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Rear heater delete, front heater valve, coolant bypass, Subaru
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T3TRIS
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PostPosted: Thu Jul 26, 2018 7:18 am    Post subject: Rear heater delete, front heater valve, coolant bypass, Subaru Reply with quote

Hello,

Weíre currently on the road driving our van back to Oregon after a paint job. I did a little bit of research on this subject but couldnít find the exact heater configuration Iím looking for.

Right before we left for our return, our mobile mechanic told us that our Subaru EJ22 conversion did not have the required (or recommended, not sure) coolant bypass. When the conversion was done, we had both the front and rear heaters, unmodified.
We since then removed the rear heater and temporarily plugged the hoses. I was planning on going under later and remove the Tís and NO, I will not throw the rear heater element away Smile
We also added a cutoff valve by the front heater core to remedy to Vanagon hot feet problem.
And to make things more difficult, our temperature gage isnít working (it goes straight to MAX as soon as the ignition is on). This one is high on my list of things to fix. Our engine does not seem to overheat.

Now I donít know if Iím supposed to plug both rear heater lines or connect them. I realize this subject has been discussed many times over but as I mentioned, I wasnít able to find our particular scenario:
- Subaru EJ22 with supposedly no coolant bypass
- rear heater removed
- front heater with cut off valve

I have no idea if having both rear heater lines plugged AND the front heater hose valve closed will create problem IF I donít have a bypass loop.

1. How do I verify if I have a coolant bypass loop? Just follow the hoses?
2. Will driving with both front and rear heater hoses blocked create coolant issues.
3. With our scenario, do we cap the rear heater hoses or so we connect them together? And if connected, do we need a flow restrictor?

Iím at the hardware store right now and am going to buy a few straight metal barb connectors and get back on the road. Since coolant will be hot, I probably wonít be able to do this properly for a few hours after we stopped.
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danfromsyr
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PostPosted: Thu Jul 26, 2018 7:35 am    Post subject: Re: Rear heater delete, front heater valve, coolant bypass, Subaru Reply with quote

I have a 1.8T.
but all I know is my friends 2.2 subie overheated in very short order when he shut off/down his heater while on a road trip with us.
he did not have the tom shiels thermostat bypass.
http://subaruvanagon.com/tom/Thermostat%20housingk.htm
and had previously removed and capped off his rear heater core.
then slid the front core to the off position while on the highway.
was on the shoulder in a couple miles.

there are 2 types of engine coolant circulation
those designed for a constant flow and those designed to have an interrupted flow on the heater loop. Subaru's need a constant flow to signal the T-stat the actual water temperature. (so do AEB 1.8Ts unless you use an ABA water pump)
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baltik
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PostPosted: Thu Jul 26, 2018 9:24 am    Post subject: Re: Rear heater delete, front heater valve, coolant bypass, Subaru Reply with quote

Connect the 2 rear heater hoses together, you now have a bypass
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T3TRIS
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PostPosted: Thu Jul 26, 2018 11:33 am    Post subject: Re: Rear heater delete, front heater valve, coolant bypass, Subaru Reply with quote

danfromsyr wrote:
I have a 1.8T.
but all I know is my friends 2.2 subie overheated in very short order when he shut off/down his heater while on a road trip with us.
he did not have the tom shiels thermostat bypass.
http://subaruvanagon.com/tom/Thermostat%20housingk.htm
and had previously removed and capped off his rear heater core.
then slid the front core to the off position while on the highway.
was on the shoulder in a couple miles.

there are 2 types of engine coolant circulation
those designed for a constant flow and those designed to have an interrupted flow on the heater loop. Subaru's need a constant flow to signal the T-stat the actual water temperature. (so do AEB 1.8Ts unless you use an ABA water pump)


Yeah, Iíve wondered about closing of everything in hot weather and having an issue! We flipped out too because the paint shop hadnít re-plugged the radiator fans and our van was spewing out coolant from the overflow tank not long after. Fortunately we noticed VERY quickly and everything seems to work fine now (we drove over 100 miles since that ordeal).
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T3TRIS
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PostPosted: Thu Jul 26, 2018 11:36 am    Post subject: Re: Rear heater delete, front heater valve, coolant bypass, Subaru Reply with quote

baltik wrote:
Connect the 2 rear heater hoses together, you now have a bypass


Thatís been my first and most solid thought but before we commit, I want to make sure we do it right. I remember reading something out there saying that if it isnít done right, thereís a chance the thermostat wonít get as much hot coolant as it should and the coolant wonít get through the radiator when it should. My memory might be flawed with that thought process but I want to make sure connecting these lines wonít create additional issues.

So far it seems like thatís what Iíll be doing once the engine is cooled down (we just arrived from over 100 miles of driving).
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Heli-mech
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PostPosted: Thu Jul 26, 2018 11:50 am    Post subject: Re: Rear heater delete, front heater valve, coolant bypass, Subaru Reply with quote

The heater core coolant path on the Subaru engine is what supplies coolant back to the thermostat housing.

Running it without a bypass loop and both front & rear heater valves closed will cause the thermostat not to open and the engine will overheat.

Looping the rear lines will act as a bypass and the engine will operate normally.

The best thing to do is to loop the lines and add a reducer in line. This allows good positive coolant pressure/flow to the front heater core and still allow a by-pass to proper bring the thermostat up to operating temperature.
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Wildthings
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PostPosted: Thu Jul 26, 2018 3:23 pm    Post subject: Re: Rear heater delete, front heater valve, coolant bypass, Subaru Reply with quote

If you are able to drive, you must have some form of bypass, maybe one your mechanic is not familiar with. Some are pretty well buried under the manifolds on the top of the engine, others are in the heater plumbing, and others right at the thermostat.

When I did my conversion I originally had one between the coolant manifold and the heater return, but didn't always get enough flow through it, so added one to the heater hoses hid above the spare tire.
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T3TRIS
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PostPosted: Thu Jul 26, 2018 8:55 pm    Post subject: Re: Rear heater delete, front heater valve, coolant bypass, Subaru Reply with quote

Heli-mech wrote:
The heater core coolant path on the Subaru engine is what supplies coolant back to the thermostat housing.

Running it without a bypass loop and both front & rear heater valves closed will cause the thermostat not to open and the engine will overheat.

Looping the rear lines will act as a bypass and the engine will operate normally.

The best thing to do is to loop the lines and add a reducer in line. This allows good positive coolant pressure/flow to the front heater core and still allow a by-pass to proper bring the thermostat up to operating temperature.


I connected them with a standard 3/4 barb brass fitting for now. Itís so warm we donít need the front heater to perform 100% anyway. We drove in LA traffic end of day, stop and go for about an hour, and our radiator fan turned on only once. We were also able to figure out our coolant temp gauge issue and it now reads normally, which is super encouraging (I had misswired an LED light that was touching the housing shorting the gauge).

Our coolant level sender is busted and our coolant alarm doesnít work. But all other signs seem to say that our coolant system is working properly. When we arrive back in Oregon, Iíll inspect more for a bypass or install a reducer where the rear heater was. Thanks for all the help!!!
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Last edited by T3TRIS on Thu Jul 26, 2018 8:58 pm; edited 1 time in total
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T3TRIS
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PostPosted: Thu Jul 26, 2018 8:56 pm    Post subject: Re: Rear heater delete, front heater valve, coolant bypass, Subaru Reply with quote

Wildthings wrote:
If you are able to drive, you must have some form of bypass, maybe one your mechanic is not familiar with. Some are pretty well buried under the manifolds on the top of the engine, others are in the heater plumbing, and others right at the thermostat.

When I did my conversion I originally had one between the coolant manifold and the heater return, but didn't always get enough flow through it, so added one to the heater hoses hid above the spare tire.


Good ideas! Iíll take a better look when we arrive back in Oregon. For now the rear hoses are looped together which seems to be doing the trick. Thanks!
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handjammer
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PostPosted: Mon Jul 30, 2018 11:13 pm    Post subject: Re: Rear heater delete, front heater valve, coolant bypass, Subaru Reply with quote

I'm also about to do a temporary rear heater delete on a subie conversion. Let's pretend I'm not really unsure if I have a coolant bypass (but probably do). Is there any reason I shouldn't connect the two hoses together, just to be extra safe?
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alaskadan
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PostPosted: Tue Jul 31, 2018 8:29 pm    Post subject: Re: Rear heater delete, front heater valve, coolant bypass, Subaru Reply with quote

You can connect them. In one of the original lines is a restrictor. If not you can make one with a piece of 5/8" solid steel round stock a couple inches long. And drill a 3/8" hole down the center of it . Put it in one of the hoses before you stick them together. I then put a hose clamp on the hose around it to keep it from moving, though I doubt it would have.
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