The other day while driving I notice (strongly noticed) that at a stop the pedal would slowly creep to the floorboard while applying pressure. I would pump it and pressure will build up and drop again. I still had brakes when having to stop quickly. As the day wore on as I went home, the break warning light came on, no brakes, had to use the hand brake. Luckily I wasn't going very fast and made it home okay.

I check the fluid level of the M/C and it was a tad below minimum which explains the warning light but not the failure.

First I suspected the servo booster was going out since I still had brakes.Now the Master Cylinder which I think is the culprit. I've ordered a replacement and should be here in a few days.

I took the M/C out today. There wasn't any obvious signs of leakage although I didn't check the bottom of the booster to see if there was any fluid had settled to the bottom.
I see that one line goes to the ABS servo and the other line goes to the secondary hydraulic cylinder. Is the secondary prone to failure?

Is there anything else I should consider? The ABS system? will that cause a full failure of the system even though I have no warning lights

 

are you sure you don't have any lines leaking?

 

I agree I would be looking for a leak if you had to loss fluid.

 

Didn't see any but it's worth another look.

 

Look behind the Driver's side wheel well, most common section of brake line to chunk, take allot of direct shots from road debris.

Caliper piston seals are another common area especially in colder weather. They start to seep then get progressively worse. Look for damp inner wheel rim.

 

Spot on ihscouts. I went ahead and replaced the master cylinder. After I got pressure, went for a short drive and it was barely braking. Put Monty back in the driveway looked under the driver side wheel and sure enough leakage from the brake hose.

Still a leaky brake line shouldn't have cause a failure of the dual system. I now suspect the brake line was going out as well as the Master Cylinder. I've seen this happen on other Brit cars. Once the weather clears up I will replace all the brake lines just to be safe than sorry later.

 

I would go with OE line if you can because it's pickled. Auto parts store line is fine for quick repair. You probably know this, you'll need a bubble flair if you buy DIY line.

The line with the leak is the most prone, the rest will look fine.

Now that you have a new master and soon will have new line put eyes on your piston seals every now and then.

 

What is a bubble flair?

 

Right line is bubble flair, European style. Left is the common style on US manufactured vehicles known as a double flair.

 

Ah got it. I'll double check it when it comes in tomorrow, tanks for the tip.