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MG MG Y Type Sticking Brakes BBS discussion at MG-Cars.info
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MG MG Y Type - Sticking Brakes
| I have a YT recently imported from New Zealand. I have had the brakes overhauled and new master cylinder seals fitted. The brakes are fine when cold but as soon as I use them for a while they start to bind making the car almost undrivable. If I press the pedal a lot when stationary they do not bind at all. One expert has not solved the problem. Any ideas? |
| P. R. Wallace |
| The master cylinder may be the problem, there should be a very small bleed hole drilled into the master cylinder almost below the filler cap. have a look inside and when you release the brake pedal there will be a small fountain or disturbance in the fluid level, if not remove the master cylinder and have it drilled, about 1/16" dia will do. Bryan |
| B Mellem |
| Many thanks for your prompt reply. I have checked and there is no turbulence when I press the brake pedal. I will get someone to remove the master cylinder. Is the problem that the system pressurises as I use the brakes? Peter |
| P. R. Wallace |
| Peter, Where abouts in Surrey are you? Can you contact me via the contacts page of www.mgytypes.org Thanks Richard YT & YB |
| R E Knight |
| If that doesn't solve the problem, maybe you should have a good look at your brake hoses. I had mine collapse internally, thus blocking the low pressure return of the brake fluid, with sticking (rear) brakes. |
| Willem van der Veer |
| Just to check that its when the brake pedal is RELEASED the oil will drain back into the master cylinder through the bleed hole. If this fails to drain then the brakes remain pressurised and will increase the braking force as the fluid heats up. The master cylinder can be removed by undoing the three nuts behind the box and brake pipe, these three nuts are on free bolts on the inside of the box so must be held by a spanner. The thrust rod does not need to be removed. Get those nuts off and its a 'piece of cake' |
| B Mellem |
| Willem makes a valid point there too Peter - what is the age/condition of the rest of the components of your brake system ... including the retractor springs inside the drums? Hydraulic lock is a real problem. Also are your brake wheel cylinders in good condition? Rusted wheel cylinders will lock open if the wheel cylinders are rusty. Are your brakes properly adjusted too? Improperly adjusted brakes will overheat, fluid expands and then boils, and it looses all compression and becomes useless. What about the hand brake? Is it one wheel or all? Paul |
| Paul Barrow |
| I must confess to a degree of ignorance on the question of the master cylinder bleed hole. My 49 Y did not have this hole drilled right through but never caused any problem. Only when it was re-sleeved and fitted with modern replacement seals did the problem arise. I can only assume that there is a subtle difference in seal design from the original. I will also add that if the cylinder is re-sleeved care should be taken to ensure the bleed hole is drilled, and de-burred on the inside. But as pointed out the brake binding will occur on all 4 wheels simultaneously if this is the problem. Best of Luck Bryan |
| B Mellem |
| Hi PR Wallace, Give me a ring on 01277373923 before you strip the M/cyl out of the car. John UMG624 |
| JC Jebb |
| Willem van der Veer, said: If that doesn't solve the problem, maybe you should have a good look at your brake hoses. Poor brake hoses is something that I experienced, it was dangerous learning curve. One of the hoses ruptured and the brake became corrupted with brake fluid. Almost needed to change my underwear that day. |
| R Taylor |
| Hello Peter. We have seen a similar on TC's when they are switched to silicone brake fluid. The silicone swells the rubber cups more then the original fluid. It was found that if you machine .010 off the front of the piston the cup ends up far enough back to uncover the bleed hole. Butch |
| R Taras |
| Butch I think the thrust rod length is adjustable and with luck can make the master cylinder piston sweep further back, there is perhaps about 3/8" adjustment, but it is some time since I had the problem. Bryan |
| B Mellem |
| PR, the adjustment on the pushrod was factory set and not for service use. the Girling and Lockheed service manuals tell you this and so do the Y manuals.the clearance between the pushrod and piston should be 1/2", this measurement can be felt at the pedal end. The clearance can be lost by badly fitting floor boards or carpet retricting the pedal from completly returning to the correct off position also badly worn clevis and clevis pin John UMG624 |
| JC Jebb |
| Quite correct John but I will tell a little story. In the 1970's travelling across Germany I noticed that the brakes were loosing pressure and needed pumping, and with a caravan hitched behind it was rather a concern. Inspecting the brakes there was no sign of fluid loss and the master cylinder level was OK. So in a camp site I set about changing the master cylinder seals which I had amongst my spares. This did not cure the problem, so I concluded that a ridge of solidified fluid had built up in the cylinder, the car then had already clocked a quarter of million miles. The solution was to change the setting of the thrust rod by about 1/8" 'bobs your uncle' problem solved for the next 2000 miles home. Probably its still the same setting. Bryan |
| B Mellem |
This thread was discussed between 24/04/2016 and 02/05/2016
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