How to bleed Campagnolo hydraulic disc brakes?

Question

How to bleed Campagnolo hydraulic disc brakes, specifically the Ekar ones?

I'm going to self-answer for future reference.

Answer 1

The bleeding procedure is (probably) identical for all hydraulic brakes by Campagnolo, but I'll focus on Ekar. Most of the steps are explained in Campagnolo's manual and the video, however it lacks some key information and has some ambiguities which I'd like to clarify.

Some hints about the tools needed:

1. DB-100 bleeding kit. It's pretty high-quality and price is OK, so I wouldn't recommend buying a cheap replacement.
2. UT-DB-011 oil level tool (blue), which is the replacement for the obsolete UT-DB010 (red), which is still shown in the manual and video. The exact width of the tool is critical, I've measured it to be 10.48mm. So even though the tool is pretty expensive for a glorified block of aluminum, I'd again recommend getting the original. The yellow plastic spacer that comes with the brakes/bike has the correct width but I think it is too soft for proper bleeding.
3. LB-300 mineral oil (red), which replaces the old LB-200 oil (blue); according to internet rumors, both oils are identical, but since Ekar (and all other newer groupsets) always comes with the red one and you don't want to mix them to avoid the oil turning brown and making it hard to identify degradation, buy the new red one. I'd also recommend getting the larger bottle (350ml) as it is cheaper per liter and you're probably going to need it anyways, as the Campagnolo brakes are somewhat "thirsty".
4. A high-quality 8mm open-ended wrench (see below) for opening the bleed valve. Unfortunately the valve nut is made of very soft parmigiano "metal", so a low-quality tool can easily round off the valve nut which probably would require you to replace the caliper.
5. High-quality allen keys in the sizes 2.5mm and 4mm - the bolts are very soft too and can be easily rounded off.
6. A disc brake rotor alignment & piston spacing tool
7. Paper towels & isopropanol (e.g. in a spray bottle, so you can easily spray it on a paper towel)

(Why colors red/blue for new/old are reversed for the oil-level tool and oil is beyond me).

Some notes about the bleeding steps as per the manual:

1. Step 1 on p. 36 can be disregarded for Ekar, as the Ekar brakes don't have free stroke adjustment.
2. In step 2 on p. 36, make sure that you insert the tool the right way!! The Campagnolo logo on the tool needs to point to the left, away from the bike, such that the little triangular spike of the tool points towards the brake hose connection. The tool easily fits into the caliper the wrong way, but then you won't fill in enough oil and the brake won't work at all even when all air was successfully removed, which can lead you to question your sanity. The brake pistons are actually offset from the center of the caliper, towards the front. The tool has a circular recession (with the logo inside) where the calipers should rest, and that recession is offset as well. If you insert the tool the wrong way, the pistons will rest on the non-recessed area, which is approx. 0.8mm too wide (they could also get jammed inside the caliper).
   
3. In step 6 on p. 37, it is critical to turn the nut just the right amount. If you don't turn it far enough, the valve remains closed. If you open it too far, you'll allow air from the environment to enter the valve while pulling/sucking with the syringe connected to the caliper. This will result in an endless stream of air bubbles entering the syringe which will again make you question your sanity. The valve nut can easily turn while fiddling with the syringe, so you'll probably have to re-adjust the nut several times during the procedure. The video suggests that you can leave the wrench on the valve (and therefore use a closed-end wrench), but in my experience this doesn't work, as the wrench's weight will pull it down and turn the valve nut inadvertently.
4. In steps 8-11 on p. 38, "aspirate" means pulling/sucking with the syringe.
5. Step 10 on p. 38 is badly translated. It is supposed to mean: While pressing down on the syringe plunger (of the syringe connected to the caliper!), pull the brake lever hard and then let it go such that it snaps back at high speed into its resting position on its own (i.e. don't let go gently, don't "accompany" the lever with your hands while it snaps back). The impact of the lever snapping back will dislodge air bubbles inside the master cylinder. This can be seen in the video but isn't explained explicitly.
6. After step 12. on p. 38 (after closing the valve), I'd recommend pulling the brake lever hard several times to dislodge any remaining air bubbles from the master cylinder.

After bleeding and/or replacing pads & rotor, you'll probably have to re-adjust the caliper position. You can do this using the oil-level tool as explained in the video, or the usual way (open the bolts, push caliper towards frame, pull brake lever while pushing the bike forwards, tighten bolts). If this doesn't work, squint through the caliper to visually check the gap between pads and rotor, and move the caliper carefully until there is a gap on both sides, then tighten the bolts. When the rotors are bent, definitely use a dedicated alignment tool and quite some force, as the Campagnolo rotors are pretty stiff and can't be straightened using a simpler method.

As a home mechanic, plan 1-2h for the whole procedure on one brake, as it can be pretty fiddly and may require re-doing some steps. Shimano brakes are far easier to bleed in comparison.

Answer 2

Good write up. A few notes:

It shouldn't take anything like an hour after the 1st one. 20 - 30 mins tops. First time, maybe an hour for those who are not very mechanically adept. If doing a pair, obviously the second one is quicker as you have most of the prep work already done.

Campag "red" oil boils at ~20 deg C higher than Magura. We've tested it in the lab here at Velotech.

Valve nuts are available as a spare - take a look at the spare parts catalogue, freely available online (select "Spare parts catalogue" in "Document Type" and find the Ekar one) - EC-DB014.

I recommend just supporting the lower syringe in a toe-strap when you let go of it - that way it doesn't swing round and undo the bleed valve further. No fiddling about then. I also don't like a ring spanner on the bleed nut - with the bevel on the nut and the lead-in on the wrench, there's too much danger of rounding the nut off.

Either the red or the blue tool is fine. The original red tool doesn't allow quite such a large piston roll-back which is why the blue tool was introduced, so there needs to be greater accuracy in the caliper locations and in the setting of the caliper if the red tool is used. We've set up scores (literally) with the red tool, with no issues ... but the frame needs to be properly and accurately faced to spec and the rotors need to be pretty straight - certainly a heat-distorted rotor will touch.

Take care in screwing in the bleed kit union at the master cylinder - you are screwing into an alloy thread and cross-threading could scrap the master cylinder - to lower the risk, screw the union in without the weight of the syringe attached. It's easier to get the union in, in a straight line.

Don't overtighten either union in the bleed port - the o-rings will crush and become less effective at sealing the joint ... light finger-tight is enough.

We find it helpful to put a very small amount of pressure on the upper syringe when doing the "pull" at the bottom, This reduces the possibility of drawing air in around the bleed port junction. Magura systems are similar in this respect (no surprise, Campagnolo and Magura co-developed the system).

After bleeding, we'd recommend pulling both levers back fairly hard towards the 'bars and securing them with either toes-straps or strong rubber bands. Leave overnight. If anything has been damaged during the bleed process (shouldn't happen but you never know), leaving the brakes pressured overnight will reveal it.