Brake fluid change glitch.

NewRider · Jun 10, 2015

Hello two wheeled folks.

I've encountered a little problem while changing the rear brakes fluid. It's not the first time but this time it went completely wrong and I don't know why. I ended having swapped the fluid with air. Bummer. Here's how I usually proceed.

Open the fluid tank and pump some of the fluid (not all) and clean the tank a bit. The brakes line are still filed with fluid at this point.
I plug the pump (can't remember it's name) to the bleed valve and untight the valve to let the fluid out.
I then fill up the fluid reservoir to the brim and start using the pump to suck out the old fluid and I continue until I see a colour difference in the fluid comming out onf the brake line.
Once the exchange done I close the valve, clean the fluid reservoir cover and rubber seal and voilÃ .

By the way I don't dismantle half the brakes system has shown in the maintenance manual. Shoul I have ?

Jokeshopbeard · Jun 10, 2015

I'm not sure what the manual says, but when changing brake fluid myself, I only open the bleed nipple when I am applying pressure via the pedal/lever from the master cylinder (M/C) and then close it whilst the system is still under pressure. It take a while but I have never encountered a problem this way. I also leave the pedal/lever depressed overnight and tap the lines with a screwdriver handle periodically to encourage any rogue air bubbles to float up to the reservoir.

Are you sure you kept the reservoir topped up throughout the process? It's pretty easy to suck air into the system if you allow the level of fluid in the reservoir to drop past a certain level.. No great trouble though, just start from step 1 again.

kuksul08 · Jun 10, 2015

I believe the rear brake bleeder is on the bottom, so it is recommended to remove the caliper to ensure you can bleed bubbles out properly.

I think you may have sucked air in yours though.

zibbit u2 · Jun 10, 2015

Yeah you need to remove the rear caliper and the shroud keeping the line secure on the bottom of the swingarm. Suspend the caliper with a zap strap to one of the pannier mounts so the bleed nipple is higher than the master cylinder, with the bleed nipple on top. Find a piece of metal/hard plastic about the same width as the rear rotor and put that between the pads to keep the caliper Pistons from over extending. A note, have a clear tube with brake fluid in it going to a overflow bottle. You'll see the bubbles and it's less likely to introduce air into the system. Bleed as per normal, pump slow full stokes, hold, then crack bleeder valve (nipple) just until fluid starts to flow, close the bleeder valve (nipple) when you're at the bottom of the levers stroke. Rinse and repeat until no air is in the system.

You're trying to suction bleed via a vacuum pump.. While it should be possible to do that, I'd just follow the manual (which I just basically described). Sometimes shortcuts take longer to fix than doing it right from the beginning.

zibbit u2 · Jun 10, 2015

I really should do a DIY front/rear brake fluid change instructions here.. Hmm

gatdammit · Jun 10, 2015

I've done car brakes for many years. Never had a problem like I did trying to get air out of the rear caliper when I did my Strada's brakes.

I elevated the caliper, ran an entire pint through with no bubbles, tapped caliper repeatedly with a hammer, tried a hand pump vacuum bleeder, etc...pedal still dropped to the floor. Only thing I didn't try was a pneumatic line bleeder but it probably would have sucked the reservoir dry too fast for me to fill anyway.

Had to swallow my pride and take it to the dealer. They used a machine but the tech did say the rears are difficult. I like to keep my bike in neutral and use the rear to keep her from rolling so saying "screw it" and rolling without one wasn't an option.

NewRider · Jun 11, 2015

zibbit u2 said:
Yeah you need to remove the rear caliper and the shroud keeping the line secure on the bottom of the swingarm. Suspend the caliper with a zap strap to one of the pannier mounts so the bleed nipple is higher than the master cylinder, with the bleed nipple on top. Find a piece of metal/hard plastic about the same width as the rear rotor and put that between the pads to keep the caliper Pistons from over extending. A note, have a clear tube with brake fluid in it going to a overflow bottle. You'll see the bubbles and it's less likely to introduce air into the system. Bleed as per normal, pump slow full stokes, hold, then crack bleeder valve (nipple) just until fluid starts to flow, close the bleeder valve (nipple) when you're at the bottom of the levers stroke. Rinse and repeat until no air is in the system.

You're trying to suction bleed via a vacuum pump.. While it should be possible to do that, I'd just follow the manual (which I just basically described). Sometimes shortcuts take longer to fix than doing it right from the beginning.

Thanks. I'll try this on first occasion. Something tells me that taking the caliper block off the wheel will do the thing. Even if I don't want to. :s

NewRider · Jun 11, 2015

kuksul08 said:
I believe the rear brake bleeder is on the bottom, so it is recommended to remove the caliper to ensure you can bleed bubbles out properly.

I think you may have sucked air in yours though.

Oh yes. There is definitively air in the lines. Even more than fluid.

NewRider · Jun 11, 2015

Jokeshopbeard said:
I only open the bleed nipple when I am applying pressure via the pedal/lever from the master cylinder (M/C) and then close it whilst the system is still under pressure.

Actually I do this same way most of the time but if one way does not give the expected results I then switch to the other technique and vice versa. This time I went through an intire botle of fresh fluid.

Jokeshopbeard said:
Are you sure you kept the reservoir topped up throughout the process?

Yes I did until I've got fed up. The ninth unsuccesful attempt...

NewRider · Jun 14, 2015

Just spent two hours dismanteling the caliper assembly and replacing rear the brake fluids and the results...

None! Nada, no go. Quite irritating really.

I've followed the maintenance guide to the best I could and to not prevail. I'm starting to wonder if there is not a bigger problem.

mentalist · Jun 18, 2015

Remove caliper bolts and turn caliper so bleed nipple is at the top.
Fit hose to nipple and apply pressure to brake whilst loosening the bleed nipple. At the bottom of the brake pedal stroke nip up the bleed nipple and then release brake pedal. repeat this procedue keeping the resevoir topped up. untill all the air is out.
this is how i've always done fluid changes over the last 30years without problems.

gatdammit · Jun 18, 2015

mentalist said:
Remove caliper bolts and turn caliper so bleed nipple is at the top.
Fit hose to nipple and apply pressure to brake whilst loosening the bleed nipple. At the bottom of the brake pedal stroke nip up the bleed nipple and then release brake pedal. repeat this procedue keeping the resevoir topped up. untill all the air is out.
this is how i've always done fluid changes over the last 30years without problems.

I get the process, Mentalist. Like OP, I did this exact procedure (plus a dozen other tricks I found on the web) for an entire weekend with no joy.

anders8 · Dec 13, 2016

Was it ever diagnosed? It's been over a year...

monocog007 · Dec 14, 2016

The reason why people have such difficulty with the rear brakes is because of the ABS circuit. It is way above the caliper, so that is the point where the air is sitting. The only way to be sure this is free from air is with something like a vacuum bleeder. Nothing else can move enough fluid in a short enough amount of time to get all the air out.

appliance821 · Dec 14, 2016

monocog007 said:
The reason why people have such difficulty with the rear brakes is because of the ABS circuit. It is way above the caliper, so that is the point where the air is sitting. The only way to be sure this is free from air is with something like a vacuum bleeder. Nothing else can move enough fluid in a short enough amount of time to get all the air out.

I think you're right that it won't be cleared by normal bleeding. The manual says to push the pads fully open. I think this is to clear the abs circuit. I would do this after flushing some fresh fluid through so you're not just pumping old stuff in the circuit and leaving it there.

On the fronts, I couldn't get a good bleed until I did this. The tying back of the lever for about 5 hours did a final firming up.

I'll be doing the rear tomorrow - see if it all works out.

gatdammit · Dec 15, 2016

For the rear, I used a manual pump, plus all the tricks and tips noted here and on other sites. Unfortunately, my local DIY garage didn't have a pneumatic pump that I normally use for brake jobs. Think those are well worth the money if you do all your vehicle brake jobs.

monocog007 · Dec 15, 2016

Hindsight is definitely 20/20, but I think the best thing to do is bleed the brakes with quality DOT 5.1 fluid before you start noticing them getting squishy. Ducati seems to put cheap crap in from the factory, as many Multi owners would tell you.

I was able to firm up my pedal by running through a bottle of Motul DOT 5.1 + a vacuum bleeder. I also took the chance to rescuff the pad with sandpaper & install EBC HH pads. The HH pads are a welcomed improvement over whatever crap the stock pads are made of.

Brake fluid change glitch.

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