mark6

Can anyone shed the light on the problem with the subaru 4-pot calipers??

It seems alot of them suffer the inner pistons not working properly and buggering the discs up,I've just had the problem too but the pistons seem to push back in with no resistance what so ever and the dust seals are fine,i was going to get a caliper service kit and strip them down but it just puzzles me how they don't seem to be sticking at all!!

Normally they would be a bit tight pushing the pistons back in if they were sticking only a little bit but they seemed fine,and when you look at the inner side of the disc its as though the pistons haven't been working at all,and when you consider the force the pistons push i know that can't be true.

Could it be anything to do with them being alloy calipers instead of steel,as alloy wheels sometimes puff up where they sit on the hub and have to be bashed off but then they go back on fine as its just the bare alloy puffing up,wondered if the same thing could happen to the calipers or does no one know??

Mark

awd wrx

Mark , the Subaru calipers are steel not alloy , what problem are you having ?

mark6

as above,the inner pistons don't seem to be working properly,put a set of grooved discs on 7 months ago and they started cracking,ordered some new ones to send the others back and when i got them off the inside of the discs were all scabby but the outside normal,pads werent sticking so it can only be the pistons not working properly or am i missing something??did a search and a few people have had the same problem.

awd wrx

yes it can be the pistons sticking , what condition are the outer dust seals in , any tears in these and the pistons will sieze , when these stick and drag the pads dont release off the discs and will overheat / crack / wear down the discs , it doesnt have to be siezed solid to do this , a slight bit of drag can cause this to happen

GingerbreadMan

iTrader: (1)

I’ve recently re-con’d mine. I can see where Mark is coming from, I read loads of posts about the inside pistons sticking. And after taking the calipers apart to find 6 seized pistons (4 of which were the inside 2 on each caliper) – I couldn’t help think they maybe a design issue.

Another interesting observation was that all of the dust-seals were intact. On the pistons, the exposed lip is plated. Over time, this plating had corroded away leaving and irregular surface where the seal sits, and thus, allowing water behind it causing the piston to eventually seize. So surely my pistons are only going to be able to move provided there is plating (or a decent seal) on my pistons – Which also led me to believe that the 4pot calipers were somehow a bit crap!!

Maybe the inside pistons don’t see much cooling as the outside ones…………. but fact is, many people are having sticky inside pistons with the Subaru 4 pots, I rarely hear stories about other problematic calipers (only when they’re 10+yrs), mine are around 6yrs old and they’ve been re-built twice now.

Rob.

mark6

When you say 6 of your pistons were seized were they seized badly?,or could you still push them back in with ease??,my calipers are almost five years old now and still look good cosmetically so i'm quite suprised that i'm having problems with them,also where did you get your service kit from and did you change the pistons as well??

And one last question, if the plating is flaking where the dust seal sits won't they let the water straight back in?and what price is the service kit if you can remember??

GingerbreadMan

iTrader: (1)

When I say seized, I mean good and stuck, no movement whatsoever. And they were absolute motherf****rs to remove !! I ended up having to use a pair of mole-grips to remove two, which obviously meant the exposed lip was nicley chewed. I wasn't going to f**k about replacing dodgy pistons, so I had them all re-made FOC by a friend. (Subaru only sell the pistons with the caliper body iirc)

Don't be fooled by your calipers looking cosmetically good, they may well be shagged. Mine looked okay too.

And yes, if the plating does start flaking, I believe over time there will no longer be a decent seal - crap eh? heres what one of mine looked like......

http://i40.photobucket.com/albums/e2..._oldpiston.jpg

and a new one.........

http://i40.photobucket.com/albums/e2..._newpiston.jpg

New seal kits are available from Subaru (2 kits @£20ish iirc), seals and pistons ara available from Godspeed too (if your prepared to wait ), I think he sells the pistons for around £20ea.


Have fun!!