Jump to content
Ultimate Subaru Message Board

03 Outback base model: front caliper rust inside Pistons clean or replace?

Recommended Posts

This is a follow up to a thread from last week about replacing a front caliper and recommendations as to used, new, brand, etc.


I started out with a garage that told me my front passenger brake was sticking, the cause of our 2003 base model outback 146k miles, pulling to the right. They recommended replacing the caliper, rotor, pads at about $600. I just did a $90 alignment and $550 worth of tires so wasn't in a position to spend another $600. I asked did they check the slide pins, they said yes that's not the issue. I declined and took it home and started looking for answers.


I finally after having our garage snowed in, was able to pull the wheel, and examine the caliper today. One slide pin worked fine, the lower one was frozen. It took a pliers and brute force to move. Once out, the good one was lubed, the bad one was bone dry.


Next once I got the pads out I found the backs of the pads against the pistons to be very rusted and the insides of the Pistons to be full of rust or dirt or both. One had rust inside, the other looked like a pipe that corroded down to 80% of its capacity.


So from here, should I clean the insides with a wire brush maybe on a dremel, or just clean away the loose debri/rust, or replace the caliper. Nowhere locally can I find a rebuild kit that includes new pistons and we have all the major chains. Subaru tells me they discontinued caliper rebuild kits.


I bought a new Subaru rotor, and pad set with the hardware. If not for the rust I'd be looking at a simple clean & lube I think. I'm still pretty new to this and not sure I'd be able to rebuild the caliper, if I could find a kit.


I'd like to finish this up, today Tuesday the 21st here in eastern PA because I'm working in an unheated garage and it's supposed to get cold again on Wednesday. I've got a bad back & neck, so working in the cold is not good for it.


Thank you in advance for any help & advice. Spiney-Dave

Link to comment
Share on other sites

if the piston boots are fine - ignore the rust and reassemble.  sometimes i'll knock the loose stuff out just for kicks 


that is surface rust and entirely benign. those pistons are thick and will never rust through before something else fails.  the bore and parts of the piston you can't see are the critical areas and covered by the piston boot. 


i've driven many years with even slight cracks in piston boots.  if you have a cracked piston boot then replace with a used caliper. 

if you're up for a little extra grunt work you can rebuild the caliper. 


even if the boot was torn i'd just assemble it as-is for today and plan to deal with it in the next two years, get your parts ready, etc. 

  • Like 1
Link to comment
Share on other sites



I've done my own car repairs on my vehicles and friends and family for 50 years, and have cleaned up many calipers that were seized or sticking. The only time the piston needs replacing, is if its badly pitted on the surface that slides into the caliper past the piston/caliper seal. Bad pits on that surface will cause fluid leaks. Rust on the rest of the piston is a non issue, as long as the end of the piston that pushes on the brake pad is relatively clean and level.


I have never had to replace a caliper on any car I've ever worked on. A piston or two, yes, but it is rare to see one bad enough to replace.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Create New...