Front Brake Caliper Leaking Fluid, Help?

[bwhitmore]

I recently had my brake calipers powdercoated and (without going into the history on the ***** that did them, because I plan to contact him on it as well) I found that two of the dust covers that seal the pistons on my left front caliper were badly cracked. Since they weren't this way when I sent them to get refinished I was at first very concerned. But upon closer inspection I figured their main purpose was to keep dust away from the actual seal (the rubber ring further down inside piston) which was intacted.

So, I installed the calipers and bled the brakes and they have sat (without the wheels) while I have been finishing the exhaust on my car for about a week now. About a day after the install I noticed a couple small drops of brake fluid on the garage floor. I thought at first it was coming from either the bleeder screws or the crossover tube, but no such luck. I tightened them, cleaned up the drops, and left it overnight. Next morning same thing. So I removed the caliper and found that the leak is coming from the area of the cracked dust covers around the pistons. It's not enough of a leak to feel in the pedal but enough to drip down the inside of the caliper and onto my garage floor. I plan to get my car back on the road next week, an I doubt any small leak is going to resolve itself. Any thoughts?

 

[Tom F&L GoR]

From all the rear calipers I've disassembled I see many with torn boots. The result of this is often that dust and dirt work their way behind the piston seal and not between the seal and piston.

The piston seal groove is not a simple square cut, the faces are a different angles and the corners have chamfers. This is all the produce a better seal when fluid pressure is applied and also to produce twist. The twist rolls the seal a little bit so that when released, the piston is slightly retracted.

** edit - the fluid side is up and the atmosphere side is down in this pic

I believe that the twist or rolling "pumps" the dirt around behind the seal. The good news is that the piston doesn't get scored. The other good news is that the fronts are sooooo much easier to replace the seals, and you can get them (and the dust boots) from Dodge, Viper parts suppliers, or specialty catalogs, like Truechoice.com. In an emergency situation, I'll bet you could even clean out the grooves and re-use everything; the back of the seals will be dimpled from the dirt, but if it's not there anymore, it will hold pressure.

Or, your calipers could have been powdercoated without disassembly. The oven can be as low as 300F, and the rubber parts might survive or might not. Sounds like they've either gotten hard or were reassembled without being cleaned. Let me know if you need part numbers.

 

[bwhitmore]

Tom,

See if you can get me a part number on the dust covers and the inner seals. I will disassemble the caliper and see if I can clean real good the groove were the inner seal goes. I am about 99% sure the inner seals are okay, but if I am going that far I might as well replace them anyway. It could just be the mating surface has some dust from sandblasting in it.

Thanks,
Brian

 

[Janni]

Here's a tip - SOAK the piston seals in brake fluid for a few hours before installing - sometimes getting those pistons back into the caliper is, well, trying. Soaking them loosens them up and they get more pliable.

 

[Tom F&L GoR]

Brembo 38mm seal 05.5955.57 $10.85 (need 2 per caliper)
Brembo 42mm seal 05.5955.59 $10.85
Brembo 38mm dust boot 20.4872.45 $3.75
Brembo 42mm dust boot 20.4872.47 $3.75
Mopar kit (seals, dust boots, and pistons for one caliper) 04723455 $$$$

 

[bwhitmore]

Tom,

Is the best place to get just the dust boots through TrueChoice? It seems to me Brembo does not sell to the public.

Thanks again.

 

[Janni]

We've always bought through TrueChoice. Brembo does not sell direct.

 

[bwhitmore]

I actually just picked up aset through Race Technologies in Socal. They were a little more expensive but they had the seals in stock (no ordering from Brembo first) and can overnight them.

 

[Tom F&L GoR]

Brian, your experience is like mine; Truechoice is a little cheaper but usually longer wait. Those are the only two places I've tried, also.

Ummm... need any 40mm rear calipers to go with those seals?

 

[GTS Dean]

Sameless. Shameless I tell you. :shakinghead:

 

[Tom F&L GoR]

Dean, you're next on my list. GTX tips but no brakes?

 

[GTS Dean]

Don't need no stinkin' brakes. They just slow you down.

 

[Tom F&L GoR]

Aeroquip, Dilusi, 40mm.... kinda sounds like a good package, no?