|
|
|
|
| Author |
|
|
Registered
Join Date: Aug 2004
Location: Houston, TX
Posts: 895
|
Early 19mm Spongy Brake Pedal
I replaced my 19mm M/C about 2 years ago and 8K miles ago. It came with a 1 year warranty. All calipers were rebuilt at that time and flex lines replaced. I remember it having a stiffer feel than prior to rebuild, but not a true completely firm pedal. Pads are Ferrodo 2500 and fluid is Motul 600.
Since then, I have had hot brake fade at DE's 2 times. The system has been bled several times over the past couple years, but I have never regained a firm pedal. Thinking that the flex lines were damaged, I replaced them with the stainless lines. The pads, rotors, fluid were also replaced and I even added the Ti brake shields about 1K miles ago. What's my next move? Rebuild the calipers again? I can't find any leaks. Others have suggested a new Master Cylinder. Some have suggested upgrading to a 23mm M/C. The pedal feel now is: first 1 inch feels like mechanical slop then 2 inches of modulation then 2 inches of sponge - 1 inch at normal leg strength, 2 inches performing leg press.
__________________
Matt 72 911T Targa - Sold Hang up the cell phone. Put down the Latte. Ignore the kids in the back seat. Use your blinker when you want to change lanes. AND DRIVE YOUR Fu@#!NG CAR!! |
||
06-13-2009, 08:49 AM
|
|
|
Registered
Join Date: Oct 2005
Location: Capistrano Beach, Ca.
Posts: 7,235
|
Sounds like a bad seal inside the MC, IMO. You say you "never had a true completely firm brake pedal," which may indicate a bad internal seal from the get-go. Given that you have refurbished the components up to the calipers--and they don't leak--I'd suggest replacing the MC. Hopefully, Bill V will respond as he, like many others, has much experience with the brake system.
__________________
L.J. Recovering Porsche-holic Gave up trying to stay clean Stabilized on a Pelican I.V. drip |
||
|
06-13-2009, 09:06 AM
|
|
|
Registered
Join Date: Aug 2004
Location: Houston, TX
Posts: 895
|
Also, I see a competitor has a "performance upgrade" 23mm direct bolt in M/C available to replace the 19mm. Looks like the 19mm core that has been bored over with 23mm guts... I'm still using the steel M calipers...
__________________
Matt 72 911T Targa - Sold Hang up the cell phone. Put down the Latte. Ignore the kids in the back seat. Use your blinker when you want to change lanes. AND DRIVE YOUR Fu@#!NG CAR!! |
||
|
06-13-2009, 12:33 PM
|
|
|
Registered
Join Date: Mar 2004
Location: Higgs Field
Posts: 22,623
|
What method do you use for bleeding them?
__________________
Jeff '72 911T 3.0 MFI '93 Ducati 900 Super Sport "God invented whiskey so the Irish wouldn't rule the world" |
||
|
06-13-2009, 06:01 PM
|
|
|
Registered
Join Date: Jul 2001
Location: Portland Oregon
Posts: 7,007
|
Hey Matt,
Sounds to me like your MC needs to be replaced, especially if its old...  I'd recommend sticking with the 19mm one as the 23mm version is really only for people using 4-piston calipers that require the additional fluid displacement. Pressure bleeding is the only way to properly bleed/flush these systems.
__________________
Steve Weiner Rennsport Systems Portland Oregon (503) 244-0990 porsche@rennsportsystems.com www.rennsportsystems.com |
||
|
06-13-2009, 06:39 PM
|
|
|
Registered
Join Date: Jan 2008
Location: NJ
Posts: 1,186
|
If you are going to replace it use a 23mm. The 23 will require more pressure for the same brake force, it is like stepping on a brick, but it will not get soft on the track.
__________________
2013 991.1 Carrera S Cab 2004 996 Turbo CAB X50 sold 2003 996 cab 6 speed Sold 1972 RS 3.2 twin plug short stroke crank fire, roll bar, sold DE instructor since 1985 |
||
|
06-13-2009, 06:40 PM
|
|
|
|
Registered
Join Date: Aug 2004
Location: Houston, TX
Posts: 895
|
The M/C was replaced with a rebuilt core at the time. I suppose it's possible it was not a good one from off the shelf.
I usually use the two person method. However, I recently broke down and borrowed a buddy's pressure bleeder, fearing my wife was trying to collect the insurance...
__________________
Matt 72 911T Targa - Sold Hang up the cell phone. Put down the Latte. Ignore the kids in the back seat. Use your blinker when you want to change lanes. AND DRIVE YOUR Fu@#!NG CAR!! |
||
|
06-14-2009, 04:56 AM
|
|
|
Registered
Join Date: Jul 2001
Location: Portland Oregon
Posts: 7,007
|
Quote:
I don't think thats the best place to save money,....... Quote:
__________________
Steve Weiner Rennsport Systems Portland Oregon (503) 244-0990 porsche@rennsportsystems.com www.rennsportsystems.com |
||
|
06-14-2009, 09:45 AM
|
|
|
Registered
Join Date: Aug 2004
Location: Houston, TX
Posts: 895
|
The MC was an OEM piece. I just assumed it was rebuilt. Came in an ATE box with literature, etc... Same unit goes for $230 now, so I don't really feel like I skimped...
I'm going to see what the warranty was. Seems like it was 1 year, which has passed. Yes, I'm going to get a bleeder with this order. Thanks for the nudge. I'll post back after replacement of the M/C with a verdict.
__________________
Matt 72 911T Targa - Sold Hang up the cell phone. Put down the Latte. Ignore the kids in the back seat. Use your blinker when you want to change lanes. AND DRIVE YOUR Fu@#!NG CAR!! |
||
|
06-14-2009, 10:26 AM
|
|
|
AutoBahned
|
re: skimped
That isn't it -- but there is a chance that even a brand new quality m/c will be ruined if the brakes are pumped too enthusiastically for bleeding. That is one reason people pressure bleed - but only one. A $10 garden sprayer maks a fine pressure bleeder -- add a hole to a brake cap and glue an adapter in there; connect the hoses and you are done. When finished spray your garden, or spray stain onto your deck or fence. Buy another $10 sprayer in the winter in 2 years; lather rinse repeat. |
||
|
06-14-2009, 11:53 AM
|
|
