shr3da

Have been experiencing brake issues for a while now.

Started at nations on the track, the brakes would randomly decide to not work as desired. By that I mean you would apply the brake, and they would not engage properly and the abs would start kicking in but I wouldn't be slowing down very fast and the pedal felt very strange, like I had no pads left. This continued throughout the day, being very random still.

When I got back to Melbourne we did a full flush of the brake system, the fluid was dirty and we used about 1 liter to flush it all out and get all the air out. We also did a bleed of the brake booster.

The brakes instantly felt better and where great but a few months later the symptoms have been getting worse up to the point where I am experiencing the same symptoms braking at 5km as i did at 150km at Wakefield, which never happened before. It has got so bad that the other day the brakes did not engage at all!

We know that air is getting into the system somehow and I am not loosing any fluid?

My question is how could air be getting into the system so quickly? and how can I fix this? It's an 03 model fyi.

Thanks, Ben

Spin9k

You seem to be jumping to conclusions saying air gets in the system. When weird things happen, better to back off and start w/a fresh look.

From your description, ABS is activating. Hummm... that would only happen if your wheel sensors indicate a problem like premature wheel lockup. What would cause that? Frozen or binding brake piston locking one wheel prematurely perhaps? Check the pad thickness across the pad to see if they are wearing at an angle could show the piston to be a problem. Check the piston boots for deteroration that lets water to rust the bore. Could be your caliper slide pins are frozen locking the caliper also.

Other things to check... have you ever overtightened any bleed screw and stripped the threads? Yes? You'll need a new caliper likely. Also inspect for cuts or nicks or wear on all fexible brake hoses. If there is air getting in to such an extend, there must be fluid getting out, inspect for leaks as a path to find the problem.

There's always the chance you have a defective master cylinder, the list goes on... but your problem sound weird enough that I'd be checking everything very carefully. Good luck.

shr3da

Thanks for the advice! The reason we believe air is the culpable is because once we did a bleed it improved the brakes. But now that I'm thinking about it the fluid was really dirty anyways so maybe it was masking another problem perhaps?

The pads are hwak hp + and only about 10 mths old.

Spin9k

Your pads per say are surely not the issue, but they can tell a story. Carefully measure the pad material depth across all four sides on each pad, inside and out. Uneven wear is not normal if it is there, and can happen quickly.

I was surprised last pad replacement to find a front & rear sticking slide bolt. I only investigated because I saw noticeable beveled wear across some of the older pads. Nothing noticeable in the braking though. They got cleaned, lubed, and sliding again.

That's not your problem, but it could be related. A jammed caliper could force the pads against the rotor, sort of preloading it to engage the ABS on one wheel as you tried to brake thereby eliminating any more forceful braking.

Good theory anyway, but you'll find the real cause soon enough, I'm sure

shr3da

Thank you for the advice, spoke to my mechanic about it this morning going down there tomorrow to try and sort this out.

shr3da

A bit of an update, did a full brake bleed including booster, was some air in there but not a lot. Problem is still present though, I have been told I need a brake booster rebuild? :/