Caliper dust seal seems deflated and/or torn. Problem?

[sugarwood]

What are the implications, and what are my options?
I assume these have been like this for a long time.
In fact, I just did a 2 day track weekend.

A new caliper costs $240.
PMB charges $300 to refresh one pair.

How difficult is a DIY reseal/refresh ?

[Porboynz]

Replacement is about as easy as changing the pads, get it clean first and you will see.

[DRACO A5OG]

Fronts easy, rears that is another story, but according to PMB, they have the front dust boots off of the 914-6 that will fit and work perfectly like our front dust boots. NO FREAKIN BARBED RING!!!!

Suga, those dust boots probably let moisture inside and may have introduced corrosion.

You really should consider a seal rebuild and cleaning of the calipers with new dust boots.

Just make sure you get SylGlide for the assembly and brass wire brush on a dremel type tool for cleaning, nothing harder you do not want to scratch the inside of the calipers.

Make sure none of the pistons have pitting or you will need to replace them. I posted pics on other threads of my rears that were leaking due to pitting on the pistons.

BTW, those were long gone before track days

[Jesse16]

Because these seals have become practically a regular replacement item for me on my 87, is there any method other than not using them at all that allows an 87 to protect the caliper piston ? I can toast my seals to crunchy bits in one track weekend at Carolina Motorsports Park, a very heavy braking circuit (for me). Probably go several seasons at most other tracks where you mostly "brush" the brakes to turn. Luckily they aren't too expensive to buy from our host, about an hour or so to remove/clean/replace front calipers with new seals.

[sugarwood]

I mentioned track day to convey that the brakes are working perfectly fine, despite the torn boots.
I am guessing they are not seals.

I found your other thread

1. Are caliper seals different than dust boots?
2. How do you know when caliper seals need replacing?
3. Does anyone have photos of the nightmare "retaining rings" of the rear? Not understanding what people are having to push down.
4. Why do pitted pistons need replacing?

[Drisump]

I'm assuming that the questions posed neeed answering:
1. Yes the seal is the barrier than keeps the fluid from leaking out ....not the dust seal that you can see.
2. Seepage or age, they will all fail at some point, I rebuilt all my callipers last summer when one wheel was starting to drag.
3. The ATE seals sold by our host for our cars a a complete nightmare. They don't go on, they easily rip when you force the the issue...ask me how I know. After ripping one I went to a local parts place and they furnished a seal kit that was made in Germany ( name escapes me) that was easy.....WTF?
4. Deep pits on the fluid side of the seal will likely leak. If brake fluid is flushed every 2 years per Porsche, they shouldn't have pitting on the fluid side of the piston. There will likely be rust on the piston between the seal and the dust cap.....carefully polish out but unless extreme, no problem. BTW the bores of the calipers should also be nice and clean with hopefully minimal rust.

Cheers

[Jesse16]

Thanks for the correction on terminology, I should have said "dust boot". I've never had the piston seal fail although they are very soft when removed after a few years of service. Not had a boot tear during install. I can get the rear boots on reasonably well now that I follow the advice of crimping in about half of the little metal grippers. Too bad there isn't a boot with more temp. resistance available.
FYI, my front ATE kit boxes from our host say made in Germany as do the rear FTE boxes.

[sugarwood]

It sounds like I can get a regular seal kit for the fronts, but I might want to explore alternative dust boots for the rear?

[sugarwood]

How to Rebuild a Brake Caliper: Saturday Mechanic

. Unlike surface damage to the piston, minor pitting of the bore is no big deal--the square-cut O-ring seals between its recessed groove and the piston, not to the outer bore.

I am reading about how a caliper works. Is my understanding correct?

First, why is there a seal? If there were no seal, there would have to be perfect clearance b/w the piston and bore. Too little and the piston can't move. Too much and the fluid goes around the piston. Sort of like oil getting past piston rings? So, there is a seal to give some play while sealing the fluid ?

So the parts that need to be in perfect tolerance are the piston and seal, since they are what trap the fluid. The bore itself is never part of the contact area. If there is a pitting in the piston, and fluid will bypass the seal there, and you lose pressure. Right?

[surflvr911sc]

Right

[DRACO A5OG]

Rear Barbed ring under the dust boot


Unlike the fronts the rear calipers do not have a lip to keep the dust boot in place


Some report no issues but I and many others have resorted to squashing down every other barb to make the sucka stay on the darn caliper

[DRACO A5OG]

Tried both Baby Food Cap and even built my on little rig. No Joy.



Squashing every other barb was the only way for me.

Here is the pitting:

[dtw]

Originally Posted by sugarwood

The bore itself is never part of the contact area. If there is a pitting in the piston, and fluid will bypass the seal there, and you lose pressure. Right?

I would amplify/clarify the last comment regarding pitted pistons with the following points of consideration:

Pitting is from corrosion. Corrosion tends to expand beyond the normal diameter of the piston, which can cause dragging/seizing. A piston frozen in the bore is either not doing any braking at all, or is dragging all the time on the rotor. Either way, no es bueno. Both scenarios result in under-performing brakes. The latter scenario can result in exciting fun things ranging from cooked/overheated rotors, glazed pads, boiled fluid, total brake failure, fire, etc.

Usually either condition can be readily observed by using one's senses. Frozen pistons stuck at the bottom of the bore will result in reduced braking capacity and sometimes 'off' or changed pedal feel. Dragging pads can result in stinky brakes, smoke, reduced acceleration capacity, blue colors on the rotor, etc. There is also going to be a LOT more heat on that corner than there is on the others. The constant heating is what glazes the pad, ruins the rotor, and worst - can boil the fluid.

Pitting results in an irregular surface (obv) and can abrade/tear the fluid seal. This can lead to low fluid levels and eventually brake failure. I have never seen a situation where all the brake fluid got squirted out catastrophically at the bore seal, but it isn't unheard of - especially on older cars that are not equipped with a low fluid sensor - to run dangerously low on fluid. Study how the braking system works - the fluid reservoir feeds the master cylinder via gravity. We keep a reservoir so that the MC plunger(s) always have fluid available on the downstroke. If there's no fluid supply, the MC will instead pull in air. The air will compress, resulting in a squishly pedal and little/no braking force.

The dust boot is important, as it keeps brake dust and other crap from compromising the fluid seal. Think of the dust boot as the first line of defense. Also, track days - while they are generally harder on the overall braking system than commuting - can do a great job of finishing off dust seals that were already on their last legs.

Changing fluid is important, because conventional brake fluid is hygroscopic (it absorbs ambient moisture in the air). Since the brake system is not 100% sealed from the environment, it will, over time, take on water. That water in the braking system will begin to corrode the metals in the braking system.

[brianlay]

Perhaps more importantly water lowers the boiling point of the brake fluid. This can lead to dangerously spongy brakes on the track.

[Drisump]

Originally Posted by Jesse16

Thanks for the correction on terminology, I should have said "dust boot". I've never had the piston seal fail although they are very soft when removed after a few years of service. Not had a boot tear during install. I can get the rear boots on reasonably well now that I follow the advice of crimping in about half of the little metal grippers. Too bad there isn't a boot with more temp. resistance available.
FYI, my front ATE kit boxes from our host say made in Germany as do the rear FTE boxes.

That's funny, I got ATE rears and fronts from our host last summer. The fronts were fine but the rears were a complete PITA..oddly enough FTE is what I sourced locally.....no problem at all.

[juanbenae]

use the brakes less at the track & your caliper dust seals will be preserved.

[sugarwood]

Originally Posted by Drisump

That's funny, I got ATE rears and fronts from our host last summer. The fronts were fine but the rears were a complete PITA..oddly enough FTE is what I sourced locally.....no problem at all.

So, I should get the FTE dust boots for the rear, and the front doesn't matter?

I still don't see how those barbs are used to keep the boot on.
Are they pinched against the boot to secure it ?

[RichardNew]

Seals are absolutely critical.

Dust boots not so much.

I usually melt them off at Homestead.



Richard Newton
How Are Your Brake Temperatures?

[Drisump]

Originally Posted by sugarwood

So, I should get the FTE dust boots for the rear, and the front doesn't matter?

I still don't see how those barbs are used to keep the boot on.
Are they pinched against the boot to secure it ?

The theory is that the fingers grab the flange that projects from the caliper body. I think the ATE ones are just a shade small for reasonably simple installation. What is strange is ATE is the manufacturer of the caliper in the first place. Like I said in an earlier post when I purchased rebuild kits from our host last summer and they provided ATE all around.....sounds like they've responded to complaints and changed the rears to FTE. Cheers

[DRACO A5OG]

Ditto ^^^

Geez, I hope so about the rears but a recent thread shows they did not, I think you got lucky