When your master cylinder 'one way valve' seal leaks you do not lose fluid
but you can lose holding pressure and throw distance. The resevoir feeds fluid
to the master cylinder (which then should get compressed into lines) but if
fluid slips back into your resevoir (past a faulty one way valve seal) you can
end up with less throw and less holding power. Double clutching might save your
gears but won't remedy the hydraulic problem.
Hydraulic units are rebuildable if your bore is still smooth enough for a new
rubber kit from Moss or TRF. If in doubt about your bore's condition probably
best to get a brand new unit, or a professional re-sleave/rebuild job from
Apple and others.
ps; if your fluid is blackened your inner rubber valve seal is probably
deteriorating.. you might have incompatible fluid melting this rubber and/or
an inferior quality rubber kit installed.
'63 TR4 since '74
Sorry, should have mentioned that it's a 68 GT6 Mk1. I will examine
the hydraulics more closely. No sign of leakage as I haven't seen a
change in the fluid level in the reservoir.
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