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MG MGA - Brake Bleeding problem

Hi Fellas,

I'm having a bit of problem while bleeding brakes.

I made my own pressurized bleeding system which started the bleeding process well. After a while it ceased to work so I started the tried and true brake pumping process.

So here's the problem, while the bleeders are closed the brake piston return to top dead end, however when the bleeder valves are open the brakes take one firm press down and the piston sticks at the bottom of the stroke.

Any thoughts?

Tysen
Tysen

Tysen

Could be the piston/bore is corroded down the bottom end of the stroke where you never go when actually braking and sticking there? It's always recommended not to use the full stroke when bleeding as corrosion in the bore might damage the seal lips.

Pete
Pete Tipping

You might need to provide a bit more info. What's the history of your car's hydraulics? Why are you bleeding the brakes? Did you rebuild the master cylinder? What was the conditon of the brakes before and what work did you perform?

If you rebuilt the MC, the seals could be tight for a number of reasons and that coupled with a weak return spring could cause your problem.

When the piston sticks, are you able to unstick it? If so, how do you do it? Or is it totally stuck and unable to return at all?
Mark

Sorry here's some more background

I'm bleeding the system because I rebuilt the Master Cylinders and all the slave cylnders and the front calipers.

When I rebuilt the MC I replaced all the seals and the spring and also made sure the holes on the top of the cylinder where clear.

Thanks
Tysen

Tysen

Forget my two penneth as you just rebuilt the MC...
Await the outcome.

Pete
Pete Tipping

Oops, a little more under re-read

Yes I am able to return it but jambing a flat bladed screw driver into the mouth of the piston hole and drawing it backwards. Its not terribly stuck, just not enough umph to come back.
Tysen

Hi Tysen, I had a similar problem with mine - it seems to be down to the new seals. They need "bedding in" first by working backwards and forwards a dozen or so times before connecting the MC back to the system - at least that is what I ended up doing using a large flat screw driver to prod the pistons and persuade them to pop back up each time. Cheers Cam
Cam Cunningham

It seems it's hit or miss with seal kits. I would just order another set from a different supplier.
Mark

Do you have your rear brake shoes full tight against the drums,if so back them off a bit and see if the residual pressure of the shoe springs will help return the piston.
wc wolcott

This thread was discussed between 25/03/2006 and 26/03/2006

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