AndrewM

Looking for a little help guys, starting to put on new rotors and noticed that it took a little more force than I thought it would to push the pistons back into the caliper. How hard should this be?
How hard to re-build the calipers if need be.
Thanks,
Drew
89 C4

jimq

maybe loosen the cap on the brake fluid res. to let out air pressure. Assume this would pertain to a C4 also.

bhensarl

Definitely pull the cap on the brake fluid reservoir. You can put a plastic bag over the opening to keep any gunk out.
Brian

garrett376

I usually need to use a pipe wrench (channel-lock) to retract the pistons - so it does take a decent amount of force. If you end up with brake pads where one pad is worn paper thin, and the other pad is not worn at all; or, when you have brake fluid leaking - that's where you determine it's time for a rebuild.

AndrewM

Thanks for the info guys, looks like I'll let the current calipers be.
Drew
89 C4

bhensarl

Another thing that can work well to retract the pistons is a C-clamp with a block of wood, or the old brake pad to push the pistons back in.
Brian

Smokin

That's exactly how we did it in "The Good Old Days"...

There is less of a chance to ruin the seals and (I feel) you can control things a little more. I am assuming that the calipers can be pushed right in on a Porsche... Some other makes require a special caliper compression tool that twists the piston as it pushes it back in the caliper. A real PITA!

Marc Shaw

I had to do this to put my new pads in when I changed my rotors too but did not think to tank the lid off the reservoir to let the air out - I'll do that next time, thanks (it is amazing what one can learn here ).
C-clamp worked well.

Marc

bhensarl

I actually got those two tricks changing out the brakes on a buddy's 4Runner. It's amazing how much easier a job can be when the car starts with a foot of ground clearance instead of four inches! But the ease of maintenance is more than offset by the fact that it's not any fun to go around corners!
Brian

Dave R.

I wouldn't bother pulling the cap off the brake fluid reservoir unless your car has been upgraded to the sealed cap style that was introduced on later 993s.

All our 964s came with vented reservoirs - the tube running from the reservoir toward the wheel well which you must clamp off when you try to apply a pressure bleeder like Motive to the reservoir.

JasonAndreas

You should be right but for some reason even without the newer style sealed reservoir cap, removing the top makes it A LOT easier to mount the clutch slave cylinder and to retract the brake caliper pistons.

jimq

Lot more area for the air to escape with the top off instead of trying to blow thru a small tube probably.

Dave R.

Well, empirical results trump theory.

I've not been motivated to remove the brake fluid reservoir cap because I've not had any trouble patiently retracting the caliper pistons with Channel Loc pliers, and I managed to get 2 hands in place to install the clutch slave cylinder. I'll keep the option in mind though.