Question for rebuilding calipers

[kyngfish]

So. Pretty sure I need to rebuild calipers as the piston seems stuck and the plastic boot is shredded. I have a couple of questions.

• How do I know if the caliper needs to be completely replaced.
• How do I know if the piston also needs replaced.
• The pelican article on the rebuild says if the piston is stuck, to bang the half on a block of wood until it comes out. Can I use lubricant like kroil to loosen it? Since this is the most likely scenario.

Cheers.

[DaveMcKenz]

I found similar problems when I went to do my pads and rotors. I talked to Erik at PMB Performance. He was very informative and told me that 30 year old calipers develop corrosion and a sticky condition he called "brake shellac" from breakdown of brake fluid and moisture absorption. When it happens in one caliper, it is happening in all of them to some degree.
PMB completely strips, disassembles, replates, then reassembles each caliper with new factory seals. All this for $150 per corner.
Well it's a lot of money, but brakes are pretty important. I think I could rebuild each of the calipers that were sticking, but I don't think the long term results would be the same as with PMB. So, I bit the bullet and ordered. I'll send back my cores when I get them swapped out.
Just something to consider. BTW their website is also very good.
Good luck,
Dave

[Baby]

Hard to tell what kind of shape the pistons are in until you disassemble. Plenty of how-tos available. I just rebuilt all four---very easy job. In my case, banging the caliper didn't help. I used compressed air on two calipers and a grease gun on the other two. Both methods work very well. My plan was to clean the shellac off of the pistons and reassemble with fresh seals, which is what i did. If the pistons had been corroded, I'd have replaced them. Again, a very simple job...almost no moving parts!

[86 911 Targa]

Originally Posted by Baby

Hard to tell what kind of shape the pistons are in until you disassemble. Plenty of how-tos available. I just rebuilt all four---very easy job. In my case, banging the caliper didn't help. I used compressed air on two calipers and a grease gun on the other two. Both methods work very well. My plan was to clean the shellac off of the pistons and reassemble with fresh seals, which is what i did. If the pistons had been corroded, I'd have replaced them. Again, a very simple job...almost no moving parts!

^^^^^
That is exactly how our local machine shop did mine.

Gerry

[eshtog]

On my 89 rather than restoring the calipers I opted to just get new OEM ATE calipers for around $250 each. After calculating shipping back and forth to PMB and factoring what I could sell my used calipers for it was almost a wash. Plus I saved down time as the calipers are readily available.

[steely]

Originally Posted by Baby

Hard to tell what kind of shape the pistons are in until you disassemble. Plenty of how-tos available. I just rebuilt all four---very easy job. In my case, banging the caliper didn't help. I used compressed air on two calipers and a grease gun on the other two. Both methods work very well. My plan was to clean the shellac off of the pistons and reassemble with fresh seals, which is what i did. If the pistons had been corroded, I'd have replaced them. Again, a very simple job...almost no moving parts!

the grease gun trick is cool and works (we used a spare master cylinder where I used to work).

They come out extremely easily this way, but you must be able to restrict one if it moves faster than the other or you will be screwed trying to get the last (stuck) one out.

once they are out, inspect pistons and caliper for scratches or damage.
The brake fluid absorbs water, and aluminum calipers may oxidize and create a grey/white powder or rust of sorts. Once cleaned up, look for pitting as evidence where this occurred and replace as necessary.

[Cook&Dunning]

My track car to street project calipers were toast. I was able to purchase new Porsche Classic calipers for less than the cost of refurbishing. (89 car)

[DRACO A5OG]

Post a pic when you can Brother M

[rockerarm]

Hi. An interesting tutorial on caliper refurbishing.

TheSamba.com :: 411/412 - View topic - Type 3 and 4 front caliper rebuild "how-to" part 1 and 2

Bill

[yelcab1]

If you can get a new caliper for $250, do that. Then sell your old ones to recover some costs.

[chris_seven]

None of the commercial caliper refurbishing companies mess with the cylinder bores.

The general procedure is use a pyrolysis oven to heat the calipers in a controlled environment to about 400degC.

This removes oil and grease and allows easy dismantling.

Once stripped the caliper halves are then blast cleaned in wheelabrator and then electroplated the same day.

Calipers are then re-assembled with new pistons, seals and refurbished bolts, tested pneumatically and despatched.

We used to work with a local refurbishing company and supplied them with basic test equipment.

We have been re-building calipers for about 10 years now and we use 6AL4V Titanium Pistons.



We have recently been working on a few sets of early 3.3 Turbo Calipers.

All of the plated fasteners were 'baked' after plating to eliminate the risk of hydrogen embrittlement.

[mepstein]

The only problem with doing it yourself or getting the calipers from a no-name rehab company is you won't get the piston bores replated. That's one the most important parts of the rehab. It's what made the original calipers last 30 years. PMB does that step so it does make it worth sending it out to them. There's plenty of places to skimp besides your brakes.

[fanaudical]

+1 for PMB. I had disassembled my calipers and found some significant internal corrosion. Sent to PMB for rebuild and got great-looking calipers back. I've had no performance issues with these since install a couple years ago.

[sugarwood]

Originally Posted by mepstein

The only problem with doing it yourself or getting the calipers from a no-name rehab company is you won't get the piston bores replated. That's one the most important parts of the rehab. It's what made the original calipers last 30 years. PMB does that step so it does make it worth sending it out to them. There's plenty of places to skimp besides your brakes.

Wait, isn't ATE the OE brake manufacturer? I'd hardly call buying a brand new OE part "skimping". Unless you have a concourse cocoon survivor with 6 miles, I don't see how one can justify refurb'ing a part for the same cost as buying a brand new OE one, especially when the new part arrives in 2 days.

[DaveMcKenz]

Originally Posted by sugarwood

Wait, isn't ATE the OE brake manufacturer? I'd hardly call buying a brand new OE part "skimping". Unless you have a concourse cocoon survivor with 6 miles, I don't see how one can justify refurb'ing a part for the same cost as buying a brand new OE one, especially when the new part arrives in 2 days.

I think he is talking about a DIY rebuild. The cost of PMB rebuilt Carrera calipers is $170 per corner including shipping both ways. The often have calipers in stock, so they will ship to you, then you can return your cores within 60 days for credit. There may be new ATE units at similar price when you factor in resale of old units. Certainly new OEM would not be skimping. Just an alternative.
Dave