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Subaru Coolant Reservoir Options

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GeorgeL Officially Full-On Dubber

231 posts · joined Feb 2006 ·

#455247
I've seen various arrangements for the coolant reservoir (pressurized header tank) and I was wondering if one is any better than another for a belly radiator system.

I was considering a flow-through reservoir at the left rear upper corner of the engine bay. (I have a '71, so no top engine hatch) This would leave the standard cooling inlet on the top of the engine, but would complicate plumbing under the bus.

An alternative is a reversed cooling inlet on top of the engine with a smaller hose teed off at a the highest point of the systemto the reservoir (not flow-through). Simpler undercar plumbing, but may not remove air from the system as readily.

Another route is to run the heater line through the reservoir. I intend to install a heater core that feeds the original ducting under the bus, so the plumbing for this might be pretty convoluted.

I've seen all of these variations, but no discussion on their relative difficulty and effectiveness. After reading all the scare stories about bleeding Subaru and wasserboxer cooling systems I really want to design a robust system that doesn't fry the engine if a bubble gets into the wrong place. Fill-n-go is my goal!

Ideas?

George

GeorgeL Officially Full-On Dubber

231 posts · joined Feb 2006 ·

#455280
Helbus wrote:Fill 'n' go header tank of about 3 litres. Can be filled easily from the back hatch.
This was the flow-through one that I was thinking of. How is the line from the reservoir to the radiator routed? Any baffling or standpipes inside the reservoir?

GeorgeL Officially Full-On Dubber

231 posts · joined Feb 2006 ·

#455302
Helbus wrote:The hose to the radiator just goes from the bottom of the back of the header tank, and then 2 metres to the radiator. No baffle in the tank, no airlocks, it runs fine. I just filled it and that was it. Had to drill two 5mm holes in the thermostat.
What was the purpose of the holes in the thermostat?

I thought that the flow through the heater circuit opened the Subaru thermostat? Do the holes replace that?

George

helbus Administrator Mad fabricator, paint and body

7,386 posts · joined Sep 2002 ·

#455309
The first time I started it, it started boiling before the thermostat opened. To get some circulation of water over the 4 metre path from top outlet to bottom inlet, the holes allowed enough circulation to allow the water to return warm enough to open the thermostat once the water heated up. It works anyway.

I haven't got the heater hose connected yet, and I am certain the loop hose I have on it has a kink in it.

I suppose in a perfect situation the thermostat would not need a hole in it, but there are a number of cars that have that original. The setup has worked on 43 degree days, idling, highway, city driving, hills, so It has passed quite a number of situations with no untoward effects.
EJ22 into Bay Microbus - Finished project build thread- click on this spot here for info

1303Steve Scirocco Rare

8,650 posts · joined Aug 2002 ·

#455398
Hi

Im going to use a stock 2.1 wasserboxer one on my car and a recovery overflow bottle as well, I cant stress how important it is to get the reservoir bottle as high as possible.

With the hole in the thermostat, it only needs to be tiny, it allows coolant to equalize each side of the thermostat when filling.

My old 1302 used a 2.1 reservoir.

Steve


GeorgeL Officially Full-On Dubber

231 posts · joined Feb 2006 ·

#455778
Helbus wrote:The first time I started it, it started boiling before the thermostat opened. To get some circulation of water over the 4 metre path from top outlet to bottom inlet, the holes allowed enough circulation to allow the water to return warm enough to open the thermostat once the water heated up. It works anyway.

I haven't got the heater hose connected yet, and I am certain the loop hose I have on it has a kink in it.

I suppose in a perfect situation the thermostat would not need a hole in it, but there are a number of cars that have that original. The setup has worked on 43 degree days, idling, highway, city driving, hills, so It has passed quite a number of situations with no untoward effects.
From what I understand, the Subaru thermostat needs water flow from the heater hose to open at all. Several sources have stated that if you simply plug the heater hose the engine will definitely overheat. Putting a small hole through the thermostat might be a way to get some water to flow, but considering the amount of water in the hoses and radiator it seems that it would take a long time for warmed water to make its way back to a thermostat if all flow went through a small hole. I'm surprised that you are getting such good results, but this probably reflects my lack of understanding of Subaru's system.

Seems strange to open the thermostat with water that has already gone through a heater core, but that is apparently the way Subaru does it.

George

subaruboxer Officially Full-On Dubber

292 posts · joined Jan 2005 ·

#456026
Hi George,

i have no holes in my thermostat and it works fine. It is important to have a full flow heater circuit. The heater valve should stay open at all times. If no heater is installed, the two two heater hoses have to be connected not blocked off!!!!!

Jörg

GeorgeL Officially Full-On Dubber

231 posts · joined Feb 2006 ·

#456200
subaruboxer wrote:Hi George,

i have no holes in my thermostat and it works fine. It is important to have a full flow heater circuit. The heater valve should stay open at all times. If no heater is installed, the two two heater hoses have to be connected not blocked off!!!!!

Jörg
My plan is to install a heater core in series with the stock heat duct, using the rear seat vents for intake and front vents for outlet. I'll have some manner of in-line fan to move the air when I want heat. I don't intend to run a valve in the line at all.

George

GeorgeL Officially Full-On Dubber

231 posts · joined Feb 2006 ·

#457492
subaruboxer wrote:Hello George,

if you want to read more about Subaru cooling check this

http://www.rs25.com/forums/showthread.php?t=40373

Jörg
Interesting article. High points are Subaru's recommendation for the use of "cooling system conditioner" (Subaru's euphamism for "stop leak") and a reasonable explanation of the heater bypass circuit. He didn't really cover the need to keep the heater circuit open to avoid overheating, though.


George

subaruboxer Officially Full-On Dubber

292 posts · joined Jan 2005 ·

#457589
Hi George,

he has not to mention the open heater circuit, because it is a website for regular Subarus, not for conversions. I found interesting, that Subaru recommends the use of destilled water. I always did that, i am into Motocross for more than 20 years, and the twostroke engines of the MX-bikes are in need of destilled water, too. And what is good for my motorcycle can´t be bad for my car´s engine.

Jörg

GeorgeL Officially Full-On Dubber

231 posts · joined Feb 2006 ·

#457788
subaruboxer wrote:Hi George,

he has not to mention the open heater circuit, because it is a website for regular Subarus, not for conversions. I found interesting, that Subaru recommends the use of destilled water. I always did that, i am into Motocross for more than 20 years, and the twostroke engines of the MX-bikes are in need of destilled water, too. And what is good for my motorcycle can´t be bad for my car´s engine.

Jörg
Distilled water doesn't have the contaminates and corrosive properties that tap water can have, particularly heavily chlorinated urban tap water.. I wouldn't use anything but distilled or DI water!

I raced motocross too, but all my bikes were air-cooled. Showing my age there...

I find it interesting that the "conditioner" (stop-leak) is recommended for the "Phase II" EJ25. Is that the single-cam version?

George

subaruboxer Officially Full-On Dubber

292 posts · joined Jan 2005 ·

#458068
Hi George,

as far as i know the Phase II EJ 25 is from 1995 to the end of 1998. The single-cam version (SOHC) came with the 2000 model at the end of 1999, at least here in Germany. Please correct me if i am wrong.

Hi richbaker78,

i think you got it right, the system gets rid of air by running through the expansion tank.

Jörg

GeorgeL Officially Full-On Dubber

231 posts · joined Feb 2006 ·

#458074
richbaker78 said:
this is the set up I was going to run with a t25 exp. tank as they are quite large and cheap.
http://www.weirdstuffwemake.com/weird/stuff/automotive/vanagon/cooling_system.html

im not sure exactly what you mean about flow through system? can anyone enlighten me? Does it simply mean that water flows through the exp. tank and thus looses any air at this point in the system.
By "flow through" (my term, there may be a better way of putting it) I mean a system where the entire flow from the engine coolant outlet goes through the header tank before going to the radiator, as is done in Helbus.

This is in contrast to a system where the header tank is either teed into the main cooling line with a single hose or placed in the heater loop like in richbaker78's setup.

The advantage I see in the flow through setup is that it has the greatest chance of capturing air bubbles, since almost all the coolant goes through the tank with every circuit. The downside is that the tank has to be big enough to slow the fluid enough to prevent the air from being entrained again and carried on into the radiator.

I'm interested in the restriction you put in the heater loop. Is that the way Subaru does it or is that your own innovation? How is the restriction sized?
subaruboxer said:
as far as i know the Phase II EJ 25 is from 1995 to the end of 1998. The single-cam version (SOHC) came with the 2000 model at the end of 1999, at least here in Germany. Please correct me if i am wrong.
I'm having a hard time reconciling the DOHC/SOHC/PhaseII terminology. I know that Subaru has gone back and forth between SOHC and DOHC. I know that the current EJ25 in use in Japan is a SOHC, and that is likely the engine I will be using as it is current and seems to be best suited to my bus.

Perusing the Subaru Japan website it is interesting to note that most of the current models are using 2.0 engines, with only the upscale models getting 2.5s.

GeorgeL Officially Full-On Dubber

231 posts · joined Feb 2006 ·

#458087
Here's another header tank setup, this one flow-through with a bypass for the heater.

http://www.outbackmotors.com/radiator%20setup.jpg

This is only a schematic, but I think that the line to the radiator should be shown at the bottom of the header tank so it won't pass air along.

Keep in mind that Outback Motorsports is primarily concerned with sand cars. For a car where the coolant level is checked every 50 miles their system is great. They don't show an overflow bottle, and the tips on their site speak of running the header tank about half full. I think for a street-driven car an overflow bottle should be provided that will purge air and keep the header tank completely full.

George

GeorgeL Officially Full-On Dubber

231 posts · joined Feb 2006 ·

#458344
subaruboxer wrote:Hi George,

here is a link with an explanation of PhaseI and II.

Pretty interesting stuff for you as a bus guy.

Jörg

http://www.rjes.com/html/phase%20i%20_%20ii%20subaru%20engines.htm
Yeah, that is good stuff, I sure wish that that outfit would fiinish their web site, though.

Reading their FAQ, it seems that the phase 1/phase 2 transition took place around 2000, but there are some "odd" engines that had phase 1 heads on phase 2 cases. If I stick to 2.5 SOHC engines from 2001 on it is certainly a phase 2.

Interesting bell housing on that site as well. I'd be tempted to use this rather than an adapter,, but the increased size of the bell housing requires body mods on a bay, and moves the engine forward about 2cm, which makes the tight intake even tighter.

George

richbaker78 Casual Dubber

38 posts · joined Oct 2005 ·

#458585
hi guys - cheers for the explanation on flow thru - that makes a lot of sense I guess - and I thought I had made my mind up on the set up!! dammit back to the drawing board- more indecision.

Im afraid I cant take credit for the cooling site or the conversion etc it was just something I found that I was gona use so cant shed any further light on it all at the moment like size of restriction etc.

As for RJES - Im using one of his housings in an early bay (mines the turbo one in the pictures section) as you will see from pics it does req a fari bit of surgery to get the turbo lump in and also a conversion to hydraulic clutch which turned out pretty simple. Nicely engineered soultion all in tho. I dont see it presented much extra work to fitting with an adaptor to be honest.

GeorgeL Officially Full-On Dubber

231 posts · joined Feb 2006 ·

#458886
richbaker78 wrote:hi guys - cheers for the explanation on flow thru - that makes a lot of sense I guess - and I thought I had made my mind up on the set up!! dammit back to the drawing board- more indecision.
Yes, there are a lot of options and I haven't settled on one yet either.

Before I saw the flow-through idea I was thinking of a header tank with one hose that was teed vertically into the highest point in the main coolant loop. Bubbles that passed that point would rise into the header tank but there wouldn't be any flow through the tank to speak of.

Downside to this is that bubbles might stay entrained in the coolent flow and miss the side trip into the header tank, particularly during start up when you are trying to purge the system of air. The flow-through seems to fix that.

OTOH, if the flow through the header tank is too great it might entrain air from the tank.

I think the best solution might be a flow-through vertical cylindrical tank with inlet and outlet at the bottom, outlet below the inlet. This would do a good job of separating bubbles and keeping them separate. Combined with an overflow bottle to keep the system full I think that this would work well. It would also make plumbing the system easier with the stock water outlet, eliminating the need to engineer a sharp elbow to turn the flow around. Since I'm working on a '71 I don't have a top engine hatch to open, so I want the header tank right next to the rear access door so it can be filled and checked easily.

George

[ Edited on Feb 24, 2006 by GeorgeL ]

richbaker78 Casual Dubber

38 posts · joined Oct 2005 ·

#458980
Ive got a 70 and no hatch either originally - but I used a cut down t25 hatch adn surround - best thing i ever did - gives awesome access and even looks pretty 'standard' . Well recommend this - it saves you hours of cursing and makes engine ins adn outs a pleasure.

PLus it changes your header tank location options :-)

GeorgeL Officially Full-On Dubber

231 posts · joined Feb 2006 ·

#459057
I've been tempted to graft in a top access hatch, but my bus is original and I really hate to do anything that can't be easily undone. OTOH, the hatch is hidden under carpet... tempting...

Maybe I'd be better off to just find a '73 with a blown engine! 🙂

George