Are these tools really neccesary for a pad change??
 

I've never changed the brake pads on my 964 C4. I've seen references to tools with the part IDs P86, which is used to pull the pads, and P83 which is used to force the pistons back. Are these tools really nessecary? How much do they cost?

Thanks in Advance,

Bill Wagner

Hey Bill, I'll be interested in what you find out. I've been reluctant to change pads becuase of several things, one is the special tools you mentioned, two you'll need to take the car to a shop with a bosch hammer to get the bleeding right afterwards, and three it just doesn't cost that much to have the shop swap pads.

i'll be interested also. i decided to defer my brake job till spring (i store car for winter)

i too was concerned with the bosch hammer b.s.

also, from what i have seen there is great price disparity on the prices of the rear pads.

i disagree with C2wrencher about the cost of having the brakes done compared with doing it yourself. having it done is obviously much more. (and you don't know if it was done right)

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Daryl 964 Targa

I think a lot of us hang out over at the Rennlist 964 board, but I'll pop this over here too.

I just did my brake pads this weekend - sans special tools. A pair of pliers or channel locks removes the clip on the front and then pull the pads out. To return the pistons to make clearance for the new, thicker pads, I use a wrench or something to stick between the piston and rotor. You can use a stick or wrap it in a rag to prevent from scratching the rotors and then pry the piston back. Slide the new pads in and return the spring.

For the rears - for those of us with the wimpy old two piston rear calipers - Use needle nose pliers to remove the retaining clip for the pins, then I flatten the tip of a 6 penny nail to drive out the pins. Make a note of how the retaining spring clip is in for reassembly - as it will pop out as soon as the first pin comes out. Repeat like the fronts for returning the pistons.

Regarding bleeding with the hammer. I've heard that the C4 is especially critical of the bleeding - thus the hammer. Don't know much about that. I've bled my C2 a couple times with no problems - unless you count the chores I had to do for my wife to make up for her having to pump that pedal for me. Of course, if you just swap pads without removing the calipers or breaking the lines open - no bleeding is necessary. Just pump up the pressure to re-seat the new pads after squeezing those pistons back so far, and re-check your fluid level. But if you bleed your own C2 - it is very possible. Just make sure you don't allow air to enter from the reservoire and just keep pumping new fluid through until it is clean. By the way - if you haven't done it in a few years - I highly recommend replacing your brake fluid this way - what a difference old, water filled brake fluid makes.

I took pictures this past weekend of a valve adjustment job, spark plug, dist caps/rotors, brake pad change, hood/deck shock change, fan belt change, etc. Look for tech articles coming up soon. I can't believe I got it all done in a weekend - and WOW! does she run nice right after a full maintenance!!!

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Brian Smith
'91 C2

Thanks serverdude! Its great to hear from those with bigger brassier ones. Could you post the link to rennlist 964 board for us "orphan owners" thanks again, might do a pad change in the spring. I also park mine for the cold snowy miserable no can drive my car months.

You really only need the hammer to bleed the four-wheel-drive hydraulics. A pressure or vacuum bleeder should work ok. Don't forget to bleed the booster circuit too..

Protect the caliper paint when compressing the pistons.

When I make a post like this I often make the same (or similar) posts at numerous web sites to collect opinions.

From what I've read (both here and at the others) you don't really need any special tools just like the others above have stated, and the job is pretty easy.

I suspected as much but being paranoid by nature I thought "what if there's that one little oddity about this cars brakes that's common knowledge to Porsche mechanics but not to me". Nothing "magical" about 964 brake pads...just use the same tactics you've been using with other cars. Changing the pads should not require a Bosch Hammer...even on a C4. Some people claim success bleeding the C4 system without a Hammer, but I'm not sure how successful or unsuccessful it really is.

Thanks Everyone http://www.pelicanparts.com/ultimate/smile.gif

Bill Wagner

You know - I just remembered something about my first pad change on my 91. The pads had an adhesive backing plate that also had another "piston" attached that slid inside of the actual brake piston. I guess it was a rather elaborate anti-squeel device. Those extra pistons made it impossible to just slide the pads straight out of the calipers. Instead, I had to remove the caliper to have enough clearance to get the pads out. I suppose - if you have these - that you could use a chisel or knife to separate the pad from the backing then remove them one at a time, but you might find yourself having to pop open the brake lines to pull a caliper.

But then again - when have you had a better excuse to flush your brake fluid and put in some super blue.

If anyone needs caliper removal advice - I learned some tricks on that one too.

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Brian Smith
'91 C2

The rear calipers on my 94 have two bleeder valves, one on the inside and one on the outside. Is there a recommended sequence/procedure for these? I know that you start with the passenger rear wheel then driver rear, passenger front, and driver front but, what about the double valves on the calipers?

Thanks

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Mike
94 C2 cab

[This message has been edited by Mike Feinstein (edited 10-04-2001).]

Hello

Those tools are not direct necessary they just help the proffesional making a jobservice effective.

Now about flushing the system without Hammer.

This came up on the Rennlist and i have the following problem.

It is a rule in german car permission that the systems have to be redunant or better said have to stay workable under the worst condition. Saefty relatet parts are not allowed to be constructet in aw way that specialtools are needed to maintain the car.

Now the problem with the hanging valves in the C4 made his round in germany and I never had to work without hammer.
The problem is a not proper working valve system caused by dirt or other failures and as far I remember only affect the early 928 and 964 C4.

Since then I try to find some absolute Informations about a workaround as the official side is to follow the specs and have the service done with the 9288 or higher Bosch tester to actuate the pump and valves.

My problem is that many from my old conections moved to other companys, retired or just faded away and the leftovers didn´t worked on those cars and have to ask someone else in the chain.


Grüsse

Roland:

Glad to see you up on the boards again. You seemed to be absent for a while...at least from anything 964 related.

I have a strange problem with the brakes on my '91 C4 that have been plagueing me for months. The problem is erratic brake squealing/screaching. Sometimes I'll step on the brakes and they'll be dead quiet, and at other times I need only touch the brakes and they make so much noise it's embarrasing. I implemented a TSB related to brake dampers and it worked for about three weeks, and then the noise came back....actually worse than ever (when it does happen). I remember someone on one of the web sites mentioning that he "power washed" his brakes to make them shut up (i.e. take a hose with a power nozzle and spray the pads/calipers with water to clean them off). I didn't see this as a solution, but I did try it one wheel at a time to try and isolate the source of the noise. It works (stops the brake noise) for a while, but ONLY for a while, and it did help me isolate the noise to the front drivers side brakes (they ARE the culprit...after a spray down everything is quiet...but about 50-100 miles later the noise is back...this is VERY repeatable).

I pulled the pads and everything looks good, at least to my knowledge it does, but even after cleaning everything out w/Brake Clean the noise will still come back. I'm figuring the noise is caused by brake dust, which might explain the erratic behaviour and why the water flush works temporarily.

This seems to be a reasonably common problem on 964s. Some people have reported success by switching to Metal Master brake pads, which apparently don't produce as much brake dust (but are apparently not that great for track use...not a concern for me).

What do you know about these types of odd problems? Your input will be greatly appreciated.

Thanks,

Bill Wagner

Hello

To much boards and to much traffic in my mailbox. I focus on the pre 964 cars and the not so well supportet 4 cylinders.

Brake noise is allways hard to grip. As a mechanic I check if the caliper is in good condition and if the surfaces on the discs are true and have no hot spots or spots caused from standing to long with the pad contactet the surface. Also check the bearings play and if the brake calipers have corrosion under the stainless channel protectors.

After that it gets very time intensive and mostly you try new pads and vibration dampers before investing time and sink more money in wear parts.

Now griping sounds is something you can handle if you hear it as the sound tells you a bit what is involved.

The sound is:
Depending on speed or pedal pressure ? Changes pitch ? gets louder while slowing down and have a specail tone short before standstill ?

The dust does affect the soundbehaviour yet normaly the dust will be blown away or grinded out while you brake.
I would suggest the next time you work on the brakepad you add some gasslots into the pad ( like Ferrari ATE caliper pads ).
And I would also suggest to have your brake hoses renewed. They also have there share in sound generating when the brakes get hot.

You also can get some heat indicator stripes on your local race shop and stick them on the caliper to find out if that caliper has a higher temperature peak then the other.

Those clores are also to get as waxpainters and you can check the heatrange from your disc with that.

Now in normal life as a mechnic you can´t fiddle and search the problem you just renew the friction partners and if it didn´t
worked you start track down the problem.
But very often the brake pads are just to old and changed there friction behaviour due to oxidation. They also do not brake as good as new pads. This is something like a 95% hit.

Grüsse

I worked in Official Porsche dealerships for a while and never saw anyone change the brake fluid on a C4 with the Bosch hammer.
Obviously, if you are going to change the fluid you would renew the 4WD fluid at the same time........

However, if you need the change the fluid for the center and rear diff lock actuators then you DO need it (mind you, I'm sure someone has done without the tool) Changing the fluid takes a while due to the volume in the reservoir.

The brakes on this car really no different to any other and the worse job is changing the fluid for the boost system. No special tools are required to change the pads, the caliper is virtually identical to the 911 Turbo of 1979 onwards in the pad clip design.

Brake squeal, unfortunately, is a fact of life for town driven 911s. Try using PBR pads. Some cars do it, some don't.

Roland:

99% of the time, the squeal, if it decides to show up at all, will occur at a time when I'm slowing down at a stop light. Usually this occurs when the speed is slow...usually 10 miles/hour or less. If I have the radio off and the window open (sometimes not neccesary because I can hear the noise inside the car with the window closed) I can actually control the amount of squeal by adjusting the amount of pedal pressure I apply to the brakes.

Now, the 1% difference occurs when I take the car out for what I like to refer to as a "high performance drive"....full speed acceleration, fairly heaving braking, etc. After doing this, the brakes squeal, and VERY badly, ANY time I apply them...the speed of the car doesn't matter. As time passes and I go back to "normal" driving, this eventually goes back to the types of noise I described above. I assume this is because the brakes are hotter during the "high performance drive".

Ring any bells?


Thanks,

Bill Wagner

Hello

The good thing on the hammer is that you can work single and just use the hammer to pump the fluid trough. ( This is why they have the long extension cord http://www.pelicanparts.com/ultimate/smile.gif yet when you are at the ends you check the lights and the resonance clap / fuel vent valve ).

But I know it is also normal to pressure bled it with a shop bleeder ( I had been to lazy to block the vent. I allways used a vacuumlifter to refill on these ) and on the race tracks you could see Porsche mechanics
( Freisinger, Kadach, Joest, Müllbauer ,... ) use the pedal methode between the runs yet they also checked or setet the brake balance by messuring the applied pressure on the piston.

The shreek short before you stand is "normal" and this problem is comon to nearly all high performance cars.
Not all have them but the brake system has a very small window for "silent friction".

The other sound seems to be heat relatet and can maybe nailed by said procedures.

Grüsse

Thanks everyone!

Bill Wagner

Just did my 90 C2. Very simple, no hammer, no big deal. The old pads had the anti vibration backing plate with the piston inserts. instead of tearing everything apart per serverdudes recommendation, just use a flat screwdriver to seperate the backing plate from the pad. it takes a while to slice through the adhesive before the pad can be removed while after which the backing plate comes out. In theory, they should come out as an assembly given the pads are worn down to the limit becasue that the only way you get enough clearance. Bit of a crap design of pad if you ask me.

I am trying to fix squeal on my 89 C4. I have replaced pads on other Porsches, i.e. 356, 912, 944, but the pads do not slide out after pushing the pistons back. There is something holding the pads in (the backing plate mentioned?). If I pry the backing plate off the pad, what do I use to reapply it?

I want to file the edges of the pads, and use a squeal stop product on the pads, which a re fairly new.

The pads can be held in with the anti-squeal "stars" which are glued to the backing plate and fit into the piston holes. You break them loose with a putty knife inserted along the backing plate (don't forget to remove them after you remove the pads). Two stars per pad to remove.

backing plate removal
 

Thanks! What do I do to put the pads back in? Apply ? adhesive? Put pads in without backing plates?