R26 Brake/Clutch Bleeding Guide

I recently drained the brake fluid on my R26 in order to completely replace it and, unbeknown to me at the time, the clutch system is hydraulic and forks off from the brake fluid reservoir, using the brake fluid to operate.

When the brake fluid reservoir is drained part of the hose taking fluid from the reservoir to the clutch drains out, but does not drain entirely, leaving stale fluid in the clutch line.

As i found out after getting the brake fluid hot at a track day afterwards, when the reservoir is refilled it can leave an air-lock in the clutch-hose, which manifests itself as the clutch-pedal hitting the floor and not springing back up, leaving no clutch when the brake fluid gets hot after repeated use (3 laps of Bedford did it for me!)

I couldn't find much information on this, but decided to try and fix it track-side to continue the day, albeit with very limited tools handy, and i figured i'd take a few photos to help anyone else out.

The hose you need to bleed is awkward to get to, and is on-top of the clutch/gearbox, to the lower right-hand side of the engine as you're looking at it, under the battery, and is best accessed by removing the battery/ECU and tray unless you have what my mate described as "entry level fisting hands".

To remove these it's just a 10mm socket for the battery terminals and what i recall was a T45 bit for the 3 battery tray bolts. Then it's just a case of unclipping the 3 ECU sockets and removing the tray. I also unclipped the thick black cable going to the spark-plugs which was getting in the way, and removed the bolt holding a bracket to the metal undertray which is annoyingly welded to the chassis, and which gives some more movement to actually get your hand where it needs to be. This leaves us with this...



The clutch hose is pretty awkward to see, so you'll want some light. It's in the area surrounded by red and is quite low down. The give-away is the metal clip on the end and the bleed nipple. A picture speaks a thousand words...



Once you've located the hose surrounded in red you'll need to make sure you can get your hand down to it to press the metal clip in and pull it out, which was pretty awkward to do, and you might need to move some cables/brackets around to get there.

Before that though we'll need a bleed hose to capture the fluid from the bleed nipple on the hose. The nipple isn't like the brakes where you open/close it with a spanner, instead the hose has 2 positions - clipped, which is closed, or open, when the hose is not clipped on and the fluid comes out of the bleed nipple. Basically, if you unclip the hose fluid will come out of the bleed nipple.

In the absence of any bleed hose handy in the paddock i had to improvise. It turns out the hose going to the washer fluid jets does the job nicely and just about fits, so i borrowed this...



Pushed it over the bleed nipple, and dropped it between a gap in the undertray and into a plastic cup to capture any fluid. A clear bleed hose would be ideal so that you can see the fluid coming out at source, but in any event this gets the job done.



The next step then is to unclip the hose by pressing in the metal clip and pulling it off. This was awkward as the metal clip was stiff. I attempted to use a flat-head screwdriver to press it down but this didn't work very well, so i opted for some paper-towel wrapped around my fingers and then brute-force, which eventually got things released. As soon as the hose was unclipped the pressure in the brake fluid system pushed out some fluid through the bleed hose, hence having it connected beforehand!

I then brimmed the brake fluid reservoir with fresh fluid and had a mate keep an eye on the fluid whilst i pumped the clutch pedal to bleed the fluid out. The clutch pedal will hit the floor and not return as soon as the hose is unclipped as there's no hydraulic pressure in the system, so you'll need to press and pull it back up. It took quite a bit of repetition to bleed everything out and get the fluid running clear as it should be. You want to make sure the brake fluid reservoir does not run low so keep topping it up!

Even after a complete brake fluid change, this is what came out!



For reference, Right is actual Pepsi Max, Middle is brake fluid that was bled, and Left in the Oasis bottle is more brake fluid as it began to run clearer. It took about 500-600ml until this was the case, so it was lucky i bought a bottle with me.

After this, and you're happy the fluid is running clear, looking like actual brake fluid rather than Pepsi, you can remove the bleed hose and clip the clutch hose back on. It should just press on firmly and then click once in place. A quick tug should ensure it is indeed clipped on properly as you don't want it coming off!

You then want to pump the clutch pedal and make sure it's firm again, which means the system is holding hydraulic pressure and the clutch is working correctly. Now all that remains is to re-clip any wires back in, bolt back in any removed brackets, re-install the battery tray, ECU, ECU plugs, the battery, battery terminals and any other plugs you've removed and you're all sorted.

This process took about 30 minutes having never done it before, but i expect could comfortably be done in a better environment with better tools inside 15-20 minutes.

If you're using the washer fluid hose as a bleed hose you might also want to clean this out thoroughly with some brake fluid cleaner before you re-attach it to the washer jets

 

It solved my problem entirely.

No.

You know that's not true

 

Hi,

Yes, sorry only just seen this.

When you pull the clip up and disconnect the hose it opens the bleed nipple. The hose has 2 positions - clipped, which is closed, or open, when the hose is not clipped on and the fluid comes out of the bleed nipple. Basically, if you unclip the hose fluid will come out of the bleed nipple.

Cheers.