What is a Clutch Hydraulic System Bleed?
Many manual transmission passenger vehicles use the very reliable hydraulic clutch system. At a minimum, the system is composed of a master cylinder, which pumps fluid through a line, a flexible clutch hydraulic line, and a clutch slave cylinder. The fluid used is typically brake fluid, though there are several types in use. In order for the clutch hydraulic system to function properly and reliably, the clutch hydraulic system must be serviced and inspected regularly, including flushing and bleeding the hydraulic fluid to prevent corrosion, air, or water from causing damage in the clutch hydraulic system. Note that this system is not the clutch, it is simply how the clutch pedal in the vehicle is connected to the clutch on the engine flywheel. The advantage to a hydraulic clutch is that they are very easily pressed, and they can increase or decrease the range of motion needed to actuate the clutch.
What does the Clutch Hydraulic System do?
Flushing and bleeding the clutch hydraulic system is performed, most commonly, during normal factory scheduled maintenance. Brake fluid becomes contaminated over time, and will change from a clear, clean fluid, to a dirty, dark fluid. When the clutch hydraulic system fluid is dirty, it acts as a corrosive agent to the many rubber components of the clutch hydraulic system. Also, air or water in the clutch hydraulic system may necessitate component replacement. This will also require the clutch hydraulic system to be flushed and bled. Many technicians use a vacuum bleeder, a specialty tool designed to suck dirty fluid out of the clutch hydraulic system while new fluid is added to the reservoir. This tool attaches to the bleeder valve on the slave cylinder, and when the valve is turned suction pulls the fluid from the clutch hydraulic system system, preventing air from entering. Once the extracted fluid is completely clean, new and free of air, the valve is closed.
When should the Clutch Hydraulic System be Bled?
The prevalent cause necessitating flushing and bleeding clutch hydraulic system fluid is factory scheduled maintenance. However, if the fluid is noted to be extremely old, dirty, and hazardous to rubber clutch hydraulic system components, a flush and bleed service should be completed ahead of schedule. Also, when there is a clutch hydraulic system fluid leak, this service will be completed to remove air from the system once the leak is repaired. Lastly, if the clutch pedal fails to actuate the clutch, the clutch hydraulic system will be bled and flushed to eliminate air from the system. This will be performed after verification and repair of the source of air, and possibly beforehand in order to discover a small leak.
Can I drive with a clutch problem?
If there is any sign that the clutch hydraulic system is not performing as originally intended, the vehicle should immediately be placed out of service, and repaired. If the clutch hydraulic system fluid is being flushed and bled as part of routine maintenance, with no symptoms noticed, the vehicle can safely be driven to a repair shop. It may seem fine to drive a vehicle even when the clutch pedal barely actuates the clutch, but very much damage to synchronizer assemblies in the manual gearbox will be damaged by driving without the clutch fully operating. This is due to the inability of the transmission to synchronize speeds as the input shaft will continue turning at the same speed as the engine.
How often should the clutch hydraulic system be bled?
Service of the clutch hydraulic system system is part of factory scheduled maintenance, and the schedule is located in the owner’s manual of most vehicle's. Most clutch hydraulic system services are performed between 70,000 and 100,000 miles, and fluid will be flushed and bled at that time. Notice, failure to adhere to factory schedule maintenance guidelines may result in premature failure of various clutch hydraulic system system components.
How are clutch hydraulic system problems diagnosed?
Clutch hydraulic system fluid bleeding requires no diagnosis. It is performed at the completion of a repair, as part of a clutch hydraulic system system flush, or as a step in testing the clutch hydraulic system system if a diagnosis requires. However, if a technician notices the brake fluid in the clutch hydraulic system master cylinder is murky, discolored, is contaminated, or there is condensation under the cap, the system will be flushed and bled.
How are clutch hydraulic systems bled?
The technician servicing the clutch hydraulic system will first remove the clutch hydraulic fluid reservoir, then the vehicle will be slightly lifted to gain access to the clutch slave cylinder bleed valve. The vacuum bleeding tool will be placed on the valve and pumped as the valve is turned to released the old fluid. New fluid will then be poured into the clutch fluid reservoir as an assistant pumps the clutch pedal slowly. The flushing will continue until the fluid comes out of the slave cylinder clean, renewed, and free of air. At that time, the technician will close the bleeder valve, top off the clutch hydraulic system reservoir, set the vehicle down, and test the clutch.
RepairPal Recommendations for Clutch Hydraulic System Issues
Many dishonest shops will recommend these services before they are due, when not performing a clutch hydraulic system service, and at the expense of the owner. Any time you feel the service is not warranted, ask why it should be performed now and consider contacting one of our certified repair facilities for a second opinion. If you are completely uncertain, you can always ask us for advice here on RepairPal.com.
What to look out for when dealing with Clutch Hydraulic System issues
Even if the fluid from the clutch hydraulic system appears clean, if the factory recommends changing the fluid as scheduled maintenance, it is still a good idea to follow the advice of the manufacturer of the vehicle. If you are concerned of being duped into an upsell, focus your attention on the factory scheduled maintenance guide in your owner's manual, and compare that to your service records. If the vehicle is overdue for the service, or if it is coming due then, it should be serviced.
Can I bleed my own clutch hydraulic system?
The clutch hydraulic system can be maintained by a DIYer with a complete knowledge of hydraulically actuated systems. This is important as testing clutch hydraulic system operation and safely servicing hydraulic components relies on this knowledge. If the complete system is not understood, damage to clutch hydraulic or transmission components is likely. Especially when poor clutch performance is the symptom.