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MG MGA - No flow from one rear bleeder screw

Changing out the brake fluid this weekend. Almost done...but wait! I cannot get any flow from the rear bleeder on the driver's side. The other three bled properly. I am able to completely remove the bleeder from the brake backing plate, without so much as a drip. I am pressurizing the MC to about 10 psi with a pressure bottle.

Blocked brake line? Any likely suspect sections?

Thx,

Rick
rpb bunch

Having done 3 of the brakes are you able to get pressure applied on the brake pedal? If so, does that rear wheel lock up? i.e. does the brake piston move?

Steve
Steve Gyles

You will have to systematically disconnect lines from the cylinder backwards until you get a flow.
Art Pearse

This wheel spins freely, and locks tight with brake pedal pressure. My take (correctly?) is the the line is free, and the cylinder is free...maybe just a plugged bleeder path in the backing plate?

My next intended action is to pull the bleeder screw and fish some 0.030" welding wire through from the outside to see if I can clear it. Comments?
rpb bunch

Rick, it's very common for bleeder screws to get bunged up with crud and for the little hole behind the taper to be blocked. With the bleed screw completely removed, and without depressing the pedal, you should get a steady drip of fluid from the cylinder bleed hole (I usually do this with all the wheel cylinders before I start bleeding). If you do get this flow, then obviously it is the bleed nipple that is at fault. If your bleed nipples are not nice and shiny plated ones, it might be a good idea to change them.
Lindsay Sampford

Thanks, Lindsey...

I've got it clear now. Flowing with nice, clean brake fluid. I suspect the orifice was plugged internal to the bleeder. I gave it a brake pedal 'push' with the bleeder open, and it started flowing more like it should. I then followed up with pressure bleeding and re-did the other 3 again.

Now on to the clutch...
rpb bunch

Raises an interesting issue. Conventional fluid should be changed every 2 years, whereas silicon can be left a lot longer. Therefore, with conventional fluid you find out problems every 2 years; with silicon perhaps every dozen years, may be? Pros and cons?

Steve
Steve Gyles

Because Silicon fluid does not absorb any water, water can collection in the lowest parts of the brake system and promote rust. I would still flush the system regularly.
Keith Lowman

This thread was discussed on 06/09/2010

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