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914 Rear Caliper Rebuild
 
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Pelican Technical Article:

914 Rear Caliper Rebuild

Herb Meeder

Time:

4-5 hours

Tab:

$60-$325

Talent:

*****

Tools:

Aerosol brake cleaner, metric brake line wrenches, metric socket and metric wrench set, floor jack, jack stands, wheel chocks, safety glasses, power brake bleeding system, turkey baster, torque wrench, bearing grease

Applicable Models:

Porsche 914 (1970-76)

Parts Required:

Rear brake calipers rebuild kit (with adjuster screw seals), speed bleeder nipples (4), brake fluid, two 25mm freeze plugs

Performance Gain:

Better braking for your 914

Complementary Modification:

Bleed and flush the brake system, rebuild the front brake calipers too
Here is the typical scenario. You are approaching your precious baby from the rear and notice that there is a dime sized puddle of DOT 3 next to the inside of one of the rear tires. Perhaps there may even be a trickle running down one of the Yokohamas. You crawl under and it seems like it is dripping directly from the parking brake actuator arm. Well, rebuilding brakes is never fun, but it really isn't that much more difficult than balancing dual carbs, so you decide to pull out the Haynes manual and give it a shot. Stumbling block #1- Haynes says that "no dismantling of the rear caliper is permitted" (those Brits. Who said that you were asking for permission?) and that you need to go buy a new one. Not so. Stumbling block #2- not every parts supplier has the correct rebuild kit. Take care to make sure that you are getting the correct kit. The seals and dust boots are there, but you need to have the 2 O-ring seals that seal the piston adjusters inside the caliper body (these are the adjusters that adjust the venting clearance.) Make sure that you have the kit that contains those 2 seals. If you don't, you will have wasted your time. Those are the guys that are causing your problem.

Another cautionary note: There is a school of thought that says that the Parking Brake Actuator Arm does not have to be removed to complete this rebuild. Well, that is mostly true. All the seals can be replaced without having to remove it. In fact, one of the most troublesome and time consuming aspects of this rebuild is the removal and fabricating of the plug that covers the retaining clip for the arm. The sleeve and the arm are not the sources of the leak (though by looking at it from the outside, it certainly seems so.) My thinking is that if you have gone to the trouble and time to pull the thing apart, why not take the extra 1/2 hour to do a truly complete job? Once you have that end plug off, you will find some grime and muck that needs cleaning. It is very unlikely that any of that will end up back in your brake system. I would clean that up, but that's me. When you get to the part that mentions removing the P-brake arm, you can skip it and not feel too guilty about doing a less than thorough job. Your option (I learned the guilt trip thing from my mom.)

Parts List

  • Rear Caliper Rebuild Kit (with adjuster screw seals)
  • Aerosol Brake Cleaner (use it liberally!)
  • At Least 1 Quart of Good Quality Brake Fluid (always buy new fluid. It breaks down over time)
  • 1 25 mm Freeze Plug per caliper (optional)
  • Speed Bleeder Nipples (optional. If you get them, get 4. One for each caliper)
  • A spot of grease (bearing grease is good)

Time to get started:

Remove the caliper from the car according to the direction in the Pelican Parts Tech article "Replacing the 914 Rear Brake Calipers"

Split the caliper in half, remove the spring clip that holds the piston dust boot on (keep these clips, one for each side. The kit supplies new ones but they are wrong for this caliper so you will either have to re-use the old ones or cut the new ones to fit.) On the inner half of the caliper remove the dust boot and use the adjuster screw to drive the piston all the way out. The adjusting gear may just fall out of the hole,. If not, it will after the adjuster screw gets pulled. After removing the piston and pulling the old seal out, look all the way down inside the caliper. Around the base of the adjusting screw is a sombrero shaped spring cap. It is held in place by a retaining clip that can be very tricky to get out (unless you have the correct tool, I don't. I used a couple of small screwdrivers chopstick style to get the clip away from the sides and then snagged the tiny hole on the clip with a bent paper clip. Not too glamorous, but it works.)

Pull out the spring clip, the cap, the spring, the adjuster screw and the "pill." I have no idea what this little capsule shaped and sized gizmo is called. It transfers pressure from a small "cup" in the P-brake pivot arm to the base of the adjuster screw. This pushes the brake piston against the disk and sets the parking brake. Remove the "O-ring" seal from around the adjuster screw. This is most likely the cause of the mysterious "P-brake leak" everyone talks about. The truth is, this is not actually the parking brake seal. It seals the adjuster screw against the inside sleeve of the caliper body.

To get the arm out of the caliper: Drill several 1/8 inch holes in a row in the quarter size plug at the end of the pivot point for the arm. Drill the holes about 1/8 inch from the perimeter. Any closer and you may drill into the caliper body and further to the center and you may drill into the end of the pivot (ask me how I know.) Knock the bit between the holes out and this will allow you to get a needle nose pliers in there to pry the entire plug out. After getting the plug out, small screwdrivers will allow you to get the retaining clip out. The arm is now ready to come out.

Pull the arm out of the sleeve carefully. There is a dust boot right under the arm. Clean it and keep it for re-use (there is no extra in the kit.)

Bruce Mackenzie adds some input on a problem I haven't run into. "When I took one of the calipers apart, the collet like assembly inside the piston came off the adjusting screw. This made it virtually impossible to take the adjuster out with the "peanut" etc. I screwed the collet back on and the assembly came right out, allowing me to remove the "P" brake arm. It has a loose ring that sort of press fits into a groove in the piston."

On the other half of the caliper, remove the dust boot retaining spring (remember to keep the spring!) and pull the dust boot. Loosen the retaining nut on the allen screw and drive the piston all the way out. Remove the piston and the seal. Pull the worm screw out through the body and remove the seal from around the adjusting screw (another potential leaker.)

Time to clean parts! It is recommended that the caliper body halves be sand blasted. If that is not an option, clean everything very carefully with copious amounts of brake cleaner and tooth brush and use a very fine emory cloth lightly on the insides of the surfaces (including the inside of the P-brake arm sleeve.) Don't use anything abrasive on the pistons themselves. These surfaces are milled and need to be mirror smooth to ensure positive seals.

OK, re-assembly is the reverse procedure. Coat the P-brake adjuster arm pivot lightly with grease and replace the cleaned up dust boot. Replace the retaining spring on the end of the pivot.

You must now "make" a plug for the end of the P-brake pivot arm. Go to your neighborhood parts place and get a 25 mm freeze plug. Turn the plug over so the plug makes a "dome" over the end of the pivot. You will find that the plug is slightly too large to fit inside the hole. Take a hand tool such as a Dremel and lightly grind the plug until it will friction fit in the hole. Now take a hammer and flatten the dome a bit and you will have a perfect replacement for the plug you drilled out earlier.

Now replace the "pill", the adjuster screw (with new "O-ring",) the spring, the spring cap and the retaining clip. Be careful when putting the seals over the adjuster screws so as not to nick or mar them. Same goes for the seals inside the piston sleeves. You don't want to have to do this again due to lack of care. Also, coat the seals with a finger tip dipped in brake fluid. This will make putting the pistons back in go much more smoothly. It will also help to keep the seals from nicking as you put things back together. The clip will once again give you some trouble but if you can get the clip to sit in the hole a bit you can place a deep socket over the adjuster screw and tap with a hammer until the clip seats. Place the adjuster allen gear in the adjuster hole and crank it around to make sure the adjuster screw is rotating properly. Use the adjuster screw in combination with a block of wood and clamp or vise to press the piston back in the caliper half. Replace the dust boot and the retaining spring that you kept.

The outer half of the caliper re-assembly is very straightforward. Use the adjuster screw in combination with a block of wood to press the piston back in the caliper half. Replace the dust boot and the retaining spring that you kept.

The last part is to reassemble the two halves of the caliper with the new fluid seals. Note that 2 of the 4 bolts are longer and go into the inner bolt holes. Torque inners first, then outers to 7 ft/lbs. Repeat to 16 ft/lbs.

My final recommendation is to replace the bleeder nipples with speed bleeders. These things are worth their weight in gold. If your calipers have both an upper and lower set, you need replace only the upper ones.

Replace the calipers according to the Pelican Parts article and bleed your entire system very carefully. While the caliper was apart you will have noticed that there are many "nooks and crannies" for air to get trapped in. After rebuilding, you may want to bleed your system several times just to be extra cautious. No brake system ever failed because you bled it too often.

Good luck with your project and if you found this article helpful or have tips to add, please let me know at my email address.

Herb Meeder 
mailto:meeder@incom.net


Herb adds:

"Another note regarding the rebuild.  Some of the earlier calipers are held together with RIBE bolts (no, I don't know what RIBE stands for.)  These bolts have a 6 point head that looks like a TORX bolt head but isn't.  The RIBE bolt has some slightly different bumps and such that will make putting them back on and torqueing them properly with a TORX socket more difficult and may result in you mangling the bolt head.  My recommendation 
is to use a TORX socket to remove them and then take them to a bolt place (look up 'Fasteners' in the yellow pages) and replace them with standard Allen Head bolts (5mm I believe.)  If you want to keep the RIBE bolts you 
will need to track down the correct tool which can be a pain to find.  Someone had once told me that they found them on the 'net for about $12.00 plus shipping.  Or you can replace them for about $8.00 and not have to wait 
for delivery of the tool.  To the best of my knowledge those bolts appear nowhere else on the car and personally, it galls me to buy a tool for a single application that, if you do the rebuild properly, you may never have to use again."

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Comments and Suggestions:
ebb Comments: I just returned from Chucky Cheese and it looks like now I can finish my rebuild! .. For me one caliper PB arm was fine but the other had a very worn and sticky seal on the arm, and this caused very poor PB action overall. I rebuilt everything on each.
October 3, 2013
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
 
Bill Comments: I have completed a rebuild of a pair of rear brake calipers, and everything went according to the article, and I think they are "good to go", but I wonder about the parking brake. I have not put the calipers back on the car, and they are still dry and empty. But I expected the inner to piston to move inward a tiny amount 0.010"? when I moved the PB lever on the caliper. But they don't move. Nothing happens. Is that because the calipers are dry? Or did I get something wrong in how I put the pill/sausage in for the inner adjuster?
April 6, 2013
  Followup from the Pelican Staff: See attached image for pill orientation. You should not need fluid for the parking brake to work, it is a mechanical connection. - Nick at Pelican Parts
Hcarraro Comments: Anybody have a source for the small parts like the worm screw and perhaps other parts?

Henry
hcarraro@hughes.net
November 16, 2012
  Followup from the Pelican Staff: Give our parts specialists a call at 1-888-280-7799. They can help you find the right part.
- Nick at Pelican Parts
 
porsche930dude Comments: I found that a Chucky Cheeze Token presses in perfectly in place of the big plug. Also found the sombrero hat surprisingly easy to install simply by clamping the clip with the pliers in one hand while pressing down the opposite side with a screwdriver. The spring is not that strong so it clipped in no problem.
November 1, 2012
  Followup from the Pelican Staff: Funny. Thanks for the additional info. We appreciate it.
- Nick at Pelican Parts
 
franko7376 Comments: Another photo..
October 6, 2012
  Followup from the Pelican Staff: Thanks for the photo. - Nick at Pelican Parts  
kbrunk1 Comments: Spoke with Pelcan Parts desk today. They recommend to not take the "plug" out as indicated in the Technical article. They do not sell the dust rubber ring aound then PB lever and at the edge of the casting and indicate this not necessary.

Per the internet, most folks are zink dipping their brake caliper casting to hold down rust and increase the life of the braking system help prevent rusting and frozen pistons. To do this all rubber must be removed from the brake casting. I am going to re-use the rubber O-ring seal. The single screw 1/8 from the edge worked great. JB Weld to reseal.

It seems all that needs to be done is make an after market new seal for the PB lever.

September 10, 2012
  Followup from the Pelican Staff: Thanks for the additional info. We appreciate it.
- Nick at Pelican Parts
 
franko7376 Comments: I just wanted to write to say thanks to Herb for putting together this article. I took some photos of my rebuild and labeled the parts. Hopefully it helps give a visual of all the parts explained in the article.
January 28, 2012
  Followup from the Pelican Staff: Thanks for the feedback and photo. Glad we could help.
- Nick at Pelican Parts
 
Lucky Comments: My adjuster screw is trashed. Are these things able to be replaced?? Will they screw out easily or do I have to remove the caliper and do some major surgery / even worse replace the caliper alltogether. Are Brembo's in my future?? 1970 Porsche 914 -
September 23, 2009
  Followup from the Pelican Staff: These calipers are a pain. I don't know of anyone who makes replacement adjusters - the best advice I have is to find a good used set somewhere (eBay), or just bite the bullet and buy professionally rebuilt ones. You don't want to cheap out with important things like brakes. - Wayne at Pelican Parts  
able2222 Comments: I removed the plug on the E-brake shaft by drilling one rather than a couple1/8 inch holes per the instructions and then inserted a sheet metal screw in the hole. A little prying with a claw hammer and it popped right out.
I sealed the 1/8 inch hole with a little JB Weld on reassembly saving chasing down the 25mm freeze plug.
August 10, 2009
  Followup from the Pelican Staff: Thanks for the additional info. We appreciate it.
- Nick at Pelican Parts
 
PaulBennett Comments: Couple of tips I learned in the process:
Begining at paragraph which reads "Now replace the "pill",
the adjuster screw with new "O-ring",the spring, the spring cap and the retaining clip. Be careful when putting the seals over the adjuster screws so
as not to nick them."

Tip #1 - At this point I feared nicking the "O" rings on the threads of the outer caliper adjuster screw and used an inch or so of electrical shrink tube over the threads, heater then ends making it small, dipped the "O" ring in brake fluid and it scampered up the shrink tube easily,
protected from the adjuster screw threads.

Tip #2: The inboard cylinder adjustment screw is held in place with a sombrero shaped hat/spring which is secured with a circlip. I placed a small deep socket with extension over the adjustment screw and used a drill press to apply force against the spring. With caliper on press table, extension rod in chuck, adjust press table height so everything is held stable allowing plenty of room for me to maneuver and adequate light from the drill press light. Make a tool by grinding the end of a small screwdriver to fit into the clip hole as there is inadequate room to use a circlip/snap ring tool.
May 30, 2009
  Followup from the Pelican Staff: Thanks for the additional info. We appreciate it.
- Nick at Pelican Parts
 

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