GT3 master cylinder ugprade for early 996s & Boxsters
2 Attachment(s)
Finally managed to sort this out. Net/net is you can convert your master cylinder to the GT3 part if you have a 996 or Boxster made before Sept. 13, 1999 but it will require simultaneous conversion to the updated brake booster, brake pushrod mechanism, and firewall seal parts. Documenting here for the benefit of others' future reference.
Parts needed: Your choice of one of these brake boosters with the updated design: 2003 996 C2 Brake Booster (TRW or Porsche Genuine options): 996-355-923-00 or 2004 996 GT3 Brake Booster (Porsche Genuine only): 996-355-923-90 And one each of these: 997 GT3 master cylinder (TRW or Porsche Genuine options): 997-355-910-30 Firewall seal update set: 000 043 204 66 Updated brake push rod: 996 423 165 05 Threaded bushing: 996 423 307 00 Pin: 996 423 308 00 Tools needed: 1/4” ratchet with extension 3/8” ratchet with extension 1/2” ratchet Torque wrenches covering values 7.5 ft/lb, 17 ft/lb, and 36 ft/lb T45 Torx bit (for the long brake booster bolts) H5 Hex bit (for intermediate piece positioning bolt) 10mm “mini” combo wrench (for the small nut that holds the two pushrods together) 16mm combo wrench (you will need two 16mm wrenches for the brake pedal to pushrod bushing and pin removal) 17mm combo wrench 19mm combo wrench 6mm 1/4” socket (or flathead screwdriver to tighten the bellows clamp) 13mm 1/4” socket 16mm 3/8” socket 22mm 1/2” socket 11mm flarenut wrench for hydraulic unit brake line connections 13mm flarenut wrench for master cylinder brake line connections Vernier calipers Small carpenter square (or vernier calipers & straightedge) to verify brake pedal height to throttle measurement Rubber lubricant or tire mounting paste. I used Super Lube Silicone Lubricating Grease that I had laying around. Tips/potential hangups:
In total, I’d rate this 3.5 out of 5 wrenches on the Pelican scale. This is a pretty messy job with the inevitable brake fluid mess and requires a fair bit of disassembly/reassembly, so if you’re unsure you should leave it to a pro. Given you’re messing with the heart of the braking system, which I’m always extra cautious about working on anyway, remember doing it wrong could result in serious injury (or worse) to you or someone else if you get it wrong. Silly I have to say this, but I'm obviously not responsible or liable for either and I'm posting this for educational purposes only. Feel free to ask any questions here or DM me and I'll be glad to help! https://cimg7.ibsrv.net/gimg/rennlis...3a990fe2ac.jpg Nearly disassembled but ABS hydraulic unit and intermediate piece still need to be fully removed. https://cimg8.ibsrv.net/gimg/rennlis...b106546b69.jpg New firewall seal and updated brake pushrod being fitted. https://cimg0.ibsrv.net/gimg/rennlis...b86e32d116.jpg Verifying clearances and test fitting before completing reinstallation. https://cimg3.ibsrv.net/gimg/rennlis...ca1c930983.jpg Fully reinstalled and brake fluid topped up ready to bleed. https://cimg5.ibsrv.net/gimg/rennlis...bda213137b.jpg Updated firewall seal and bellows fitted. |
Thanks for the update! As far as I understand, an updated brake booster and push rod is not required to use the 997 GT3 MC. Were you having issues with just the 997 GT3 MC?
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It depends on when your car was made. Porsche did a mid-model year cutover in Sept of 1999 to an updated booster, pushrod, and firewall seal design. If your car has the older parts the GT3 MC is not a direct bolt on and you will need to update the others in order to make it work.
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This needs to be a sticky. I have a March 1998 build and this is a mod I will likely do in the future.
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Bumping this thread. Find it timely.
My car was built on 3/19/1999. I am going to do the upgrade. Looks like I will have to get the extra parts. Bummer. |
Glad you found it useful.
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Are there differences between these brake boosters? one is better than another? Regular C2 one is readily available and much cheaper.
2003 996 C2 Brake Booster (TRW or Porsche Genuine options): 996-355-923-00 or 2004 996 GT3 Brake Booster (Porsche Genuine only): 996-355-923-90 This one from the bay seems to include all the parts needed. https://www.ebay.com/itm/TRW-Brake-B...cAAOSwuSZe1-~t |
Originally Posted by 911ren20
(Post 16867773)
Are there differences between these brake boosters? one is better than another? Regular C2 one is readily available and much cheaper.
2003 996 C2 Brake Booster (TRW or Porsche Genuine options): 996-355-923-00 or 2004 996 GT3 Brake Booster (Porsche Genuine only): 996-355-923-90 This one from the bay seems to include all the parts needed. https://www.ebay.com/itm/TRW-Brake-B...cAAOSwuSZe1-~t I've got the same questions. What are the advantages to this upgrade? Thx! |
I didn't have to do **** on my 99 boxster. bolted the 997 gt3 MC right in. Better pedal feel for sure.
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Originally Posted by Quadcammer
(Post 16868238)
I didn't have to do **** on my 99 boxster. bolted the 997 gt3 MC right in. Better pedal feel for sure.
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great write up . Thanks for this
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Originally Posted by 911ren20
(Post 16868503)
Does your car have the last 6 digit Vin numbers before 620337 or after?
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Bringing this back from the grave...
I see that some of you with late build 99's have been able to do this as a bolt on. My 99 is newer than the cuttoff vin. For those who've done it - is it literally just unbolting the old MC and dropping in the new 997 MC? No new newer 996/996 booster required? This is on my spec boxster. 997 Thanks! |
Originally Posted by 911ren20
(Post 16867773)
Are there differences between these brake boosters? one is better than another? Regular C2 one is readily available and much cheaper.
2003 996 C2 Brake Booster (TRW or Porsche Genuine options): 996-355-923-00 or 2004 996 GT3 Brake Booster (Porsche Genuine only): 996-355-923-90 This one from the bay seems to include all the parts needed. https://www.ebay.com/itm/TRW-Brake-B...cAAOSwuSZe1-~t Is this all for improved pedal feel and ostensibly better stopping power? |
Better feel, and I believe more rear bias
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