Need help! Brakes lock themselves on whilst on track!


Darragh_K said:
If its only one wheel , its the round square sectioned seal in the caliper. That seal is the only thing to control the return movement of the piston.
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Okay. I'll get the rebuild kit sorted then, cheers
Would I still be able to push the piston back with my hands if this seal was broken? Or does it use like a vacuum from the fluid to pull the piston back inside?
 
jesse888 said:
Okay. I'll get the rebuild kit sorted then, cheers
Would I still be able to push the piston back with my hands if this seal was broken? Or does it use like a vacuum from the fluid to pull the piston back inside?
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Usually you need a multi-grips to squeeze the piston back . If its seized solid pop the piston out and put a skim of red rubber grease on the seal , it should help for now.

The seal actually swells up , and is in full face to face contact with the piston when its extended , which it shouldn't , When working properly the seal rotates a tiny bit from the grab of the piston sliding through it , when the brake is released , the seal wants to return to being flat , this pressure is what returns the piston , theres no vacuum :)
 
It was hard to get out at first but once I got it out it now slides in and out pretty easy, I need grips to get it to slide back out again but goes back in with just hand pressure.
Have bought rebuild kits for them anyway as I don't want this happening on track again. No control over the car what so ever so had to brake mega early to make sure it was going to stop.
So you pretty sure the seal is Likly to be my issue?
 
Yeah its the most likely cause for the symptoms you wrote.

Id still replace the hoses while you are at it
 
Yeah I've got it all ordered and on the way. Cost me over £400 and I've not got great discs or pads lol worth it for sure though. Will let everyone know how it goes next week.

Rep added btw
 
Have you cleaned off the layer of rust behind the squeal shims in the pad carrier?
This can be the cause a lot of problems when everything gets heated up.
Dunx
 
I've cleaned the little channels off that the pads slide along if that's what you mean? Of not what part so you mean? I'm waiting on a rebuild kit and the rest of my parts so got plenty of time to clean these up properly
 
It's the bit the top and bottom of the pads toutch. You have to pull off the shim thing and scrape or chip off the layer of rust the carrier.
Also do this on the rear.
Dunx
 
Okay mate I'll defo do that aswell, cheers.
 
Tegiwa Imports said:
It'll be a brake line failure. Luke had the same when he was on track at Cadwell.
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The flexible brake lines yeah?
Got them coming in the post, hopefully all this will sort the problem.
 
Still having the same issue!
Rebuilt the front calipers. New discs, pads and lines aswell. All rebled and its still locking the wheels up.
Even when I come off the pedal it's still locking the wheels.
Have no idea what this could be? Supposed to be on track tomorrow!
 
Could the master cylinder be the culprit? I'll take anyone's ideas on this.
It only locks one wheel. Drivers front. The pedal does not come back up when I release pressure, just stays flat.
 
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Puggie said:
what happens if you disconnect the brake servo?
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Will give that ago.
I pulled the abs fuse in the engine bay and now all is well! When the wheels lock without the abs I lift off and the pedal comes back to me and the brakes release.
Must be something electrical?
 
That's a very strange situation! No fault codes?
 
Kozy said:
That's a very strange situation! No fault codes?
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I haven't looked yet. Need to learn how and where to find the plug then I'll have a look and post my findings.
 
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