Triumph · 1970–1977The Stag Archive

How-To & Repairs / Brakes

Freeing seized brakes and brake overhaul

A safety-critical overhaul of the Stag's servo-assisted front discs and rear drums. Covers freeing seized calipers and wheel cylinders after the car has stood, renewing flexible hoses, flushing to fresh DOT fluid, checking the servo and bleeding the system thoroughly.

Tools needed

  • Trolley jack and axle stands
  • Brake spanner set (proper flare-nut spanners for hydraulic unions)
  • Piston winder / rewind tool where required
  • Brake bleeding kit (one-person kit or an assistant)
  • Wire brush, brake cleaner and clean rags
  • Torque wrench for caliper carrier and wheel fasteners

Parts needed

  • Caliper overhaul kit or exchange calipers
  • Wheel-cylinder overhaul kit or new cylinders
  • All flexible brake hoses (renew as a set)
  • Fresh DOT brake fluid to the specification in the workshop manual
  • New pads and shoes as required
  • Copper washers and any specified locking hardware

Warnings

  • Braking work MUST be done to the workshop-manual specification. If there is any doubt about the finished job, have it checked by a competent person before road use.
  • Brake fluid strips paint on contact — protect surrounding bodywork and wash any spills off immediately.

Steps

  1. 01. Chock, raise and support the car properly

    Chock the wheels remaining on the ground, raise the car and support it securely on axle stands on firm, level ground. Never work under a car supported only on a jack.

    Warning:Braking work is safety-critical. If any step is beyond your confidence, have the finished job checked by a competent person before road use.

  2. 02. Assess the symptoms and the fluid

    Typical signs are pulling under braking, a binding brake, a poor / spongy pedal, or brakes seized after the car has stood. Draw a small sample of the old fluid — dark, cloudy fluid is a strong indicator that moisture has been absorbed and the system is overdue for a full flush.

  3. 03. Overhaul or renew the front calipers

    The Stag runs servo-assisted front discs. Remove the calipers, strip and inspect the pistons and seals, and either fit an overhaul kit or fit exchange calipers if pitting or corrosion is beyond a simple hone. Refit with fresh pads.

  4. Owner-uploaded photo slot
    Front caliper stripped. The front caliper off the car and stripped for inspection or overhaul.

  5. 04. Overhaul or renew the rear wheel cylinders

    Strip the rear drums and inspect the wheel cylinders. Seized cylinders, weeping seals or scored bores mean an overhaul kit or new cylinders. Fit fresh shoes at the same time and adjust as specified in the workshop manual.

  6. 05. Renew all flexible hoses

    Flexible brake hoses perish internally with age even when they look fine outside — a collapsed inner liner can act as a one-way valve and cause a brake to bind. Renew all the flexible hoses as a set, not individually.

  7. Owner-uploaded photo slot
    Old vs new flexible hose. An old flexible hose next to its replacement, with any obvious deterioration visible.

  8. 06. Check the servo

    With the engine off, press the pedal several times to exhaust the servo, then start the engine — the pedal should sink slightly as vacuum assistance comes in. If it does not, investigate the vacuum supply, the check valve and the servo itself before signing the job off.

  9. 07. Flush to fresh DOT fluid and bleed thoroughly

    Flush the entire system through with fresh DOT fluid of the specification given in the workshop manual, then bleed each corner in the manual's sequence until the pedal is firm and the fluid runs clean and bubble-free. Change brake fluid roughly every two years thereafter.

  10. Owner-uploaded photo slot
    Clean fluid during bleeding. Fresh, bubble-free brake fluid running clear from a bleed nipple during the flush.

  11. 08. Road-test gently, then progressively

    Start with a low-speed brake check in a safe area, confirming the car pulls up straight and the pedal stays firm. Build up progressively and re-check every union you disturbed at the end of the drive.

Related faults

No directly linked fault-finding entries yet.

Further reading

Figures and procedures should be confirmed against the official Triumph workshop manual; for safety-critical or specialist work, consult a specialist.

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