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MR 69ER:
G'day people I've got a 69 big block roadster & i've got a problem with my braking system. After bleeding the complete system rear first then the front I get a good peddle for about 500k's then loose it. When I say loose it I mean all the way to the firewall the brake warning light comes on then eventually they pull me up. I have replaced all four calipers with complete new ones & also replaced my master cylinder with a new one but some how air is getting into the system. If I bleed the brakes they come good again and so on. No I am not cooking the brakes and I am using the right brake fluid, I have also replaced all the fluid in the brake lines when I had the new calipers & master cylinder put on. If anyone can shed any light on my situation I would appreciate it as I am getting sick of contiually having to bleed the system every couple of months.
Thanks
Steve:20:20:20:20

George80ONE:
Hi Steve,
A question. When you have to re bleed the brakes, do you get any air out of the lines? If so, you are not fully bleeding them. My mechanic bled the rear first, then the front and then the rears again. If there is still air in the lines then you can jack the rear of the car up and this will force the air when bleeding the brakes, to the highest point which will be at the rear. So the last bleed should be at the rear.
Also, check that the discs are running true. One of my problems with my brakes was that the discs needed machining. Over a long distance, the uneven movement against the rear calipers was causing problems.
Hope you can fix the problem.
George.;35

MR 69ER:
G'day George
Yes we do get air out of the lines and we do the back again after we have done the full cycle and the peddle comes back really good but like I said after a good hundred k"s I can feel it getting worse & worse and then eventually nothing at all. I have also had all four discs machined (which I forgot to mention in my earlier thred) so I dont think it could be the discs. I have heard though that if your rear wheel bearings were not the best that this could be creating a problem simular to what you mentioned, this is known as piston slap but one would think that with brand new calipers and no evidence of leaking brake fluid that the rubber seals around the piston would be doing their job and not letting air in, I am at a loss.
Steve:20:20:20

Brutus:
Steve...I'd suggest you may have far too much runout in your discs which is causing your brakes to pump the pistons.
Check out this thread from another forum which should shed some light on your problem.
http://www.digitalcorvettes.com/forums/showthread.php?s=&threadid=3490

MR 69ER:
Brutus all that makes sence but wouldn't the piston seals prevent air fron getting in and also would there not be traces of fluid leeking?
Steve:20:20:20

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