Clutch Faults For older and classic cars
Problems with your vehicles clutch is your clutch slipping making a strange noise?
Clutch Faults guide
Here we will help you understand possible causes and what might be need to fix them from possible simple adjustment. to faults needing clutch or parts replacement. This article is for older cars with clutch cable, chain or connecting rod. For modern cars see hydraulic clutch problems for modern cars.
What is Clutch Slip?
When the Clutch Slips. speed rises without a corresponding increase in speed of the vehicle.
How to check
The Clutch normally slips during engagement When the pedal is depressed there should be no movement in the clutch when it is fully engaged. To check Clutch Slip With the handbrake hard on and top gear engaged it should be possible to stall the engine by slowly letting in the clutch, otherwise the clutch is slipping. Slip of this kind will very rapidly wear out the clutch as its constantly moving without full grip.
Common causes of Clutch slip-on older cars with clutch cable or chain or even a rod.
Common causes of Clutch slip are worn friction linings this is normal for high mileage cars or when no information when the clutch was replaced. Other causes can be oil or grease on friction linings this could be from possible oil or fluid leaks or water mixing with oil and fluids example of this floods or going through deep water.
Slip will also result if the Clutch pedal adjustment is too tight on older cars there must be some free movement in the clutch pedal.
on older cars Normal clutch wear tends to reduce the free pedal movement so that occasional re-adjustment is required. There should be about one inch (25 mm) of free movement in the pedal.
Another possible cause can also be on older cars weak clutch springs or the release levers seized or even worn on pins and levers allowing too much play this might not be visible at first but check for worn or even cracked arms as these can bend or move under pressure. This cause excessive free pedal movement so that the effective movement of the pedal is insufficient to disengage the clutch
How is the clutch adjusted?
The clutch on nearly all cars is operated hydraulically or by a cable. Early car will probably have a cable or chain from the pedal to gearbox housing by levers to engage disengage clutch for changing gears.
If cable is used some slack must be maintained in it before it exerts pull on the clutch release lever. This is because as, the clutch friction linings wear the clutch "closes up" slightly and this tightens the release cable. also, without the free play cables and arms can stretch and bend as in the saying riding the clutch (driving with foot constantly on the top of clutch pedal can cause Premature wear.
If there is no slack in the cable a situation will eventually arise where the clutch cannot fully engage because the cable is too short. This will cause the clutch to slip and wear very rapidly. The clutch cable is a stranded steel wire passing through an outer casing. The steel wire has a nipple attached to each end, one for connecting it to the clutch release lever and one for connecting it to the clutch pedal. The outer casing is located against points at each end. When the clutch is disengaged the inner wire is placed in tension and the outer casing in compression. The adjustment point is at one of the outer casing abutment points. Adjustment at the clutch end but it may be at the other end of the casing, often on the engine bulkhead.
On old cars the clutch may be operated by a rod and then the length of the rod is adjusted to provide the required slack in the clutch pedal. Again, on old cars, a chain was sometimes used in the clutch operating linkage and adjustment is provided to by a chain to adjusted obtain a little slack in the chain when the clutch is fully engaged.
Note: The amount of clearance required at the adjustment point is very small, only a tenth of an inch or not much more but this will give perhaps one inch of free movement at the clutch pedal. By free movement this is slack before the pedal requires much pressure to move it. The essential thing is to make sure slack exists at the clutch pedal.
Possible Faults needing possible dismantling and clutch or parts replacement
- Wear in the clutch mechanism
- Uneven contact of friction lining
- Broken clutch release levers
- Broken anti-rattle springs on release levers
- Worn thrust bearing
- Distorted clutch disc
- Distorted pressure plate.
- oil or grease on the linings.
- Clutch shaft bent
- clutch discs Splines may be worn on shaft
- clutch release levers and bearing pins worn
- Clutch out of alignment with engine due to faulty engine mountings or loose bolts
- Cracked diaphragm spring.
Possible Faults checks
Judder or clutch Jerk may be due to uneven contact of friction linings or a distorted clutch disc and/or pressure plate. A distorted or worn pressure plate will cause drag, as will the same fault in the clutch disc.
If the engine has been removed at some time The clutch shaft may be out of alignment with the engine, due to faulty or worn engine mountings
A clutch disc that has become tight on the shaft splines will cause clutch drag possibly for lack of use, but so will oil or grease on the friction linings, Also, the clutch diaphragm spring may be broken.
Wear in the clutch mechanism, worn thrust bearing spigot bearing faulty, clutch release levers and bearing pins worn broken anti-rattle springs on release levers, broken springs in clutch disc—rattle due to these springs is most noticeable when the engine is idling.
Noise due to thrust bearing is usually only present when the clutch pedal is depressed. The cure for these faults requires the dismantling of the clutch. If the thrust pad becomes loose in its cup this will cause a scream or whistle when the clutch is disengaged. The cure is to fit a new release bearing.
Clutch engages suddenly even when operated normally. May be due to wear on the friction linings, or to oil or grease on the linings. Distorted pressure plate and/or clutch discs Splines may be worn on shaft.
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