AU XR8II front brake caliper issue ?

galaxy xr8 · 13-03-2021, 09:05 PM

Hi guys I have a slight issue with my XR8, the passenger side front caliper the bottom piston seems to be not releasing right, I only just flushed and changed brake fluid 2 months ago, but in saying that prior to this change the vehicle has seen very little use and I believe from this the piston may have some slight rusting which is stopping the piston from retracting as normal.

I first noticed it when I jacked the car up and the wheel would not spin freely, so upon further inspection I have since found that one of the pistons will push out under load as normal but it doesn't then retract and locks the pads against the rotor, I did a quick flush this evening and noticed the fluid from this line alone is not clear like it should be and the fluid is fresh, so I'm assuming that over time and from lack of use this piston has developed moisture and rust and has seized slightly.

Since flushing once it has free'd up a little but after a few pumps again this same piston doesn't release and with every pump it just gets harder against the rotor.

Would numerous more flushing of this line eventually clean this and free the piston or am I up for a kit to be put through ?

Anyone have any suggestions ?.

Cheers.

undertow · 13-03-2021, 10:05 PM

You could try working the piston back and forth to free it up then flushing the fluid. I don't think flushing alone would dislodge much.

If it just has the standard brakes both the kits and whole calipers (new or refurb or used) are pretty cheap and easy to get.

galaxy xr8 · 13-03-2021, 10:25 PM

Thanks mate, yeah I plan to do just that tomorrow, I didn't have a clamp or such at my disposal , so since having borrowed one I am going to work the piston back and forth tomorrow and see if it improves, hopefully.

snap0964 · 14-03-2021, 12:37 AM

The std pistons are phenolic with a bonded metal ring that contacts against the pads - so they can look like metal.

Yeah, that's your best bet, initial test with caliper undone restrain one piston with a wood block or clamp, wind in the
other with a clamp, extend it with a wood block in place - obviously, be careful you don't pop it.

Does sound though that piston may be slightly angled with the seal over time, and binding.
Anyways, test first.

**Peuty** · 14-03-2021, 11:48 AM

Agree with the above for sure. If it turns out to be a piston corrosion issue, I'd consider upgrading to BF 322mm brakes, instead of rebuilding - though it depends on your budget. Rebuild kits are certainly cheap enough.

galaxy xr8 · 14-03-2021, 08:36 PM

Thanks guys, yeah after clamping the good piston down and then forcing the troublesome one in and out numerous times and flushing some fresh fluid through it has free'ed up a little, so I will take it for a good drive when I can and over time it will either loosen and come good or not.