Brake Rebuild questions (simple?)
 

I'm getting ready to rebuild calipers, replace the rubber brake line hoses & replace/bleed the brake fluid (on my '72 911) and have a couple simple questions:

1) Have much brake fluid should I have on hand to flush out all the fluid in the system and replace with new?

2) Beyond a pressure bleeder (found a great DIY kit in the tech articles) are any special/unique tools needed or recommended?

3) I've read a number of threads and tech articles but I'll ask again anyway...any tips or hints on any of these procedures? What about rusted connections for the rubber hoses?

Thanks much!

When you remove the calipers you might find the hard metal lines should probably be replaced as well. They have a tendancy to be siezed up and will twist off while you try and remove them from the caliper. Get yourself a set of braided steel lines to replace the rubber lines.
What I do is buy a basic cheap brake fluid to use during the rebuild but not for use during the flush and bleed process. You will need at least 2 pints. You might try Ate super blue and that way it is easy to tell when the new fluid has arrived at your caliper. I would suggest you remove the reservoir and clean it up before putting new fluid in. I just replaced my m/c and was surprised by the gunk built up on the bottom of the reservoir.

For me, re-building the calipers was easier than getting them off. Compressed air works great from removing the pistons. I am sure you have read the tech articles but make sure you block off the opposing piston when you use air. Also - make sure you keep your fingers out of there when doing it. After I dismantled my calipers, I soaked them overnight in parts cleaner and used a wire brush on them. They cleaned up nicely and best of all - the improved breaking is an amazing improvement!!

Use new rubber lines - the braided steel lines are dangerous because they cannot be inspected. If you use them at all, try to get TUV approved ones - or at the VERY least, DOT approved ones & replace them every year or two. There are numerous threads on this.

I also like the blue/amber fluid alternation described above. Only Ate lets you do this, but they make a good fluid - DOT 4-200.

I'm sure there is a tech article or book chapter that explains these procedures - what resources do you have on hand or have read? (i.e. what is your level of expertise and preparation on this work?).

Generally, you will want:
- small box end wrench (7 mm IIRC)
- catch bottle & tubing
- pressure bleeder (old pump sprayer w/ drilled and fitted brake reservoir cap is what I use)
- Brake Cleaner sray can(s)
- brush to clean out caked in brake dust
- old screwdriver or pad puller
- hammer
- 4 mm pin punch
- pad spreader or old, thin pad and pry bar(s)

To Check the Rotors:
- Dial Indicator & Holder
- micrometer (I cheat and make multiple measurements with a vernier caliper).

To Rebuild Calipers:
- rebuild kit(s)
- lid from jar of Coleman's Mustard (I used a pick and my fingers, but the ironic cleverness of the Mustard jar lid is too great for me to resist, so I acquired one for next time - search on that term for the thread - it is used to push the seal ring down into the bore)
- Turkey Baster Bulb (mark it DANGER - BRAKE FLUID) - use this to remove bulk old fluid from the m/c/.
- Pick (to remove piston seal)
- {quote:} * Unisilikon TK 44 N 2 Porsche # 000.043.117.00 is the preferred assembly lube for the calipers
factory assembly paste for the internal o-rings/pistons. There are many assembly "lotions" on the market, Porsche's stuff is the best. It not only aids assembly, it speeds up the break-in process. The Porsche assembly paste is Klüberfluid 9 R 100 and manufactured by Kluber Lubrication. The seal kits for the 964 and 993 come with a ketchup packet of the stuff but I'm not sure if that is the case with the seal kits for earlier models. $30 at Pelican (telephone them)

http://www.hillmanimages.com/912/brake_pistons.html

http://www.pelicanparts.com/techarticles/911_caliper_rebuild/911_caliper_rebuild.htm


- Take a look at the rear parking brakes while you're in there...


- Flare Nut Wrenches for lines
- Torque wrench & appropriate sockets, wrenches, and etc. to remove caliper.
- pbBlaster or Kroil (not WD-40) AND start spraying anything that looks rusty or corroded with white or grey stuff (even a little bit) right NOW. Spray and tap the joints with a small metal hammer or wrench etc. 3-4x per day.

I might have 2 cans of fluid if I were doing the whole thing - open one at time so the other ones will stay fresh. Do the Fronts, drive the car until the pedal feels right, then do the Rears - don't do all 4 at once.

Chamfer edges of new pads before installation. Don't use that nasty anti-squeal goop.

I suspect there a lot of other tips spread thru various threads - somebody should collect them all in one spot. That public spirited citizen could be you!

Here is a technique I use with the compressed air. 1/4" pieces of plywood inserted as shown allows the pucks to pop out far enough to remove by hand but not too far so only one side pops out and the other stays.

Also included a another version of a "high tech specialty tool" to help install the rear piston dust boots.

http://forums.pelicanparts.com/uploa...1182191797.jpg
http://forums.pelicanparts.com/uploa...1182191777.jpg http://forums.pelicanparts.com/uploa...1182191817.jpg

Good Luck

Thanks to you all for the responses. Every little tidbit of information is VERY helpful!

Sub'd. Just bought my parts and brakes ironically just started squealing a bit...

If you have S calipers I have 2 usable pistons you can have. Two of mine were pitted so I got stainless ones. Currently I have removed and cleaned the fronts and replaced the rubber lines so that's all I know so far. Great timing for your thread.

If no air compressor, then you can get the pistons almost all the way out by using the pedal - take the caliper off & put some plywood between the pistons - press carefully on the pedal....

Others have used grease guns, bike pumps, & who knows what else...

Here is one thread link:

Dust Boot seal Caliper problem;
http://forums.pelicanparts.com/porsche-911-technical-forum/305475-caliper-problem.html

I did not do a caliper rebuild but I did pads not too long ago and got some good local advice.

There is a lot of debate between rubber and SS lines. The local tech geeks around here (Sacramento) recommended the Stop-Tech SS lines. I used them and they are beautifully put together.

I also used ATE Blue, one can.

My power bleeder failed, Pelican took it back quickly and without question. This left my 12 year old son and the technique I used with my dad. It/he worked great and he felt included in the process.

I used Porterfield R4-S pads and I liked them so much I also put them on my Mercedes.

I recommend buying a GOOD quality flare nut wrench.

I twisted off a short hard line and my local dealer had one in stock for $10. So be careful and note the GOOD flare wrench, that's how I know.

To compress the pistons I use a couple of small blocks of wood and woodworking C clamps. The kind with the wooden screw handle that allow you to creep up on the compression slowely.

Make sure you have a very good plan for pad seating procedures. The Stop-Tech website had a description that worked very well for me.

Good luck and enjoy the project.

I'd avoid mineral-based solvents inside the caliper although outside should be pretty safe. Dunk the entire caliper in hot soapy water, rinse with clean water and blow dry until all moisture is gone. Keep hands as oil-free as possible when assembling the pistons and seals. Use rubber lube or equivalent to assemble the pistons. I think it was John Walker who might have suggested using Dow 111 under the dust boots.

Don't end up buying a new master cylinder following manual bleeding. Pump the pedal only halfway to floor (use a stop to prevent excessive travel) or use gravity or pressure bleeder.

BTW, gravity bleeding will only consume 1/2-1 liter to change/bleed the entire system. Don't waste resources.

Sherwood

I just rebuilt mine completely a couple months ago, it was not difficult at all. Here's my observations:

You'll need compressed air to blow the pistons and cleaner out of the calipers. Those pistons really pop - carefull! I used some pieces of pine board to catch them and the board got dented - deeply. Keep your fingers out of there.

I submerged my calipers in paint thinner for a couple days to loosen the grime, then I wire brushed them clean. It's very messy, do this outside on some newspaper.

Don't split the calipers, just reach in there and clean up the cylinders with a red scotchbrite pad and some brake cleaner - they should be clean of any corrosion and residues. Some staining may remain, but they should be clean and smooth. Same with the pistons. Don't drop those, they are precision machined and dropping onto concrete may ruin them.

The rebuild kit goes in easily. I used silicon brake lube to put the pistons back in - helped make it easier. I was able to seat the dust covers with a couple 4" C-clamps and some scraps of wood, silicon lube made this easier, too.

I buttered the backs of the pads with orange anti-squeal and let it dry before assembling - much less messy.

You'll need 12" channel lock pliers to wrestle those front dust caps off. I cleaned out all the old grease with solvent and repacked the bearings while I was in there with a synthetic blend bearing grease.

Either do one caliper at a time or make detailed sketches, take pictures, etc. so you know how they go back together. I used a paint pen to make reference marks, that helped a lot.

You'll need to make a 20 degree jig to set the piston angle correctly. I made mine out of a piece of scrap sheet metal.

Measure your rotors and determine if they need replacing. Mine were well within spec and I had them machined inexpensively. Some say this is not necessary, but I wanted to do it right and do it once.

While you're doing the rears, take the time to completely disassemble and clean the parking brake components. Hopefully you will not need to replace the shoes, they are ludicrously expensive for what they are - four dinky shoes that sell for $125!
Put it together and adjust the parking brake to spec while the wheels are off - much easier. Adjust the cable ends, too.

I used the gravity bleed method to flush out the old fluid and the new after it was all together. Don't let the reservoir run dry! Final bleeding was low-tech pumping the pedal, aided by speed-bleeder valves, which I highly recommend - sold by our host, best 12 bucks I've spent on the 911.

Clean yourself, your tools and your work area often - it's a messy job and you WILL spill brake fluid. Cleaning will help keep it away from your paint, which it will permanently mar even if you clean it off immediately.

If you are replacing the front hoses, note how they are routed around the stuff in the wheel well before removing them. Don't overtorque brake line fittings, they don't need it and the chance for damaging them is great.

If you can't loosen prepped fasteners on the first try, resist the temptation to 'muscle' them off. Take a deep breath, apply more PB and try the next day. Save yourself the headache of creating more problems than you intended to fix in the first place.

Easy on the new pads until they break in! Long downhill coasting at lower speeds while gently pulsing the brakes will help them seat correctly.

When you are done, the pedal should be high and hard and the braking unbelievably strong. I was amazed that it got that much better; the braking on my old, worn brakes was good to begin with, afterwards it was enough to really push you hard into the seatbelt.

I found that two quarts of Castrol GT LMA was enough to do the job with a little left over.

Good luck! I found this to be a most satisfying project.

there is a thread w/my name on it re getting access to the hard to reach lower rear caliper bolt; also put snap-on or snapon in the search engine

I agree re the flare nut wrenches - Craftsman should be ok tho

I don't use the compressed air method any more. It's easier to just use the existing hydraulic system. Just use a vice grip C-clamp thingie (vice grips with "C" jaws) to hold one of the pistons while you remove the other. Use the brake pedal. Piece of cake. Less dangerous. This way, the calipers are done by the time you remove them.

I usually just get a quart of brake fluid whenever I need some. It's not that much more than a pint and it's plenty sufficient for whatever I'm doing including complete system bleed.

Thanks everyone for the replies/information. This will make the project go MUCH smoother. Now I need to order the parts from Wayne!

Caliper Rebuild
 

I did mine a few months back, give them a good break in period before doing any hard driving. When you think you are done bleeding them, do it again. Tap the calipers lightly with a mallet as you are bleeding, you will be amazed at how much air you will get out. DO NOT let the resevior run dry and don't let the peddle go to the floor when bleeding. Good luck.