First Brake Pad Replace

[bagpiper46]

My 81 SC is about to get it's first Brake pad replace today. Parts supplied by our host. Got one question before I tackle this seemingly easy task. Will a turkey baster be OK to siphon off a bit of brake fluid before I begin? It seems full so I don't want to risk overflow in the reservoir. Can I then put the same fluid siphoned back in when the job is completed to fill the reservoir back to full? In other words will the Brake fluid have melted plastic from the baster by the time I refill the Master cylinder?
And why are their no clips to hold the front brake pad retaining pins in like the Back brakes? (Have not looked yet so I'll probably answer that myself upon inspection, just curious)
This is my first time so be gentle with me.
Thanks

[porschenut]

Yep, removing a little fluid with a turkey baster is the way to go, and you can certainly put that fluid back in IF it has not been contaminated in any way. It's much better to top it off with fresh fluid when you're done. The fluid won't melt the plastic so you don't have to worry about that.

Can't helpyou with the question about the retaining clips. Maybe someone else can. BTW, I assume you mean that this is the first time YOU have changed the pads, rather than the first time the pads have ever been changed on the car....?

[livi]

I use a 20 ml syringe (Iīm a doc ) to remove and refill. Works perfectly.

I seem to remember the same thing about the retainers. Only on one axis - canīt remember which though.

Good luck!

[bagpiper46]

I would assume that they have been changed a few times, just not by me. If they were original they lasted 93,000 miles!
Thanks, off to get a turkey baster!

[Gunter]

If they fluid is older than 2 years, flush the whole system.
No need to get a baster, flush the old fluid out through the right rear bleeder nipple. Leave the nipple open (Yes, open) put a small clear hose on the bleeder, the other end into a glass bottle and pump the pedal until the new stuff appears. Keep refilling the reservoir and repeat the flush on the other calipers.
Close the nipples, pry back the old pads, clean the area, insert new pads. Bleed again individually.
Of course, if you don't know when the calipers were rebuild, that might be in order. Get a Bentley, you'll love it.
Bentley SC Repair Manual 470 would come in helpful to fully understand how your system works.
Regarding clips: Not sure if Porsche used ATE exclusive or if Girling was also used.

[bagpiper46]

Well after 3 hours the job is done! Took it out for a quick spin and they work!! Got a little nervous when I first pushed the peddle and needed to pump them up a bit. Is this normal? They worked OK, a different feel and not as strong as before. I read it takes a few weeks/miles to get them broken in. The 2 inner rear were down to no gap in the middle. The rears are definitely easier than the front. Real fun trying to get the front pads in and out! 2 blood blisters left hand from that! Fluid was changed a year ago by Denver area Dealer when I had my 90k service and they wrote me a book about all the work they should do. Well 8k miles later car is still running great and now I have one less item to do from their great book! All in all not a bad job for a beginner. Thanks for the parts and the great book from our host. Will get the Bentley Manuel next month before I tackle the valve job.

[FrayAdjacent911]

Originally posted by Gunter
If they fluid is older than 2 years, flush the whole system.

What he said. If you have never drained the fluid, it's probably time.

[Nine9six]

When installing new pads, did you have the rotors turned?
I dont know about the SC, but the Carrera manual recommends it.
Its also a good idea to bevel the edges of the new pads at a 45 degree angle with a file. This will reduce the likelyhood of squeel.
The pads need to bed in before they will operate at their optimum.

[bagpiper46]

Did not have the rotors turned as they looked good. Fluid was changed 1 year ago. Did siphon out about 2 oz of fluid with a baster. Just checked it each wheel and sucked a bit off the top of the screen. Don't think I need to replace the fluid as the MC was full at the end of the day. Does it matter which way the little rear cotter pins go in? 1 side is definitely wrong if that is the case.

[edward993]

"...Got a little nervous when I first pushed the peddle and needed to pump them up a bit. Is this normal?..."

Yup. After one removes/replaces pads, ALWAYS pump the brake pedal a few times until it gets hard. When you r&r the pads, you move the piston back into its bore, away from the rotor surface. Pumping the pedal simply pushes the piston back out where it needs to be. But if you forget, and you have a sloped driveway, you may just pull the car out, go for some brake, and have nothing as you plow into the street. Not sure why you had trouble with the front pads, though. They aren't any different to replace than the rears.

Edward

[bagpiper46]

The reason the fronts seemed more difficult I think is the PO used a lot more anti squeel glue. They were just harder to pull out and seemed to be a tighter fit going back in as well. Still happy I did it myself as with each completed task boosts my confidence for the next repair. Thanks to the Board I can afford a P-Car on a state employee salary.

[Wil Ferch]

Look here for what I say about squeel..use the 3M anti-squeel stick-em sheets....and *don't* use the goo...

Brakes squealing, help!

squealing brakes...any fix?

- Wil

[Gunter]

bagpiper: Feels good to do it and get more confidence.
You didn't need to flush but, bleeding is necessary because the fluid in the calipers deteriorate more than the rest because of heat-issues.
Even brake fluid contains a small percentage of water and over time, the moisture travels to the lowest point in the system meaning: calipers.
That's one of the reasons why pistons rust (Freeze up)
When you bleed, you actually get fresh fluid into the calipers and excercising the pistons will ensure free movement.
The other thing is: Did you check the 20 deg. index on the pistons?
Pretty important. Also, sometimes the new pads fit too tight; it is alright to actually file the steel edges so they don't stick.
Good point about the 3M sheets, Wil.

[petrolblue83911]

-Not sure on the pad's/piston needing to seat, but if you're pedal is sinking unless you pump it, you need to re-bleed! don't drive around like that its dangerous as hell!!

[bagpiper46]

I have good pressure after the initial three pumps. Will bleed a little to get fresh stuff to the pistons. They work fine. Thanks

[ianc]

Did you check the 20 deg. index on the pistons?
Pretty important.

Gunter (not to hijack, but...),

I hear about this every once in awhile and I don't understand the importance of it. Can you explain it? Thanks very much,

ianc

[Wil Ferch]

the angle provides a non-uniform "push" on the backside of the pads....to compensate for the non-uniform pressure the friction side of each pad sees against the rotor....

..it helps even-out the applied pressure and it evens out the wear....

...hope you don't mind me answering....

- Wil

[ianc]

Nope, that's fine.

Thanks Wil!

ianc

[Gunter]

Well said, Wil.
ATE brakes are used on a variety of vehicles and one can make a ~20 deg template out of cardboard or sheet metal.
Many years ago I looked closely at this and it made sense.
When the brake is applied, the pistons force the pads against the rotor and the friction/rotation wants to deflect the pads.
I have seen pads with uneven wear because of the indexing in the wrong position. (Either due to wrong installation, or rotation on their own) The position can be corrected by pushing the piston out against a worn/thin pad, remove the old pad and, by using channel-lock pliers on the end of the piston, carefully rotate until the approx. 20 deg is achieved. Just make sure about the right direction/position by imagining what happens during braking. You'll see, it makes sense.

[Wil Ferch]

Gunther:

- follow up question.... I know about the 20 degree angle tool...but was always unsure how to rotate the puck ( if positoned wrong) to get back to the correct orientation...without scoring up the outside surface of the pucks. Wouldn't your Channel-Lock method be a bit severe?....is there another way?

- Wil