DIY - Heater Bypass Valve

While I'm waiting for my new triple core Mark Preisendorf radiator to arrive, I thought I'd deal with some other cooling system odds and ends.

Most of us E9 owners are aware that our cars do not have a conventional heater contol valve that shuts off the flow of coolant through the heater core. Instead, the core is always plumbed, and the heater lever merely opens and closes the flaps on the heater housing. In hot weather, many of us can feel the heat coming off the heater housing. The a/c systems in these cars, never great to begin with, can certainly do without this extra heat load right next to the a/c evaporator.

There have been threads (http://www.e9coupe.com/forum/showthread.php?t=8581&highlight=heater+valve) discussing what is necessary to bypass the heater core. The quick and dirty way is to simply disconnect the two heater hoses from the heater core pipes that protrude through the firewall and splice them together. For those living in hot climates, this is fine, but here in New England, on those spring drives, I USE my heat. A second approach is to install a valve, like in a 2002, that simply stops the flow of antifreeze into the core. However, there is concern that this approach, which does not allowing the coolant to circulate, may cause overheating problems. Clearly what is needed is a full heater bypass valve that, when opened, sends coolant through the core and, when closed, bypasses the core without blocking the flow.

For reference, the hoses into the firewall are shown below (hose clamps removed). The top hose goes to the back of the head. The bottom hose (on my L-Jet M30B32) feeds the metal pipe that runs under the intake manifold.

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IMG_2730-1024.jpg


It is easy to imagine the valve that we need. It is shaped like a letter H. The top legs of the H are connected to the heater pipes at the firewall, and the hoses go into the bottom legs of the H. When the valve is open, it should block off the center section but allow coolant through the legs to and from the heater core, and when the valve is closed, it should bypass the core by diverting the coolant coming up the left leg, through the center section, and out the right leg. But how do you locate one the right size, and what adaptations to you need to do to make it work in the E9?

In a perfect world, we'd find a bypass valve that:
--Has 3/4" pipes (this is the size of the heater pipes protruding through the firewall)
--Has a 1.5" center-to-center (2" edge-to-edge) spacing between the pipes (this is the spacing of the heater pipes protruding through the firewall)
--Is metal

In practice... one out of three ain't bad, and close is good enough for horseshoes and hand grenades.

To locate a usable valve, I went on eBay, typed in "heater control valve," and spent an hour looking at lots of pictures, eventually finding three that are widely available through both the AC Delco and the Four Seasons cataloges. They're all cheap (less than $35). Because it's impossible to tell what will work and what won't until you actualy test-fit them, I simply bought all three. I think the total bill was about $60.


img_2726-1024.jpg
IMG_2726-1024.jpg


Note that all three of these have a lever on the end of the valve, which is, in turn, actuated via a vacuum dashpot. So in order to change from the heat to the no-heat setting, you could either remove the vacuum dashpot and simply move the lever (or wire it in position), or leave the dashpot installed and connect and disconnect it from the intake manifold to flip between enabled and bypassed.

Note also that, to connect any of these three candidate bypass valves to the two heater hoses, the heater hoses need to be either trimmed or lengthened.


AC Delco 15-5533
Verdict: This should work.
Advantages: The pipes are almost exactly the same spacing as the heater pipes, allowing clean attachment to the pipes on the firewall.
Disadvantages: The pipes are 5/8", not 3/4". And it's plastic.


img_2727-1024.jpg
IMG_2727-1024.jpg


The first one is AC Delco 15-5533 (Four Seasons 74781). This is not a classic "H" shape, but it has two inlets and two outlets. The one I bought came without the vacuum actuator, so the lever controlling the valve is plainly visible and completely exposed. In this picture, the flow of coolant in is supposed to be from the top right. The tube size is only 5/8" instead of the correct 3/4", but you can snug the hoses down with hose clamps. And, the spacing of the two tubes on the left is about 1.5" center-to-center -- almost exactly the spacing of the two heater pipes on the firewall. Unfortunately, the part is plastic -- an anathema to those of us who pride that our E9s don't have the plastic junk endemic in the cooling systems of newer BMWs.

The pic below is a test fit of this valve using two short 3/4" rubber hose sections to hold it onto the firewall. In order to have clearance for the lever, the lever must go on the left (away from the intake manifold). This forces you to install the valve upside down from the previous photograph, so the inlet side is lower left, where you can just barely see it. The outlet side is plainly visible upper left. The hose going to the metal pipe under the intake manifold is swung to the side. The hose coming from the back of the head is not visible.

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IMG_2733-1024.jpg


In the photo below, I've swung the outlet hose back toward the valve so you can see that the natural elbow in this hose will allow the excess to simply be cut and the hose connected (I have not yet cut it; this is a test fitting). The hose from the back of the head will need to be lengthened with a 3/4" barb coupling and brought into the inlet at lower left (not visible).

img_2734-1024.jpg
IMG_2734-1024.jpg


So you can see that this should work. If you look up this part number on line, you'll see the vacuum actuator bolts on top of the lever, so it would be on the left. It looks like there's sufficient room for it.


AC Delco 15-5543
Verdict: This should work.
Advantages: The pipes are 3/4". And it comes with hoses on it, allowing quick attachment to the heater pipes on the firewall.
Disadvantages: The pipes are slightly too far apart. And it's plastic.


img_2728-1024.jpg
IMG_2728-1024.jpg


The next one I tried is the AC Delco 15-5543 (Four Seasons 47607). This looks to be exactly what you need, although, like the 5533, it is plastic. The pipes are 3/4" -- the right size. It's H-shaped with the actuator on the top. It even comes with two 4" sections of 3/4" hose on the ends, allowing quick attachment to the heater pipes. The inlet end isn't labeled, but I assume it's the one opposite the valve, or upper left, In this first pic below, I do a quick test fit. The 4" rubber hoses are longer than they need to be, so it sticks out a bit far.
img_2731-1024.jpg

IMG_2731-1024.jpg


Below I've trimmed the 4" hoses down to about 2". Unfortunately the pipes on this valve are slightly further apart than those on the firewall, and the shorter you cut these hoses, the more difficult a time they have mating up securely to both sides. Also in this pic, I swing the hose from the intake, showing that, like with the 5533, it looks like this hose can simply be cut just after it makes its elbow turn and then clamped directly to the pipe. Also, as with the 5533, the inlet hose from the back of the head (not pictured) need to be lengthened in order to be connected to the valve. The vacuum actuator can be taken off and the lever flipped manually, or if you like, the actuator can be used to close the valve; just hook a vacuum line to the intake manifold.
img_2732-1024.jpg


IMG_2732-1024.jpg


AC Delco 15-5302
Verdict: I have my doubts.
Advantages: It's metal.
Disadvantages: The pipes are slightly too far apart. One pipe is 3/4", the other is 5/8". There may be clearance issues.


img_2729-1024.jpg
IMG_2729-1024.jpg


I looked long and hard for an H-shaped metal valve, and this was the only one I could find. Initially I thought it was The Grail, but the vacuum actuator is on the side, and valve, pipes, and the vacuum actuator sit at an angle with respect to each other. Further, what is marked as the inlet tube is 5/8" whereas the outlet tube is 3/4". Also, the outlet and inlet tubes extend unequal distances. Individually none of these are showstoppers, but they make a clean installation challenging. In the pic below I have the valve cajoled into hanging there on the firewall. You can see that the tubes are slightly too far apart to mate cleanly with the firewall tubes, though slightly longer stub hoses would solve this problem. In this position, this could work, but technically the flow arrow is pointing the wrong way.
img_2735-1024.jpg

IMG_2735-1024.jpg


In the pic below, we turn the valve around so the flow arrow is pointing toward the heater, and you can see that there's a clearance problem, with the body of the valve hitting the #6 intake plenum.
img_2736-1024.jpg

IMG_2736-1024.jpg


So, it looks like either of the two plastic bypass valves -- the 5533 and the 5543 -- will work. As much as I dislike putting plastic in the cooling system, unless I can find a better metal bypass valve, I'll likely go with one of these. Plus, the color and the look and feel of the metal valve, to me, are somewhat at odds with the rest of the rest of the engine compartment. Of the three, interestingly, the 5533 seems to be the least visually intrusive. The 5543 is a quicker and easier adaptation, but that vacuum dashpot is sitting pretty high and looks fairly un-BMW-like (of course you could take it off). On the 5533, the dashpot unscrews, but on the 5543, it is a more integral part of the assembly, not as easily removed.

To finish up the adaptation and extend the inlet hose from the back of the head, I've ordered a length of Gates 5/8" heater hose (28491, $10.03 at Amazon) and Gates 3/4" heater hose (28492, $9.64 at Amazon), and several brass right angle 5/8" and 3/4" fittings (eBay; PEX fittings look like they'll work).

I'll amend the post when the final installation is done.

--Rob
 
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David

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On my 74 there isn't enough room for the valve. But I did slip a hose from the manifold to the back of the block, bypassing the heater core. The inside of the car had to have dropped at least 5 degrees.
 

Stevehose

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+1 the difference is huge

On my 74 there isn't enough room for the valve. But I did slip a hose from the manifold to the back of the block, bypassing the heater core. The inside of the car had to have dropped at least 5 degrees.
 

deQuincey

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+1 the difference is huge

hi steve
i have seen this work with admiration and interest, but it has been made in a csi
i feel that a cs is a fair different arrangement due to the disposition of the hose that arrives to the manifold under the rear carburetor

could you post some pics and explain your setup ?

i will try to do it this winter
 

Stevehose

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I have a different bypass setup now with the triple webers, but all you have to do is disconnect the 2 hoses at the firewall where they go to the heater, cover the holes then clamp the hoses to a 3/4" brass elbow from a hardware store:

IMG-20120912-00617.jpg


And just leave it hidden down below. Takes 5 minutes. Optional: blow out the coolant from the heater to remove all liquid for long term storage. 61Porsche gets the credit for this mod. Lowers the cabin temp by several degrees with no heat soak.

hi steve
i have seen this work with admiration and interest, but it has been made in a csi
i feel that a cs is a fair different arrangement due to the disposition of the hose that arrives to the manifold under the rear carburetor

could you post some pics and explain your setup ?

i will try to do it this winter
 

'69 2800cs

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I have this mod waiting to go in sometime soon.

What are y'all doing for reducing the heat from the exhaust? I have the foam seal around the shifter, but over time the tunnel gets very warm.
 

David

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I'm not sure about foam around the shifter, but there should be a rubber "boot" which fits around the shifter to seal off the tunnel. This helps a little. I also installed Dynamat thermo insulation on the floor and tunnel which did nothing. Somewhere on this forum is a thread about adding a heat shield between the exhaust and the tunnel under the car. I haven't tried that yet. The heater core bypass is key.
 

deQuincey

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I have a different bypass setup now with the triple webers, but all you have to do is disconnect the 2 hoses at the firewall where they go to the heater, cover the holes then clamp the hoses to a 3/4" brass elbow from a hardware store:

IMG-20120912-00617.jpg


And just leave it hidden down below. Takes 5 minutes. Optional: blow out the coolant from the heater to remove all liquid for long term storage. 61Porsche gets the credit for this mod. Lowers the cabin temp by several degrees with no heat soak.

thank you,
it seems simple but not reversible !
hummmm, probably i will try the other way, here you can have good drving days dry and cold in autumm and even in winter, not to speak about spring ! lovely sunny cold mornings,...
regards
 

Stevehose

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Yes, I don't need heat here, it hasn't been reconnected in 2 years

thank you,
it seems simple but not reversible !
hummmm, probably i will try the other way, here you can have good drving days dry and cold in autumm and even in winter, not to speak about spring ! lovely sunny cold mornings,...
regards
 

Sven

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Heat shield

What are y'all doing for reducing the heat from the exhaust?

Some photos of a heat shield I got from La Jolla. PN 51.48.1.832.850. It's from an e12/e24. Bolt on ready. You will need to drop the transmission support enough to slide the shield between the frame and transmission carrier. I did trim one edge a bit. But after installation I realized it probably was not necessary. I also have a 36" long custom aluminum heat shield over the cat. and center resonator further back.

On the body metal there is a ceramic coating from Lizard Skin on the underside of the tunnel and their acoustic insulation on the top side along with the 1/4" or 1/2" Dyna foam material on top of that. It does not get hot. You can still feel the warmth from the exhaust, but compared to the heat of the sun coming in through the glass, both the heater core and exhaust contributions seem pretty minor (although every little bit probably helps).
 

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deQuincey

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H valve working principle

i have a basic question on the H valve installed

i can not really understand what is the way in which this valve works:

in my opinion the best way would be:
position 1: the circulation of coolant is the standard one, from the head through the internal radiator and back to the sysytem
position 2: hot water coming from the head, is bypassed towards the thermostat housing, and the other route is blocked

but i can not understand how the valve is doing this, this is how many hoses is blocking/enabling the valve ?

i mean, when the bypass is done, are the "standard" hoses blocked ?
or on the contrary the fact is that the valve only opens the bypass and thus the main flux is going through it because the pressure drop is smaller there than that through the internal radiator ?
 

Luis A.

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It turns out there was a "water valve" which was optional on some (all?) E3 models.

B0018837.png


While we are all worried that the coolant flow simply can't be shut down, that's exactly what this valve appears to do since it's a one-conduit design.

Has anyone actually seen this valve on an E3? Any thoughts about its design, which completely shuts off the water flow without any bypass...?
 

deQuincey

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good point luis

i have no answer

but i have checked the early e3 diagrams, and the part is not there

but it is in the airconditioned optional group 64
 

Stevehose

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I would want nothing to do with shutting off coolant flow from the back of the head to the thermostat housing!
 

Luis A.

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I would want nothing to do with shutting off coolant flow from the back of the head to the thermostat housing!

But... Does it really shut it off? Aren't there coolant channels between the head and the block (cylinder jackets) and therefore the coolant would just flow down that way and back to the pump. I will propose the only reason that outlet pipe is in the back of the head is to supply hot coolant to the heater core. In fact, it's rather small to conduct any meaningful amount of cooling flow that can't simply flow down to the block and back to the pump. Am I not thinking this correctly?
 
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Stevehose

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When I had my head off recently I looked closely at that area and it appeard to me to be large enough to allow a decent amount of coolant through it. Since the heater core is always getting flow, I personally wouldn't stop the flow out of the back side and stagnate it back there. These heads are borderline under cooled to begin with and I want all the coolant I can get through all areas. Especially where I live.

But... Does it really shut it off? Aren't there coolant channels between the head and the block (cylinder jackets) and therefore the coolant would just flow down that way and back to the pump. I will propose the only reason that outlet pipe is in the back of the head is to supply hot coolant to the heater core. In fact, it's rather small to conduct any meaningful amount of cooling flow that can't simply flow down to the block and back to the pump. Am I not thinking this correctly?
 

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Follow-Up to Heater Bypass Valve Installation

I thought I'd post a follow-up to the heater bypass DIY I posted last winter.

The valve has worked flawlessly. I manually leave the lever on the bypass setting during hot weather. I drove the car 1900 miles round trip to The Vintage in Winston-Salem. Without the heater core being hot, the a/c had no trouble keeping up. The idea that the flipping of the lever under the hood was a seasonal thing, rather than something that required convenient passenger compartment actuation, made sense.

Until the fall.

Maire Anne and I took the E9 to Vintage at Saratoga a few weeks ago. It was chilly enough on the morning we left to drive home that I opened the hood and flipped the lever under the hood to the on position. Heat quickly started to pour into the passenger compartment. Too much heat, in fact, likely due to the foam on the heater box flaps being deteriorated. After 30 minutes of driving, I needed to stop the car, pop the hood, and close the valve. And, of course, the heater core was already hot; it took a good while for it to cool back down, even with the valve closed.

When I got home, I began thinking about the best way to be able to have passenger compartment control over the valve. I came up with two ways. You can do it manually with a cable, or automatically with a vacuum-actuated diaphragm.

I tried both.

I ordered an $8 generic choke cable from Jegs. The cable has the advantage over the vacuum actuator that you can give it a little tug and crack open the valve just a little. The problem is that the cable has to have a straight shot at the valve's lever, and there's not a hole in the firewall directly behind the valve for the cable to come through; the closest convenient hole is for the wiring harness, way offset to the left. I think, for this to work, you'd either need to drill a hole through the firewall (which, in my youth, I wouldn't've batted an eyelash at, and now, I recoil in horror at the thought), or send the cable up to the front of the engine, then loop it back around to come at the valve from the front. I think I'd resent seeing the cable every time I opened up the hood.

So I tried the vacuum actuation method. It turns out you can buy such as setup here (http://www.myraceshop.com/Heater_Bypass_Valve.html), but I rigged one up myself.

The Four Seasons valve is meant to have a vacuum actuator on it; it just happened the one I bought didn't have it. So I dropped $15 and bought one with the actuator on it. If you connect the actuator to a vaccum source, it'll close the valve; disconnect it and it opens the valve. To control it from the passenger compartment you need an electronic vacuum dashpot. I found one from the emission control of an old 2002 I had in the parts bin, and wired it up (see pic). Testing it before installation, it seemed to work. The center of the dashpot gets connected to the source of suckage (the intake manifold). The other dashpot port gets connected to the actuator on the valve. Start the engine and apply 12V to the dashpot. The valve closes, bypassing the heater core. Disconnect power or vacuum and the valve opens, enabling the heater core. I thought, other than the desire to crack it open less than fully, this will work perfectly. I prepared to install it.

And then I thought about it more carefully.

The way the vacuum actuator on the bypass valve works is that it is normally open -- without vacuum applied, the valve is open, bringing the heater core in line. And the way that the electronic dashpot works is that it, too, is normally open -- without power applied, it is open. So with the engine off and no vacuum, the heater core would be in line. With the engine on and the dashpot unpowered, the heater core would still be in line. It was only with the engine on and voltage applied that the heater core would be bypassed. This was really the opposite of what I wanted. I didn't want hot antifreeze to get into the heater core as soon as engine and power were shut off.

I looked for four-port heater bypass valves that were normally closed, and couldn't find one.

And then I began to wonder. I was using an electric dashpot to control a vacuum actuator to control the valve. I wondered if, in fact, there were valves with direct electric controls.

There are.

The first one I found is from Thermotion (http://www.thermotion.com/images/file/Data Sheet-4-Port Valve w-Electric Actuator-web.pdf). The valve itself is very similar in design to the Four Seasons valve, but with an electric actuator. Thermotion also sells an electronic control module for the valve. Thermotion appears to only sell to distributors. I found a link on ackits.com to the valve (http://www.ackits.com/merchant.mvc?Screen=PROD&Store_Code=01&Product_Code=31-60027&Category_Code=); they appear to sell it for about $60. But that doesn't include the electronic module.

Then I found something in a place I should've searched last year -- oldairproducts.com. I've bought a/c odds and ends from them for a/c retrofits and rejuvs. Their catalog (http://www.oldairproducts.com/pdf/2013_oldairproducts_catalog.pdf) shows not only a cable-actuated valve (25-1018 and 25-1019), but also an electrically-actuated valve, with a little rotary control you can use to set the valve to whatever opening you want, so it addresses the problem the vacuum-actuated solution does not. The valve is shown here (http://www.oldairproducts.com/catalog/heater-cores/50-1555/heater-valve-p-3667.html). Like the Thermotion valve, the oldairproducts valve looks very similar to the Four Seasons valve, so it should fit. The cost is $103 shipped.

I was about to order it when I looked at the pics and saw the size of the plug on the end of the wiring harness. That plug has to go through the firewall... somewhere. I was planning on snaking it through where the main wiring harness goes through. The thing is so big there's no way it'll fit through there. I suppose I can chop the plug off, snake the cable through, then solder the wires and heat-shrink over the solder joints. But it all gave me pause.

I'll probably order the oldairproducts electrically-actuated valve. But first, I want to scope out how and where to get the cabling through the firewall.

--Rob
 

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Peter Coomaraswamy

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Rob, any chance of running the cable through the space between the heater pipes? There is some spongy stuff back there, but that sounds like a great product for Texas where you definitely want the heat off in the summer but the heat can be a plus in the winter when the driving is actually tolerable.

Thanks for the info!
 

rsporsche

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since i will probably rarely drive my coupe when it is really cold, i've thought about just having the lever under the hood ... but when i recover the seats, or just pull the seatcovers off and add a seat heater element. i find that it has to be really cold for me to turn on my heater. but if its cool, i will turn on the seat heater.
 

Stevehose

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I've had mine bypassed for a couple years, the few times I've driven in weather in the 30's the sunlight and a fleece are all that was needed to warm the cabin once the engine contributed it's part.
 

thehackmechanic

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Revisiting the idea of the manual cable

I am the first to admit that part of the appeal of older cars is that they don't have things like electrically-actuated climate control doohickeys that can fail. Bowden cables basically don't fail. Thus, do have pause about retrofitting an electrically-actuated heater valve into a car that didn't originally have one, and agree that a cable-actuated device is a better period-correct solution. I will re-examine where the Bowden cable would need to go through. The advantage of the electrically-actuated solution is that since the electrical cable is electrical not mechanical, it can go through anywhere; it doesn't need a straight shot at the lever on the valve.
 
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