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List members:

I am thinking a lot about how to plumb my Vanaru transplant. Hobart and
others
are VERY emphatic about the need to move coolant past the thermostat as the
engine warms.

I note, however, in the Subaru engine manuals for my 1994 Legacy 2.2 engine,
that THERE IS ALREADY A BYPASS which runs from the aluminum pipe under
the intake manifold to the heater return pipe. In fact, there are two short
sections
of rubber hose which take the water from a fitting in this pipe to the air
intake and
then back to a short branch off the heater return pipe.

Do I infer that this bypass is insufficient? Was it insufficient in the
Legacy?

Since I have done the SA 180 degree rotation of the aforementioned pipe, I
will
be able to route the radiator feed directly from the flywheel side of the
engine
forward without having to build the large "L" shaped plumbing required to
bring
the radiator feed forward from near the left rear tail light that others
have built.
The heater end of the rotated pipe will feed the "burp" tank which stays in
its
original position on the rear splashguard. So goes my theory.

Now a question: Can I feed the "burp" tank this way and use the "burp" tank
out pipe (just as was done in the Vanagon) to route more water back to the
heater return to create more bypass flow, if necessary? The reason I want
to
do this is that I imagine that the "burp" tank will capture more bubbles if
water
actually flows through it. A variant of this question is: why is the
"standard"
procedure a routing of the radiator feed water past the burp tank; why not
route
the bypass water past the burp tank, if, as Hobart says, the engine only
sips
from the radiator, but the flow in the bypass circuit must never cease!

Please stop me from cooking my engine if you have reasons to believe this
design won't work!!

Thanks

John



John Mates
jmates@...
(503) 264-8023

John Mates wrote:

Since I have done the SA 180 degree rotation of the aforementioned pipe, I
will
be able to route the radiator feed directly from the flywheel side of the
engine

John,
You raise some interesting questions for which I have no answers, but I'm sure
the list can comment.
I do wonder how you reversed the "pipe" under the throttle body? I was going to
do this, but upon closer inspection, I realized the mounting bolts holes were
not identically positioned on each end. Did you drill new holes to match up to
the block? Subagon minds want to know!
Thanks,
Larry

Larry:

On my engine, the mounting holes are exactly symmetrical and
one can reverse the pipe without altering anything EXCEPT -- the
radiator feed extension end of the pipe interferes with the bell on
the rear of the engine, sooo ... I sawed it off.

I left about 3" of pipe to clamp the hose to. I could not bead
the end of this aluminum cast pipe so I carefully sawed a couple of
parallel shallow grooves around the pipe for the rubber hose to grab.

In addition, the heater hose end of the pipe would strike the
intake manifold next to the power steering pump, but since this end
is a steel tube, bolted on to the Al casting, I carefully bent it just
enough to let it peek through between the power steering pump and the
manifold.

So now the radiator feed end is aimed at the Vanagon plastic
radiator feed tube and the heater feed end is aimed at the stock
position of the burp tank.

John

John Mates
jmates@...
(503) 264-8023

John Mates wrote:

List members:

I am thinking a lot about how to plumb my Vanaru transplant. Hobart and
others
are VERY emphatic about the need to move coolant past the thermostat as the
engine warms.

I note, however, in the Subaru engine manuals for my 1994 Legacy 2.2 engine,
that THERE IS ALREADY A BYPASS which runs from the aluminum pipe under
the intake manifold to the heater return pipe. In fact, there are two short
sections
of rubber hose which take the water from a fitting in this pipe to the air
intake and
then back to a short branch off the heater return pipe.

Do I infer that this bypass is insufficient? Was it insufficient in the
Legacy?

On my '90 Urabus and '92 Legacy, it appears the cooling system is plumbed as
follows (Urabus orientation): coolant runs through the engine and out the
large port on the top-left-rear of the motor, then into the top of the
radiator, and out the bottom to the thermostat housing. The heater coolant
runs out the port on the top-right-front of the motor (out of the above
mentioned "aluminum pipe"), through the heater core(s), then back to a pipe an
inch or two away from the output port. This pipe runs down to a point near the
thermostat housing, and a short section of hose completes the circuit returning
the coolant back to the business side of the thermostat. Is your '94
different?

At least one heater valve must be open for hot coolant to make its way to the
sensing side of the thermostat. Or you can, like I did, install a smaller
diameter bypass line from the heater in line to the heater out line (in effect
bypassing both heaters). This way, you can shut both heaters off without
frying the motor.

I'm guessing here, but I imagine the Subaru heater core has a valve which
diverts hot coolant through the core then to the thermostat or bypasses it
directly to the thermostat, depending on the heater setting. Or perhaps
there's always hot coolant flowing through the core and you control heat in the
pass. compartment by opening flaps to control air flow through the core. In
any case you always have coolant flow to the thermostat.

Since I have done the SA 180 degree rotation of the aforementioned pipe, I
will
be able to route the radiator feed directly from the flywheel side of the
engine
forward without having to build the large "L" shaped plumbing required to
bring
the radiator feed forward from near the left rear tail light that others
have built.
The heater end of the rotated pipe will feed the "burp" tank which stays in
its
original position on the rear splashguard. So goes my theory.

Now a question: Can I feed the "burp" tank this way and use the "burp" tank
out pipe (just as was done in the Vanagon) to route more water back to the
heater return to create more bypass flow, if necessary? The reason I want
to
do this is that I imagine that the "burp" tank will capture more bubbles if
water
actually flows through it. A variant of this question is: why is the
"standard"
procedure a routing of the radiator feed water past the burp tank; why not
route
the bypass water past the burp tank, if, as Hobart says, the engine only
sips
from the radiator, but the flow in the bypass circuit must never cease!

Please stop me from cooking my engine if you have reasons to believe this
design won't work!!

It seems to me that you could run the heater outlet into the top of the
expansion tank, then out the bottom to the heaters. This would, as you say aid
in burping air out of the heater circuit. However, I don't know whether this
would aid in burping air from the main coolant circuit. How many bubbles in
the main circuit will take the heater circuit route? With the KEP plumbing,
the expansion tank is on the main coolant circuit and any air that finds its
way past the 'T' to the expansion tank tends to rise and end up in the
expansion tank. With your method, perhaps you could still bleed the system
using the KEP bleeder and elevating the van appropriately.

You could just try it. Watch the dash gauge and/or use the water on cylinder
method (pretty foolproof) to determine if the system is working properly.

Good work!

Dick Myers
'88 Urabus
Grass Valley, CA

Dear Dick (and other interested parties):

I can't find a record of having sent this note out, but if I have, please
accept my apologies! While I was writing this, a mail from Hobart came in
emphasizing that the `94 2.2L engine "bypass" circuit is not enough flow,
even with the rear heater wired open, to keep the thermostat in touch with
the real engine temperature. So some of what follows is already answered.

But perhaps some of the rest is of interest...

Thanks for your thorough response and encouragment. I have included some
remarks interspersed in the text of our mails:

=========================================================================

John Mates wrote:

List members:

I am thinking a lot about how to plumb my Vanaru transplant. Hobart and
others
are VERY emphatic about the need to move coolant past the thermostat as

the

engine warms.

I note, however, in the Subaru engine manuals for my 1994 Legacy 2.2

engine,

that THERE IS ALREADY A BYPASS which runs from the aluminum pipe under
the intake manifold to the heater return pipe. In fact, there are two

short

sections
of rubber hose which take the water from a fitting in this pipe to the air
intake and
then back to a short branch off the heater return pipe.

Do I infer that this bypass is insufficient? Was it insufficient in the
Legacy?

On my '90 Urabus and '92 Legacy, it appears the cooling system is plumbed as
follows (Urabus orientation): coolant runs through the engine and out the
large port on the top-left-rear of the motor, then into the top of the
radiator, and out the bottom to the thermostat housing. The heater coolant
runs out the port on the top-right-front of the motor (out of the above
mentioned "aluminum pipe"), through the heater core(s), then back to a pipe
an
inch or two away from the output port. This pipe runs down to a point near
the
thermostat housing, and a short section of hose completes the circuit
returning
the coolant back to the business side of the thermostat. Is your '94
different?

--> There is a difference, YES -- On my `94 2.2L engine, this Al pipe has
three objects screwed into it: (1) A sensor which goes to the computer;
(2) a sensor which goes to the overheat LED on the dash AND (3) a
small hose connector adjacent to the sensors from which a hose ascends
to the air intake duct body (and presumably hot water ascends in the
hose) ... there is another small hose which takes coolant from the air
intake back down to a small metal branch of the heater return pipe
which
travels down to the thermostat and enters the thermostat through the
short section of hose mentioned in the above paragraph. So perhaps my
engine has a bypass and yours doesn't? Apparently my bypass heats the
region around the butterfly valve of the air intake ...

A bit more info ... when I was checking to see how much $ a replacement
Al pipe would be so that I could replace the one I hacked to death,
I noticed that the turbo'ed version had one more sensor plugged in -- a
regular temperature sensor which innervates the `94 turbo's genuine
analog temperature meter in the instrument panel ... otherwise, the
pipe seems
identical and could be used in place of my plainer version and would
give
me the true temperature reading that you and Tom were looking for.

At least one heater valve must be open for hot coolant to make its way to
the
sensing side of the thermostat. Or you can, like I did, install a smaller
diameter bypass line from the heater in line to the heater out line (in
effect
bypassing both heaters). This way, you can shut both heaters off without
frying the motor.

---> This was my plan, but I wonder if it is necessary, given my
pre-existing bypass. This hose is only about 3/8" diameter.
I should have remarked above, that this hose, from the flat
aluminum cross pipe up to the air intake and back down to the
heater return pipe, is called the "bypass hose" in the Subaru
engine manual for 1994 2.2L Legacy.

I'm guessing here, but I imagine the Subaru heater core has a valve which
diverts hot coolant through the core then to the thermostat or bypasses it
directly to the thermostat, depending on the heater setting. Or perhaps
there's always hot coolant flowing through the core and you control heat in
the
pass. compartment by opening flaps to control air flow through the core. In
any case you always have coolant flow to the thermostat.

----> Hobart told me that the Subaru coolant always flows through
the Subaru heater cores, but my manuals don't show me clearly
enough what the deal is in `94s.

Since I have done the SA 180 degree rotation of the aforementioned pipe, I
will
be able to route the radiator feed directly from the flywheel side of the
engine
forward without having to build the large "L" shaped plumbing required to
bring
the radiator feed forward from near the left rear tail light that others
have built.
The heater end of the rotated pipe will feed the "burp" tank which stays

in

its
original position on the rear splashguard. So goes my theory.

Now a question: Can I feed the "burp" tank this way and use the "burp"

tank

out pipe (just as was done in the Vanagon) to route more water back to the
heater return to create more bypass flow, if necessary? The reason I want
to
do this is that I imagine that the "burp" tank will capture more bubbles

if

water
actually flows through it. A variant of this question is: why is the
"standard"
procedure a routing of the radiator feed water past the burp tank; why not
route
the bypass water past the burp tank, if, as Hobart says, the engine only
sips
from the radiator, but the flow in the bypass circuit must never cease!

Please stop me from cooking my engine if you have reasons to believe this
design won't work!!

It seems to me that you could run the heater outlet into the top of the
expansion tank, then out the bottom to the heaters. This would, as you say
aid
in burping air out of the heater circuit. However, I don't know whether
this
would aid in burping air from the main coolant circuit. How many bubbles in
the main circuit will take the heater circuit route? With the KEP plumbing,
the expansion tank is on the main coolant circuit and any air that finds its
way past the 'T' to the expansion tank tends to rise and end up in the
expansion tank. With your method, perhaps you could still bleed the system
using the KEP bleeder and elevating the van appropriately.

---> All coolant will rise to the top of the engine into the level and
flat aluminum cross pipe we've been talking about. I'm assuming
that there will always be flow through the bypass circuit, no
matter what temperature the thermostat sees (i.e., the
thermostat
doesn't SHUT the bypass circuit). If so, this would be the most
consistently flowing coolant circuit and should carry the air
right into the burp tank which sits above the aluminum pipe
which
is the highest liquid point on the engine.

Air caught in the radiator circuit would stay caught until either
the owner bled the radiator with the KEP bleeder or until it moved
through the circuit after the thermostat opened and wound up being
split between the heater and the radiator circuits at the cross
pipe back on top of the engine.

Hobart says that the engine only "sips" occasionally from the
radiator circuit, although, presumably it "gulps" when the
engine
gets really hot, so I'm guessing that, particularly when the
engine
is cold, the bubbles would be caught better in the bypass
circuit
than in the radiator circuit.

I guess one final thing motivates me to do it this way. The Vanagon
coolant burp tank was on the Vanagon bypass circuit, not on the main
radiator circuit, or so I read my Syncro diagrams for 1986.



You could just try it. Watch the dash gauge and/or use the water on
cylinder
method (pretty foolproof) to determine if the system is working properly.

---> I guess I'll just have to try it out, as you say. Maybe a little
of your design courage will rub off on me. Jeez, I don't want
to
ruin my engine though!

Good work!

Dick Myers
'88 Urabus
Grass Valley, CA


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John Mates wrote:

Larry:

On my engine, the mounting holes are exactly symmetrical and
one can reverse the pipe

John,
Thanks for the info-guess I'll have to use a later model engine next
time!
Larry