ausmini :: View topic - Clutch and Brake Master cylinder questions

1 Canyou/do you/is it necessary to hone the bore of the piston tube when over hauling and fitting a new kit?
Not essential, unless there is corrosion or scoring. But then you should sleeve it or buy new.
2 On the bog standard original metal reservoir type the only difference I can see internally is the spring in the brake one has rubber seals both ends is that all?
The brake one has a flow restrictor valve at top, it's not a seal.
Bores may be different- clutch should be 0.750", brake either 0.750" (850) or 0.700" most of the rest except 998 Cooper (0.625").

3 People are not wrong about worn clevis pins :shock:

but what do you do about the worn holes in the end of the plunger where it attatches to the pedal? - one is almost keyhole :cry:

I weld them up with MIG (used to use stick weld) then redrill.

Author:	Wombat [ Sun Nov 19, 2006 6:55 pm ]
Post subject:	Clutch and Brake Master cylinder questions
1 Canyou/do you/is it necessary to hone the bore of the piston tube when over hauling and fitting a new kit? 2 On the bog standard original metal reservoir type the only difference I can see internally is the spring in the brake one has rubber seals both ends is that all? 3 People are not wrong about worn clevis pins but what do you do about the worn holes in the end of the plunger where it attatches to the pedal? - one is almost keyhole

Author:	drmini in aust [ Sun Nov 19, 2006 7:12 pm ]
Post subject:	Re: Clutch and Brake Master cylinder questions
Wombat wrote: 1 Canyou/do you/is it necessary to hone the bore of the piston tube when over hauling and fitting a new kit? Not essential, unless there is corrosion or scoring. But then you should sleeve it or buy new. 2 On the bog standard original metal reservoir type the only difference I can see internally is the spring in the brake one has rubber seals both ends is that all? The brake one has a flow restrictor valve at top, it's not a seal. Bores may be different- clutch should be 0.750", brake either 0.750" (850) or 0.700" most of the rest except 998 Cooper (0.625"). 3 People are not wrong about worn clevis pins but what do you do about the worn holes in the end of the plunger where it attatches to the pedal? - one is almost keyhole I weld them up with MIG (used to use stick weld) then redrill.

Author:	miniron [ Sun Nov 19, 2006 9:04 pm ]
Post subject:
Bit more info on the valve in the brake master cylinder referred to by the DOC. It's actually called a residual pressure valve and its purpose is to maintain a low pressure in the brake lines of drum braked cars when the brakes are off to ensure the wheel cylinder seals are slightly expanded. This is supposed to stop air entering the brakes through the wheel cylinders when the pistons move slightly due to brake drum ovality etc when the brakes are off. Cars with discs all round don't need them but cars with front discs and rear drums still need them. Only in the rear brake section if you have a dual master cylinder with front discs and rear drums. Regards RonR

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