Raptord

iTrader: (10)

I've been having a recurring issue during the winter where some of the pistons in the front calipers will start leaking brake fluid. I say recurring because the same thing happened last winter as well.

When it started last year, I took the calipers off and took the dust boots, pistons and seals out, assuming some of the seals were broken/cracked. That was not the case; they were all in perfect condition. So I put everything back together, and lo and behold, it stopped leaking for the rest of that winter.

Fast forward to a couple weekends ago, they started leaking again. The first time I noticed it was during a very cold weekend, the coldest so far this winter. (around -30°C (-22°F) during the night). I now have the calipers off the car once again, and again all the seals are in good condition. I'm in the process of putting everything back together, and I'm assuming it will once again stop leaking for this winter, if last year was anything to go by.

The pistons have never leaked during the summer, and that's despite tracking the car.

I've owned the car for 7 years now, and never had this happen until last year. Other things worth knowing about:

- In the spring before last winter I changed the pistons to the Racing Brake SS pistons, along with their blue dust boots. I can't remember if I changed the seals as well, as I remember I had problems getting some pistons back in the calipers with the replacement seals (pistons simply refused to go in past the seals, even with all my weight trying to get them in).

- Until last winter, my car was always garaged overnight, so it wasn't in the cold as much as it is now.

Has anyone ever had leaking pistons despite seals being in good condition like this? I am planning on splitting the calipers in two this spring to really give them a good once over, as I've had a bunch of various issue with them that are getting really annoying. It's getting to the point where I almost want to just buy some used ones that hopefully won't have these issues, as I've never heard of anyone else having similar problems with theirs.

Also, I noticed the seals have a bit of a tapper on their outside side. Is the widder part of the tapper supposed to go in facing the internal part of the cylinder, or the external?

killerpenguin21

iTrader: (20)

Mine do it too when it gets cold enough, even though it's stored inside all winter (garage just gets residual heat from the building).

The stainless Pistons shrink more in the cold, as well as the seals rb uses. The first seal design was even worse and my calipers leaked the brake system dry 2 winters ago. RB sent me redesigned seals for free which I ran all last year, and this winter they only dropped maybe a capful of fluid on one side however it hasn't been below freezing here much this year.

Raptord

iTrader: (10)

Seems like an RB SS piston problem then. I just contacted them, will see what they have to say about this. I had installed their high-temp dust boots along with the ss pistons, and now those are ruined since they had fluid leak on them.

killerpenguin21

iTrader: (20)

I basically just rebuild once a year and am honestly getting fed up with the stock calipers. I can't manage more than like 2 events before I have terrible brake shudder from either deposits or sticking dust boots.

Raptord

iTrader: (10)

What do you mean by dust boots sticking?

killerpenguin21

iTrader: (20)

As they harden I keep getting chunks stuck along the edges of the piston which then jams up the piston motion.

Raptord

iTrader: (10)

Of all the brake issues I've had, that's one I haven't experienced yet (knock on wood).

2winscroll

I have rebuilt mine Girodisc seals and have no problems. It is more than likely the rubber is getting hard and contracting when extremely cold. The piston would not shrink more than .0005" that would not cause a leak, like I said it's probably the rubber the seals are made out of. M2C

2winscroll

When installing the Pistons use silicone spray they go together much easier. Brake fluid sucks!

killerpenguin21

iTrader: (20)

both of us are running racing brake stainless Pistons with high temp silicon dust boots and racing brake seals which as far as I know are not equivalent to oem or oem replacement

2winscroll

Don't get your panties in a bunch penguin. You are using stock calipers with aftermarket pistons and seals. I'm just saying try the Giorodisc seals I would bet that fixes your problem. The properties of rubber are much more susceptible to temp changes that stainless steel. Seals are square cut, the bottom of the groove in the caliper is cut on an angle to help with slightly retracting the piston when pedal is released.

killerpenguin21

iTrader: (20)

nothings in a bunch lol, it was just a shortly worded post sorry.

basically, im not sure that the grooves and seals on the rb stuff are equivalent to oem is my point, girodisc seals may not work. like i mentioned, RB did made at least one revision to the seals but im not exactly sure when, and i believe it was to make them thicker.

Raptord

iTrader: (10)

The seals I have are definitely not square, they have a very slight bevel. So are you saying the side of the groove that's furthest from the pad is a bit wider?

2winscroll

If my memory serves me, I believe the bottom of the groove in the caliper is slightly deeper on one side. Causing the seal be tighter on one side of the piston. Aftermarket Pistons are the same size so seals should work fine. Just keep the aftermarket dust seal.

Jonno99

Does the SS piston upgrade actually make much difference to the feel of the brakes?