Rear heater delete, front heater valve, coolant bypass, Subaru

[T3TRIS]

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.

[danfromsyr]

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)
_________________

[baltik]

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

[T3TRIS]

[T3TRIS]

[Heli-mech]

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.

[Wildthings]

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.

[T3TRIS]

[T3TRIS]

[handjammer]

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?

[alaskadan]

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.