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T3TRIS Samba Member
Joined: October 30, 2017 Posts: 299 Location: Portland, OR
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Posted: Thu Jul 26, 2018 7:18 am Post subject: Rear heater delete, front heater valve, coolant bypass, Subaru |
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Hello,
We’re 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 couldn’t find the exact heater configuration I’m 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 T’s and NO, I will not throw the rear heater element away
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 isn’t 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 don’t know if I’m 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 wasn’t 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 don’t 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?
I’m 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 won’t be able to do this properly for a few hours after we stopped. |
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danfromsyr Samba Member
Joined: March 01, 2004 Posts: 15141 Location: Syracuse, NY
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Posted: Thu Jul 26, 2018 7:35 am Post subject: Re: Rear heater delete, front heater valve, coolant bypass, Subaru |
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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) _________________
Abscate wrote: |
These are the reasons we have words like “wanker” |
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baltik Samba Member
Joined: April 08, 2015 Posts: 440
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Posted: Thu Jul 26, 2018 9:24 am Post subject: Re: Rear heater delete, front heater valve, coolant bypass, Subaru |
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Connect the 2 rear heater hoses together, you now have a bypass |
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T3TRIS Samba Member
Joined: October 30, 2017 Posts: 299 Location: Portland, OR
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Posted: Thu Jul 26, 2018 11:33 am Post subject: Re: Rear heater delete, front heater valve, coolant bypass, Subaru |
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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, I’ve wondered about closing of everything in hot weather and having an issue! We flipped out too because the paint shop hadn’t 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 Samba Member
Joined: October 30, 2017 Posts: 299 Location: Portland, OR
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Posted: Thu Jul 26, 2018 11:36 am Post subject: Re: Rear heater delete, front heater valve, coolant bypass, Subaru |
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baltik wrote: |
Connect the 2 rear heater hoses together, you now have a bypass |
That’s 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 isn’t done right, there’s a chance the thermostat won’t get as much hot coolant as it should and the coolant won’t 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 won’t create additional issues.
So far it seems like that’s what I’ll be doing once the engine is cooled down (we just arrived from over 100 miles of driving). |
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Heli-mech Samba Member
Joined: February 11, 2008 Posts: 44 Location: Halifax, N.S.
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Posted: Thu Jul 26, 2018 11:50 am Post subject: Re: Rear heater delete, front heater valve, coolant bypass, Subaru |
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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 Samba Member
Joined: March 13, 2005 Posts: 50332
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Posted: Thu Jul 26, 2018 3:23 pm Post subject: Re: Rear heater delete, front heater valve, coolant bypass, Subaru |
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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 Samba Member
Joined: October 30, 2017 Posts: 299 Location: Portland, OR
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Posted: Thu Jul 26, 2018 8:55 pm Post subject: Re: Rear heater delete, front heater valve, coolant bypass, Subaru |
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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. It’s so warm we don’t 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 doesn’t work. But all other signs seem to say that our coolant system is working properly. When we arrive back in Oregon, I’ll inspect more for a bypass or install a reducer where the rear heater was. Thanks for all the help!!!
Last edited by T3TRIS on Thu Jul 26, 2018 8:58 pm; edited 1 time in total |
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T3TRIS Samba Member
Joined: October 30, 2017 Posts: 299 Location: Portland, OR
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Posted: Thu Jul 26, 2018 8:56 pm Post subject: Re: Rear heater delete, front heater valve, coolant bypass, Subaru |
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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! I’ll 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 Samba Member
Joined: April 19, 2018 Posts: 44 Location: Seattle
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Posted: Mon Jul 30, 2018 11:13 pm Post subject: Re: Rear heater delete, front heater valve, coolant bypass, Subaru |
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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 Samba Member
Joined: January 09, 2013 Posts: 1856 Location: anchor pt. alaska
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Posted: Tue Jul 31, 2018 8:29 pm Post subject: Re: Rear heater delete, front heater valve, coolant bypass, Subaru |
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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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