fletch's question thread

[Mitch Wright]

I believe the Porsche reservoir that Pete is using uses a single cap but has divided compartments. Tilton also makes a smaller version of the reservoir that I used.

[fletch]

Looks like I ventured into an area of varying opinions! Let me say, I appreciate hearing both/all sides of the issue. It helps inform decision making to know what others have thought and done. So, thank you. I'd like to put a few of my thoughts out there for further consideration. I'm not hoping to change anyone's mind, except maybe my own.

Seems to me that Subaru made a smart choice in splitting the braking system into RF/LR + RR/LF. This maintains some sort of balance under compromised braking. In failure situations, compromises must often be made. They also put the redundancy where it mattered - splitting the pressurized side in its entirety, while still using a single brake reservoir. The pressurized side is far more complex and is... wait for it... under pressure! The low pressure portion of the OEM brake system is minimal, consisting of the tank and its connections to the MC ports. Certainly, relocating the reservoir results in additional opportunities for failure - custom adapters, hose connections, etc. Anecdotal evidence from a few forum searches indicates leaks in the low pressure portion are possible.

My planned solution is to relocate the OEM brake reservoir and construct custom hose adapters for mating with the MC and the reservoir. Given my remaining build time there would be months (years?) of time for static testing of the relocated reservoir and hose connections. I plan to retain the OEM fluid level sensor so that during operation I’d get an indication of low brake fluid.

Initially I thought I’d just leave the clutch reservoir alone - buried under the dash - since it’s much less likely I’d need to fill/bleed that system. Then I thought about combining the reservoirs. Hence my initial question.

Having thought it through a bit more I’ve decided that the one condition I’d like to avoid is having the car locked in gear with only the e-brake available. I’m not confident the drum brakes will be able to bring the car to a stop in a controlled fashion when it’s in gear.

Which leads me to the conclusion that I’ll be keeping the brake and clutch reservoirs separate. I might or might not relocate the clutch reservoir and still don’t know if I’ll choose one or two reservoirs for the brake system. Anyway, those are my thoughts at this point. Thanks again for yours.

[Bob_n_Cincy]

They also put the redundancy where it mattered - splitting the pressurized side in its entirety, while still using a single brake reservoir.

If one side of the Subaru system fails, it will totally drain the reservoir that feeds it. The Subaru brake master cylinder has a divider in the reservoir to maintain the redundancy through the low-pressure side.

Bob

[lance corsi]

I doubt a single reservoir with no separator would pass inspection in Ohio. I wouldn’t run mine without discreet chambers. Had a clutch slave cyl leak down once, far from home. Made it home clutchless but at least I had brakes!

[fletch]

The Subaru brake master cylinder has a divider in the reservoir to maintain the redundancy through the low-pressure side.

Wait. Really!??! I did not realize that. Now I'm wondering how the level sensor works with the split chamber. I'll have to look it over more carefully tonight.

[fletch]

It's very difficult to tell, but looks like there is a vertical divider in the OEM brake reservoir that extends from the bottom about 1/3 of the height of the tank. Also the level sensor is a float style and only sits inside the (fore|aft) portion of the tank. (I can't remember which, but will update this post when I look it over again.) I'll probably end up cutting apart one of these to see what's inside since I've got two and one of them is super dirty.

UPDATE:
The OEM reservoir has two structural ribs that connect to the float retainer, but allow fluid to flow between all 3 sections of the tank. The ribs and slots are pretty easy to see in the top view. There is also a divider in the OEM reservoir. It sits below the MIN level in the tank, just forward of the rear structural rib. This is easier to see in the side view.

IMG_3177.JPG
IMG_3178.JPG

Thinking I'll relocate the factory reservoir and preserve the separation between fore/aft sections by using separate hoses to the MC. Still unsure about relocating the clutch reservoir, but I am convinced I won't combine it with the brake reservoir.

[fletch]

I know these are the bee's knees, but I'd rather not spend $200 on a tool I'll use once or twice. Does anybody have one they want to loan, rent or sell?

[fletch]

I know these are the bee's knees, but I'd rather not spend $200 on a tool I'll use once or twice. Does anybody have one they want to loan, rent or sell?

Gonna ask once more before I pull the trigger and just buy one.

[DSR-3]

I don't know what tool you are referring to, but if it's bender, I have one for loan. If it's a flare tool, they can be had for less I think. You can get good pre-made lines in a variety of lengths, in fact I have some "leftovers".

[Hobby Racer]

Gonna ask once more before I pull the trigger and just buy one.

I've used many other flare tools, and they were all terrible. Just get the Eastwood one, you won't regret it. I've never had a bad connection using it.

In fact its on sale right now for $179!

[fletch]

I've used many other flare tools, and they were all terrible. Just get the Eastwood one, you won't regret it. I've never had a bad connection using it.

In fact its on sale right now for $179!

Just bought it.
https://www.eastwood.com/professiona...ring-tool.html

[fletch]

Having just pressed my replacement rear wheel bearings into the hubs, I realized I may want to have longer studs. Did I just waste a set of wheel bearings?
Who's installed longer studs and under what circumstances should I plan to do likewise?
As ever, thanks for the insight!

[Mitch Wright]

I use my Eastwood tool often on projects money well spent and by far the best I have used for brake and fuel lines.

[Bob_n_Cincy]

Having just pressed my replacement rear wheel bearings into the hubs, I realized I may want to have longer studs. Did I just waste a set of wheel bearings?
Who's installed longer studs and under what circumstances should I plan to do likewise?
As ever, thanks for the insight!

I installed Longer ARP studs without disassembling the hubs. (I think M12 x 1.5 threads) I might have gone through the ABS sensor hole to install them.

I used https://www.summitracing.com/parts/ARP-100-7717


studs.jpg

PS: I think better studs are essential for any autocross or track driving. While autox our donor Impreza the front aluminum rims would get hot from brake rotor heat. This expanded the rims and stretch the studs. This would cause the lug nuts to seize as the thread pitch didn't match the lugnut. The only way to remove the wheel was to snap off the studs. After this happened 4 or 5 times. I went with the arp studs. no problem ever since.

[fletch]

I installed Longer ARP studs without disassembling the hubs. (I think M12 x 1.5 threads) I might have gone through the ABS sensor hole to install them.

I used https://www.summitracing.com/parts/ARP-100-7717


studs.jpg

PS: I think better studs are essential for any autocross or track driving. While autox our donor Impreza the front aluminum rims would get hot from brake rotor heat. This expanded the rims and stretch the studs. This would cause the lug nuts to seize as the thread pitch didn't match the lugnut. The only way to remove the wheel was to snap off the studs. After this happened 4 or 5 times. I went with the arp studs. no problem ever since.

Oh wow. Good to know. I never would have guessed.

[fletch]

Anybody have trouble aligning the rear lower trailing arms (from the donor) to the spindles? The two "ears" on the trailing arm are nearly parallel to the centerline of the car, while the spindle mount points are canted inward. We wrestled them into place, but this doesn't seem optimal.

[fletch]

I've been thinking a bit about the heater lines and have an idea that makes sense to me but is different from what others have done. I’m wondering if I’m missing something and wanted to run it by you all.

In AZPete's write up, for example, he ran the Subaru heater loop up to the front of the car to supply his Vintage Air heater core instead of using the FFR loopback hose. I’m thinking that we’ve already got lots of hot engine coolant up at the front of the car, namely the main coolant loop to the radiator. Consequently, I’m thinking about installing the FFR heater loopback hose and teeing off the main radiator loop to supply the heater core. Basically piping the heater core in parallel with the radiator with an on/off valve in the heater loop.

In that arrangement we won’t even need a “bypass” valve to maintain coolant flow since the radiator loop will always be flowing. Like I said, I’m wondering if we're missing something in our proposed design. The only thing we can think that might be an issue is insufficient flow through the heater core since the radiator pathway may be lower “resistance” (pressure drop).

What do you guys think of this approach?

[Ajzride]

I'm not too sure of the dynamics of it, if the heater core would pull enough flow out of the radiator line to do any good. But if you do what you are talking about you would definitely not have any flow through the heater core until after the engine was completely warm and the thermostat opened up. Using the dedicated heater lines you start getting flow as soon as the engine fires up and it gets warmer with the engine.

[Bob_n_Cincy]

I've been thinking a bit about the heater lines and have an idea that makes sense to me but is different from what others have done. I’m wondering if I’m missing something and wanted to run it by you all.

In AZPete's write up, for example, he ran the Subaru heater loop up to the front of the car to supply his Vintage Air heater core instead of using the FFR loopback hose. I’m thinking that we’ve already got lots of hot engine coolant up at the front of the car, namely the main coolant loop to the radiator. Consequently, I’m thinking about installing the FFR heater loopback hose and teeing off the main radiator loop to supply the heater core. Basically piping the heater core in parallel with the radiator with an on/off valve in the heater loop.

In that arrangement we won’t even need a “bypass” valve to maintain coolant flow since the radiator loop will always be flowing. Like I said, I’m wondering if we're missing something in our proposed design. The only thing we can think that might be an issue is insufficient flow through the heater core since the radiator pathway may be lower “resistance” (pressure drop).

What do you guys think of this approach?

I'm not too sure of the dynamics of it, if the heater core would pull enough flow out of the radiator line to do any good. But if you do what you are talking about you would definitely not have any flow through the heater core until after the engine was completely warm and the thermostat opened up. Using the dedicated heater lines you start getting flow as soon as the engine fires up and it gets warmer with the engine.

Like AJZride said. In the OEM setup, the heater core loop flows before the thermostat opens. The heater in an OEM Subaru work great as the heater get all the heat and doesn't send hot water to the radiator until the heater core can't cool the engine enough. If you plan on driving it in the cold, I would plumb oem. But I would add a small (1/8") bleeder hose from the top of the heater core to the degas tank to prevent air pockets in the heater system.
Bob

[fletch]

AJ, Bob,
Thank you for the comments. I'll use the OEM heater loop.

AZPete, curious to know if you used a bleeder hose for your heater loop. I know you had a bleeder valve, which I assume you only used during first fill of the coolant loop. Bob's bleeder hose would operate continuously.

[AZPete]

You are correct that I only used my bleeder valve in the heater line during the initial bleed. Bob's suggestion to run a hose shows what we all knew previously - that Bob has more experience and probably more brain cells!

[fletch]

Alright, my 818 brain trust...
When our donor arrived from the auction, the bleeder port on the radiator (passenger side top) was snapped off. We need somewhere to connect a bleeder hose and are considering options.
1) Drill out the hole & JB weld in a hose barb.
2) Seal the hole and tap a hole for a hose barb somewhere closer to the cap.
3) Seal the hole and replace the cap with a non-pressure relieving one for a cap that always flows through the overflow port.

We like #3 because it's easy to seal the hole and our chances and getting a decent tap elsewhere in the radiator seem pretty low. Is there a problem with removing the pressure relief cap since we always planned to use a 1.3 bar cap, cap the overflow port, and retain the 0.9 bar cap on the degas tank?
Thanks everyone for the input.

[Ajzride]

can You restate #3, I’m not quite clear on your intent.

[fletch]

can You restate #3, I’m not quite clear on your intent.

Sure. Sorry to be confusing.
The hose barb off the top passenger side of the OEM radiator has been snapped off. For #3, we'd seal that hole. Then replace the OEM pressure relief cap on the radiator with a cap that flows continuously and has no pressure relief function. The coolant that flows through that cap will exit the radiator through the normal overflow port. We would repurpose the overflow port on the radiator for the bleeder hose. The engine coolant loop should still be protected by the pressure relief cap on the degas tank. Hope that's clearer. If not, say so.

[Bob_n_Cincy]

Sure. Sorry to be confusing.
The hose barb off the top passenger side of the OEM radiator has been snapped off. For #3, we'd seal that hole. Then replace the OEM pressure relief cap on the radiator with a cap that flows continuously and has no pressure relief function. The coolant that flows through that cap will exit the radiator through the normal overflow port. We would repurpose the overflow port on the radiator for the bleeder hose. The engine coolant loop should still be protected by the pressure relief cap on the degas tank. Hope that's clearer. If not, say so.

I am doing #3 right now and it is not working out very well. All the "blanking caps" I can find don't seal well enough.
My radiator is aluminum, so I'm going to weld on an aluminum bung like this one.
https://www.summitracing.com/parts/sum-220071

[fletch]

I am doing #3 right now and it is not working out very well. All the "blanking caps" I can find don't seal well enough.
My radiator is aluminum, so I'm going to weld on an aluminum bung like this one.
https://www.summitracing.com/parts/sum-220071

Thanks, Bob. In principle, there's nothing wrong with #3, but execution might be a challenge. I'm working with the OEM radiator and was planning to modify the OEM cap. It sounds like I might end up having the same issue as you. Especially since the overflow portion of the OEM cap is only designed to seal against atmospheric pressure. One would think the aftermarket blanking caps would be better at that. If we proceed with option 3 and our cap leaks, we may need to epoxy our own blanking plate in place. We'll probably go ahead with 3 and keep in mind that we might need to find an alternative later.

Just a curiosity... Given your experience, would you expect the leakage problem to show up during go-kart stage, or only after a long stretch of driving, or only under hard driving, etc.?

[Bob_n_Cincy]

Thanks, Bob. In principle, there's nothing wrong with #3, but execution might be a challenge. I'm working with the OEM radiator and was planning to modify the OEM cap. It sounds like I might end up having the same issue as you. Especially since the overflow portion of the OEM cap is only designed to seal against atmospheric pressure. One would think the aftermarket blanking caps would be better at that. If we proceed with option 3 and our cap leaks, we may need to epoxy our own blanking plate in place. We'll probably go ahead with 3 and keep in mind that we might need to find an alternative later.

Just a curiosity... Given your experience, would you expect the leakage problem to show up during go-kart stage, or only after a long stretch of driving, or only under hard driving, etc.?

WIth all the connection in the cooling system, I recommend pressure testing the whole system before go kart stage. I have one of these testers, but I don't know if there is an adaptor that fits the degas tank. https://www.amazon.com/Radiator-Pres...%2C137&sr=8-17

I learned the hard way, I blew of a 1-1/4" hose at a track day that killed the rest of the day. I would test too at least 30 psi.

[fletch]

What are folks doing for their AWIC loop? Are you using a degas tank + overflow reservoir w/ dip tube? Fully closed system?
We're working on the plumbing of pretty much everything over the next few weeks and want to be sure we don't miss anything.

[grabera7]

I was just talking to someone on Facebook that Y branched their AWIC lines into their turbo and AWIC and then Y branched them back after. I’m curious if this is common?

[Bob_n_Cincy]

What are folks doing for their AWIC loop? Are you using a degas tank + overflow reservoir w/ dip tube? Fully closed system?
We're working on the plumbing of pretty much everything over the next few weeks and want to be sure we don't miss anything.

My AWIC System in NON-Pressurized. I will start at my bosch pump, located at the bottom of the firewall, in front of the right rear wheel. It is down low in the system to make it self priming.
Out of the pump, I ran a 3/4" hose to bottom port on a sirocco radiator in the front of the car. Keeping the hose even with the bottom of the car the best I could.
I went into the bottom port of the radiator so the pump would push any air out the top radiator hose. That 3/4" radiator hose runs back (right side) to the AWIC cooler on the engine.
The output of the AWIC cooler runs down to the input of the bosch pump.

To get any air out of the system, I have 2 small 1/4" hoses connect to the AWIC cooler. One at the high point and on at the lowest point. Then I have a 1-quart reservoir tank mounted a little higher than the AWIC Cooler.
Top of cooler goes to top of the tank to take any air out of the system. The bottom of the tank goes to the bottom of AWIC cooler to replenish fluid. I run standard antifreeze solution to prevent freezing and corrosion.

Do not connect awic system to the engine coolant system. The engine system is around 200 degrees. The awic is below 100 degrees.

tank2.jpg tank.jpg tank3.jpg tank4.jpg

[Frank818]

Brian you've seen mine, hopefully you took pix of it.

I have a 3-gal tank up front and the cooler at the rear. The cooler is slightly higher than the tank, which is not very good when you put water in the system, it's more complicated but the tank helps a lot to push the water up.
I have no pressure issues, been using that exact setup/parts since 2006!

[fletch]

Wondering if - no, deeply, sincerely hoping that - we can run heater & A/C hoses here. Can anyone confirm this is OK?
IMG_3372.jpg

[Ajzride]

I think that will be in the way of the door, but I'm not positive.

[aquillen]

Here is an image of that area with the door in place from one of my posts. The arrows and circle were for purposes explained there, not for your question. But you can see what is in that area. I don't think you can get hoses where you have them, have to stay to the left of the main chassis square tubing and get under it, not over it.

[fletch]

Ack. Thanks Art. Better to fix it now.

[Ajzride]

For the AC, I used a pair of 90 AN fittings to come out of the unit and go straight into a bulkhead in the firewall. Once you get past the firewall there is much more room to work.

Grab a 10-pack of 5/8" 90s, it will make your life much easier routing in that area (at least for the heater).

https://smile.amazon.com/Eldon-James...s%2C154&sr=8-4

I'm also working on a modification to the heater circuit and the radiator return circuit that I hope will make it tremendously easier to fill and bleed the system with a heater core in place. Even with a vacuum system I'm struggling to get it to fill and burp the radiator, block, and heater core all at the same time. I should have it complete in the next 10 days and will let you know how it worked out. It wouldn't affect the routing near the firewall where you are now.

[fletch]

Thanks AJ. I'll look forward to what you have to say about bleeding the coolant & heater loop. We do have a front mount gas tank so space on the other side of the firewall is also at a premium. Once you get through the firewall are you routing down through the mousehole?

[fletch]

Here is an image of that area with the door in place from one of my posts. The arrows and circle were for purposes explained there, not for your question. But you can see what is in that area. I don't think you can get hoses where you have them, have to stay to the left of the main chassis square tubing and get under it, not over it.

Art, where's your coolant loop? I don't see it in that picture.

[Bob_n_Cincy]

I have 4 lines going through the right side mouse hole. 1.25" tube to the radiator. Two 3/4" hoses to my AWIC exchanger ane on 5/16" hose that bleeds air from the top of the radiator. Where you have the hoses, it will block the side sail from going on.

mousehole.jpg

[Ajzride]

Once you get through the firewall are you routing down through the mousehole?

Yes, through the mouse hole.

Attachment 125106

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