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MG TD TF 1500 - master cylinder push rod adjustmen


How do I adjust my master cylinder push rod? Breaks have been adusted and bled... But my pedal still goes down to the floor - I get some stopping power but it sure is a "little" scary.

The Workshop Manual stresses that the brake pedal should move no more than half an inch or 13 mm from its normal resting place before the pushrod starts to move the piston in the Master cylinder. To adjust the pushrod to this setting requires taking the side cover from the pedal box to get at the pushrod and its locking nut. Push the rubber boot covering the pushrod back towards the master cylinder to ensure that the pushrod is free of crud and that its locking nut and clevis end are free of rust. Loosen the locknut and turn the pushrod itself until you determine that you have the pedal free play described above, and then tighten the locknut again, and pull the rubber boot back into place against the locking nut. There isn't a lot of room in the pedal box to do the job, and it will take some time.
Gene Burgess

If they worked before, sounds like it is still a 'bleed' problem... lots of fluid? Did you re-adjust the brake shoe adjustment screws?
gblawson (gordon)- TD#27667

I agree with Gordon,,,sounds like a bleed problem,,, I wouldn't mess with the rod untill I was absolutly sure that the system is free of any air...

Were the brakes working properly befor you tried adjusting them???? Might even be a problem in the master itself.. like leaking seals...

I guess we need a bit more of the brake history to properly trouble shoot this problem,...

Steve Wincze

i agree with the comments here. the service manual basically says don't touch the adjustment on the rod from the factory setting. if you extend the rod the piston cup connot retract far enough to uncover the balance hole in the master cylinder. so unless the P.O. "tinkered" around...i would say bleed system again and if that does not solve your problem the service manual says readjust the brakes (if unable to adjust at the wheel perhaps your pads need replacing), rebuild master cylinder as the piston cup is not retracting completely or the small balance hole is blocked in the cylinder. regards, tom
tom peterson

This was a "new" master cylinder from Moss. The whole brake system is new from Moss. It could be a bleed problem - but I would have expected to have to pump the pedal up to get it work - but that's not a problem. I took the inspection plate off and the nuts were all the way at the end of the adjustment rod near the master cylinder. I tried moving the lock nut both ways - by the space in there is soooo confined that I'm thinking that maybe I have to take the floor board off to get to everything. I wasn't even positive I was moving it in the correct direction... I could get a vaccum bleeder just to make sure.... What is the consensus of the group?

The easiest way to check for rod adjustment is to open the drivers door and on your knees just use your hand to push the brake pedal. You should have about 1/2"-3/4" free play before the pedal feels like it its touching something.
Also try pulling the hand brake all the way on and then try the brakes. If you then have a reasonable pedal you must re-adjust rear brakes and even have to add a shim to bring out the brake shoe heels a little further.
Have you checked the actual internal diameter of your brake shoes. The new drums measure 9". I have found that after .050 oversize you have to shim the shoes or get thicker linings.
Sandy Sanders

If the pedal goes to the floor, adjusting a half an inch or so will make no difference whatsoever. Either still air in the system, or perhaps a bad master cylinder? And as Tom says, did you adjust the brake shoes? George
George Butz

Pedal goes aout half way to the floor right now... I adjusted the rear brakes until they just scraped on the refished drums when turned (but that was a while ago - When just went out to look at the car, I lock up the hand brake the break pedal travels a reasonable amount of distance. However, I did have to pump the pedal to get it up.... OK - so I'll purge the lines again...

Try hose clamps to isolate where the air is trapped.If there is no difference then disconnect at the master cyl and bleed it vigorously there. Now fit a short 3/8 bsf bolt in place of the tube nut adapter sealed with an "o" ring this will give you a solid cylinder to check the throw.
see thread for 26 April.

Ray Lee

Make sure fronts are also adjusted. Turn the adjuster until the drum is locked. Then back off one or at most two turns. Then really forcefully apply the pedal to make sure the shoes are squarely seated in the drum, and repeat. This can make a major difference. George
George Butz

It is scary. I had the same problem and it was solved with a rebuilt kit for the master cylinder, and for the rear brake cylinder that leaked.
Denis L Baggi

Remember to do 'both' fronts on both sides!
gblawson (gordon)- TD#27667

George. I feel certain that you meant two clicks not turns.
nit pickin Sandy
Sandy Sanders

Sandy, oops- two clicks. George
George Butz

One click?
gblawson (gordon)- TD#27667

OK, since you can't do one and a half... Seriously, sometimes I have found from tight/locked one click still drags quite a bit, and it takes two. But sometimes one is perfect.
George Butz

When I do 'one'click, and it drags a bit, I know they will all quickly wear down that little 'drag'bit and all be equal... have had the car 'pull' if i do one of them 2 clicks. Last time I did it, I had smoke pouring out one rear wheel.. quickly evened up.
gblawson (gordon)- TD#27667

When I have adjusted my brakes from full lock/tight to one click off, there can be a slight drag on the brake shoes. I have found that by getting in the car and pumping the brake pedal a number of times, this seems to recenter the shoes to the brake drum and any drag disappears or becomes so slight that it of no problem. After an adjustment, I have taken the car out for a run and have applied the brakes severly several times. When I return and jack up the wheel that had some miner drag, I found it had disappeared.
George Raham
TD 4224
G. L. Raham

This thread was discussed between 23/04/2008 and 11/05/2008

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