I hope this may help someone... :cool:
I've just been through a couple of hours long struggle of bleeding our Scenic RX4 hydraulic clutch. :(
Normal bleeding (2 man: press clutch, close nipple, release clutch, open nipple, etc.) did not work well at all, except to get rid of some really dirty brake fluid. Gravity bleeding did nothing at all. These first two processes which I tried just managed to get even more air into the system.
What did work well and fairly quick was reverse bleeding under pressure (1 man job).
Here's how I did it...
On the clutch slave cylinder I connected a 40 cm (can be longer) transparent bleeding hose to the bleed nipple. Then remove the retaining wire clip with thin nose pliers, and carefully pull out the hard line metal coupler about 3 to 4 mm to allow flow through the bleeding nipple. This can be tricky... pull a bit too much and the hard line coupler comes out too far, letting air into the system!
I filled a clean oil can (one you can pump with your thumb and which has a long thin spout that can fit into the transparent bleeding hose) about half full with the recommended Brake Fluid.
Open the Brake Fluid Reservoir up top to allow air and fluid to feely push up. Have a smallish syringe handy to extract excess brake fluid from the reservoir.
Pressurize an air compressor with a thin nozzle fitted that can fit tightly into the transparent bleeding hose - a tight fit here is important.
Now fill the transparent bleeding hose with brake fluid using the oil can, perhaps 5 squirts or so, nearly to the top of the hose. You only loosely insert the oil can spout into the hose to allow air to escape as fluid enters. This hose filled with fluid now acts as a temporary reservoir. Remove the oil can.
Insert the air compressor nozzle into the transparent bleeding hose and let it blow! You will see the liquid moving steadily down the hose into the nipple of the clutch slave cylinder. If the liquid only moves a little and does not keep going down the hose, then the hard line coupler may not be pulled out enough (wiggle and pull slightly, just a bit may do the trick). Stop blowing before all the liquid vanishes into the clutch slave cylinder! Refill the hose using the oil can. Blow again. Repeat.
While doing that, air bubbles appear in the Brake Fluid Reservoir up top. At first the fluid level may not rise much because air is being released. Later smaller bubbles, then less bubbles, then no bubbles, then the fluid rises. Use the syringe to draw off excess fluid from the reservoir (tie your transparent hose with a clothes peg to a cable somewhere to free your hands). You can continue this procedure to make sure there are no more bubbles coming through and keep topping up the transparent bleeding hose so that there's no ingress of air from the other end below.
Once you're satisfied the air is out, simply push in the hard line coupler, fit the wire retaining clip, pull off the transparent bleeding hose, draw off excess fluid from the reservoir with the syringe until on the Max level line, close the reservoir and clean up any mess.
After this process (about 10 to 15 minutes) my clutch was back to normal again and gear shifts were easy and smooth.
I've just been through a couple of hours long struggle of bleeding our Scenic RX4 hydraulic clutch. :(
Normal bleeding (2 man: press clutch, close nipple, release clutch, open nipple, etc.) did not work well at all, except to get rid of some really dirty brake fluid. Gravity bleeding did nothing at all. These first two processes which I tried just managed to get even more air into the system.
What did work well and fairly quick was reverse bleeding under pressure (1 man job).
Here's how I did it...
On the clutch slave cylinder I connected a 40 cm (can be longer) transparent bleeding hose to the bleed nipple. Then remove the retaining wire clip with thin nose pliers, and carefully pull out the hard line metal coupler about 3 to 4 mm to allow flow through the bleeding nipple. This can be tricky... pull a bit too much and the hard line coupler comes out too far, letting air into the system!
I filled a clean oil can (one you can pump with your thumb and which has a long thin spout that can fit into the transparent bleeding hose) about half full with the recommended Brake Fluid.
Open the Brake Fluid Reservoir up top to allow air and fluid to feely push up. Have a smallish syringe handy to extract excess brake fluid from the reservoir.
Pressurize an air compressor with a thin nozzle fitted that can fit tightly into the transparent bleeding hose - a tight fit here is important.
Now fill the transparent bleeding hose with brake fluid using the oil can, perhaps 5 squirts or so, nearly to the top of the hose. You only loosely insert the oil can spout into the hose to allow air to escape as fluid enters. This hose filled with fluid now acts as a temporary reservoir. Remove the oil can.
Insert the air compressor nozzle into the transparent bleeding hose and let it blow! You will see the liquid moving steadily down the hose into the nipple of the clutch slave cylinder. If the liquid only moves a little and does not keep going down the hose, then the hard line coupler may not be pulled out enough (wiggle and pull slightly, just a bit may do the trick). Stop blowing before all the liquid vanishes into the clutch slave cylinder! Refill the hose using the oil can. Blow again. Repeat.
While doing that, air bubbles appear in the Brake Fluid Reservoir up top. At first the fluid level may not rise much because air is being released. Later smaller bubbles, then less bubbles, then no bubbles, then the fluid rises. Use the syringe to draw off excess fluid from the reservoir (tie your transparent hose with a clothes peg to a cable somewhere to free your hands). You can continue this procedure to make sure there are no more bubbles coming through and keep topping up the transparent bleeding hose so that there's no ingress of air from the other end below.
Once you're satisfied the air is out, simply push in the hard line coupler, fit the wire retaining clip, pull off the transparent bleeding hose, draw off excess fluid from the reservoir with the syringe until on the Max level line, close the reservoir and clean up any mess.
After this process (about 10 to 15 minutes) my clutch was back to normal again and gear shifts were easy and smooth.
Bleeding Scenic RX4 Hydraulic Clutch
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