DGI

$224.49 plus free shipping and a lifetime warranty

https://www.fcpeuro.com/products/por...er-99735591030

I was considering doing this to my 1999 C2 (Jan '98 build) but since it may not be as plug and play as I expected, i'll just hold off. I dont track the car anyway. Planning a brake fluid flush soon and figured it would be the right time to do it. Oh well

GVA-SFO

This is still very strange to me. After changing the "break switch", I had about two months of driving, with no "4460 error", and suddenly, just got it again !
(In my case, I have a TRW master cylinder on a 986 (Boxster S), ..that have PSM.
I really love BIG TIME the change in feeling of the brake offered by this mod (TRW large MC). should mention that my 986 has 350mm floating rotors in the front, with monobloc 6 cylinder caliper (Brembo Big brake kit).
I'm not really ready to work back, but really hate to have this error.

@jpurban, did you got any news about the "portless" version, does it fix the problem ? If available, how do we order this MC ?

jpurban

I looked everywhere for a master cylinder with a larger piston AND a design compatible with the Bosch 5.7 system also used on BMW and Audi. Unfortunately, the 25mm piston in our car from the factory is the largest available, as far as I could determine.

So, we're stuck with the "soft" feel of the factory MC if you want your PSM to function.

I bled the snot out of the factory MC and finally got it to an acceptable firmness after an hour of pressure bleeding + traditional pedal pumping. The pedal travels more than I prefer, but I can and will live with it. I'll bet that I ran a liter of brake fluid through the system to achieve the results I have.

I miss the GT3 MC feel, but it is nice that I no longer get the ABS /PSM errors every 30 minutes.

pete95zhn

Solution for the problem: https://rennlist.com/forums/996-turb...r-psm-fix.html

lowpue

finally read this thread....i know what my next mod is when i do a brake flush....thanks Nickshu for sharing

246GTSA

I tried the solution offered by @Flewis763
Very simple and easy install of a JEGS adjustable proportional brake valve (63022) with some new lines from the 997 MC to the JEGS valve, and from the JEGS valve to the ABS pump.
No ABS / PSM warnings and that nice stiff (very little travel) brake feel.
This is on a 2001 Carrera 4
Thank you @Flewis763 great simple idea that allows us to use the 997 MC.

fyeun001

Hello,

Great post! I am performing the swap as we speak. Does the reservoir simply just pop off? Thanks in advance!

Franco

cds72911

Yes. It pops into rubber grommets.

thurstonpowers3

So here is my issue so far:

2002 C2 with PSM. 997 GT3 MC, High temp fluid bleed multiple times through whole system. One week into driving the car the PSM/ABS failure lights came on driving down the highway around 60MPH. Turned the car off and back on with no faults returning. Bleed the system again and put 1500 miles on the car with no issue. At the track yesterday and the car has performed flawless for 6 sessions ( 3 for my wife and I each). 4th session comes up for me and the ABS/PSM failure light comes on again down the back straight into turn 4 causing the right front tire to lock up. Does anyone know why the issue would be this intermittent? I am finding others are having the 4460 fault appear immediately or everytime the car exceeds 30MPH but this is not my experience. I just ordered the Jegs proportioning valve and will install that.

246GTSA, Which brake lines did you use to install that proportioning valve as the link shows OP made his own but it appears you used factory lines.

246GTSA

Hi @thurstonpowers3, I had the brake lines made up at a local hydraulic shop that specialises in making hydraulic fittings and brake lines. Took about 1 hour, they had my car and the valve to work with for placement etc. Total cost was about $40.00

thurstonpowers3

Thank you! That is very helpful.

De Jeeper

Any chance u have a colasped soft line or a caliper issue on the corner? U may have an additional issue since the mc has been good for a while.

Cogito_Ergo_Zoom

The most likely culprit is probably the part you changed, the master cylinder, but there's also just the possibility that something else has gone bad, including the ABS/PSM hydraulic unit itself, all which you would want to eliminate to avoid frustration.

Fault code 4460 -- Pressure sensor

Possible cause of fault:
- Short circuit to ground/voltage or open circuit in circuit to control module terminals 25, 26 and 42
- Plug connection on stop light switch faulty (aka brake light switch)
- Adjustment of the stop light switch not OK
- Wiring/ plug connection faulty
- Pressure sensor faulty (replace hydraulic unit)

thurstonpowers3

It has stainless lines and I just replaced the pads recently and the caliper seemed free but I will double check everything. Thank you for the input.

Cogito_Ergo_Zoom

Good news is I've managed to figure out what was required to do the update conversion from the pre-Sept 13, 1999 master cylinder & brake pushrod design to the later one to allow the upgrade to the 997 GT3 MC. I went with the combination of the 997 GT3 mc and the 996 GT3 brake booster. In addition to the later design booster and pedal pushrod this also requires updating some parts at the firewall where the pushrod passes through. I'm just buttoning up the final details and will make a detailed post of what's required to get the job done including part numbers and tools needed later.

One of the last things to do is make the final brake pedal height adjustment, so I have a quick question for those that have already installed the GT3 mc, especially for those that are tracking their cars: how much did your brake travel change under heavy braking? Did you find the resting pedal height too high and need to make adjustments to the pushrod length to compensate?

With the bore size difference the pedal travel will be reduced of course and with all the new parts installed and not having adjusted anything the brake pedal is sitting about 28mm above the throttle. FWIW, Porsche specs 45+5mm, but that setting is likely assuming and compensating for the longer stroke of the smaller C2 mc bore.

Any feedback or even better direct measurements like below from those that have this done already would be appreciated.