A slipping clutch rarely fails all at once. It creeps up on you. The car feels a bit sluggish pulling away, the revs flare when you overtake, and one day you notice you're pressing the accelerator harder to keep up on the motorway.
Catching it early won't save the clutch, because once it's slipping it's on its way out. But it does give you time to plan the repair rather than having the car let you down at the worst moment.
Here are the signs to look for.
1. The revs rise but the car doesn't speed up
This is the classic one. You put your foot down, the rev counter climbs, but the car barely picks up speed. The engine is making the power, but the clutch can't grip hard enough to pass it all to the gearbox.
It usually shows up first in higher gears and under load, so try accelerating firmly in fourth or fifth from low revs. If the needle jumps and the speed doesn't follow, the clutch is slipping.
2. A burning smell
A slipping clutch generates a lot of heat. The friction material on the clutch plate cooks, and the smell is sharp and acrid, a bit like burning paper or hot brakes. You'll often notice it after a hill start, towing, or a stop-start traffic jam.
One whiff after a botched hill start in a car park isn't a disaster. Smelling it regularly is a sign the plate is wearing quickly.
3. The biting point has moved up
As the clutch plate wears thinner, the point where the clutch starts to engage moves higher up the pedal travel. If you've had the car a while, you might notice you're now lifting your foot almost all the way before it bites.
A high biting point on its own doesn't always mean the clutch is finished. Some cars have a self-adjusting clutch that can move the biting point, and a hydraulic problem can also change how the pedal feels. But combined with any of the other signs here, it points to a worn plate.
4. It struggles on hills and when loaded up
Hills, a full car, a roof box or a trailer all ask the clutch to hold more torque. A worn clutch that copes fine on a flat road will often start slipping as soon as you add a load. If the car feels gutless going uphill, especially when it used to pull well, the clutch is a likely suspect.
5. Juddering when you pull away
A shudder through the car as you set off can come from a glazed or contaminated clutch plate, worn engine mounts, or a failing dual mass flywheel. It doesn't always mean slipping, but it's a sign something in the clutch area needs looking at.
6. New noises when you press the pedal
A whirring, rumbling or squealing noise that changes when you press or release the clutch pedal often comes from the release bearing. Rattling at idle that goes quiet when you dip the clutch can point to the dual mass flywheel. Neither is a slipping clutch as such, but they tend to wear at the same time.
What causes a clutch to slip?
Most of the time it's plain wear. Every time you pull away, a tiny bit of friction material comes off the clutch plate. Eventually there isn't enough left for the springs to clamp it tightly.
How quickly that happens depends a lot on how the car is driven. Riding the clutch, slipping it to hold the car on hills, lots of towing and heavy stop-start traffic all speed things up. A clutch on a gently driven car can last well over 100,000 miles. One that tows a caravan every summer might be done in half that.
Oil is the other common cause. A leaking crankshaft seal or gearbox input seal can soak the clutch plate, and an oily plate slips no matter how much material it has left. If that's the cause, the leak needs fixing at the same time as the clutch, or the new one will go the same way.
Occasionally the problem is hydraulic. If the clutch isn't fully releasing pressure because of a sticking slave cylinder or a pinched hose, it can behave like a slipping clutch. That's much cheaper to fix, so a good garage will rule it out first.
Can you keep driving on it?
For a short while, gently, yes. But a slipping clutch only gets worse, and the heat it creates can damage the flywheel and pressure plate too, which adds to the repair bill. Eventually it will stop transmitting enough power to move the car, usually on a hill or when you pull out of a junction.
If you've noticed the signs, it's worth booking the repair sooner rather than later.
What gets replaced?
Most of the cost of a clutch job is labour, because the gearbox has to come out. For that reason, clutches are almost always replaced as a kit: the clutch plate, the pressure plate (or cover) and the release bearing. Doing all three together means you're not paying to have the gearbox removed again a year later.
On cars with a dual mass flywheel, the mechanic will check its condition while everything is apart. If it's worn, replacing it at the same time makes sense for the same reason. Some kits include a solid flywheel or a new dual mass flywheel. Others don't, so check what's in the box.
We stock a wide range of clutch kits and clutch parts for most popular makes. Clutch kits are very specific to the engine and gearbox, so match the part number from your old kit, or send us your VIN and we'll help you find the right one.
A quick word on a high clutch pedal after a new clutch
A new clutch plate is thicker than a worn one, so the biting point will usually feel lower and slightly different for the first few hundred miles while it beds in. Go easy on it to start with. Avoid towing, hard launches and long hill starts until it settles.
This article is a general guide only. If you're unsure about the condition of your clutch, have it checked by a qualified mechanic.