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Discussion Starter · #1 ·
I decided to spend my Sunday installing a 997 GT3 Master Cylinder in my 987.2 Cayman S.

I saw several DIY posts on the Internet and it was a pretty straight forward process. I am however seeking some advice.

The brake pedal after a four corner bleed goes completely to the floor 4-5 times before brake pressure builds enough you can feel something approximating a firm pedal. When I performed the 2 person bleed I did see fluid moving at each corner, but its obvious there's still plenty of air left in the system.

I did see in the instructions that after the first bleed I should take it out to a deserted area and activate the ABS several times to burp the system before performing a second 4 corner bleed. My issue is that I wouldn't describe my pedal as mushy, I'd describe it as not working (as mentioned 4-5 full pumps to really get any pressure in the system).

Now the particular directions I followed did not include a bench bleed (many sets of instruction do suggest a bench bleed). I assumed (right or wrong) that since I was going to have air in the system either way that I'd be able to bleed the assembled brake set up without the bench bleed.

I've seen no leaks around the abs hard lines, or coming out of the brake booster, or around the grommets where the reservoir seats into place.

So my question, do I need to disassemble my installation and perform a bench bleed or is this expected pedal feel prior to 'burping' the ABS? Any advice on completing my project would be appreciated.

(also, I'd been using a two person bleed because I wanted to be thorough, I also have a Motive pressure bleeder as well as a caliper vacuum bleeder. I'm pretty familiar with a regular bleed process though replacing a MC is definitely new for me as is this burping process related to the ABS).
 

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Discussion Starter · #3 ·
did you do the inside bleeder first and then the outside.. right?

Lemon
I actually did the opposite, outside nipple followed by inside nipple. I had thought when bleeding you always when furthest from the MC to closest (RR, LR, RF, LF) and I had extended that concept to the bleed nipples and did outside first.

Is there a reason you'd do inside then outside?

Also, in looking at past articles, I wonder if I should also try to bleed the clutch?
 

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Use your pressure bleeder - full of fluid - and start over on the bleed. I did this for years and it worked great. Make sure the fluid runs clean with zero air in tube. Also bleed the clutch slave if you have a MT, as they share a fluid reservoir.

Cheers,
 

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Ive always done a bench bleed when installing a new MC. Im not sure if it would do any good at this point since you have done a bit of bleeding already. When I installed my GT3 MC it took quite a bit of fluid to get bled properly. Unfortunately for me I was using Motul fluid in prep for a track weekend. Pricey. I would say keep bleeding. Keep doing the 2-man bleed and use a brisk pedal action. You must have a pretty large bubble in there. Always satisfying to finally see it come out. And I think your right, outside nipple first then inside. Thats how I do it anyway. Once the outside port is closed, no bubble will make it over there. When its right you will know. Its a much firmer pedal.
 

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I use the Motive dry pressurized to 2.0 bar or 29 psi as stated in my 'ebay manual'. I'm sure a lesser pressure will work too. I have found that being very patient and just cracking the bleeder enough to get flow works very well. The manual says to start with the outer bleeder first in the usual order rr, lr, rf, lf. Good luck.
 

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I also did a bench bleed. I swapped flex lines at the same time and went around the car twice to bleed the system. I pumped up my Motive (I dont actually put fluid in the motive, i just overfill the bowl a little and refill as needed.) I bled outer first which, as an engineer, made most sense to me. Opened each bleeder a little bit so it was coming out slowly. Then went in the car and gave the pedal one slow stroke. After that, the car felt about the same as before I started. I did a bunch of ABS and felt some funny stuff going on, bled it another round the same way, and got exactly what I wanted.
 

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Cycle the ignition a few times as it seems to cycle the abs pump. The re attempt the two person bleed, maybe with a bit of motive pressure. That should get it. I did the above with mine, minus the motive.
 

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the reason i do inside first is that the brake line hose attaches nearer to the inside hose first than the outside ..


lemon
Not to turn this into a bleed debate, but if you do the inside first, then the outside, the next bubble that comes through will stop at the inside chamber. But to each his own.
 

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Not to turn this into a bleed debate, but if you do the inside first, then the outside, the next bubble that comes through will stop at the inside chamber. But to each his own.
its the opposite.. your bleeding it out.. inside chamber cleared of bubbles first, then outside chamber...

Lemon
 

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You can use a Durametric to cycle each wheel's ABS while bleeding. I did this after a GT3 brake install and it helped but did not totally solve the problem. Using a pressure bleeder per Krokodil's suggestion eventually worked.
 

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its the opposite.. your bleeding it out.. inside chamber cleared of bubbles first, then outside chamber...

Lemon
Nope, unless your bubbles sink to the bottom and go through the cross over tube to the outside chamber. You have to remember, there may be a new bubble coming through the line, as in the case of a new MC.
 

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Outside piston or inside piston first? I don't think it matters. Air bubbles float to the top. What IS important in my opinion is to bleed ENOUGH fluid from the first one you do to purge all old fluid and possible air from the line all the way back to the master cylinder. I try to bleed a good 500 cc from the outside right rear first then can bleed much less from all the others because I then know that the only old fluid remaining is in the lines and the caliper itself. Same with air. It has all been purged in the first bleed. Sombody mentioned using the Motive dry. I do that too but it is VITAL that one refill the reservoir during that first bleed and then again before each caliper. You don't EVEN want to let it run dry. I saw a guy do just that on an RS4 last fall and it took 2 man bleeding and LOTS of Motul to get that corrected. On the other hand , I was using my Motive wet once and had a hose split and pump one litre of DOT 4 into the engine bay of my Audi. Not good. If you ever have that happen, flush it with water quick. I did and saved the paint.
 

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Discussion Starter · #15 ·
Just to close the loop I had a chance to get back under my car again this weekend.

I hooked up the Motive pressure bleeder as someone suggested and waited for my wife to help with the two person bleed process. While I just had the Motive on I did some pumping with all four corners still closed. I have no idea if this did anything but since I had 10 minutes to kill I figured it might work like a bench bleed (albeit the two hard lines that attach to the side are connected and not plugged as they would be in a bench bleed).

We performed the Motive pressure bleed assisted two man process. I went through nearly an entire bottle of brake fluid and was starting to think that maybe I need to remove the MC and start over. Just as I was finishing up the bottle my wife said she could no longer push the pedal all the way to the floor! I hopped in and sure enough I had a mushy pedal that showed signs of resistance. A far cry from the 4-5 full pumps with no resistance before getting a hint of pressure.

Proceeded to bleed the other 3 corners both nipples and the pedal was much firmer than I expected, as I knew I still needed to burp the ABS. The pedal is much firmer engages quicker and has a much better defined end point than the stock MC.

I took the car around to burp the ABS and will definitely complete the bleed next weekend (what can I say I work slow). But the pedal feel is already a substantial improvement over the stock set up for sure. Exactly what I was looking for. I suspect this will be like the SSK I installed last month. At first it feels different and within a few week it feels normal and you can't even remember how the old setup felt. Between the two changes I have crisp tight shifts and now a firm consistent feeling brake pedal.

Thanks to everyone who helped with their suggestions. It was indeed a matter of just bleeding it thoroughly and I think the Motive pressure assist helped.
 

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At tech tactics this past weekend, bleeding order was asked. The Porsche Tech (I don't remember his name) said inside, outside, then inside again. I normally do outside first and have not had any problems.
 
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