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MG MGA - MGA Hydraulic System

I am toward the end of a ground up restoration. I have all new brake pipes, clutch pipe, brake hoses, clutch hose, clutch slave, clutch assembly, clutch disc, and a rebuilt master cylinder. My 4-way brass fitting that includes the brake light circuit is new but the other fittings are used. There are no fluid leaks in the system and the system has been successfully bled.

When I have a helper apply the clutch pedal I observe the following:

1. The clutch slave moves the clutch release lever about 10mm - the normal distance.

2. Then slowly (6 seconds) the lever forces the clutch slave piston back 90%.

3. As the lever forces the piston back the fluid in the master cylinder rises.

There does not seem to be eough hydraulic pressure to keep the clutch disengaged. The clutch pipe diameter is larger that the brake pipe diameter.

Should all pipes have the same diameter?

gerard hutchinson

Gerald, you have a leaky cylinder somewhere. The hydraulic pipe diameter does not affect pressures.
A Pearse

Gerard,

The master cylinder is faulty. As you say, the clutch forces the fluid back into the master cylinder.


Mick
Mick Anderson

The clutch pipe is larger to enable return of fluid to permit instant engagement of the clutch as fast as you can take your foot off the pedal. Normal motion of the clutch slave is about 5/8-inch with full pedal travel. Slave cylinder returning with pedal down, accompanied by rise of fluid in th4 reservoir, indicates leakage past the master cylinder piston. Master cylinder rebuild didn't take, needs to be done again.

Barney Gaylord

I was afraid of that!!
gerard hutchinson

Has anyone had a master cylinder rebuilt by White Post Restorations? Will they honor their lifetime wartranty?
gerard hutchinson

I had a M/C re-sleeved only, not rebuilt, by White Post. I did the rest of the rebuild myself. I had the M/C in the car for 5-10 years using DOT-4 brake fluid before selling that one. Never had any problem so I never had the need to see how good the warranty was. I suspect that they only give lifetime warranty for their rebuilt units. you would have to call them to find our for sure. If I had to do it over again, I'd do it the same way, White Post resleeve with a personal rebuild. W/P has been around for many years and does work for Brit cars and US cars as well.

Just one happy customer,
Chuck
C Schaefer

That makes me feel more confident. Thanks Chuck.
gerard hutchinson

This thread was discussed between 30/06/2008 and 02/07/2008

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