[Cloud9...68]

I picked up a couple of cans of brake fluid to bleed my brakes from a very reputable shop in town, and the owner showed me a blow-up diagram of the 968 braking system that gave me some pause. He told me that getting all the air out of all the bends and twists of tubing, particularly around the ABS control unit, is no small task. And I have to admit, when I tried bleeding them last year with a Motive pressure bleeder, I didn't come close to getting all the air out, and had to have it finished professionally. Yet many on this forum have stated that the procedure is very easy with the Motive unit, so I'm wondering what I'm doing wrong.



Could someone please tell me:



- Is there a bleed fitting around the ABS control unit (I forgot to ask, as my head was spinning as I was looking at the maze of lines in this car's system)?



- Are there any other fittings in the system I need to be aware of and bleed?



- Is it better to start with the inside bleed screw on the calipers and work outward, or vice versa, or does it matter?



- Any other suggestions?



I have a DE the weekend of July 14/15, and the last thing I need is a spongy brake pedal! Thanks.

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[PorscheDude]

I think it is best to start farthest from the master (longest line, passenger rear) working your back to the shortest line (driver front).

You may need to bleed the clutch as well.

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[flash]

yes, farthest first, then to the nearest



make sure you have AT LEAST 11psi in the bleeder - i usually run about 15



check it frequently for pressure and fluid

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[Cloud9...68]

Thanks, but I understand the part about starting from the fitting farthest from the master. My question more pertains to the tubing around the ABS unit. I'm going to be replacing the bias valve, which I understand connects to the ABS control unit, with one from a Turbo Cup (per the recommendation from Pete of RS Barn and others), so I'm going to have the right front fender liner off. What, if anything, do I have to do to get the air out of the mass of tubing going into and out of the ABS unit? Or does the pressure from the Motive unit take care of that?



Sorry for all the questions (about this and in my other post about the clutch line/master/slave cylinder repacement), but with a DE coming up, I want to make sure all this stuff is safely squared away.

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[flash]

the bleeder took care of that when i did it on mine



p.s. - be prepared to cuss and yell and make a mess - that thing is a royal pain to get the fitting lined up

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[Cloud9...68]

[quote name='flash' post='37896' date='Jul 5 2007, 08:17 PM']the bleeder took care of that when i did it on mine



p.s. - be prepared to cuss and yell and make a mess - that thing is a royal pain to get the fitting lined up[/quote]



<img src="/forum/images/smilies/968/dry.gif" class="smilie" alt="" /> OK, thanks for the warning. I'll be sure to make sure the kids (mine any any neighbors) aren't within earshot...

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[rustech]

Don't be afraid to let the fluid flow at speed out the calipers either, that will ensure the air moves along. I never have issues bleeding the system, but am also not afraid of passing a little extra fluid through. Good luck.



BTW, you'll love the bias valve.

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[Cloud9...68]

OK, now that I'm finished with the clutch line/master/slave cylinder replacement (Flash, you were right, it really wasn't very difficult), I'm ready to tackle the brake bias valve. One immediate question - did those of you who have replaced these remove the brake lines on the ABS control unit in front of the bias valve? It's going to be very hard to get a wrench on the valve behind these lines, but I'm a little hesitant to take all these lines off (although, since I'm going to have to bleed the system afterwards anyway, this may not be a big problem). Given that these are are hard metal lines, how easy is it to move them out of the way once they're disconnected? If so, how did you do it? They all seem to be connected to the fender from behind.



Thanks in advance - I'm a little hesitant to start randomly disconnecting brake lines before I hear from some of you who have done this before.

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[flash]

i did not remove those lines - yes, it was a royal pain, but i did manage it

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[Cloud9...68]

I had to interrupt the project to run a few errands, but in the short time since that I have fiddled with it, I found that a wrench will fit on the upper fitting between the surrounding brake lines, so not removing the lines does appear to be the most logical way to go about this. I sprayed some penetrant on the upper and lower fittings to loosen things up as much as possible, and will tackle the removal of the old bias valve after dinner. Looks like another project that just requires a lot of patience.

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[Cloud9...68]

Piece of cake! The brake bias valve replacement, that is (haven't bled the clutch and brakes yet - that's tomorrow's project). Yes, the bias valve is sandwiched pretty tight between the ABS regulator and the brake line that goes into the top of the valve, but I came up with a simple trick that made the job VERY easy. I simply removed the nut holding the ABS unit to the black flange that's attached to the chassis, and then carefully, using a pair of pliers, bent this flange far enough back to clear the thread that the nut went into. This allowed me to lower the ABS unit just enough to provide the extra clearance I needed to easily place the new bias valve into its home on the top of the ABS unit.



In addition, I removed the vertical brake line on the right side of the ABS unit, to the right of the letter "H" which is stamped on the unit. This gave me room to turn both the 19 mm wrench to tighten the bias valve to the ABS unit, and the 11 mm wrench to tighten the brake line to the top of the bias valve. Once I figured this out, it took me all of five minutes to install the new bias valve. If I had thought of it sooner, it would also have made removal of the stock bias valve much easier as well. When I was done installing the new bias valve, I simply bent the flange back, and re-installed the securing nut. The flange suffered no damage as a result of the slight bending I did.



The picture below was taken after I had removed the ABS control unit securing nut, bent the flange back, and removed the vertical brake line. It's kind of hard to see because the flange is black, but you can see how I bent the flange back if you look closely at the area in the picture just below the thread at the bottom center of the ABS unit.



I hope this helps others who are planning to do this mod. I can't wait to get the system bled so I can test it out, though I suspect I won't feel much of a difference until I get out to the track next weekend.

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[Cloud9...68]

I should have asked this before starting, but how many cans of brake fluid do you guys typically go through to flush the entire system using a Motive power bleeder? I've already used up almost a whole can just on the right rear wheel (which of course is the one farthest from the reservoir), so it doesn't look like the two cans I bought is going to be enough. Thanks.

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[JWahlsten]

I typically use only one can for the whole system. If I have done some major repairs, like a master cylinder, it will take more. I don't think I've ever seen more than two used.

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[bob blackwell]

Me too, one liter has always been enough. You are right, the other calipers will take less fluid to bleed than the right rear. Good luck, Bob Blackwell.

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[flash]

make sure the screw is only "cracked" loose, and not wound out too far - 1/4 turn should do it

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[Cloud9...68]

Got it done with just under two cans. So, I guess I'm more wasteful of the brake fluid than you guys, but at least I know my fluid is clean!



One thing that surprised me is that despite the fact that I had to open the lines to install the turbo cup bias valve, and consequently filled the effected lines with air, resulting in a pedal that initially went all the way to the floor, I hardly saw any bubbles, even from the front right brake. The pedal is very firm now. I'll make sure to stop hard enough to engage the ABS a few times on my test drive(s), and the re-bleed the right front again if needed.



Thanks for all the advice on this - everything went very smoothly overall. I was lucky to be able to do all of this (new clutch master/slave cylinder and stainless braided line, along with the aforementioned brake bias valve) during a rare-as-hen's-teeth cool spell in Austin in July. And just when they're having all the Save-The-Earth-From-Cooking-Itself (or whatever they're calling it) concerts around the world...

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[Cloud9...68]

OK, maybe I'm being too anal here, but after having taken the car for a spin, the brake pedal feels like it might be just a touch squishier than before I did the turbo bias valve install, although it may be just my imagination, as I hadn't driven the car in about two weeks. It seemed to get better as I drove it, though.



I know this is very difficult to convey across the internet, but for those of you who have installed the turbo bias valve, did you notice any difference in pedal feel? Should I just drive it for a few days, and then bleed just the right front brake one last time? As I said before, I saw virtually no bubbles as I beld the brakes, and I sure flushed plenty of fluid through the system.



One thing I didn't do was open the bleed screw at the cylinder itself. I didn't think this was necessary, since I didn't open anything up near the master. Is there any reason I should open this bleed screw as well? Thanks.

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[Mark]

I admit I cheated and had RSBarn do my bias valve this past week while replacing the hoses and both the master and the slave but my pedal is like a rock now. <img src="/forum/images/smilies/968/smile.gif" class="smilie" alt="" />

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[Eric_K]

The valve shouldn't change the pedal feel. You probably still have a little air trapped in the system. If your master has a valve on it, I would bleed it too. I usually get the most bubbles out of the valve on the master.



Eric

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[Cloud9...68]

[quote name='Mark' post='38020' date='Jul 9 2007, 06:43 AM']I admit I cheated and had RSBarn do my bias valve this past week while replacing the hoses and both the master and the slave but my pedal is like a rock now. <img src="/forum/images/smilies/968/smile.gif" class="smilie" alt="" />[/quote]



Just goes to show, when something doesn't appear to be quite right, it probably isn't. My pedal isn't terribly squishy, but it's definitely not "a rock." Next step is to do the bleed valve on the master; from Eric_K's post, it sounds like that could potentially finish it off.



I don't know what it is about me and brake bleeding. I did the whole clutch master/slave/high pressure line replacement, and turbo cup brake bias valve installation, without a lick of trouble on either one, and now I'm struggling with something as trivial as getting my brakes bled. Sheesh!

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