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MG MGF Technical - Changing Brake Pads

Hi all,

I need to lower the inner piston on each front caliper. If I use the bleed screw to release some brake fluid, do I need to have a piece of rubber hose leading into a container of brake fluid in order to stop air getting into the system (as in the workshop manual). Or can I just allow the fluid to seep out into a cloth and then top up the master level when I'm finished.


Best to use a tube into a container with some clean fluid in, just to be on the safe side - the last thing you want is spongey brakes.

BTW why do you need to lower the inner piston on each front caliper?

Ted Newman

I think not. You don't want to open the bleed valves - if you do you are very likely to get air into the system.

Just sqeeze the piston gently back into the cylinder with a G-Clamp (or other specialised tool). (You have to screw the back ones in I believe, but the fronts are a straight push).

Watch that you don't end up with a full master cylinder. If you do, then remove some fluid with for example a syringe. Do one side at a time and pump the brakes well to seat the new pads between sides as this this put some fluid back into the slave and give you space to do the other side,

Roger documented what you have to do in the archive, I believe, in easier to understand terms than the WS manual.



If you're going from well-worn to new pads then it's quite likely that the master cylinder will overflow when the pistons are pushed right back. The last thing you want is brake fluid dripping over the bodywork. I found it easier (not having a syringe) to stick a bleed hose over the nipple (to stop the fluid going all over the hubs), stick the end of the hose in an old tin to catch the fluid, open the nipple half a turn, and let the fluid slowly drip into the tin. Good old gravity will do the trick without any air getting in to the system (as long as Anna K isn't playing and you let the master cylinder run empty). You can judge when enough fluid has been drained. There's no need to have any fluid in the tin. Just don't touch the brake pedal!

Good luck, Kes.

Problem is I can't move the inner piston back by hand -the pads a very worn. This is why (in the absence of having the clamp ???) I need to release some fluid. I am following Rogers instructions which are very good but I got stuck with the piston and had to re-assemble everything. I'll try the bleed routine later today.


When pads are very worn the piston extends a long way and it is easy for it to become out of line with it's bore and jam slightly. Release of the bleed nipple can also help here as it removes a small amount of resistance that is stopping the piston from returning.

You must make sure that when your returning the piston from a long way out that the piston is square to the body. If need be you may need to use two levers in a siccor action so that effort is applied from both sides of the piston. (through the worn pad I suggest) Failing this some simple and cheaper piston retractors are available from halfords and such like.

Roger Parker

This thread was discussed between 28/06/2000 and 01/07/2000

MG MGF Technical index

This thread is from the archive. The Live MG MGF Technical BBS is active now.