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Luddite · 28-01-2020, 02:38 PM

On to the bleeding.

Tip: ALWAYS READ THE MANUAL!
Earlier this month, I was browsing the workshop manual for fuel filter information and spotted a section mentioning bleeding the ABS unit, which I'd never seen before, despite referring to this manual numerous times over the past eight years. It says:

"Bleeding of the ABS braking system
Before bleeding a brake pump, move back the calliper pistons... to drain in the pump the air collected near the ABS control unit
Bleeding must be carried out by means of the corresponding joints placed near the callipers and the brake cylinders.

Evo ABS pump schematic

Important
Do not undo the fixing screws of the joints of the pipes on the ABS hydraulic control unit, unless control unit replacement is necessary."

I don't think I've ever done that for the rear caliper so maybe that was the missing link preventing a successful bleed. Bear that in mind if you're thinking of doing this job yourself.

The MityVac comes with various connectors to cater for different braking systems but I used an old one from a manual bleeder as that has a nylon clip, which makes a tight seal and stops the pipe popping off.

Adapters

I also applied some PTFE tape around the bleed nipple in case the MityVac could draw air in past the threads. It was satisfyingly snug when I wound it back in.

Taped bleed nipple

The actual bleeding process was so much quicker and easier than the traditional way (as you'd hope). The first advantage of the MityVac was that you can use it to drain the reservoir before you start so you don't have to pump the old fluid all the way through the system.

Once connected to the caliper and pumped up, I cracked the nipple and the fluid began flowing. Be aware that the fluid drains pretty quickly so you need to keep a close eye on the reservoir to ensure it doesn't run dry. I propped the pump next to the airbox and just kept topping up the reservoir while a continuous flow of DOT 5.1 ran into the MityVac. After three reservoirs full and with the fluid running bubble-free, I closed the nipple and removed the MityVac. Another advantage of the MityVac is that the old fluid stays within the pump so less chance of an accidental spillage.

It was only a five-minute job to replace the caliper. So, how did it feel? For a moment I was disappointed as it still felt spongy (spot the deliberate mistake!). I'd forgotten that I'd previously pushed the pistons right back and, once the pads had been pumped against the disc, it felt perfect.

Of course, the real test will be how long will this last?

Hopefully, by pushing the pistons back, raising the caliper, filling with DOT 5.1 and using the vacuum bleeder, I'll end up with a more permanent solution.

I shall report back in due course.

Even if I do need to re-bleed the caliper, the MityVac makes it so easy, it won't be the chore it used to be. In fact, I might just do the front brakes now, even though they don't need it, just to use up the rest of the DOT 5.1.

28-01-2020, 02:38 PM	#2
Luddite Registered User Join Date: Aug 2011 Location: Southampton Bike: M1100evo Posts: 2,465	On to the bleeding. Tip: ALWAYS READ THE MANUAL! Earlier this month, I was browsing the workshop manual for fuel filter information and spotted a section mentioning bleeding the ABS unit, which I'd never seen before, despite referring to this manual numerous times over the past eight years. It says: "Bleeding of the ABS braking system Before bleeding a brake pump, move back the calliper pistons... to drain in the pump the air collected near the ABS control unit Bleeding must be carried out by means of the corresponding joints placed near the callipers and the brake cylinders. Evo ABS pump schematic Important Do not undo the fixing screws of the joints of the pipes on the ABS hydraulic control unit, unless control unit replacement is necessary." I don't think I've ever done that for the rear caliper so maybe that was the missing link preventing a successful bleed. Bear that in mind if you're thinking of doing this job yourself. The MityVac comes with various connectors to cater for different braking systems but I used an old one from a manual bleeder as that has a nylon clip, which makes a tight seal and stops the pipe popping off. Adapters I also applied some PTFE tape around the bleed nipple in case the MityVac could draw air in past the threads. It was satisfyingly snug when I wound it back in. Taped bleed nipple The actual bleeding process was so much quicker and easier than the traditional way (as you'd hope). The first advantage of the MityVac was that you can use it to drain the reservoir before you start so you don't have to pump the old fluid all the way through the system. Once connected to the caliper and pumped up, I cracked the nipple and the fluid began flowing. Be aware that the fluid drains pretty quickly so you need to keep a close eye on the reservoir to ensure it doesn't run dry. I propped the pump next to the airbox and just kept topping up the reservoir while a continuous flow of DOT 5.1 ran into the MityVac. After three reservoirs full and with the fluid running bubble-free, I closed the nipple and removed the MityVac. Another advantage of the MityVac is that the old fluid stays within the pump so less chance of an accidental spillage. It was only a five-minute job to replace the caliper. So, how did it feel? For a moment I was disappointed as it still felt spongy (spot the deliberate mistake!). I'd forgotten that I'd previously pushed the pistons right back and, once the pads had been pumped against the disc, it felt perfect. Of course, the real test will be how long will this last? Hopefully, by pushing the pistons back, raising the caliper, filling with DOT 5.1 and using the vacuum bleeder, I'll end up with a more permanent solution. I shall report back in due course. Even if I do need to re-bleed the caliper, the MityVac makes it so easy, it won't be the chore it used to be. In fact, I might just do the front brakes now, even though they don't need it, just to use up the rest of the DOT 5.1. Last edited by Luddite; 28-01-2020 at 02:44 PM..