Pinpoint Test A: Clutch Slippage

Manual Transmission and Clutch






Pinpoint Tests

Pinpoint Test A: Clutch Slippage

Normal Operation

The clutch is designed to transfer the power from the engine to the transmission, which may be either stationary (starting) or rotating at a different speed (upshifting or downshifting). The clutch is functioning correctly when both the engine and transmission are rotating at the same speed with the clutch engaged. Clutch pedal movement is transmitted by fluid pressure, which actuates the clutch release hub and bearing. The clutch release hub and bearing pushes on the spring center towards the flywheel. The diaphragm spring pivots at the fulcrum, relieving the load on the clutch pressure plate. Steel spring straps riveted in the clutch pressure plate cover pull the clutch pressure plate from the clutch disc, disengaging the engine torque from the transmission.

This pinpoint test is intended to diagnose the following:
- Clutch pedal
- Clutch hydraulic system
- Clutch disc
- Clutch pressure plate



PINPOINT TEST A: CLUTCH SLIPPAGE

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A1 INSPECT THE CLUTCH PEDAL


- Ignition OFF.
- Block the wheels and apply the parking brake.
- Depress and slowly release the clutch pedal.
- Does the clutch pedal release without binding?

Yes
GO to A2.

No
INSPECT the clutch pedal.

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A2 CHECK THE HYDRAULIC SYSTEM


- Ignition OFF.
- Depress and release the clutch pedal.
- Is there residual hydraulic pressure at the bleed screw?

Yes
INSTALL a new clutch master cylinder.

No
GO to A3.

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A3 CARRY OUT A STALL TEST


- Start the engine.
- Block the wheels and apply the parking brake.
- Place the transmission in 4th gear.
- Increase the engine speed to 2,000 rpm and slowly release the clutch pedal.
- Does the engine stall within 5 seconds?

Yes
The clutch is not slipping. VERIFY the customer concern.

No
INSPECT the clutch components for damage.

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