Car Ownership 101: Bleeding a hydraulic clutch system

It's a handy skill
by Paulo Rafael Subido | Aug 5, 2018

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The hydraulic system that actuates the clutch in your manual-transmission car will not last forever. Just like every wear item in your car, this will fail eventually. Back in the day, a clutch cable was used, but newer cars utilize a hydraulic system. If you are handy with a socket wrench and ratchet, this job is quite easy.

Things to remember

You can buy a cheap lower-clutch repair kit, but changing the whole assembly is a better idea. Brake fluid is highly corrosive and can destroy paint. Work with care. Rinse off with water immediately if it gets on any body panels. To increase the longevity of hydraulic parts, change the fluid once a year or when you notice discoloration in the reservoir.

The gear

You will need:

-brake fluid

-clutch master cylinder

-clutch slave cylinder

-eye and hand protection

-rags and water

-a flashlight 

Important things to check

-Clutch hydraulics will not fail without warning. If you find it harder to shift into gear, and if the clutch pedal feels mushy, it is time to take a closer look at the system. Don’t wait. Do the repair soon.

- Do not mistake this for a slipping or worn-out clutch disc. That’s a completely different job.

How to repair a clutch hydraulic system

 

1. Check the fluid's color

What is the color of the clutch fluid in the master cylinder reservoir? If it is dark and mucky, that’s a sign that something is wrong. Now, locate the clutch slave cylinder. This is usually positioned on the gearbox housing, near the clutch pressure plate and release bearing. On a front-wheel-drive car, this is easily accessible from under the hood. On a rear-wheel-drive car, you may need to get the car on a lifter.

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2. Disassemble with care

Undo the clutch slave first. Be delicate with the metal clutch line and fittings. You don’t want to damage any of the lines. Be prepared to catch any clutch fluid using a bottle of some sort. Chances are it is filthy and black. Remove the clutch master cyclinder. You may have to undo a lever in the driver-side footwell before undoing the nuts on the firewall. 

3. Clear the line

Flush the clutch line by pumping clean brake fluid into it by using a clean oil can and flexible hose. Now install the master and slave cylinder but do not over tighten the fittings. Fill the reservoir with new brake fluid.

4. Bleed the clutch system

Ask a companion to pump the clutch pedal repeatedly, and then hold it down firmly in place. With the pedal down, open the bleed screw to let any air out. You will hear a hissing sound if you are doing this properly. Repeat the pumping (bomba) and firm (pirme) cycle until all air is out of the system and the clutch pedal feel returns to normal.

5. Clean as you go

Clean up any spilled brake fluid with water. You can now hit the road again.

 



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PHOTO: Paulo Rafael Subido
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