The design of the clutch of the car GAZelle Next

On GAZelle Next vehicles equipped with a mechanical gearbox, a dry single-plate clutch with a central diaphragm pressure spring is fitted.

The clutch is located between the engine and the gearbox.

It is designed to disconnect and connect the flywheel, located on the engine crankshaft, and the gearbox input shaft.

Diagram of the GAZelle Next clutch structure
Fig. 1. Clutch: 1 — driven plate, 2 — clutch housing, 3 — flywheel, 4 — friction linings, 5 — pressure plate, 6 — diaphragm spring, 7 — release bearing, 8 — release sleeve, 9 — fork ball pivot, 10 — release fork, 11 — clutch slave cylinder rod, 12 — slave cylinder, 13 — spring, 14 — piston.

The clutch consists of a driven (friction) plate, a clutch cover with pressure plate and diaphragm spring, and a release mechanism.

The pressure plate is mounted in a pressed steel cover bolted to the engine flywheel.

The driven plate is mounted on the splines of the gearbox input shaft and is clamped by the diaphragm spring between the flywheel and the pressure plate.

Diagram of the hydraulic release actuation
Fig. 2. Hydraulic clutch release actuation: 1 — brake master cylinder reservoir, 2 — connecting hose, 3 — cab front panel, 4 — clutch pedal bracket, 5 — return spring, 6 — clutch pedal position sensor, 7 — clutch pedal, 8 — master cylinder piston pushrod of the release actuation, 9 — master cylinder of the release actuation, 10 — hydraulic release actuation pipework.

The hydraulic clutch release actuation consists of the master and slave cylinders, the clutch pedal, the hydraulic release actuation pipework and the connecting hose.

The clutch pedal is connected to the master cylinder by a pushrod fitted with an adjustment assembly.

A spring returns the pedal to its initial position.

The sensor informs the engine management system electronic control unit of the clutch pedal position at any given moment.

The master cylinder is connected by a hose to the reservoir mounted on the brake master cylinder (the reservoir is common to both master cylinders).

Brake fluid is used in the hydraulic clutch release actuation.

Required materials and tools:

  • DOT-4 brake fluid (for topping up and replacement).
  • Clear bleed hose and container for used fluid.
  • Set of spanners (including 8 and 10 mm for the bleed valve).
  • Graphite grease for the clutch pedal bushes.
  • Rags, safety glasses and gloves.

Possible clutch faults and remedies

Cause of fault (Remedies)

  1. Incomplete clutch disengagement (the clutch drags):
    • Difficult movement of the driven plate hub on the gearbox input shaft splines — clean the splines.
    • Distortion of the driven plate — replace the driven plate.
    • Diaphragm spring fingers not in one plane or worn — replace the pressure plate.
    • Air in the hydraulic actuation system — bleed the system.
  2. Incomplete clutch engagement (slipping, reduced acceleration performance):
    • Reduced diaphragm spring force — replace the pressure plate assembly.
    • Wear of the friction linings, flywheel and pressure plate working surfaces — replace the driven plate, flywheel or pressure plate.
    • Oil contamination of the driven plate friction linings — eliminate the causes of oil ingress, replace the driven plate.
    • Difficult movement of the driven plate hub on the splines — clean the splines.
    • Diaphragm spring fingers not in one plane or worn — replace the pressure plate.
    • Slow return of the slave cylinder piston to its initial position with the pedal fully released; blockage of the master cylinder compensation port or swelling of the seal — clean the cylinder or replace the seal.
  3. Incomplete clutch engagement (noticeable judder when engaging):
    • Wear of the friction linings — replace the driven plate.
    • Oil contamination of the friction linings — eliminate the causes, replace the driven plate.
    • Diaphragm spring fingers not in one plane or worn — replace the pressure plate.
    • Loss of elasticity of the driven plate leaf springs and damper springs — replace the driven plate.
  4. Increased noise and vibration during clutch operation:
    • Breakage or loss of elasticity of the driven plate damper springs — replace the driven plate.
    • Lack of lubrication or defects of the release bearing — replace the bearing or the sleeve with bearing.
    • Wear of the driven plate friction washer — replace the driven plate.
  5. Pressure is not held in the release actuation (when the pedal is pressed gently it reaches the stop but the clutch does not disengage):
    • Contamination of the master cylinder or heavy wear of its bore — flush or replace the master cylinder.
    • Wear or damage of the master cylinder piston seal — replace the seal.
    • Fluid leakage through the slave cylinder seal, loss of pipework tightness — replace the seal or slave cylinder, tighten the pipework fastening.
    • Presence of air in the hydraulic actuation — bleed the actuation, remove the air.
  6. Increased noise in the clutch with the engine running:
    • Lack of lubrication or defects of the release bearing — replace the bearing or the sleeve with bearing.
    • Weak tightening of the hydraulic actuation connections — tighten the connections.
  7. Squeaking of the clutch pedal bushes:
    • Lack of grease in the plastic clutch pedal bushes — grease the bushes with graphite grease.
    • Wear of the plastic clutch pedal bushes — replace the bushes.
    • Breakage or loss of elastic properties of the return spring — replace the spring.

Fluid replacement and clutch bleeding

Since the hydraulic clutch release actuation and the service brake system share a single reservoir, the working fluid in the hydraulic clutch release actuation is replaced when the brake fluid in the hydraulic brake actuation is changed.

According to the manufacturer's recommendation, the fluid should be replaced every thirty thousand km or every 2 years of operation (whichever comes first).

DOT-4 brake fluid is used in the hydraulic clutch release actuation.

This fluid is hygroscopic (it quickly absorbs moisture from the air).

Condensation formed in the master and slave cylinders causes corrosion of the parts and failure of the hydraulic actuation, so we recommend replacing the fluid regardless of mileage.

Location of the bleed valve on the slave cylinder
Fig. 3. Air bleed valve on the clutch slave cylinder.

We remove the protective cap from the air bleed valve on the clutch slave cylinder.

We fit a hose onto the valve and lower its end into a container with a small amount of brake fluid.

We ask an assistant to press the clutch pedal sharply four or five times at intervals of one to two seconds, and then hold it pressed.

We unscrew the valve ¾ of a turn.

The old (dirty) fluid will flow through the hose into the container.

As soon as the fluid stops flowing, we tighten the air bleed valve.

Constantly monitor the fluid level in the reservoir, not allowing it to fall to the ‘MIN' mark on the reservoir wall, since at a lower level you may not notice the moment when the clutch actuation section in the reservoir is completely drained and air will enter the system.

In that case the hydraulic actuation will have to be bled. Top up with new brake fluid if necessary.

In this way, the old fluid is gradually displaced by the new fluid without draining the hydraulic system.

We repeat the operation until the fluid is completely replaced (clean fluid without air bubbles must flow from the hose).

After replacing the fluid, we fit the protective cap onto the bleed valve.

We top up the brake fluid to a level of 15–20 mm from the top edge of the reservoir. We close the reservoir with the cap.