hanzonn

Greetings Friends,

There are lots of topics on this subject, but I haven't been able to find the answer I'm looking for. I'm planning on doing a brake overhaul on my '89 G-model (replacing pads, caliper rebuild, replace brake lines, flush the entire system), w/the exception of the master cylinder. I bought a pressure system that will force the fluid into the reservoir & into the rest of the system. I could hire a German Profi, but they're crazy expensive. So, my questions are:
- I've read to "pressurize" the system by depressing the brake pedal 2" - and to keep air from entering. Since I'm flushing the entire system, is this necessary?
- Should I be doing one caliper at a time (rebuild, replace line, bleed)? Or...
- Can I just drain or flush the entire system, do the work, then worry about re-filling/bleeding when the repairs are completed & the parts are back together?

Bottom line, I'm just looking for the proper sequence to be as efficient as possible and to keep air out to the system. BTW, this won't be a one-day project; more likely over a week or several weekends, so the disconnected lines are likely to be open & exposed for that time (in garage).

Danke Schoen, Greg

psychoideas

I'd rebuild all of the calipers, reinstall with whatever new components you are changing, and then fill and bleed the system starting with the caliper farthest from the master cylinder.
But that's just me.

Amber Gramps

^^^ Yep.

You will likely want to do the hard lines as well as the soft lines on the trailing arms. They were about $8.00 US when I did mine a couple years ago.

Go ahead and take everything apart, let all the fluid drain out, and refill when you have it all back together. Start your fluid flush and fill in the back and make sure you keep your reservoir full or you will have to start over.

A cool tip I picked up here is to change the color of fluid you are using so you know for sure you have flushed the system. On my other cars I always watch for the fluid to flow clear or to loose the milky haze that is a sign of moisture in the fluid.

If you have a vacuum system you don't need a helper. I would rather have a helper and do it the old fashion way.

Put a pcs of clear tubing on the bleeder valve and run it into a clear soda bottle.

One guy pushes the brake pedal firmly, the other guy opens and closes the bleeder valve on the caliper quickly (before the pusher reaches the floor). Repeat this as many times as it takes. When the fluid is bubble free and the same exact color as the new fluid you move on.

It's a simple job if you have good tools. Always use a box end on the bleeder valve and a line wrench (flare nut wrench) on the brake lines. The fittings are soft and need the extra bite of the line wrench.

(For some reason I have a recollection of using my crows feet too...)

Enjoy.

KaiB

Yep to all the above, but...

I dislike the manual bleed/flush method. It is FAR too easy to over extend the master and cause havoc there. Far better off with a pressure jug like the $50 Motive.

Steve Weiner-Rennsport Systems

What he said.

I've seen FAR too many ruined master cylinders from "manual" bleeding than anything else. If one doesn't have a pressure bleeder, replace the MC before you start the process now, otherwise you will do it all again later and waste a few litres of fluid.

hanzonn

Greetings All,

Thanks for the great advice. Looks like the most efficient method is to take everything apart & repair everything in on fell swoop.

Danke

hanzonn

I finally got around to replacing (vs. rebuilding) the rear calipers on my '89 3.2. Now on to bleeding - I bought the Motive pressure bleeder, filled, connected, & pressurized it. Brake fluid promptly leaked out of an overflow tube from under the left front of the car. Nowhere in the directions or on any of the posts does it mention this. I've heard that you may have to pinch off the overflow line? Help is appreciated! Thanks, Greg

Amber Gramps

Pinching that line sounds logical.

I adapted a vacuum pump and canister to bleed my brakes via the bleeder valves on my recent reassembly.

KaiB

yep, pinch it.

Otherwise, well, you know...

Amber Gramps

Well look at that. My current project is brake related:

http://forums.pelicanparts.com/porsc...t=930+calipers

Mark Salvetti

Although slow, our earlier cars can be bled by gravity if you don't have something like a Motive to pressurize the master cylinder. You don't even need a helper:
https://rennlist.com/forums/performa...-bleeding.html

I rebuilt the calipers on my SC and then refilled and bled the system using this method. Worked fine, even for a track day. To speed things up I pre-filled the calipers with brake fluid before reconnecting the brake lines.

Mark

Ed Hughes

Hi Greg, I guess too late now, but the depressing of the pedal is just enough to take up "slack" on it. I did it with a 2 X 4 wedged from the front of the seat to the pedal. When you unhook the brake lines, it will keep you from having a bunch of fluid drip out-you'll just get a few drips at each corner.

Hope things are well!

jellonailer

Not sure on an 89 but on my 964 there is also a clutch bleed nipple on top of the gearbox that I think is on the same brake system. I bleed that too.

I wouldn't even begin to think about doing this without the Motive pressure bleeder either.

85911

What is the issue with manual bleeding? References in posts are to extending the pedal too far. The Porsche manual says for manual bleeding "Have helper pump pedal several times. Then hold pedal down firmly on last pump.
Open right rear caliper bleeding screw and allow fluid to expel. Close bleeder screw."

There is no mention of a critical pedal travel distance.

Thanks.

Ed Hughes

Porsche is also in the parts business. You run the very real risk of tearing the internal seal in the MC with full pedal travel.

I bled many a time with SpeedBleeders and short <1/2 pedal strokes. Never push pedal to the floor.