Rear Brake not working at all

I have a strange issue on my SW breaks.

my ABS light behaves normally (it turns off when I ride over the 10km/h)

The rear brake gets no pressure at all. I loosened the pipe (I think) that goes to the rear brake and it is completely dry, no oil, no pressure, nothing



The pipe to the far left of this image seems to be going to the rear:

OK, are all the brake reservoirs full?

Yes, i bleed the front brakes with both master cylinders (left and right lever)

I was wondering if the ABS module is somehow closed to the back brake pipe

I never had ABS on mine. Were the brake systems fluid changed on at least every other year basis to prevent corrosion from Florida famous humidity?

Hopefully not a stupid question. Even though you have fluid in the master cylinder, is it like the brake handle just pulls clean to the the hand grip or do you have pressure in the brake handle? If there is no pressure at the brake handle, you may have air in the system. Unfortunately when I recently bled my brakes, I introduced air into the system and I had to use a Mityvac to remove the air. It took a while but finally I got it done. you would need some kind of vacuum bleeder in order to do this if there is air in the system because just pumping at the handle doesn’t do much. Don’t ask me how I know this.

Remember also there is a particular sequence on using the nipples on each front and rear. IF you use a Mighty Vac use just enough vacuum to keep the fluid moving, pumping the handle vigorously isn't necessary.
I'll add it's a 1-man job if you can find some of the tubing that they use for home O2 equipment. This lets you stand by the revisors and add fluid while using the MV.

I messed mine up when I did the brake bleed but corrected it as above- I bought SpeedBleeders to install so I don’t have to deal with that again in the future.

Never any question is stupid i really appreciate the responses. There is pressure, but imho not enough.

I'll have to borrow my friend vacuum pump and trim


Thank you so much.

It was driving me crazy. I doubted the abs module, but I've never heard of one go bad so sounds like the bleeding is the issue to look into first.

Thanks again.

If you decide to go the SpeedBleeder route like I did, you will still need to vacuum bleed because if there is air in the brake lines, it’s not compressible enough to get the ball valve and spring to move of the SpeedBleeder. Once the lines are fully fluid filled, you can SpeedBleed very quickly (and I have them on my ST1100s which I’ve used for years, including on the clutch slave cylinder- works very well and quickly).

Even with the MityVac, it took a fair degree of effort/ time to fully purge to lines

That's awesome, can't wait to get that air out.

I'll look into the speed bleeder


Thank you again

Just as an aside, one day a while ago, I discovered that if I pulled my rear brake lever 'very very slowly' it would pull right back to handle grip, nil pressure. However, if I pulled it in the usual manner, or 'jabbed' it, it worked fine.

Master cylinder seals to blame. This may not be related to your particular issue but it's food for thought.

Erdoc48 wrote:

I messed mine up when I did the brake bleed but corrected it as above- I bought SpeedBleeders to install so I don’t have to deal with that again in the future.

What brand and product number of brake bleeders did you purchase?

So i tried with a vacuum pump applied to the rear nipple and still no oil coming through. At that point i totally disconnected the oil pipe from the rear caliper and i still had nothing, the vacuum pump kept the negative pressure.

I assume the rear caliper is gone. I tried taking it apart but everything is stuck I'm just considering getting a used one and that might be the whole cause of the problem.

ttyllc wrote:

So i tried with a vacuum pump applied to the rear nipple and still no oil coming through. At that point i totally disconnected the oil pipe from the rear caliper and i still had nothing, the vacuum pump kept the negative pressure.

I assume the rear caliper is gone. I tried taking it apart but everything is stuck I'm just considering getting a used one and that might be the whole cause of the problem.

I may have misunderstood, however, if you disconnected the brake line from the caliper, and still weren't able to draw any brake fluid through the brake line, then the problem is before your caliper. It sounds like you may have a blockage (hydrolocked) in your line.

Actually i excluded the brake line completely i had 5ye vacuum pump on the bleeding nipple and disconnected the brake line.

Does that make more sense ?

Yes it does. With your fluid bleeding vacuum setup, is there a way to test whether you can draw brake fluid through the brake line without it being connected to the caliper? This would isolate where the problem is ... i.e. the brake line or the caliper.

I'll have to figure out a way.
Any idea where to find a good used rear main caliper? Not parking.

Webike seems to be the most competitive but still quite a cost.

Not sure I can recover my original (if it's even worth it)

Interesting, have you checked the cylinder itself to see if fluid would run out of it at the handlebar?

No fluid going out at the master cylinder.
Yes, it's a mystery

Blockage of some sort, try to draw a vacuum on the supply side?

I think I phrased it wrong the reservoir is full there is a pressure going to the front brake it's just the rear brake line that gets no fluid coming out of the ABS modulator. I guess the rear brake hasn't worked in a long time on this bike due to a bad caliper and so I have to discover what's got what's stuck for sure I know it's the rear caliper at the moment the next thing to check is the brake line from the ABS module to the caliper and if that's clear the problem is in the ABS module. I do not know if there is any sensor that my trigger closing the rear brake output on the ABS module

MUCHoldERwingguy wrote:

Blockage of some sort, try to draw a vacuum on the supply side?

I agree ... it appears somewhere there is a blockage. Personally, I'd try to figure out where before throwing good money at unnecessary parts. Prescription without a thorough diagnosis is malpractice in medicine.

I agree, but the rear caliper is completely stuck for sure

ttyllc wrote:

I agree, but the rear caliper is completely stuck for sure

I don't know about our machines but in the car/truck world, calipers can be rebuilt (by the D-I-Y'er) with the proper kits.

I assume the SWing's could be rebuilt as well if finding an affordable new or used unit is difficult.

Rear callipers live a rough life, and often get mild corrosion in the seal groove that pushes the seal hard onto the piston and makes them very difficult to extract. You definitely don't want to use a tool on the outer sealing face of the pistons but I have got some pliers that expand inside them that are very useful to get them moving. My first suggestion (assuming you get fluid pumping through the line to the calliper) is to use the brake fluid pressure alone to shift the pistons. You may need to prevent one piston from popping right out using a g-clamp to give the other one a chance to move free. You can also cap off the fluid supply port and then use a grease gun on the nipple to drive the pistons out.

Once the pistons are out you can easily clean out any remaining gunge, pull out the seals and scrape the grooves carefully clean, and fit new seats (and pistons if needed). Much cheaper than a new calliper.

Very valuable input. Thank you

Welcome to the forum, sorry to hear your brake issues, ABS issues/failures are very rare, not a common topic, the SW600 has CBS or Combined Brake System, so if your rear brake does not get pressure, neither will the linked front caliper center piston, your braking is really diminished. Sometimes is very hard to diagnose over the net, just try to share any findings no matter how insignificant, it may be a clue, obviously this must have been an existing condition with scooter when you got it, if not  

 Well, good luck, Florida neighbor, if I was close, I come take a look

Be sure to share the knowledge when you do get this sorted out.

The has a bike combined braking system so if the left lever has no pressure it won't be activating the central piston in the front caliper either. Could that be the cause of the problem?
To bleed the brakes you need to do the front first (that's the lower nipple) and then the rear.
Apologies if I'm teaching granny to suck eggs and you've already done this.

https://i.servimg.com/u/f19/20/42/99/59/cd3e9c10.jpg

https://i.servimg.com/u/f19/20/42/99/59/b7527010.jpg

Here’s the Speed Bleeders from their site…they sell them in a 2-pack for the front and the single for the rear brake

Awsome information everyone. Thank you very much.

I made some progress last night when I started taking apart the caliper. It turns out the bleeder was completely clogged LOL. I suspect that is what is going on to the abs module as well. I'll try compressed air and some needles to try to clean it.

i was able to do a vacuum test on the brake line from the ABS modulator to the rear caliper and it looks like its not obstructed

I'm having a really hard time to separate the caliper body from the bracket, one of the pins is completely seized and the cylinders as well are not moving (i'm very careful with those though.

Yes I did get the bike some time ago and the breakes seemed to be ok, but when I had to stop in emergency I quickly realized that I had bought a bike with breakes issues and stopped on the abck of a stopped car and caused quate a lot of damage to my bike and a dislocated shoulder (the previous owner didnt deem it important to tell me. Im not happy) . Sorry for the sad story, but i figured Id shed some light on the situation

PB Blaster, Kroil are 2 good penetrants, soak, tap repeat repeat and repeat, you have gone this long so take your time at least you have an idea now just what you are dealing with.

Yeah, exactly

That's what I've been doing

We'll make it

By the looks of your weather for the next few days HEAT maybe need in more than one place.

Not yet, today it's still going to go up to 80

Funnily enough, I wondered if a blocked nipple was part of your problem.

I had a bear of a job removing the pad pins on my Swing, it lived near the coast (or possibly in the sea) with a prior owner and was quite corroded in all sorts of places. I used penetrating oil, heat and finally an electric impact gun to break the pad pin loose. Make sure to use a fresh hex bit when you do the removal. If the hex head bolt rounds out, you can (sometimes) hammer an appropriately sized Torx bit in for another try.
I was greatly relieved when the pad pin finally moved, and replaced it with a new one, with some copperslip grease on the threads.

Yeah, I'm going in that direction. I used penetrating oil an impact gun on the 14mm socket that didn't do anything. I have to try heat. The Allen wrench one came off easy tho

run some more vacuum test on the ABS modulator.

Noticed that the lever that should pump front and rear brake lines only pumped oil on the line that goes to the front brake. This seems like a defect of the ABS modulator. shouldn't there be pressure on both brake lines when the left master cylinder is pressed?

I tried with compressed air and also with the vacuum pump. Interestingly when I blow compressed air in the rear brake line i get flow toward the master cylinder, not the other way around under any circumstance

Welcome to the forum. I can see you've done some extensive testing and I'm wondering, could the problem be in the delay valve?

It's the delay valve somehow connected to the rear brake?

It distributes the pressure ratio when you operate the rear brake. I think it's something like 65% to rear brake and 35% to the front brake.

Makes sense, but the rear brakes line is not connected to it in any way.

The rear brake line comes directly out of the ABS modulator and there is no oil at all coming out of that output

Does the ABS modulator shut completely off the rear brake under any condition?

ttyllc wrote:

It's the delay valve somehow connected to the rear brake?

Yes, fluid flows from the left/rear brake master cylinder to "ABS modulator" or a splitter if no ABS, then is split to delay valve and rear brake line/hose, when certain preset brake pressure is reached (as to squeezing brake lever harder/or faster), the delay valve is forced open and fluid is ported to front caliper center piston, at that point "same" pressure is applied to rear and front calipers, is not a proportional valve is shut or open. When rear brake is applied "lightly" the front is not pressurized.

A "Proportional Valve" is commonly used on cars to limit brake pressure to rear brakes and prevent rear wheel lockup, fluid flows all the time, even with ABS systems, cars maintain this feature in case ABS failures. In any case not the case in the SW600.

I stand corrected. zrx212's explanation makes more sense; i.e. 'delay valve'. IAC, the delay valve is involved somewhere down the line.

Loosemarbles wrote:

I stand corrected. zrx212's explanation makes more sense; i.e. 'delay valve'. IAC, the delay valve is involved somewhere down the line.

I fixed my explanation to make it more clear/correct

So it seems that in my case the abs module is faulty bc no pressure at all goes to the rear brake line ever

ttyllc wrote:

Makes sense, but the rear brakes line is not connected to it in any way.

The rear brake line comes directly out of the ABS modulator and there is no oil at all coming out of that output

Does the ABS modulator shut completely off the rear brake under any condition?

There are three independent pressure/output ports in the ABS modulator, front caliper, front brake delay valve, rear caliper. ABS modulators/pumps are designed to release and quickly reapply brakes, etc. Are you sure fluid and pressure are coming out of line going into the ABS pump from master cylinder, freely ?, disconnecting input lines to modulator, should basically gravity drain reservoirs, unless lines are obstructed/collapsed either that or the pump passages are contaminated/block by old fluid, in any case you don't have an ABS fault

Yes, I'm sure that both master cylinders are sending fluid and pressure to the abs modulator. In fact the front brakes work efficiently when either lever (left or right) is pressed.

The only output that gets no pressure or oil is the one to the far left of the OP picture (that's where the rear brake line is directly connected)

" In fact the front brakes work efficiently when either lever (left or right) is pressed. "

Well, that definitely would point to a fault/blockage in the ABS modulator, is a hard pill to swallow, but you can find modulators on eBay from $50-$250, I would check wiring/sensors/reset ABS, etc. JIC and possibly blow air thru ports, both ways, etc. Maybe that port was tripped/closed/blocked by sticking rear brake, etc., or , maybe smack it a few times "gently" with a rubber mallet Not a normal condition, time to try not normal repairs.

The brake/abs section of "Service manual" is kind of vague some on description/operation details.

Yeah, i did everything you described.

Blew air, tapped in every direction and i only had flow when i put compressed air IN the rear brake line out and i got flow toward the left lever master cylinder

I got a used abs module for about 80. It's on its way. We'll go from there.

I suspect all the sensors work because when i start the bike the ABS light comes on and then when I ride it it turns off as it should so I think all the electronics work

I agree with your comment regarding the manual being vague and that's probably because there is not much to it there should be pressure going to both front and rear when the left master cylinder is pressed.