Time for new calipers?

[Robcat77]

I was having problems with sticking rear calipers on my '84 Targa. After some great thread research here, I tackled replacing the old rubber brake lines and rebuilding the calipers.
Two of the pistons (on on either side of car) were pretty badly seized and required quite a bit of effort to remove.
Pistons cleaned up very nice - no real pitting or any damage. I cleaned as much of the crud out of the cylinders, but as you can see there is some pitting. I installed all the new seals, greased everything back up and re-assembled. Things are working great now, no more pad rubbing, and no leaks.

But due to pitting, will I need to replace these soon?
When you get them from PMB - do they re-bore/re-surface the cylinders?

[Robcat77]

also...the little rubber grommets were disintegrated that hold the brake pad sensor cable. Any body ever purchase these kinds of little things, or just make something out of rubber hose or something? A lot of rubber things are getting old and crumbly after 35 years!

[Trackrash]

IMO those bores don't look bad. The area to be concerned about is where the seal sits. Yours don't look bad there, at least in that one shot.

The bigger issue are the pistons. If they are nice and smooth, with no pitting or flaking, you should be good to go.

[shadowjack1]

PMB will replate them foe you. I would send them in and have peace of mind for the next 35 years. Bleed them once every two years.

[jlex]

I just overhauled the front calipers on my '88. From what I recall, I don't believe the pistons actually travel on the pitted outer portions of those bores. You're probably okay. To keep a check on it, when the car's in neutral, make sure it's able to easily roll on non level surfaces. After fixing my fronts, it's amazing how easily the car now rolls in neutral.

[porsche930dude]

there is no seal riding on the bore so it doesnt really matter. As long as you sanded it down enough that nothing sticks out and binds. Every caliper iv ever rebuilt was like that or worse

[Jack Stands]

Just getting my rear calipers from my 914-6 back from PMB. They do such a nice job that it’s worth sending them in.

[Superman]

Originally Posted by porsche930dude

there is no seal riding on the bore so it doesnt really matter. As long as you sanded it down enough that nothing sticks out and binds. Every caliper iv ever rebuilt was like that or worse

This. ^^^^

Take some steel wool to it, install new rubber using silicon grease. New pistons, if necessary. The pistons have to be in good shape. The calipers, less so.

[Robcat77]

Thanks everyone. Good to know that the piston does not ride on that outer portion of the bore.
And Trackrash, yes the outer area where the seal sits cleaned up nicely on both calipers.
Those copper rings were kind of a bear to get seated right - one side always wanted to lift up, but with persistance they seemed to seat right finally.

Next up are the fronts along with the new rubber lines. The PMB refinished ones are on the wish list, but I'm hoping I should be good to go for a while. Big difference already with the rears not grabbing all the time. I think the old rubber brake line was the true problem.

[juanbenae]

be advised that after a caliper rebuild you will have to bleed them a few times to achieve a good stiff pedal. it may have to do with air in the lines or bubbles sticking to the interior of the caliper so tap the caliper with a rubber mallet a few times during the bleeding process.


even after you have all the air out they still may be exhibiting a soft pedal. to address this you need to get some heat in them to reseat the pistons in the correct spot before they will stiffen up. search soft pedal after caliper rebuild and there will be a great deal of info on this phenomenon.

[Robcat77]

/\ /\ good to know. Thx.

[fizeus]

Your calipers seems good.
The simply need some love and, as others say, probably new pistons if yours are pitted.
Rust on the outer part of the bore is not a problem because the sealing is between the bore and the piston is only assured by the gasket...that should be replaced in your case (like the dust cover the has already left water to enter and attack the bore)

[RWebb]

this is a great time to replace all the old rubber hoses with new rubber ones

[Robcat77]

RWebb - Replacing the rubber hoses was the start of the whole project. I read that sometimes old hoses can cause calipers to not release pressure properly - which mine were doing.
Rears are done, now need to tackle the front. I've also ordered proper caliper seals/covers for the fronts too. May as well clean them up as well.

[RWebb]

do you have this special tool set?

[Jesse16]

Big shout for PMB, if you can afford to get calipers from them you'll be happy for a long time. The price really isn't much more than getting a pair for any other decent car at your FLAPS as I remember.

[Robcat77]

RWebb - I do not have any special tools for the job. Rear caliper cleaning/re-assembly seemed to go pretty well. But I did have a bear of a time getting the copper clip on the outer seals to seat properly.

[RWebb]

buy some mustard, the jar is Porsche's own brake paste

there are better piston compressors ou there but that one is ok & cheap

[seafeye]

I had done caliper exchange with our host Pelican. Couldn’t have been easier: