Brake Check Valve

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Brake Check Valve

Postby Todzilla » Tue Jan 02, 2018 6:22 pm

Greetings all

Apologies if the answer to this already exists within the forums; my initial searches didn't reveal much.
I am planning on replacing my GT BMC and booster with the larger STI items. I have acquired a booster/BMC from an SG9 Forester, however I do not have the check valve. I have finally found a vendor who is willing to supply the required part without an STI VIN, but I want to make sure I am ordering the correct item. Is anyone able to provide details of the check valve/hose assembly? Or suggest a comparable part that will work?

Todd
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Re: Brake Check Valve

Postby bigBADbenny » Tue Jan 02, 2018 9:18 pm

viewtopic.php?f=6&t=34980

DIY parts translation info ^
Once you have the p/n you can check useage info across the models.


My brembo’s work great with the stock 2.5t Gt-b booster, are you upgrading or doing service replacement?
I researched it a little & post 104 sums it up, stock brakes may be a little more responsive albeit with a stiffer pedal feel.
http://legacygt.com/forums/showthread.p ... 077p7.html

So from research, some Subaru boosters have an integrated check valve, others have the valve integrated into the brake booster vac line/hose, visible as a slight hump & sleeve on the hose.
So you just need the hose for that model booster and then to make an airtight termination at the inlet mani end, either direct or via a stepped adapter preferably crimped.

But if I just hit my bookmarked opposed forces parts link, go to braking, master cylinder diagram:
http://opposedforces.com/parts/legacy/e ... tration_2/
Choose the mc assy at #9...
http://opposedforces.com/parts/info/26401AG000/
It’s common to 6mt Gt-b, WRX & STi, but the booster isn’t...
So follow the useage info link eg to a WRX or STi model and bingo, there’s various choices of the booster vac hose with the integrated check valve.
http://opposedforces.com/parts/impreza/ ... _cylinder/

Given booster vac lines are very hard, a custom line & check valve might be the go pending fitment...
You’d probably go an 08+ Wrx hose as that & Postfl Gt share the same plastic inlet mani.

Since the OF info kinda craps out as regards the hose p/n’s I’d just do the exact same search’s on eg Partsouq...

However as the lib Gt mc is same as STi & the STi booster is used across every Impreza model, I fail to see the point of the exercise unless I’m missing something big :)

However for those following along iirc member hyrax upgraded his 2.5i, I’ll dig up the link...
https://www.google.com.au/search?biw=32 ... qt6zpuj3So
& tuner ThrottleHappy aka kido, Matt, McMatt etc does a trick in the tune to increase idle or cruise vac to up the pedal somewhat :P
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Re: Brake Check Valve

Postby Todzilla » Wed Jan 03, 2018 11:12 am

Thanks for the all the linked resources, Benny - very useful! I remember previously reading the thread on the Legacy forums you linked to - some good info there.

The reason for my investigating fitment of an STI MC is to attempt to improve the mushy pedal feel on the GT. I have so far replaced the stock rotors with DBA T3s, HEL braided lines, decent fluid and Dixcel pads; while I am very satisfied with the system's stopping power, the pedal feel up top still annoys me and from reading through forum threads, others seem to have achieved decent results with the larger bore MC.

I wish the larger STI MC mated up to the Liberty booster, but unfortunately the bolt holes are not in the same location. So I need to confirm the use of an inline check valve before swapping the entire booster/MC assembly.
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Re: Brake Check Valve

Postby bigBADbenny » Wed Jan 03, 2018 12:26 pm

I’ll take a peek at A: my engine bay and B the partsouq listing which should have the p/n...
Was the sg9 booster or mc from a turbo?
Is that the combo you’re going with?
Did you use eg a power bleeder?
Considered a master cylinder stopper?
Or the ThrottleHappy tune?
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Re: Brake Check Valve

Postby bigBADbenny » Wed Jan 03, 2018 9:37 pm

So hyrax got his mc & bb from an my05 blob Sti...
He claimed it has the largest bore size of any Subaru.
viewtopic.php?f=10&t=15482&start=60#p254194
Yet the same mc p/n is used across all gen2 imp, gen2 foz and gen3 lib variants...
So could he be referring to a JDM spec c mc?

Anyhow, I’d firstly put an mc stopper on the car to tame the extra firewall flex imparted via your other braking mods :)

Vendor corgiwerkz may be able to make you one, failing the usual sources :)

And spongey brakes is symptomatic of incorrectly bled brakes or old fluid.

Also how is abs activation? Does it work at all?

Vac hose p/n’s:
26140FE00
(Inlet mani end)
26140FE020
(booster end)
26144FE000
(alloy pipe)

Via: https://partsouq.com/en/catalog/genuine ... &gid=10126
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Re: Brake Check Valve

Postby Todzilla » Sat Jan 06, 2018 3:57 pm

Thanks for digging up that info, Benny - much appreciated. In addition to what you sourced, I also found reference to part nr 26140FE131, allegedly the vac hose containing the check valve which the LegacyGT guys have transplanted into their existing vac hose for the booster/MC replacement.

From what I understand, specific year STI components are a Bosch-supplied booster (with inline check valve) and 17/16" MC (with inline check valve), while the GT has a different booster (with integrated check valve) and 15/16" MC. I'm happy to be corrected on the above, however.

I fully intend to fit a MC stopper, and I'm due to replace fluid as well. I'm satisfied that the fluid replacement was performed correctly last time (with use of a power bleeder), but of course it's worth confirming if this is my issue. I certainly don't lack braking effectiveness, in fact I'm quite impressed at how well it pulls up (ABS is triggered) - it's only a matter of pedal feel for me.

While I'm not married to the idea of fitting the new booster, I am interested to see how much difference it makes to braking feel, and should a stopper and a bleed fail to satisfy me then it's a relatively inexpensive thing to try... provided I can obtain the correct components.

Also, a retune is definitely in my future...
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Re: Brake Check Valve

Postby bigBADbenny » Sat Jan 06, 2018 5:02 pm

A part number for the big bore mc would be the thing...
I’ll have to try dig up a jdm spec c parts list, iirc it’s a hell of a job requiring Russian or Japanese translation...
The way in being a spec c specific part number... maybe a gearbox or turbo, for example...
As regards the mc stopper, I’d say the type to suit a stock mc won’t fit the big bore mc, just bear that in mind before proceeding :)
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Re: Brake Check Valve

Postby bigBADbenny » Mon Jan 15, 2018 9:41 pm

Here’s a good thread on the subject...
http://legacygt.com/forums/showthread.p ... 81067.html
I’m googling the p/n pages using s203 as keyword :P
JDM STi:
https://partsouq.com/en/catalog/genuine ... &gid=10126


.
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