Are you experiencing a clutch problem, such as leakage or a strange feeling in the clutch pedal? If so, it could be due to an issue with your clutch slave cylinder. Knowing what the signs and symptoms of a bad slave cylinder are can help you determine the cause of the problem quickly – saving you time and money on unnecessary repairs.
In this article, we’ll dive into the warning signs that indicate a failing clutch slave cylinder, how to diagnose it, and questions about replacement and cost. So read on to learn everything you need to know to fix this inconvenience!
What Does The Slave Cylinder Do?
Before we dive into the symptoms of a bad slave cylinder, let’s take a brief look at the basics of what a slave cylinder does and how the clutch system works, so you can better understand the symptoms and what is causing them.
The slave cylinder is a part of a hydraulic system that works in tandem with the clutch master cylinder to engage and disengage the clutch in vehicles with manual transmission.
To have a smooth gear change, you have to disengage the engine power flow, and between the engine and you being able to shift gear is a clutch disc (also called friction disc or friction plate). This clutch disc is pressed against the flywheel with an external force from the pressure plate. And here’s where the slave cylinder comes into play.
When you press the clutch pedal in your car, the force is converted into hydraulic pressure by the master clutch cylinder, which pushes hydraulic fluid through the lines to the slave cylinder. Without it, it would be impossible to shift gears.
Different Types of Clutch Slave Cylinders
There are two types of slave cylinders. The external slave cylinder, which is mounted on the outside of the transmission bell housing, and concentric, also called the internal slave cylinder (CSC), which is fitted around the gearbox shaft inside the transmission bell housing.
External Slave Cylinder
In an external slave cylinder, which also is the traditional and most common slave cylinder, the transferred pressure from your foot is used to actuate a clutch fork that moves the release bearing back and forward, which disengages the clutch from its input shaft.
Concentric or Internal Slave Cylinder
However, concentric slave cylinders are getting more and more popular in modern cars due to their advantages of fewer moving parts, better alignment geometry, and precise release bearing travel.
This slave cylinder combines a hydraulic cylinder and a release bearing inside the transmission bell housing. And when you press the clutch pedal, hydraulic fluid is forced into the slave cylinder, which compresses a series of concentric rings onto a release fork, disengaging the clutch.
Unfortunately, like many other car parts, the slave cylinder doesn’t last forever and is a fairly common cause when your clutch starts behaving strangely. So let’s talk more about the common symptoms of a bad slave cylinder.
Symptoms of a Bad Clutch Slave Cylinder
One of the most common problems with a bad slave cylinder is leakage, and there are usually one or more symptoms that often give a good indication of what you’re dealing with. So here are 5 of the most common symptoms of a bad slave cylinder that you may have noticed.
1. Abnormal Clutch Pedal
No one knows your car better than you, and one of the first and most obvious symptoms of a bad clutch slave is a change in the clutch pedal. Suppose there’s a strange feeling as you depress it, such as if it feels spongy or soft or doesn’t release very well. It’s a good indication that the slave cylinder is starting to fail.
When this happens, 9 out of 10 times it’s due to a leak caused by worn-out or damaged seals. But it could also be caused by other things, such as if a release bearing is about to fail or if the brake fluid level at some point was too low and the air got into the system.
A particular spongy feeling is an indication of air in the system. You’ll need a complete clutch bleed to get the air out of the system. And even though you may be able to shift gears, the clutch won’t be able to engage fully, causing unnecessary wear and tear on your clutch and transmission. But you also have to determine how the air got into the system in the first place.
If the release bearing is bad, you usually hear grinding noises when depressing the clutch. You might notice the pedal getting harder and harder to push as the bearing worsens.
2. Difficulty Shifting Gears
If your slave cylinder is going bad, you might find it difficult to shift gears to get any gear in at all. This is because the hydraulic pressure needed to disengage the clutch is not enough. Depending on the severity of the problem, you may be able to “pump” up the pressure needed to shift gears.
If there’s a leak, the pressure will likely disappear when you don’t drive for an hour or so, and you may only have pressure at the very bottom of the pedal.
This is not something you want to drive around with for too long or at all. If the pressure completely disappears while driving and the clutch pedal sticks to the bottom, you’ll have to brake until the engine dies. It’s easy to panic and freeze in such a situation, which could result in an accident.
It would be best if you got the problem fixed as soon as possible for your safety and to avoid unnecessary wear and more expensive repairs.
3. Low or Contaminated Brake Fluid
Low or contaminated brake fluid are both symptoms commonly associated with clutch problems. And an abnormal clutch pedal feeling, along with low brake fluid, usually is a strong indication of a leak in the system, most often at the slave cylinder or the master cylinder.
If you haven’t had your vehicle serviced for a long time, wear from rubber seals, and moisture can also contaminate the brake fluid, which will have a big impact on its performance to fully engage the clutch. Luckily there’s an easy way to check this – open your hood and check the color of the fluid in the master cylinder reservoir.
If you find your brake fluid color is dark brown or black, you probably found the answer to the problem. Either way, it means it’s time for a brake fluid change.
4. Leaking Brake Fluid
Although the slave cylinder can go bad without leaking, most of the other symptoms mentioned result from a leakage. While it’s possible it can be a hose or a hydraulic line, most times, it’s a worn seal at fault. Wear and tear, and a harsh environment eat on the rubber seals inside the slave cylinder, and sooner or later, they may start to leak.
With that said, any visible signs of leakage or wetness around or underneath the bell housing and transmission point toward a faulty slave cylinder. But, if the leak is closer to the cabin’s firewall and there is wetness around the master cylinder. Then there’s where the problem lies.
Any leaks in the clutch system will almost always have a noticeable change in the clutch pedal. And you should check the master cylinder reservoir to see if there’s any brake fluid missing.
5. Clutch Pedal Bottoms
Normally when you press the clutch pedal, you should feel some resistance in the pedal from the position all the way to the bottom. However, if the resistance in the clutch pedal suddenly disappears and the pedal might even stick to the floor, you most likely have a problem with a bad slave cylinder.
In such events, the clutch will not engage and disengage properly or at all. It’s likely your slave cylinder needs to be replaced, so you should consider having your vehicle towed to a mechanic for immediate repair.
Causes of a Faulty or Failing Clutch Slave Cylinder
Before making any rash decisions and starting throwing tools around you, ready to replace the slave cylinder, first, let’s take a closer look at what could cause your CSC to malfunction.
To begin with, normal wear from changing gear is usually what causes the clutch slave cylinder to go bad in the first place. Seals begin to fail, and pistons give up, resulting in fluid leaks and air and moisture getting into the system.
However, what could lay behind premature wear is contamination reaches any part of the clutch slave cylinder. This includes dirt, debris, or other contaminations finding their way into the cylinder or brake fluid, causing damage and tear, which can lead to a faulty or failing clutch slave cylinder.
Another possible cause is if the seals were already damaged before or during installation by someone who needed to be more careful.
Suppose you know it’s not long since you replaced the slave cylinder or clutch; there’s a chance it was damaged. If so, you may get it covered by the warranty from the manufacturer or the repair shop that did the work.
How do You Diagnose a Bad Slave Cylinder?
For someone with little to no knowledge of cars, it can be hard to tell whether or not the slave cylinder is at fault. Although I have already mentioned several clues suggesting this throughout the text, here are a few steps you can follow:
Step 1: Start by looking for leaks or damage to the master clutch cylinder. This includes checking both the part of the master cylinder located inside the cabin under the dashboard and on the outside of the cabin’s firewall. Pay attention if there’s less brake fluid in the reservoir since the last time you checked.
Step 2: If the master clutch cylinder looks fine, you want to look for wetness around the slave cylinder. However, depending on your vehicle, the accessibility of the external slave cylinder may vary.
And if your vehicle has an internal slave cylinder, you can often see fluids between the gearbox and the bell housing from underneath the car. You may have to remove a plastic cover.
Step 3: Another way is to test the slave cylinder with the help of a friend, family member, or neighbor. Have them sit inside the car and press and hold the clutch all the way to the floor while you observe the slave cylinder’s pushrod.
It should move outwards as the clutch pedal is depressed. If the pushrod does not move or moves only slightly, the slave cylinder is likely faulty and should be replaced.
Step 4: Suppose there’s no sign of a leak and no change in fluid level in the reservoir. In that case, it could be fluid bypassing back into the reservoir when depressing the clutch pedal.
If so, you’ll want to put a brake hose clamp on the rubber part of the fluid line between the master cylinder and slave cylinder, jump back into your car, and put your foot on the clutch pedal.
With this done and if everything is in order, the pedal should pretty much be rock-hard and don’t move much. If there’s little to no resistance, you likely have a dead master cylinder instead of a slave cylinder.
Can I Replace the Slave Cylinder Myself?
If you suspect that your vehicle’s slave cylinder is at fault, there are two options for replacing it. DIY or take your car to an auto repair shop. If you consider yourself a handy person and want to save some money, a DIY approach may make sense.
Many times, replacing an external slave cylinder is relatively easy and quick, depending on the accessibility of your specific vehicle.
You can acquire the necessary parts and tools, watch tutorials online to get an idea of the steps involved, and then make the repair yourself. Note that you also have to bleed the clutch system after replacing the slave cylinder.
On the other hand, if your car uses the concentric slave cylinder that requires transmission removal or lacks confidence in your mechanical abilities, you may prefer having a professional handle the task.
Either way, you can take your car to a nearby shop and have them do the replacement. It’s important that the job gets done right so that your car’s clutch remains functioning properly.
Bad Slave Cylinder Replacement Cost
When looking at the replacement cost of a clutch slave cylinder, the prices vary significantly depending on the type of slave cylinder your car uses. While the part itself usually ranges in the same pricing, it’s the amount of labor required to replace a concentric slave cylinder that breaks the bank.
The average total cost of a clutch slave cylinder replacement is between $200 and $250, where labor cost comes down to about $120 to $150 and the part itself around $100. However, for a concentric slave cylinder replacement that requires transmission removal, you can expect to pay up to $900 or more.
This is because the estimated time to replace an external clutch slave cylinder is around 1 hour on most vehicles, compared to 8 hours for the concentric type. So with a labor rate of $50 to $100 an hour, the total cost quickly adds up.
TIP: When removing the transmission to change a concentric/internal clutch slave cylinder, also consider replacing the clutch since the labor cost is the most expensive part.
Frequently Asked Questions
Can You Drive Without Slave Cylinder?
Technically, you can start and drive a car without its slave cylinder, but it is not recommended as it will result in unnecessary tear or damage to the transmission. Additionally, shifting gears can be difficult and potentially dangerous if the clutch is not properly disengaged.
Can Slave Cylinder Fail Without Leaking?
In most cases, when a slave cylinder fails, it is due to leaking. But with that said, it’s still possible that other things could be the culprit, such as a faulty cylinder. However, you also want to ensure it’s the slave cylinder and not the master cylinder leaking or bypassing fluid back into the reservoir.
Can a Slave Cylinder Get Stuck?
While it is not common, a slave cylinder can get stuck due to debris or corrosion that can form inside the cylinder. This can cause it to jam and not allow for full movement when it is activated by the master cylinder, causing poor brake performance. In this case, you will need to replace it.
How Long Do Clutch Slave Cylinders Last?
Clutch slave cylinders typically last between 80,000 and 100,000 miles. However, regular maintenance and inspections can help extend the life of the cylinder and ensure that it remains in proper working condition for as long as possible.
Can You Replace the Slave Cylinder Without Removing the Transmission?
In most cases, the slave cylinder can be replaced without removing the transmission. However, internal slave cylinders always require the removal of the transmission. In that case, it is also recommended to replace the clutch. If you are unsure what type of slave cylinder your car uses, contact a professional.
To Wrap It Up:
When wrapping it up, the slave cylinder is an essential part of the clutch system in a vehicle with manual transmission. It works in tandem with the clutch master cylinder to engage and disengage the clutch. There are two types of clutch slave cylinders, external and concentric/internal. A bad slave cylinder can cause a variety of symptoms, such as:
- Abnormal Clutch Pedal
- Difficulty Shifting Gears
- Low or Contaminated Brake Fluid
- Leaking Brake Fluid
- Clutch Pedal Bottoms
It is important to be aware of these symptoms and to have the slave cylinder checked and possibly replaced to ensure smooth gear changes and avoid further damage to the transmission. Replacing an external slave cylinder is often an easy DIY task. However, you must know how to bleed the clutch system afterward properly. The cost of replacing a slave cylinder can vary, but as long as you don’t have to remove the transmission, it is generally a fairly affordable repair.