Clutch Diagnosis

No clutch will last forever. The facings on the clutch disc wear as the miles accumulate. Stop-and-go driving with lots of shifting is obviously harder on the clutch than open highway driving. Pulling a trailer, off-roading and aggressive driving can also accelerate clutch wear.

The worst thing any driver can do is ride the clutch. Slipping the clutch excessively when starting out or when creeping along in traffic sends the temperature of the clutch soaring. If the facings get too hot, they may start to burn giving off an odor similar to burnt toast. If the clutch isn't given a chance to cool., the disc may be ruined along with the flywheel and or pressure plate.

When the clutch disc becomes worn, the reduction in thickness may reduce the clamping force exerted by the pressure plate. Most diaphragm clutches actually exert more pressure as the disc wears due to the geometry of the spring and release mechanism. But once the disc is worn beyond a certain point, pressure starts to drop, increasing the risk of slipping under load. With older coil spring-style clutch covers, pressure drops in direct proportion to disc wear.

When a clutch starts to slip, the slippage will be most noticeable when the engine is under load, as when lugging at low speed in a high gear, when driving up a hill, when accelerating to pass another vehicle or when towing a trailer. The more the clutch slips, the hotter it gets and the most it wears. This accelerates the problem even more and may result in additional damage to the flywheel and pressure plate.

Another cause of premature clutch failure is oil contamination from a leaky rear main crankshaft seal, transmission input shaft seal or engine oil leak. Oil on the clutch facings will cause them to slip and gram unevenly. The result is typically chattering and jerking when the clutch is first engaged, and slipping when the clutch under load.

Oftentimes, and apparent clutch problem really isn't the clutch, but the clutch linkage or something else. Many late model vehicles have a hydraulic clutch linkage with a master cylinder attached to the clutch pedal and a slave cylinder on the bell housing. The internal piston seals on the master and slave cylinder can develop leaks that allow a loss of pressure when the clutch pedal is depressed. This may prevent the clutch from disengaging or allow it to engage prematurely. The pedal may also feel soft and have less than normal resistance. Slave cylinders develop leaks more often than master cylinder because the slave cylinder is the lowest point in the system. Any rust or dirt in the hydraulic fluid is therefore more apt to settle in.

Consult your ASE certified technician at A-1 Auto repair for cost and repair on all your clutch problems.

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