403 brake problems

Firstly, I'd try to identify if the problem is the master cylinder.

Use vice grips to clamp off the flexible hose to the rear and both of the front flex hoses.

If you get no pedal it MUST be the master cylinder.

If you get a pedal, release the flex hose to the rear. If you still get a pedal, it must be the fronts.

Now you can selectively release the front hoses to narrow it down.
 
Clamp the hoses close to the entry point.

I once had an MG Midget I could not get a clutch pedal on.

By accident I grabbed the hose while my partner was pumping the pedal. It was pulsating! The hydraulic force was actually expanding the hose rather than pushing the clutch lever.
 
Clamp the hoses close to the entry point. I once had an MG Midget I could not get a clutch pedal on. By accident I grabbed the hose while my partner was pumping the pedal. It was pulsating! The hydraulic force was actually expanding the hose rather than pushing the clutch lever.

That is exactly how I found my last set of R8 hoses were the cause of poor "pedal". I could actually feel one of them expanding longitudinally. Pedal free play also was marginally too much, and reducing that slack brought the pedal up surprisingly (although I shouldn't have been surprised....). I've surely learned not to use NOS hoses but get new ones made locally.
 
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