Water cooled heat

[GS guy]

I didn't want to distract from other build threads, but wanted to explore in a little more detail about using the heated water available in water cooled conversions to heat the interior of our rides.

Please feel free to add in other ideas and solutions for providing "water based" heat to the cabin.

To briefly recap, the Subaru conversions require continuous flow through the heater system plumbing (out the upper water manifold near the flywheel, back in between thermostat and water pump) in order to properly heat the thermostat so it will open and operate properly. However, continuously circulating heated coolant into the cockpit - especially in summer - not so hot! (or is that too hot??)

Enter the Ford Explorer 4-way coolant valve, suggested by 56SemaRag:



Located back by the engine it "should" provide the right combo of heated water when you need it in the cockpit, plus heated water when needed at the thermostat. Per 56SemaRag's description - it recirculates the hot water back into the engine when vacuum is applied, and sends water to the heater when vacuum is cut off. It seems like this may function better in our uses by reversing the logic? No vacuum, and it simply recirculates to the engine, apply vacuum and get heat? I wonder if some simple hose direction changes at the valve might accomplish this?

In some general researching, I noted Summit sells this valve, and it looks like they also have a cable controlled 4-way valve - for more of a manual control operation (but at twice the cost of the vacuum controlled valve). I suppose one could even adapt one of the Bug heater control levers to work this valve?



I had some concern that having the valve "all open" or "all closed" might provide too much heat without any regulation? In hindsight, I'm thinking this is likely not too much of a problem as you also have the circulation fan control: off and up to 3 on speeds to regulate how much heat you're getting. I also noted this looks to be SOP for the aftermarket heater system vendors like Vintage Air - their hot water valves work full on or full off.

Another possible option: Many conversions like mine use front mounted radiators. This means heated water is already available up near the dash from the lines going to and from the radiator. Why not use these? Tap into each side and fit an on/off single action water valve, with heater core up under the hood (or dash). This seems to make a lot of sense, if I'm not missing something obvious? Of course you'd still have to fit a "loop" hose for the heater fittings at the engine for the thermostat operation. I think this idea may need some more consideration for my build.

Now what about the heat exchanger?
Summit offers a nice compact unit, but it only offers unidirectional heat flow with 2 fixed outlet ports. If only looking for heat at your feet, this looks like a nice unit (PN 991102-1):



This looks to be good option vs. the old Mojave universal heater unit.

But what about defrost? I know the later model Bugs had a pretty nice system for controlling heat flow direction already built in. I guess to use it you could add one of these heater systems below the rear package tray (maybe taking in air from inside the cabin) and blowing down into the original built in heater ducting system. I know if I were doing this to a Bug, that's surely the direction I'd take. But in my case, I'm building a tube frame fiberglass body buggy - with NO heater system, ducting, or anything else. I've got to start from scratch and it needs to be pretty compact - and I like to apply the KISS principle as much as possible. I'm only questioning myself whether I'll need windshield demisting or not, and to incoporate that into the build. This surely won't be an all weather car, but I definitely want some heat for those cool spring and fall mornings and evenings. Maybe utilizing some form of cable operated duct dampers controlling heat to the floor with windshield "always on"?

Vintage Air has several heater systems available and a couple with integral windshield demist/defrost, but they are a little large to be cramming up under the dash of the typical glass body buggy. I'll have to search a bit more to see what else is out there.

Let's hear you ideas!

[Ghia Nut]

While certainly not the cheapest way to do it and if money were not an object...
Id try using one of these


Its an expensive man's answer to heat thought as these are usually aroun 100+ bucks, even the chineese ones too.
In my mind it would hook up to our heater ducts in the rear. Then you could use one of those heater booster fans to draw air through it into the cabin.
If it were possible to flip the polarity by chance, like they do on ceiling fans, you could maybe draw air through the cabin and out which I would assume to provide negative pressure and act like poor mans ac

[RottenRawb]

I like your idea here:
Another possible option: Many conversions like mine use front mounted radiators. This means heated water is already available up near the dash from the lines going to and from the radiator. Why not use these? Tap into each side and fit an on/off single action water valve, with heater core up under the hood (or dash). This seems to make a lot of sense, if I'm not missing something obvious? Of course you'd still have to fit a "loop" hose for the heater fittings at the engine for the thermostat operation. I think this idea may need some more consideration for my build.

Are you saying, keep the loop back in where the heater hose would normally go and just run off a coolant line up front?

and then how do you route the water valve?

[GS guy]

RottenRawb,
Yes, keep the coolant loop at the engine - upper water manfold down to the water pump inlet. This just short circuits the radiator and plumbs "uncooled" water back into the water pump inlet, keeping the thermostat happy. My engine mimics the OEM plumbing with all the bypass hoses - the turbo and throttle body coolant/heat hoses also follow this route, but through the fill reservior. I removed the original heater hard line from near the water pump that ran up next to the upper manifold hose connection, and replaced the upper manifold line with a screw in NPT/hose fitting - so in my case I'd have to fit a hose from there back down to the waterpump.

I think it would help when tapping off the main coolant lines to put some directional or Y fittings exiting and re-entering the radiator lines - instead of T fittings. A simple straight shut-off valve in that line should be all that is needed (instead of the 4-way valve) for delivering heat to the heater core. Those are also readily available in both vacuum and cable controlled versions. Maybe a bleeder fitting up at the heater core too?

The only draw back I can think of is if the engine tends to run cool and doesn't circulate enough hot water through the main lines? Seems improbable, but I guess something to consider.

[Buggin_74]

As I mentioned in the other thread you have to be super careful with these engine as the heaterloop controls the thermostat like GSguy said above.

Subaru and most vehicles these days have coolant constantly flowing through the heater core, if you don't want heat the air flow is just not directed through it, simple.
If there is no airflow through the heater you won't feel the heat but the return back to the water pump is still hot.

If you had a heater tap You would have it sending full flow to the heatercore all the time then cut it back abit if it was too hot.

By adding the heater tap you are messing with the flow so it's going to be very easy to create cold shock situation with the thermostat.
Most of the vanagon guys were experiencing this problem as the heatercore is so big the coolant on the way back had shed so much heat it closed of the thermostat.
A block called Tom Shiels cames up with an excellent solution.
Its a flange for the thermostat that gets the heater return away from it and allows a second bypass hose to control the thermostat.



I've got one of the 4 way heater taps same as the one above from an Explorer (mines out of an Aussie Holden Commodore but is the same part).

Heres a diagram I did on the flow, alittle less complicated than the above one





This was my heater setup I never got round to fitting, the heater tap with the vacuum diaphragm removed and hooked to the beetle heater cables and a Mazda heater core boxed up with a fan.
was going to mount it under the back seat.

[56SemaRag]

Good info gents!

I think this has to be looked as an entire system including the evaporator if you are looking at complete climate control. If you aren't running A/C then by all means run it through the heater core turn on the fan when needed.

The minute that you decide to want A/C, the heater core and it's function becomes very important. I doubt if many will run an OEM climate system in their VW's because of fitment issues. If the aftermarket heater/AC system chosen doesn't operate like the OEM one, then the heater core can't have coolant flowing through it when heat isn't desired. But the system still needs to loop regardless. Several of the aftermarket systems do not have the heater core and evaporator separated my a mix door or flap like modern vehicles. They are positioned in series with one another

Each system has to be looked at as a sum of it's possible components and the desired outcome of the owner. Heat only or heat with A/C.

[56SemaRag]

While certainly not the cheapest way to do it and if money were not an object...
Id try using one of these


Its an expensive man's answer to heat thought as these are usually aroun 100+ bucks, even the chineese ones too.
In my mind it would hook up to our heater ducts in the rear. Then you could use one of those heater booster fans to draw air through it into the cabin.
If it were possible to flip the polarity by chance, like they do on ceiling fans, you could maybe draw air through the cabin and out which I would assume to provide negative pressure and act like poor mans ac

That's cool....errr HOT!

[Buggin_74]

I doubt if many will run an OEM climate system in their VW's because of fitment issues.

I kept all the climate control out of my donor Legacy, I was going to fit it into my bug but like you say space limitations is the problem.

Wes here in Aus fitted all the digital climate control to his bug but he had to cut alot up to fit it and the passenger has lost alot of leg space from the fan, core and ducting.

Alot of people with watercooled conversions fit a heater core under the backseat and duct it into the original VW heater system.
Works well, that was my plan.
Means heat can always flow through the heater core and it's nice and close to the engines still.
All the way to the front through ther heater and all the way back is along way for coolant to travel and still control the thermostat.

[GS guy]

I think Buggin_74 has a good point - the cold shock of turning on the heater (opening the 4-way valve) could create unexpected results at the thermostat, like causing it to close - even if only temporarily.
Fitting a heater core and blower under the rear package tray would be the ticket. As Buggin mentioned - just let the water flow through it 100% of the time, and turn on the blower fan when heat is needed. Simple and effective.

I tried something similar many years ago, but with an oil cooler. Fan mounted above the package shelf, small plenum underneath with oil cooler ducted into the original heat ducts. It worked great when the oil was hot. Unfortunately, the oil never seemed to get quite hot enough in the winter to open the in-line oil thermostat! Car also had a well sealed dog-house cooler, and my idea of an alternate "heater" didn't pan out too well.





So something like this, but with a water/heater core instead?

For my buggy project though, the Vintage Air 506101 with servo controlled water valve and defrost/heater control is looking real good. Used a cardboard mock-up and looks like it will fit under the dash.

[Buggin_74]

Here's the article on the flange by Tom Shiels which is an effective solution to the problem.

http://subaruvanagon.com/tom/Thermostat%20housingk.htm

A heater core like the one you posted earlier mounted inside the car somewhere so its recirculating and the outlets ducted into the heater channels under the backseat would work well.

One other solution would be a turbo water pump
They have extra spigots for the turbo water lines which could be used for the same purpose.

[56SemaRag]

One other solution would be a turbo water pump
They have extra spigots for the turbo water lines which could be used for the same purpose.

What a great thread, unfortunately due to fitment I will be running mine under the dash. The aftermarket high volume STi pump is the one I planned on running from the get go. With the turbo creating heat the thermal variance created by the four way should be minimal.

Would like to see some pictures of the Subaru heater-AC retro fits into VW's

[ambrynmc]

So would you loop through the turbo for your thermostat loop instead of the heater core?

[56SemaRag]

So would you loop through the turbo for your thermostat loop instead of the heater core?

This is how mine is going down. I may not have the TB loop depending on whether I go stock or aftermarket TB.
The turbo loop will be uninterrupted, the TB might be and the heater core loop will be altered. It's all pascals man, as long as it remains unrestricted, plenty of flow around the thermostat everything should be fine. Lots of good info being thrown around by think tanking this conversion stuff. It makes air cooling seem so bland to me now....

[GS guy]

Interesting cooling ideas from Tom Shiels using the bypass port:
http://subaruvanagon.com/tom/Cooling%20System.htm

I think I'm following how this works - hotter water always flows next to the thermostat via the bypass port, while the "cooler" heater water flows downstream of that, closer to the pump impeller inlet. I guess this biases the hotter recirculating water at the thermostat. Seems like a good idea for remote (dash located) heater systems? I might have to consider this - although my water pump already has 2 inlets besides the radiator connection. I'll have to see how they're confugured.

I'm thinking of feeding the heater water back into water pump inlet as stock - this way there is always flow to the heater (when the valve is open), regardless of actual thermostat operation. My cooling layout fairly closely follows the original flow layout, as described in the SAE paper. Now not decided about what to do with the upper water manifold heater outlet - hence the ?

Here's my planned cooling diagram:

[RottenRawb]

I am just more confused then I EVER was.