Different question about rear heater & Subaru conversion

[tuanis]

I have an 89 vanagon w/ and EJ25 conversion done by the PO. From what I've read, some conversions require a feedback loop with the rear heater in order to properly cool. The PO removed the heater, but connected the lines together underneath the rear bench. I have no cooling issues, and really don't want to introduce any.

That said I'm about to revamp the aux battery under the rear seat, and install a propex while I'm at it so I'd like to get those hoses out of there. Is there any reason I can't remove the hoses that go under the rear seat from their respective T fittings, then connect those fittings together underneath the van? I'd be eliminating some length from the tubing connecting the lines but I'm not sure that matters?
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1989 Westfalia - 2.5L Subie
1988 VW Westfalia - Stolen

[vanis13]

You can definitely do that
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83.5 Westy with Subaru 2.5, 4 spd manual, center seat, COLD A/C on 134a!, Winter camp heated with an Espar B4 gasoline furnace

www.SuperVanagon.com - some stuff I make

[Wildthings]

You are going to short circuit your front heater by doing so and may end up without much of any heat. I shorted between the two tees under the floor, but cut a short piece out of a smaller diameter hose that would just go into the jumper hose to act as a restrictor.

If you have some other sort of heater bypass you may not need this one at all can could just replace the two tees with straight couplings.

Note that there was originally an orifice in the rear heater system to force more of the water to the front heater.

Pictures of exactly what you have would be nice.

[wesitarz]

You should examine all of your heater hose for bloating and rot. All you need is 2 Tees with a 3/8" (1/2" hose) between the heater lines (PEX fittings are cheap and work with 5/8" hose).

[fxr]

[harvgwen]

As said above you can do that, but most of your heater coolant will be bypassing your front heater and you won’t get much heat when you need it. (It won’t be any different than what you have now). As was also alluded to above, you should do what you’re proposing to do, but with a restrictor. Stepping it down to a short piece of 1/8 hose will do.
As I see it, the reason you always need some flow of coolant is that the Subaru thermostat (I don’t know if this is similar with a VW engine) needs to have some coolant flow to the back side of it, otherwise the t-stat will never sense that the coolant temperature is increasing and it will remain closed and you will overheat your engine. If you always kept your front heater valve partly open, you wouldn’t need the bypass hose at the back, but we want to close the front heater off completely when it’s hot in summer. On mine, I have a rear heater and I’ve wired the shut off valve to full open to achieve this flow. I may plumb this a little differently in the future, as it’s not ideal in hot weather.
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1986 Westfalia Vanagon, 2.2 Subaru
Okanagan Valley, British Columbia

[Wildthings]

[JeffRobenolt]

100% what they are saying about cold weather needing a a restrictor in the bypass to force coolant to go up front.
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For OEM Subaru and SixStar parts and harness modications
AVsubaruconversions.com

[4Gears4Tires]

Why even have the rear heater loop at all? I put in straight couplers when I did my EJ25 swap. At 10F I was considering getting plumbing insulation and wrapping my lines. I wouldn't want any less heating.
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'87 Syncro Ferric Oxyhydroxide Superleggera Edition
'85 Westy Sciuridae Domus Edition

[tuanis]

Thanks for the great help as always everyone.

Sounds like a restrictor is the way to go, funnily enough our front heater has never worked very well (we had a very cold roadtrip through ohio when it was -3* a few years back) so I can hopefully kill two birds with one restrictor sized stone here.

I'm also going to go on the hunt for a diagram of the cooling system, it sounds like I've got some more to learn there.
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1989 Westfalia - 2.5L Subie
1988 VW Westfalia - Stolen

[4Gears4Tires]

Why don't you just clamp the line with a hose clamp and see if your motor starts to overheat. That will let you know 100% whether you need that extra loop at all.
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'87 Syncro Ferric Oxyhydroxide Superleggera Edition
'85 Westy Sciuridae Domus Edition

[JeffRobenolt]

[harvgwen]

Which is what I was trying to say, but Jeff said it much more clearly than me.
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1986 Westfalia Vanagon, 2.2 Subaru
Okanagan Valley, British Columbia

[Wildthings]

The way I understand it, on a Subaru car the coolant flow to the heater is on full bore all the time and thus returns to the engine quite hot, especially when the air flow through the heater is blocked off providing no heat to the cab. This means that the thermostat sees water that is very close to engine temperatures. When the heater is getting full air flow the return temperature is lowered causing the thermostat to stay closed longer thus letting the engine get hotter so it will provide hotter water to the heater core increasing heat output. This can not be fully mimicked with a Vanagon heater system, but sufficient return water from the heater loop is required for the thermostat to function at all, thus the bypass. With the heat on the less bypass you have so the returning coolant from the heater loop will be cooler and the hotter the engine will run, so just like in the Subaru car the more heat asked for in the cab the hotter the engine will get to provide such.

[a914622]

For some understanding of the coolant issues with the Subaru install do a google search “#4 coolant reverse mod” . There are some good videos that explained what is needed to make a happy engine.

Most of the mods use one of these. https://phenixindustries.com/product/an-to-metric-fitting-06-m20-x-1-50-extended/


If you put on a turbo water pump it have an extra coolant in port. Good place to return the coolant. Or if it’s the 08 model there is a spot on the casting for the same return.

Doing that mod lets you change you heater to what you want, like changing to an under the seat Honda pilot heater in the back so all the coolant lines are outside!!! Then add an mr2 vacuum valve and wire the relay so it only opens if the fan is on !!

Good luck

Jcl
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87 gl powerd buy 2.5subaru
75 914 getting 2.2t subaru scratch that SVX subaru

[4Gears4Tires]

Is this taken care of with the reversed coolant manifold?
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'87 Syncro Ferric Oxyhydroxide Superleggera Edition
'85 Westy Sciuridae Domus Edition

[vanis13]

[Wildthings]

[wesitarz]

It's not a #4 reversed coolant manifold mod. It's a mod intended to improve coolant circulation through the #4 cylinder/head by adding a coolant flow line from the block at #4 to the heater return line. Does it work? Maybe. It does add hot coolant to the heater return to the thermostat functioning as a feedback loop so the overall running temp might improve.

[tuanis]

Closing the loop on this (sorry for the bad pun )

I got the van up on a lift yesterday to tackle this project. I clamped off the coolant lines on both T fittings to prevent coolant loss, and removed both of the rear heater hoses from their respective Ts and pulled them out from under the rear seat. I got some new 5/8" heater hose and connected the Ts back together underneath the van. I used about 10" of coolant line. The T's are close together and I wanted enough length to be able to loop without kinking the line. I also installed a steel spacer in the line (5/8 OD x 1/4 ID x 3/4 Length) to force some coolant up to the front heater.

The hardest part of the whole thing was getting the original heater hoses off the T. They were old and gummed on to the Ts and there's not a lot of space to work. Once I got those off the rest of it was fairly easy. The whole project took about 2.5 hours, and we weren't working very fast.

I've only put about 10 miles on the van so far (in stop and go traffic), but the engine temps seem to be consistent with what they were before the change. Also the front heater is definitely putting out better heat now.
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1989 Westfalia - 2.5L Subie
1988 VW Westfalia - Stolen