Subaru EJ25 into a Vanagon BASIC COOLING SYSTEM questions

[crobox]

Hi there-
I'm getting somewhat close to the end of installing a Subaru EJ25 into a 1990 Vanagon. I've gotten through most of this build by consulting all the great online resources out there, but the cooling system is still a mystery to me.
I guess the reason for this is that most of the pictures online don't seem to match my Vanagon cooling system setup.

I'm hoping someone can walk me through this. I know it's not rocket science but I just need to know which hose to hook up to which hose.

V1 (Van 1): This is one of the main under-body tubes going up to the radiator.
V2: The second big under-body tube from the radiator comes up to something I'm calling the "coolant manifold." There is a smaller diameter tube stub coming out of the coolant manifold, pointing towards the engine, that I am calling V2.
V3: Also emerging from the coolant manifold is another smaller diameter hose which crosses over the top of the engine to the driver side, just under the lip of the deck lid opening. I'm calling this V3.

H1&2: Also in this photo are the heater hoses, which I've labeled H 1&2. I assume that these connect to the metal tube stubs emerging from the EJ25, also seen in this photo. But, which one goes to which one? Does it matter? I've also seen people add an "H" type crossover between the heater lines using two "T" fittings, but this doesn't make any sense to me! Is that required?

In this picture we see:

E1 (engine 1): The connection at the thermostat, which I believe is where the coolant returns to the engine.

And in this picture we see:

E2: The other main coolant connection on the EJ25, which I think is the water pump outlet. And...
V3: Another view of V3, the tube that emerges from the coolant manifold and crosses over to the driver's side.

Obviously I also need to plumb in the expansion tank and the overflow tank.

To be honest I would love it if someone could just say "Well, connect E1 to V3, etc."
OR, point me to the correct online resource for this. I've seen the diagrams at subaruvanagon.com but I find them confusing.

Thanks so much,
Christian

[Wildthings]

Your coolant tower is going to disappear and you may want to cut out the part of the firewall where it attaches. The only hoses of concern that now attach to it are V1 and the top unmarked hose that is the heater supply hose.

V1 is your hose feeding to the radiator, it attaches to your Subaru coolant manifold at E2, though many people alter the manifold so it sticks out the opposite corner of the engine right near where the coolant tower was. If you are set up to weld aluminium you can modify your own manifold though getting the angle correct the first time around would be a challenge, otherwise just buy one of the pre-modified ones various vendors sell.

You need some form of heater bypass. The stock Subaru heater system has coolant flowing through it at all times, and you must in some way mimic this or the thermostat will not work correctly and you will get severe overheating. The "H" pipe is fairly simple and doesn't seem to affect the heat much if it is installed far forward. Mine if over the spare tire. There are lots of options and opinions on how to do the bypass. You need a way to supply the heater loop as well, not sure what is on the 1.5L that could be used, though welding a nipple into the reversed manifold is one way to go.

You need to figure out how you are going to cool your automatic transmission. I have an air to oil cooler installed in front of the radiator with a thermostatically control bypass valve installed in the lines.

[crobox]

Wow, great... thanks Wild Things.

Your post cleared up several things for me.
I did not know that the coolant tower (what I was calling the Coolant Manifold) goes away. That explains why I never see it in any of the pix.

So...

V1 attaches to E2.
(Another thing you've cleared up for me is what is meant by "reversing" the Subaru coolant manifold. I am in fact an excellent aluminum welder but I don't think I'll bother. Running a hose around the engine just seems easier and I'm actually building this van on a tight timeframe.)

And then, I suppose that the large hose feeding the coolant tower (which I did not label) then connects to E1 (thermostat) ?

Now regarding the heater hoses... I now understand from what you wrote which are the two heater hoses. (One of the hoses that I THOUGHT was a heater hose comes out of a T from the large diameter radiator hose just before the coolant tower... I suppose that I simply discard that one.) Does it matter which heater hose goes to which metal tube from the EJ25 coolant manifold?

I understand what you wrote about the bypass. Will do.

Now what about the expansion tank? Where the hell do I plumb that thing in?

Regarding the transmission cooling... I installed an air-to-oil cooler under the van.

I might fabricate a scoop of some sort to force air through it...

Thanks so much,
Christian

[skills@eurocarsplus]

i used the small car routing:

works 100%
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[candyman]

I dont know why but the cooling system was one of my favorite parts of doing the conversion. It just felt good imagining, fabbing, routing and then having it work as planned. Same with the diy wire harness

[Wildthings]

[crobox]

OK I have finally wrapped my head around all of this.

(It's funny to see how many things I got wrong in my first post with pictures)

One last question:
Regarding the two heater lines which come back from the van: One is the flow TO the heaters and this one goes to the coolant manifold. The other hose is the return FROM the heaters and this one goes to the Subaru's built-in bypass to the thermostat.
But how do I know which line is the TO and which line is the FROM?

It's easy to trace the hoses from the rear heater... and one has a valve on it... which one is which?

Thanks a bunch,
Christian

[skills@eurocarsplus]

your hot coolant FEED from the subaru crossover pipe will go to the line with the heater valve shut off
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[hardway]

The hot coolant leaving the engine goes to the coolant distribution manifold. The heater supply and radiator supply (hot side) both exit the manifold. Heater and radiator return go to the left side of the van in the stock configuration. Your coolant return pipe from the radiator is broken in your photograph. That is on the cold return side. The hot side is usually worse. You need to do something about the pipes.

There are lots of diagrams of coolant systems for Subagons out there. I do not run a Subie motor but I can guaranty that the bypass system to make the thermostat work is the hardest part.

[crobox]

[crobox]

[hardway]

The long plastic coolant pipes have a steel insert in the ends. That insert is beaded or flared. The plastic has a barb at the ends. The flare reinforces the plastic barb. The barb gives mechanical purchase to retain the hose and clamp. The plastic pipe cracks through behind flare. Then the steel insert creeps out of the pipe.

So now the hose can move on the pipe. Leakage occurs and later a bad day.

[wesitarz]

Google subaruvanagon coolant systems images. Easiest crossover feedback loop to the thermostat is two Tees between the heater hoses. I use PEX 3/4x3/4 x1/2 Tees and a bit of 1/2 inch hose. 3/4 inch fittings will fit 5/8 hose.The effective opening is 3/8 inch for the crossover.
I've used 1.5 inch marine exhaust hose fitted over the plastic pipe past the brass insert and double clamped it with no problems.

[wesitarz]

If you have an extra tube on the coolant pump for an oil cooler you can Tee some hot coolant from the hot heater line as a feedback loop.

Without an extra nipple welded on the coolant manifold for hot coolant access and you want a flow-through design expansion tank, you can Tee off the hot heater line to the top of the expansion tank with bottom back to the heater return using reducers (1 inch to 5/ for your feedback loop. With the heater valve closed you still have continuous flow through the expansion tank and a feedback loop. You can adjust the opening of the Tee in the heater return to be either 3/8 or 1/2 inch opening cheap and easy with PEX fittings.

[16CVs]

The best diagram I have seen is at RJES website form England. It is clearly labeled and easy to read and understand.

Stacy
_________________
1987 Syncro Westfalia Triple knob (bastard)
1989 Syncro Tristar Triple knob "Swedish"
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Samba member # 14980
Call anytime number 650 722 4914 .
Keep Your van running and upkept tastefully for the love of the hobby.
Don't let your van end up in an "abortions" thread.

[wesitarz]

A #4 cylinder cooling mod would function as a feedback loop to the thermostat as well. Two kits available or I found an M20 x 1.5 male by 1/2 NPT female fitting on Amazon + 1/2NPT barb fitting + PEX Tee to the heater return for cheap.

https://www.youtube.com/watch?v=8GHttsdHIR8

[crobox]

[crobox]

When you're working on something like this, you just think about it all the time. You don't have a choice!

So I've come to understand the function of the bypass in terms of the thermostat function.

For the most part I am following the Small Car system arrangement. I have so far plumbed everything other than the bypass.

Here is the standard Small Car coolant diagram, with which I'm sure most folks are already familiar:

The first question I have is: Doesn't the section of the system with the expansion tank (outlined in pink below) function as a bypass?

I imagine that the answer is that the hot coolant flowing through the expansion tank has cooled down just a bit by the time it's gotten through there, and then it mixes with the coolant from the radiator - which has cooled down a lot - and so it suffers from the same set of circumstances as the heater return line.

So my next question is...

Why could you not just use T fittings to arrange a bypass such as I have photoshopped in the above image (pink arrow)? This seems to accomplish much the same task as the Small Car plumbing and the Tom Shiels spacer, but without the added time and expense of modifying the coolant manifold or the stock Subaru bypass...

Cheers,
Christian

[crobox]

For what its worth, the coolant diagram from RJES, seen here, shows the hot side supply line for the heaters coming in on the line without the control valve... which is the opposite of the info provided above by Mr. Skills@eurocarsplus.

Hmmm...

[Wildthings]