Brake Caliper Seal Replacement

[espooner]

2002 Boxster S, 37,000 miles, moderate track use. I am a fairly good mechanic, in general.

My Boxster pretty well toasted its brake rotors the last 5 days at Watkins Glen, and needed a thorough going-over. Pulling the pads, I noted the outer dust cover (deal) on one of the calipers was burned, and came out in my hand. Pretty well like burned toast. So along with rotors, screws, Pagid Oranges, etc. I ordered new dust covers (outer seals).

My question is whether there is a trick to putting these in. I expect getting them out involves pressing in the pistons, and prying them out with a screwdriver or such. Re-inserting new ones may be more challenging. Any known tricks? Pistons depressed into cylinders or projecting out slightly? Special or helpful tools? Any help would be appreciated.

Eric

[ericinboca]

2002 Boxster S, 37,000 miles, moderate track use. I am a fairly good mechanic, in general.

My Boxster pretty well toasted its brake rotors the last 5 days at Watkins Glen, and needed a thorough going-over. Pulling the pads, I noted the outer dust cover (deal) on one of the calipers was burned, and came out in my hand. Pretty well like burned toast. So along with rotors, screws, Pagid Oranges, etc. I ordered new dust covers (outer seals).

My question is whether there is a trick to putting these in. I expect getting them out involves pressing in the pistons, and prying them out with a screwdriver or such. Re-inserting new ones may be more challenging. Any known tricks? Pistons depressed into cylinders or projecting out slightly? Special or helpful tools? Any help would be appreciated.

Eric

I rebuilt all four of my calipers in February on my '04 986S, replacing all the bore seals, pistons, boots and bleeder screws.

If all you are replacing is the dust boot, you don't really need to remove the pistons. Just press the pistons back in and pull the boots off. They have a lip that fits into a recessed area on the caliper, and the top of them fits into a recessed area on the top outer edge of the piston, but the boot is reinforced at those parts and you should be able to pull them right off. Below you will note I caution on the use of a tool with the pistons, but if all you are doing is the dust boots, you can use a dental type tool to help get them out.

If you want to go the full monty, here is way more detail than you asked for :D ....but be sure you read my caveat on doing the full monty below.

You have to disconnect the fluid line on the back of the caliper to inject air to make the piston come out. As such, you should just remove the whole caliper.

With the caliper off, and the brake line dripping into a bucket, use plenty of brake parts cleaner to wash everything down and getting as much fluid out. You don't have to do this, but if you don't, when you apply the air pressure, you are going to splatter nasty brake fluid all over the place. You can remove the bleeder screws too, and spray into those and into the back until you feel like most of the fluid is out.

Then you need some blocks of wood; best to have some of different thicknesses. Place blocks between the pistons so when you apply the air pressure, these things hit something other than each other. And be careful, they come out with significant force.

Use the different thicknesses to get the pistons most of the way out. Then you can pull them out with your hand if you got them far enough out. Don't use any metal tool on the pistons. You can scratch and ruin them.

It is a bit like a puzzle sometimes to figure out what thickness of blocks to use to get all four pistons out far enough at the same time to pull them out, but it will make sense once you start.

Inspect the pistons. If you boots are shot, and you've had a few track days where you were down to nothing on your pads, you will probably find a little bit of rash on the sides near the top. If this is all you have, just at the top, they can be reused, IMO. If they are scored on the sides in a place that would make the scratch go past the seal, then resuing them runs the risk of leaking past the bore seal.

Look into the cylinder and half way or so down, you will see the bore seals - one per cylinder. You get these out with a dental type tool. These are inexpensive and readily available. I've seen them at sears as well as lowes. If you pull the seal out, you should replace it, because you do not want to run the risk of cutting or tearing it at all.

Go crazy with the brake parts cleaner. Clean, clean, clean, clean - but only use brake parts cleaner, or brake fluid itself. NOTHING else in the cylinder but one of these two chemicals.

When you reinstall the bore seals, you lube them with a silicon grease (came with my piston rebuild kits from Brembo - have more if you want the name) like you lube the ring on an oil filter. Then you bend them (because the rings' inside diameter is slightly larger then the diameter of the cylinder, and fit them into the little recessed area in the cylinder.

The pistons go in next. No grease on them.

And then put a tiny bit of the grease on the lip of the dust boots to make them fit easier on the lip of the caliper...try not to get any grease on the outside of the boot though, because it will gum up with dust.

Once all back together, flush your brake fluid, and then bleed them a couple of times too.

I've found my dust boots don't last long. It depends on what tracks I am visiting, but I am watching them more carefully now, and replacing them at least, sometimes twice a year. It seems to extend the life of the pistons because the dust doesn't have as much chance to damage the top edge.

I trust you know the pistons are different diameters.

Full Monty caveat -

Unless you have experience some serious uneven wear,(unattributable to difference in grip in your tires) leaks, or have a jillion track miles, you probably don't need to rebuild the calipers completely. I've done it once in 15K track miles, and the bore seals were only marginally worn.

BTW, someday try pagid yellow up front and black in the back. I get WAY more life out of the yellows, and the blacks, being a little more aggresive, is like a poor man's brake bias. They work nice with yellows upfront. Also, I found better cooling using the GT3 RS brake spoilers.

Edited April 1, 2009 by ericinboca

[catmanluge]

Yoy might want to replace you inner seals if you cooked the outers seals the inners are most likely dead.

They are knock back seals otherwise you will have the same problem again!

2002 Boxster S, 37,000 miles, moderate track use. I am a fairly good mechanic, in general.

My Boxster pretty well toasted its brake rotors the last 5 days at Watkins Glen, and needed a thorough going-over. Pulling the pads, I noted the outer dust cover (deal) on one of the calipers was burned, and came out in my hand. Pretty well like burned toast. So along with rotors, screws, Pagid Oranges, etc. I ordered new dust covers (outer seals).

My question is whether there is a trick to putting these in. I expect getting them out involves pressing in the pistons, and prying them out with a screwdriver or such. Re-inserting new ones may be more challenging. Any known tricks? Pistons depressed into cylinders or projecting out slightly? Special or helpful tools? Any help would be appreciated.

Eric

I rebuilt all four of my calipers in February on my '04 986S, replacing all the bore seals, pistons, boots and bleeder screws.

If all you are replacing is the dust boot, you don't really need to remove the pistons. Just press the pistons back in and pull the boots off. They have a lip that fits into a recessed area on the caliper, and the top of them fits into a recessed area on the top outer edge of the piston, but the boot is reinforced at those parts and you should be able to pull them right off. Below you will note I caution on the use of a tool with the pistons, but if all you are doing is the dust boots, you can use a dental type tool to help get them out.

If you want to go the full monty, here is way more detail than you asked for :D ....but be sure you read my caveat on doing the full monty below.

You have to disconnect the fluid line on the back of the caliper to inject air to make the piston come out. As such, you should just remove the whole caliper.

With the caliper off, and the brake line dripping into a bucket, use plenty of brake parts cleaner to wash everything down and getting as much fluid out. You don't have to do this, but if you don't, when you apply the air pressure, you are going to splatter nasty brake fluid all over the place. You can remove the bleeder screws too, and spray into those and into the back until you feel like most of the fluid is out.

Then you need some blocks of wood; best to have some of different thicknesses. Place blocks between the pistons so when you apply the air pressure, these things hit something other than each other. And be careful, they come out with significant force.

Use the different thicknesses to get the pistons most of the way out. Then you can pull them out with your hand if you got them far enough out. Don't use any metal tool on the pistons. You can scratch and ruin them.

It is a bit like a puzzle sometimes to figure out what thickness of blocks to use to get all four pistons out far enough at the same time to pull them out, but it will make sense once you start.

Inspect the pistons. If you boots are shot, and you've had a few track days where you were down to nothing on your pads, you will probably find a little bit of rash on the sides near the top. If this is all you have, just at the top, they can be reused, IMO. If they are scored on the sides in a place that would make the scratch go past the seal, then resuing them runs the risk of leaking past the bore seal.

Look into the cylinder and half way or so down, you will see the bore seals - one per cylinder. You get these out with a dental type tool. These are inexpensive and readily available. I've seen them at sears as well as lowes. If you pull the seal out, you should replace it, because you do not want to run the risk of cutting or tearing it at all.

Go crazy with the brake parts cleaner. Clean, clean, clean, clean - but only use brake parts cleaner, or brake fluid itself. NOTHING else in the cylinder but one of these two chemicals.

When you reinstall the bore seals, you lube them with a silicon grease (came with my piston rebuild kits from Brembo - have more if you want the name) like you lube the ring on an oil filter. Then you bend them (because the rings' inside diameter is slightly larger then the diameter of the cylinder, and fit them into the little recessed area in the cylinder.

The pistons go in next. No grease on them.

And then put a tiny bit of the grease on the lip of the dust boots to make them fit easier on the lip of the caliper...try not to get any grease on the outside of the boot though, because it will gum up with dust.

Once all back together, flush your brake fluid, and then bleed them a couple of times too.

I've found my dust boots don't last long. It depends on what tracks I am visiting, but I am watching them more carefully now, and replacing them at least, sometimes twice a year. It seems to extend the life of the pistons because the dust doesn't have as much chance to damage the top edge.

I trust you know the pistons are different diameters.

Full Monty caveat -

Unless you have experience some serious uneven wear,(unattributable to difference in grip in your tires) leaks, or have a jillion track miles, you probably don't need to rebuild the calipers completely. I've done it once in 15K track miles, and the bore seals were only marginally worn.

BTW, someday try pagid yellow up front and black in the back. I get WAY more life out of the yellows, and the blacks, being a little more aggresive, is like a poor man's brake bias. They work nice with yellows upfront. Also, I found better cooling using the GT3 RS brake spoilers.

[espooner]

Thanks to both - very helpful, and sorta what I was thinking.

Eric

[garyman42]

I rebuilt all four of my calipers in February on my '04 986S, replacing all the bore seals, pistons, boots and bleeder screws.

I trust you know the pistons are different diameters.

Eric - can you help with part numbers for bore seals? Porsche offers sets of 36mm or 40mm dust seals (but

not one set with both sizes), but no bore seals.

I have a RF caliper with a hanging caliper piston, and need to rebuild with the piston seals. Can't find

the parts.

Thanks,

--Gary

[espooner]

I replaced just the outer seals (dust covers, they are called). If you have a caliper piston hanging, you probably need the INNER seals as well. The parts numbers are the same as for the 996 1999 to 2004, which has the same front brakes. They ARE 36 and 40 mm, with the larger bore in the front. I ordered them from Pelican Parts. I looked them up this AM, and the outer seals should be

951-351-917-00-OEM 36 mm. You will need two of each (inner and outer piston) for each side you are doing, for a total of 4 @ $19.50 ea.

951-351-917-01-OEM 40 mm. You will need two of each (inner and outer piston) for each side you are doing, for a total of 4 @ $19.50 ea.

Since you have to pull the calipers off the hub carrier, you should replace the bolts 999-073-402-01-M100 (2 per side or 4 @ $5.25 ea.)

Be SURE to re-assemble with anti-seize compound on the bolts. My local independent service did not do so on the previous rotor replacement. The bolts were seized into the hub carrier and stripped the threads coming out. Cost for this mistake on his part $2700.00 for new hub carriers, parts, labor.

I could find nothing for the bore seals, either. I would call Sunset Porsche or your local dealer.

Replacement is a non-trivial task, but do-able for a person with reasonable mechanical ability.

Good luck, and let me know if I can help otherwise.

Eric