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STI Master Cyl. and Brake Booster SWAP SUMMARY for LGT


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As per request from swine, I started this thread to break down everything I've read from this thread . Hopefully the mods can sticky this thread

 

http://i.imgur.com/mQkmH.jpghttp://i.imgur.com/UPdqH.jpg

 

WHY DO THIS SWAP?

I'm sure most LGT owners feel that their brake pedal is subpar and inadequate compared to other cars they've driven. Many have tried replacing oem pads, rotors, Stainless Steel lines, Master cyl. brace, and even a brembo swap or Big Brake Kit, only to find that the brake pedal feel still has not improve much.

 

Finally, swine and many others who's done the STI brake master cyl. + brake booster swap can confirm that doing this mod is single-handedly the most effective way to get a firm and confidence inspiring braking feel like that of an STI.

 

SUMMARY:

 

1) You need a 04-05 STI Master Cylinder and Brake Booster (~$80 used on ebay)

 

2) You need the check valve from the STI.

If your STI master cylinder/brake booster didn't come with the vacuum hose. You can buy it from the dealer for ~$18. (Part #: 26140FE131)

Take it out of STI hose and shove it in the LGT hose with a BIC pen(cap off). This will not be easy but with enough patience, you can shove it in.

Make sure the bullet side of the check valve goes towards the engine and the flat side goes towards the firewall.

 

#7 from the diagram is the vacuum hose with the check valve inside

http://i.imgur.com/kr5Ic.gif

 

 

3) Bench bleed the MC before install or use a power bleeder.

 

4) Make sure the rod length on the new STI booster is the same as the LGT booster. (It will cause brake lockup problems if it's not the same)

 

5) Install everything and bleed the brakes.

 

For those who have done this mod successfully, feel free to add any tips or useful info for this swap.

Edited by maniaxzero
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Do you have P/Ns for the STI MC and Booster? And not sure where the check-valve fits in the description above. It doesn't show on the diagram, and I don't see it in the picture, so any help is appreciated.
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Do you have P/Ns for the STI MC and Booster? And not sure where the check-valve fits in the description above. It doesn't show on the diagram, and I don't see it in the picture, so any help is appreciated.

 

I dont have the P/N for the STI MC/Booster but here's a link for the part

http://www.ebay.com/itm/05-06-07-SUBARU-IMPREZA-WRX-STI-OEM-BRAKE-BOOSTER-MASTER-CYLINDER-GD7-EJ257-/290677186936?pt=Motors_Car_Truck_Parts_Accessories&vxp=mtr&hash=item43adb5e178#ht_1904wt_1163

 

As for the check valve, it's basically inside the hose, you have to cut open the STI hose, take out the STI check valve and stick it in your oem legacy vacuum hose. Reason being that the legacy hose is 4x longer than the STI hose.

 

//Correction from atchipmunk:

On the Legacy, the brake check valve is not built inside of the booster. It is external to the booster, but uses a different type of mounting than the STi booster. The LGT check valve is on the end of the hose and is press-fit into a rubber sealing grommet on the booster itself. On the STi Booster, there is a 3/8" Hose connection for the vacuum line.

Edited by maniaxzero
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great thread and great tips that i had to learn the hard way. (adjusting the booster rod to the appropriate length for example, mine was to long and caused gradual brake lock up to eventual complete lock. Shortened the rod by 3-5 turns and i was good to go).
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Also, the reason why this is necessary is because the OEM legacy brake booster has the check valve built inside the booster. Where as on the STI Booster, it's located inside the vacuum hose. So when you swap to the STI setup, you also need to put the check valve on the vacuum hose. Hope that makes sense

 

Well, that's not exactly correct. On the Legacy, the brake check valve is not built inside of the booster. It is external to the booster, but uses a different type of mounting than the STi booster. The LGT check valve is on the end of the hose and is press-fit into a rubber sealing grommet on the booster itself. On the STi Booster, there is a 3/8" Hose connection for the vacuum line. I'll take some pics of both to show what i'm referring to...

 

I'll actually be doing this swap either this week or next and going to take a lot of pictures and measurements and will be writing a DIY Walkthrough of the whole process. I'm not going to use the STi check valve though. I'll be using an inline brake check valve from either a Toyota Supra or Nissan S13 or S14...

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One other thing for anyone looking to do this swap...

Depending on where you get your parts from, in addition to bench bleeding the M/C you might also want to consider flushing the s**t outta your master cylinder as well. Most of us will probably buy these parts from a recycler or off of ebay, etc. The problem with these places is that they pull the parts and store them. Depending on how they're stored, crud and contamination can develop inside...especially since brake fluid is hygroscopic and absorbs moisture from the air. When I got my STi M/C there was A LOT of contamination inside of it...almost looked like they stored the damn thing outside in the rain. I used a LOT of brake fluid to flush out the thing MULTIPLE times and you shoulda seen the crap that came out of this thing...definitely not stuff you would want to push into your brake system. Just doing a regular bench bleed wouldn't have done it either. Anyway, I took a pic or 2 of how I flushed it so when I do my DIY Walkthrough i'll post those as well...

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Well, that's not exactly correct. On the Legacy, the brake check valve is not built inside of the booster. It is external to the booster, but uses a different type of mounting than the STi booster. The LGT check valve is on the end of the hose and is press-fit into a rubber sealing grommet on the booster itself. On the STi Booster, there is a 3/8" Hose connection for the vacuum line. I'll take some pics of both to show what i'm referring to...

 

I'll actually be doing this swap either this week or next and going to take a lot of pictures and measurements and will be writing a DIY Walkthrough of the whole process. I'm not going to use the STi check valve though. I'll be using an inline brake check valve from either a Toyota Supra or Nissan S13 or S14...

 

You're absolutely correct about the location of the check valve on the lgt booster. I just popped open the engine bay and saw what you were referring to.

 

The information I had before was from reading through the other thread and making a summary out of what i've read. I havent done this swap yet.

 

Thanks for the correction.

 

One other thing for anyone looking to do this swap...

Depending on where you get your parts from, in addition to bench bleeding the M/C you might also want to consider flushing the s**t outta your master cylinder as well. Most of us will probably buy these parts from a recycler or off of ebay, etc. The problem with these places is that they pull the parts and store them. Depending on how they're stored, crud and contamination can develop inside...especially since brake fluid is hygroscopic and absorbs moisture from the air. When I got my STi M/C there was A LOT of contamination inside of it...almost looked like they stored the damn thing outside in the rain. I used a LOT of brake fluid to flush out the thing MULTIPLE times and you shoulda seen the crap that came out of this thing...definitely not stuff you would want to push into your brake system. Just doing a regular bench bleed wouldn't have done it either. Anyway, I took a pic or 2 of how I flushed it so when I do my DIY Walkthrough i'll post those as well...

 

Really looking forward to that DIY Walkthrough and how you properly flushed the MC..

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Yeah, originally I was thinking about using the stock LGT check valve and running the side that usually goes into the booster into a hose and then running that hose to the STi booster. Problem is that that end is larger and would require a 1/2" ID hose, where the STi booster port is for a 3/8". I could make I work with some step-down adapters, but in the end it would look a bit hobbled together (read: ghetto-rigged). I'm a stickler for things looking "right" so that's kinda outta the question.

Anyway, I'll post a pic of how I flushed my M/C when I get back home to my computer later...

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For those that have done the conversion, Did you find that after setting the rod at the same length as the stock booster, the engagement point for the brakes was further down?

 

I just finished up and took it for a test drive. It is certainly a way better and more solid feel...but the pedal has to travel further (maybe and inch or two) before anything happens. I'm afraid to lengthen out the rod to remedy that for fear of the brakes locking up like others have experienced.

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Ok, flushing the M/C is merely a matter of pushing clean fluid through the M/C to push out the dirt and crud, etc. You could use the traditional bench bleeding technique and keep filling the reservoir and pushing fluid through the M/C till no more dirt, etc. comes out. Since my STi M/C didn't come with the reservoir, I couldn't do it that way. So, I found a container that just fit the M/C in it...filled it with brake fluid and sat the STi M/C in it...

http://i277.photobucket.com/albums/kk56/atchipmunk/05%20LGT%20Wagon/MCflush-1.jpg

 

Then it was just a matter of depressing the piston in the M/C to suck in and push fluid through the M/C. The fluid in the container would obviously get dirty from the fluid being pushed through the M/C and I would just empty it and replace the fluid with fresh brake fluid until no more crap came out. I actually had to refresh the fluid at least 7 or 8 times before no more crap came out. Anyway, that's it in a nutshell. Unfortunately, I forgot to take any pics of how dark the fluid got while I was doing it since my hands were covered in brake fluid, etc. I can tell you that it was pretty ugly and i'd hate to have pushed that crap into my brake system had I only done a bench bleed to fill the M/C with fluid...

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For those that have done the conversion, Did you find that after setting the rod at the same length as the stock booster, the engagement point for the brakes was further down?

 

I just finished up and took it for a test drive. It is certainly a way better and more solid feel...but the pedal has to travel further (maybe and inch or two) before anything happens. I'm afraid to lengthen out the rod to remedy that for fear of the brakes locking up like others have experienced.

 

I didnt match mine when I installed, say I can't comment specifically on your issue. However the cleavis is very much an adjustable tool, and you should be tuning it for your expectations.

 

I hesitantly suggest don't let the brake lock up scare you. It starts very very mild and gradually progresses as the car is driven. It's readily apparent what's happening and not even the least bit dramatic. I would try 3-4 full turns out and see what you think. I can still feel alittle slack in mine that I could adjust out(not as significant as yours), but I am more then content and just going to let it ride.

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Wonderful thread.

 

Somewhat related, after destroying a few brake line male hex heads, I bought this:

[ame=http://www.amazon.com/gp/product/B00004SBBE/ref=oh_o03_s00_i00_details]Amazon.com: Vise-Grip 4LW Locking Wrench with Wire Cutter: Home Improvement[/ame]

 

Haven't used it yet, but I hear it is an excellent way to remove brake lines when a flare wrench will just round out the hex head.

 

Looks like this:

http://ecx.images-amazon.com/images/I/41v3IO4MfDL._SL500_AA300_.jpg

[CENTER][B][I] Front Limited Slip Racing Differentials for the 5EAT now available for $1895 shipped, please inquire for details! [/I][/B][/CENTER]
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