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MG MGB Technical - Fluid Dip Bottom Brake Petal

Hi Gents,
Getting down to smaller fish to fry on my 72 mgb roadster.
I have noticed a small drip of brake fluid that looks like it's coming down the brake petal pathway and dripping off brake foot petal.
I am assuming this petal goes bake through some linkage to the master cylinder.
Does this sound like some minor seal issue or what?
How difficult is the repair? I've never been inside the black box under the master cylinder. Can this box be easily removed to see components inside and make repairs? Any watchouts for the ameteur or should I take this one to the shop?
I have been through the entire brake system outside the master cylinder. Have good brakes and no pull etc. Periodically I have to add fluid, but it's a relatively small leak. Thoughts?

Best regards,
Doug
DT Toms

Thread Title Should be Fluid Drip :-), early this morning lol.
DT Toms

The drips of brake fluid are likely comming from the seals in the master cyclinder where the rod from the brake pedal enters. It likely is due for a rebuild. While they can be rebuilt in place it is not a lot of fun and makes a mess, if the bore is in poor shape you will need to pull it any way. Take the cover off the black box and you will see the pedal linkae and the leaky end of the master cylinder. To remove it you need to disconnect the brake and clutch lines, remove the pedals(One bolt), and than remove the pedal box.
John H

Brake fluid will dissolve paint and ruin carpets. So, keep that in mind when you get it on your hands and touch the body.
Richard Morris

The paint under the brake cylinder has probably been removed by the leaking fluid. It's best to remove the pedal box to clean and paint the area under the pedal box. I have rebuilts lots of master cylinders in ither cars with no problem, but I did a rebuild on my MGB master cylinder and 6 months later I had to remove it again because it started leaking.

Clifton
Clifton Gordon

Personally, I won't rebuild a master cylinder, as the leakage is invariably caused by bore wear, and the new seals won't last. Replacement is the preferred option when possible, but it is your money after all.
Martin Layton

Martin, I agree. When it started leaking the second time I replaced it with a new cylinder, that was over 8 years ago.

Clifton
Clifton Gordon

If you are confident enough to rebuild the cylinder I would try that first (honing the cylinder lightly to remove any wear points). If the new seals still leak you can always install a replacement cylinder.
Be warned that the MGB dual cylinder is a rather challenging thing to rebuild the first time you do one.
If you are having a shop do the work you will probably find it more cost-effective to just have them install a replacement cylinder.

Rich
Rich McKIe

Thanks guys. Sounds like putting in new seals and honing is something I can manage. If the new seals don't hold, I'll beg the wife for some more money :-)

Best regrds,
Doug
DT Toms

That's the sensible route to go.
I find that the "Replace it with new upgraded parts" crowd suggests replacing everything, usually for safety's sake, when in many cases the old parts can be reconditioned or just reused, and are often much better quality than the replacements commonly available. Back in the 80's I made my living restoring MGs and that attitude was prevelant in the restoring community at the time. If I had all of the restorable T-series parts that I scrapped back then I could get rich on E-bay!.
By all means, if a rebuild doesn't work out replace the part, but there really is little harm in trying a rebuild. Just be careful that first time you pull out of your driveway!

Cheers,
Rich
Rich McKIe

I don't agree. The relatively small bored master cyl is subjected to quite considerable wear and whilst seals may seal in the short term are not likely to hold up very long. Bearing in mind the difficulty in doing this job the last thing that you need is to have to do it twice. Fit a new cyl and be done with it and also confident that it will last for many more years.
Iain MacKintosh

I was in the same boat as you are about a year and a half ago. I had a drip down the pedal. I looked at the price of a new one and a rebuild kit. I decided to rebuild it last year. Today I replace the master as it started leaking again.

I replaced it without disconnecting the clutch line so I do not have to bleed that line again.

Don
DWM

Don,
What is the procedure and what allows you to replace without disconnecting clutch line? Is the cluth line and brake systems ran off seperate masters? The small refill is for the clutch and the larger 2 chamber master for the brakes? So you just disconnect the brake line and not a space issue replacing brake master?
Best regards,
Doug
DT Toms

Don,
You mention replacing it without disconnecting the clutch line?
Is this normally done just to make it easier to get out?
I assume the brake line goes into the brake master and the clutch into the snaller reservoir?
Any tricks for total replacement, or just pretty straight forward disconnecting linkage etc?

Thanks, Doug
DT Toms

The brake master and clutch master are both mounted in the same pedal box frame. Most posts have said that to replace the brake master you have to take both out. I found that you can take the brake master out without having to disconnect the clutch line. Disconnecting the clutch line is a pain and bleeding the air out after is even more of a pain.

To get the brake master out, You have to take the cover off, remove 6 bolts in the engine compartment on the pedal box and two from under the dash, disconnect the master push rod pin, pull out the push rod, disconnect the two (Duel line Master) brake lines, push or pull out the large black plug under the dash, Unbolt the two bolts holding the master to the frame. Once all this is done the pedal box will move enough to wiggle the brake master out without disconnecting the clutch.

One tip. On the master, install the upper bolt through the mounting hole before attaching the reservoir. Then it is easier to get the nut on from the outside when remounting.

Don
DWM

This thread was discussed between 06/04/2007 and 16/04/2007

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