If you drive a manual car and something doesn’t feel right with the clutch pedal, a faulty clutch slave cylinder could well be the culprit. The clutch slave cylinder is involved in engaging and disengaging the clutch, making it a really important component.
If something goes wrong with the cylinder, it’s important to get it sorted as soon as possible – a faulty clutch slave cylinder can cause gear changing issues, and even damage your transmission in some cases. Fortunately, there are some common tell-tale symptoms to look out for, so you can address the problem and get back on the road.
What is a Clutch Slave Cylinder?
Clutch slave cylinders can be found on cars with manual transmissions. It’s an important part of the transmission system, which works together with the clutch master cylinder and other components to disengage the clutch when the driver changes gear.
The process begins when the driver depresses the clutch pedal. This causes the master cylinder to transfer the pressure onwards to the slave cylinder. This pressure is transferred through a system of hydraulics; moving liquid through the system. When the clutch slave cylinder receives this pressure, a rod is extended, which in turn presses against a fork or lever that disengages the clutch. The system allows drivers to change gears smoothly and safely.
What Can Go Wrong?
Because the clutch slave cylinder depends on hydraulics to function correctly, leaks are the most common issue to afflict them. Over time, regular use can wear down the component, allowing the transmission fluid inside to leak out. This means that the pressure within the cylinder is insufficient for it to properly carry out its function of disengaging the clutch.
If ignored, a faulty clutch slave cylinder can go on to cause further damage to your car. You’ll notice that gear changes become more difficult, and the clutch pedal feels less responsive. This not only makes driving more difficult and less safe, but can also damage other parts of the transmission system.
What are the Symptoms?
Dodgy clutch slave cylinders should never be ignored. If your car has this issue you can expect to see the following symptoms:
- The Clutch Pedal feels Soft
One of the commonest symptoms of a failed clutch slave cylinder is also one of the easiest to spot – you’ll notice that the clutch pedal feels ‘soft’ as you drive. The pedal will offer your foot less resistance than usual, and this problem is typically caused by a leak in either the master or slave cylinder.
- Difficulty Shifting Gears
Another symptom you’re likely to notice when you’re behind the wheel is having trouble with gear changes. You might find the clutch pedal doesn’t return to its resting position as quickly as normal, or remains depressed once you’ve removed your foot. These symptoms suggest a lack of pressure in the hydraulic system that controls whether the clutch is engaged or disengaged, and is often the result of a leak in the clutch master or slave cylinder. If the pedal won’t lift from the floor at all when you remove your foot, the master cylinder is the more likely culprit, and you should pull over as soon as it is safe to do so. Driving a car without a functioning clutch is dangerous.
- Low Transmission Fluid Levels
If something feels off with your clutch pedal, it’s a good idea to check the car’s transmission fluid levels. If the fluid is low, top it up, and check the level again soon after. If you find the fluid level is low once again, a leaky clutch master or slave cylinder could be the reason.
- Low Brake Fluid, or Contamination in the Fluid
Checking your car’s brake fluid should be your next port of call if you suspect something is going wrong with the clutch. Low levels suggest a leak, which could be traced back to a clutch slave or master cylinder. Contaminated brake fluid tells a similar story: over time, the rubber seals in these cylinders can degrade, allowing detritus to migrate into the brake fluid as it passes by. Thankfully, contaminated brake fluid is easy to spot – you can expect it to look darker in color than usual, and cloudy. If you’re unsure what brake fluid should look like, fetch a fresh bottle from your local garage or gas station for a handy point of comparison.
- Floor or Engine Bay Leaks
If your car’s clutch slave cylinder is failing, you can also expect to see some visible leaks. Check underneath your vehicle for any pools of liquid, and check the engine bay, too. As mentioned earlier, leaky cylinders can’t maintain the requisite pressure to function properly, and should be replaced.
- Unusual Engine Noise
If you notice a loud noise while the car is in gear and you’re holding down the clutch pedal, it could be that one of the clutch cylinders is leaking, hence unable to hold the release fork properly in place and properly disengage the clutch.
A combination of these symptoms is a reliable indicator that something isn’t right with your clutch, and the clutch slave cylinder is a likely suspect. However, do bear in mind that many of these symptoms could actually be the result of a faulty clutch master cylinder too. For this reason, it’s best to consult a trusted mechanic to confirm your suspicions, and see which cylinder is at fault. If the master cylinder fails, this is usually a much bigger issue and should be addressed immediately.
A Simple Test
If you possess some knowledge about how things should look under the bonnet, there’s a fairly simple test you can carry out in your own garage, to ascertain whether you have a leaky clutch slave cylinder – you’ll need an assistant to give you a hand.
- Pop the bonnet, and locate the clutch slave cylinder
- On the front of the cylinder, you’ll see a hydraulic rod – normally, depressing the clutch pedal would cause this rod to extend
- Have your assistant get into the driver’s seat and depress the clutch
- While they do so, check to see whether the rod extends
- If it does extend, the cylinder is working as it should
- If the rod does not extend, the slave cylinder needs to be replaced
Even if your car passes this test, you should still consult a mechanic if you’re experiencing problems with the clutch. As hardy as the mechanism is, there’s still plenty that could go wrong, and things will probably deteriorate if you don’t seek assistance.
Once you suspect that a failing slave cylinder is the culprit of your clutch troubles, the next logical step is to seek out repairs.
The exact price will vary depending on the make and model of your car, the extent of the damage, and labor costs in your area, but you can expect it to fall in the range of $150 to $200 for both parts and labor. Because the clutch slave cylinder is a relatively inexpensive component to replace, doing so in a timely manner can save you a lot of money further down the line, by preventing the failing cylinder from triggering other problems.
What Else Could go Wrong?
As you’ve probably gathered by now, a car’s transmission system is a complicated affair, and despite its hardiness there’s plenty that can go wrong. Below we note a few other common clutch-related issues:
- Broken, stretched, or loose clutch cables
On some cars, a system of cables, rather than a hydraulic system, disengages the clutch. Over time, they can become deformed, and stop performing their function properly.
- Debris on the clutch disc
The clutch disc has a friction surface on each side, and acts as the point of connection between the engine and transmission. It can be engaged and disengaged, allowing the engine to carry on spinning even when the wheels are still. A buildup of detritus on the disk prevents it from engaging as it should, causing slippages and grinding.
- Leaks elsewhere in a hydraulic system
The copper pipes connecting the master and slave cylinders can spring leaks as well as the cylinders themselves, reducing pressure in the system
It’s a good idea to be roughly familiar with these issues, so you’re in a better position to advise your mechanic should you need to bring your car into the shop.
Protecting your Clutch
The clutch on most modern cars will last between 50,000 and 100,000 miles before it needs to be replaced – it’s a sturdy system. However, there are a few ways you can help to increase its lifespan:
- Change gears smoothly, by getting familiar with the biting point of your clutch – depress quickly when you change gear, and release at a steady speed
- Leave the clutch half depressed as infrequently as possible – it should be either fully depressed or entirely released
- Use your handbrake, rather than hovering on the clutch, to stop yourself from rolling backwards on a hill start
- Pull off at a low RPM, around 1,100
- Avoid revving the engine