There is a lot of emphasis placed on always and regularly checking the brake fluid. But there isn’t as much emphasis on checking the vehicle hydraulic clutch fluid.
This is because the hydraulic brake and clutch fluid use similar hydraulic principles and have plenty of components in similar. It is not surprising therefore that there are many hydraulic clutches that use brake fluid. It is a good idea to always check the user manual to find out of your car uses brake fluid in its hydraulic clutch system.
If this is the case then the hydraulic clutch system in your car is hygroscopic. This simply means that the clutch system is able to suck up moister over time from the air.
Note that water will compress even more than the hydraulic fluid. A fluid that is saturated by water will cause the pedal to feel more spongy. This is the case with both the brake system and the clutch system.
Consider using our table of contents below for easier navigation.
- Hydraulic Clutch
- Manual Clutch
- Bleeding Clutch
- Air In Clutch
- Slave Cylinder Vs Master Cylinder
- Frequently Asked Questions
Hydraulic Clutch
The truth of the matter is that there is really no such thing as the clutch fluid. Simply put, the vehicle hydraulic clutch fluid is actually brake fluid that has been added to the clutch master cylinder.
Whenever you press on the clutch pedal, the fluid moves from the master cylinder and gets into the slave cylinder. The resultant pressure created then engages the clutch which then makes it possible for you to change the gears.
Once the clutch is engaged, you will then release the clutch pedal and the brake fluid will move from the slave cylinder and back to the clutch master cylinder.
A hydraulic clutch uses a different type of system than a manual or mechanical clutch. The hydraulic clutch uses, as the name suggests, hydraulic fluid to shift the clutch disc.
This type of clutch depends on the master cylinders and slave cylinder to create and control the pressure needed to engage the clutch and engage the clutch pedal. The majority of cars that are built from the 1990s moving forward have a hydraulic clutch.
Vehicle Hydraulic Clutch Fluid Function #1: How The Hydraulic Clutch Works
The hydraulic clutch comprises a reservoir that inside contains the hydraulic fluid. Whenever you press on the clutch pedal, you create pressure in the fluid. This pressure will then disengage the clutch plate allowing you to disengage the gear that you are in as well as engage a new gear.
Simply put the hydraulic fluid works to activate a hydraulic piston. The tube has a piston that is similar to the hydraulic that you will see on the screen door.
The piston is responsible for disengaging and engaging the clutch via several connections. This is why hydraulic fluid often is referred to as the vehicle hydraulic clutch fluid. Keep in mind that there is no difference between the hydraulic fluid and the brake fluid. This fluid is contained in the clutch master cylinder.
Whenever the clutch pedal is engaged the resultant pressure turns into hydraulic pressure which then moves from the clutch pedal to the slave cylinder. There is a rod that runs from the slave cylinder that then activates the clutch fork.
This clutch fork will then cause the clutch release bearing to move which in turn causes the clutch pressure plate to release. The result is a disengagement of the clutch.
The hydraulic clutch, therefore, makes use of hydraulic fluid as opposed to a cable to cause the clutch disc to move. The clutch master cylinder and the slave cylinder are therefore crucial in maintaining the pressure spending on how the clutch pedal is engaged.
There is no clutch system or gear stick on an automatic car. This is the same for an electric car.
Let’s take a closer look at this process.
Vehicle Hydraulic Clutch Fluid Function #2: Hydraulic Clutch Process
There are two main parts to the hydraulic clutch. These parts are the clutch engagement and the clutch disengagement. Let’s find out more!
Vehicle Hydraulic Clutch Fluid Process #1: Clutch Engagement
For the engagement to take place, the driver needs to press on the clutch pedal. This causes the beginning of the diaphragm clutch working process.
Keep in mind that the pedal is always attached to the clutch plate. This is why the clutch plate will begin rotating.
The surfaces of the clutch plate that can cause friction can make contact with the pressure plate as well as the flywheel.
The pressure plate will provide pressure onto the spring. This will then cause the spring to contact the splined sleeves.
Now you will have an attachment of the pressure plate, the friction surfaces, the splined sleeves, and the clutch plate as well as the flywheel causing there to be an engagement of the clutch.
Vehicle Hydraulic Clutch Fluid Process #2: Clutch Disengagement
For the disengagement process to begin, the driver needs to release the clutch.
This causes the splined sleeves to move backward causing them to release pressure from the pressure plate as well as the clutch plate.
This in turn causes the flywheel to release from contacting the clutch plate. This causes the rotation on the clutch plate to slow and then stop.
This results in a disengagement of the clutch plate.
Manual Clutch
A manual clutch also called a mechanical clutch or a cable-actuated clutch will utilize a cable to cause a clutch disc to move.
They are an older system that came before the hydraulic clutch and were common on cars that were manufactured before the 1990s. Modern cars however feature the hydraulic clutch plate. That said, motorcycles often use mechanical clutch systems.
Vehicle Hydraulic Clutch Fluid: Workings Of A Manual Clutch
The manual clutch is one of the more simple systems on a car…or was. The clutch pedal is connected by a steel cable to the clutch assembly directly. Whenever you press the pedal, you will cause the cable to move which in turn moves the clutch fork and then actuates the clutch throwout bearing. This in turn causes the clutch plate to disengage.
Since there is no hydraulic system, the clutch feels a lot heavier, if you started out driving manual cars then you know how difficult pressing the clutch pedal was on older model cars.
The mechanical clutch being directly connected to the clutch system will mean that the driver will need to engage more with the clutch.
Clutch Fluid Vs Brake Fluid
Many drivers have often asked themselves if there is a difference between the brake fluid and the clutch fluid? There are some people who think that there is a difference.
However, both the brake fluid and the vehicle hydraulic clutch fluid are pretty much the same thing. The only major difference that would cause you to choose between a different brand of brake or clutch fluid is the type of brake or clutch system in your car.
Vehicle Hydraulic Clutch Fluid Differences #1: Brake Fluid
The brakes in your car work as a hydraulic system. This, therefore, means that how effective they will work will depend on the type and condition of the brake fluid.
This brake fluid and the hydraulic braking system are what ensure that you are able to use a small force to press the brake pedals and stop your car.
Vehicle Hydraulic Clutch Fluid Differences #2: Clutch Fluid
As we have mentioned multiple times throughout this post, there is really no such thing as clutch fluid. Vehicle hydraulic clutch fluid is implied brake fluid that is added to the master cylinder. Whenever you press on the clutch pedal, the brake fluid in the master cylinder will flow to the slave cylinder.
It is this pressure that is created in the slave cylinder that will engage the clutch. This then lets you shift from one gear to the next. Once you have engaged the clutch, you will then release the clutch pedal causing the fluid to go back to the master cylinder.
Vehicle Hydraulic Clutch Fluid Differences #3: Brake Fluid Tips
It is easy for the brake fluid to deteriorate when it mixes with moisture. This is something that it can do when exposed to the air. The brake fluid will therefore lose its hydraulic properties once it has sucked up too much moisture from the air. Simply put it will lose its viscosity.
As a result, when you press down on the brakes, the fluid will move quickly. At this point, you will need to replace the brake fluid. You may also need to change the brake fluid once you realize that it has taken on a different color such as black.
At this point, you will need to bleed the brakes.
When dealing with the clutch system, you will need to change the brake fluid if there is a leak in the master cylinder. Once you find that the brake fluid is contaminated, this can also cause the slave cylinder to damage the master cylinder.
Bleeding Clutch Master Cylinder
There are several steps to bleeding the clutch master cylinder.
Step 1: Preparing To Bleed
Before you can even get to bleeding the master cylinder you will need to find the clutch slave cylinder of the car. If you can find the clutch fork you should find the slave cylinder attached right next to it.
Having found the slave cylinder, find the bleeder valve. This can appear just like a small nut with a small diameter. On the tip of the valve is a rubber cover. This helps to keep out the debris and the dirt.
You will require a tube that is able to fit on top of the bleeder screw and offer a nice seal. Keep in mind that the whole setup need not be perfect. All you need now is something that is able to suck out the air as well as the hydraulic fluid from the slave cylinder and into a container. The other end of the tube will go to the drain pan, small container, or a small bucker.
Step 2: Opening The Bleeder Valve
You will need to work with a partner. Ask them to put firm pressure on the clutch pedal until it hits the floor. As they do this take a wrench and use this to loosen the slave cylinder valve.
Continue loosening the valve till you hear air coming out. In a short while, you will also be able to notice the hydraulic fluid coming out. This is bleeding. Ensure that you hold down the container to allow the fluid to get into it.
It is better to use the flare nut type of wrench for bleeding both the clutch and the brake. This is because the wrench can hold to the bleeder tightly which then reduces the odds of stripping the nut.
Step 3: Closing The Bleeder Valve
Take the wrench and tighten the bleeder valve back up. Ensure that your partner never releases the clutch pedal as you do this. This is because releasing the clutch pedal after bleeding will then suck up air right back into the clutch system.
Once you have tightened the bleeder valve, you can now ask your partner to slowly release the pressure off the clutch pedal to its normal position. Check to see if you can find fluid in the master cylinder. You may need to add more fluid.
Once you find that the fluid level has dropped after you have tightened the bleeder screw, there could be a leak. This could occur in the clutch line, in the slave cylinder, or even in the master cylinder.
One thing to note is that even the tiniest leak can cause major issues and thus needs fixing. You may find that you need to replace all the parts. Sometimes though you may be able to rebuild both the master and slave cylinders and save yourself a lot of costs.
Step 4: Repeating The Process
You will need to ensure that there is no air left in the clutch system. For this, you will need to repeat steps 2 and 3. In this case, you will need to get your partner to press down on the clutch pedal till it hits the floor.
Next, take the wrench and use this to open the valve until you can hear air coming out. As soon as the fluid starts leaking out close and tighten the slave cylinder valve.
Do this again and again until there isn’t any air.
Step 5: Add Extra Clutch Fluid
Let your partner release the clutch pedal slowly and let it go back to its normal position. Head off to the master cylinder and open the reservoir.
Add the extra brake fluid to the reservoir until you find that the brake fluid has reached the full line. Ensure that it doesn’t overfill.
Step 6: Testing The Clutch
Now start the car and press down on the clutch pedal. You should notice that the clutch has become a bit firm. You may also change gears to see if they have become smooth or they are slippery.
Once you find that the gears are changing smoothly then they are working great.
Air In Clutch Master Cylinder Symptoms
The clutch master cylinder is available in manual transmission cars. If you have some issue with your clutch system, the mechanic will often start by checking the clutch master cylinder for air.
A clutch master cylinder that has air will mean that the clutch is unable to work properly and can result in a hazardous driving experience.
So how do you tell as a driver that you have air in the clutch master cylinder?
If you make any changes to the clutch master cylinder including replacing the brake fluid, you will need to bleed out the air.
Before you look at the symptoms of air in the clutch master cylinder let’s first discuss how it works. The brake fluid or hydraulic fluid in your car’s clutch master cylinder will enter the slave cylinder and the clutch system when you press down on the clutch pedal.
The clutch system works from a hydraulic perspective. If there is air in the hydraulic system, the pressure will significantly reduce as the air pockets will reduce the hydraulic pressure.
It is important therefore to ensure that there is no air in the master cylinder.
Vehicle Hydraulic Clutch Fluid Symptoms #1: Clutch Pedal Feels Soft
Whenever you press down on the clutch pedal it should feel firm. This is when your clutch system will be performing at its optimum.
However, if you pressed down on the clutch pedal and it felt soft or spongy, then this could be a sign that you have air in the master cylinder. To fix the problem you will need to bleed the master cylinder.
Vehicle Hydraulic Clutch Fluid Symptoms #2: Clutch Feels Different
You may be driving your car of late and have noticed that you are stalling. May drivers tend to blame their driving skills for this.
However, there could also be a good chance that there is air in the master cylinder. It is also possible the brake fluid in the master cylinder needs a top-up.
Vehicle Hydraulic Clutch Fluid Symptoms #3: Leaks In The Clutch Master Cylinder
Over time the vehicle hydraulic clutch fluid will break down. For the clutch system to work properly, the vehicle hydraulic clutch fluid needs to be in a good state. If you notice that your clutch fluid has changed color or the clutch pedal is becoming softer, then it’s important to change the fluid.
If you notice that the vehicle hydraulic clutch fluid is changing color even after a recent replacement then it’s possible that the issue with the seals and the gaskets and there could be corrosion in the master cylinder. Leaks in the master cylinder will also let air in which will cause the clutch pedal to feel soft and spongy.
Vehicle Hydraulic Clutch Fluid Symptoms #4: Sticking Pedal
If there is a leak in the master cylinder, air will also get in. This can cause the brake fluid to absorb moisture.
In turn, the moisture quickly deteriorates the brake fluid causing it to become less viscous. As a result, it loses its hydraulic properties.
One of the ways that this manifests is through a sticking brake pedal. This can cause a dangerous situation when driving.
Slave Cylinder Vs Master Cylinder
One of the main questions that car owners and drivers have is what is the difference between the slave cylinder vs the master cylinder?
Well, firstly the master cylinder is the one that connects directly to the clutch pedal. Whenever you press on the clutch pedal the brake fluid or hydraulic fluid gets into the slave cylinder. This will in turn generate hydraulic pressure.
Pressing the clutch pedal disengages the clutch which separates power from the engine with the transmission.
This, therefore, makes it possible for the driver to shift gears safely as the transmissions and the engine are now disengaged.
By releasing the clutch pedal, the master cylinder sucks up the hydraulic pressure and fluid causing the engine and transmissions to once again join through the flywheel.
On the other hand, you can think of the slave cylinder as the other part of the hydraulic clutch system or a counterpart of the master cylinder. It also has a hydraulic piston. Once the fluid gets into the slave cylinder, this forces the piston to move.
Frequently Asked Questions On Vehicle Hydraulic Clutch Fluid
Do Automatic Cars Have A Clutch
There is no clutch system or gear stick on an automatic car. This is the same for an electric car. That said, automatic cars will feature a shifter. This lets the driver select between neutral, drive reverse, or park.
Do Manual Transmissions Have Fluid
Yes, manual transmissions have fluid that is amber or brown in color. The most ideal manual transmission fluids include SAE80W, 80W-90, SAE 90, and 75W-90. In certain cases, your mechanic may recommend a multi-grade engine oil or automatic transmission oil.
What Is Transmission Fluid Made Of
Transmission fluid is often made of crude oil. But there is also synthetic transmission oil that is built from chemicals that are less likely to break down when exposed to extremely high heat.
Is Clutch Fluid The Same As Brake Fluid
Yes, the clutch fluid and brake fluid are one and the same thing. The only difference is that the brake fluid is contained in the clutch master cylinder. Whenever you press onto the clutch pedal, the brake fluid will move from the master cylinder to the clutch slave cylinder. The resultant pressure engages the clutch.
