normal flare or bulge that you have on coolant pipes where you slip the rubber hose over them. Is it ok to clamp a rubber coolant hose over a smooth pipe end or do I have to put a flare on it somehow? I've done this for brake lines but haven't seen a similar tool big enough to handle 5/8" pipe.
 

Neil

Supporter
Great feedback -- very helpful! Will try to stuff a 5/8 aluminum tube through what little room is left in the spine and move my temp sender into the T-stat bypass line. Thanks everyone for the great advice!

I'll be using aluminum tubing that comes in a big coil and when I cut it to length the ends will just be smooth and without the normal flare or bulge that you have on coolant pipes where you slip the rubber hose over them. Is it ok to clamp a rubber coolant hose over a smooth pipe end or do I have to put a flare on it somehow? I've done this for brake lines but haven't seen a similar tool big enough to handle 5/8" pipe.
"Is it ok to clamp a rubber coolant hose over a smooth pipe end or do I have to put a flare on it somehow?" NO! IT IS NOT OK! There are flaring tools for large thinwall aluminum tubes. Ask someone in the EAA (Experimental Aircraft Association)- maybe you can borrow one. I had a friend who built a very fast off-road racing buggy powered by a modified 2L Pinto engine. For a radiator, he used a big oil cooler from a giant Piaseki heavy-lift helicopter mounted upright behind the cockpit. It worked well until the pressure blew off a hose between the engine and radiator. He was almost scalded by that episode. Lesson learned- ALWAYS put a bead on tubing ends!
 
Knew a fellow who ran heater hose though a fiberglass firewall. One day the fiber glass sawed the hose and scalded his wife's feet to the point she was hospitalized.

Some sort of a bead is needed. Even a little bubble flare will do or over time, the hose will lose elasticity and if there is no bead, it'll slip off, dumping the coolant. With a bead it'll just leak a little and give you warning.
 
Anyone out there using this layout for their heater hose routing? I've got a T-fitting in the coolant line coming into the radiator (right side of the picture) going into the heater core, then back out into another T-fitting that joins the flow out of the radiator and back to the water pump.

The result has been an intermittent heater that takes a very long time to warm up (long past when the coolant temp gets to 180 degrees) when it does decide to work at all. Yesterday, I got the car up to operating temperature and felt the smaller lines coming off the T-fittings into and out of the heater core -- both were very hot. But when I went to the other side of the bulkhead fittings, the lines (the two on the left side of the second picture) were cold to the touch all the way from the bulkhead to and from the heater core.

What I'm trying to figure out is if this is a result of air trapped in the heater core (a distinct possibility) or that these T-fittings don't allow the opportunity for coolant to properly circulate throughout the heater core. I can understand that on the high pressure side (coming out of the engine), the flow would easily make its way through the smaller diameter hose into the heater core, but it doesn't seem clear that returning from the heater core, the coolant flow would necessarily join the flow back to the water pump. I could see that being a"loop" of stagnant coolant. If so, would it help to have an angled fitting in place of one or both T-fittings so that the flow of return coolant out of the heater core would join the stream rushing back to the water pump at less than 90° angle?

Does anyone have experience with this set up?
Pasha, I see what appears to be a heater control valve in the lower hose in the footwell (2nd photo), have you confirmed its opening when the switch is set to open it? If it's not opening you won't get any flow through the heater loop. You can try replacing the valve with a short section of straight pipe to see if flow/heat improves. Good luck.
 
Pasha, I see what appears to be a heater control valve in the lower hose in the footwell (2nd photo), have you confirmed its opening when the switch is set to open it? If it's not opening you won't get any flow through the heater loop. You can try replacing the valve with a short section of straight pipe to see if flow/heat improves. Good luck.
Thanks, Michael! The heater control valve was not opening at first and that was traced to a bad rheostat in the Vintage Air control panel. After replacing it, the valve would function collectively correctly, but still no heat. It seems the design I came up with was just no good. Rerouted it all per the recommendations on this thread and it works great now. Starts to warm up way before the thermostat opens. Still not getting a tremendous amount of heat but it eventually gets toasty enough. I attribute that to the tiny heater core and the 12 feet of pipe and hose the coolant has to pass through from from the engine to the heater core.
 
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