Intruders-Alert

I know this topic has been covered ad nauseam, but I’m having trouble with the front brakes. I rebuilt the caliper and now I have a even mushier brake lever. So far I have tried bleeding the master cylinder by using the thumb over the banjo bolt hole trick, the old pump- open bleeder-close bleeder- release lever method, vacuum bled about 5 reservoirs worth of fluid through the system, squeezed the lever and cracked the line at the caliper, tried reverse bleeding and cussed at it. So far none of that has gotten the air out of the system. The lever is still spongy enough to squeeze the lever all the way in to the throttle grip. I’m all out of ideas. Anyone have any others? I looked for leaks as well and I’m not seeing any. I’m lost.

Hmmm, I can see why you are perplexed!

To be the best of help, we'll need some more information, please.

Was the system totally functional before you rebuilt the Caliper? Why did you rebuild it? Was it leaking?
When you had that Caliper off, might you have checked the Master Cylinder Seals/Bore?
How old was the Fluid? Was it dark?

Designer wrote: ↑

Wed Apr 27, 2022 3:06 pm

Hmmm, I can see why you are perplexed!

To be the best of help, we'll need some more information, please.

Was the system totally functional before you rebuilt the Caliper? Why did you rebuild it? Was it leaking?
When you had that Caliper off, might you have checked the Master Cylinder Seals/Bore?
How old was the Fluid? Was it dark?

Before I rebuilt the caliper, I exchanged the fluid because it was old and discolored(bike sat for 3 years). When I did this, I bled it out and the lever got really firm. After I fixed some other problem that developed in other areas of the bike, I took it for a test ride and noticed I didn’t have the stopping power I should have. Got home and looked and the brake disk was oily. Took the caliper off and noticed that the slide pins were rusty and, I assumed the oily disk was from the caliper seals leaking so I got a rebuild kit. I cleaned up the pistons and bores, replaced the seals and put everything back together. Now I cannot get the lever firm again like it was before I took it apart. I did not check the master cylinder bore/seals, but considering that I had a firm lever before the caliper rebuild, I imagine this is not an issue. I’m open to any suggestions though.

Sometimes if you can't get the last bit of air out you can strap the lever back to bars and leave it overnight. This pushes any air bubbles up to the MC and when you release the lever they are pushed out into the reservoir. Position the bars so the MC bore is level when you do this.

But it sounds like you still have a fair bit of air in the system still.

I'm a big fan of the syringe - you can draw and push the same fluid back and forth without having to remove the syringe and I find this can be helpful. Best to wrap some teflon / plumbers tape around the bleed nipple threads so you don't draw any air in through them.

Thanks. I’ll give that a try. Just so I know that I’m not being overly critical of the brake lever, if it is bled well how far back should I be able to pull it if I give it a good squeeze?

00Vs1400GLP wrote: ↑

Wed Apr 27, 2022 3:58 pm

Thanks. I’ll give that a try. Just so I know that I’m not being overly critical of the brake lever, if it is bled well how far back should I be able to pull it if I give it a good squeeze?

It should be really firm like it was before you pulled the caliper. You shouldn't be able to pull it all the way back to the bars.

Stock these bike came with metal plates between the piston and brake pads. It is there to help prevent brake squeal. These metal plates are powder coated and over time the powder coat will start to bubble and will cause EXACTLY the problem you are having.

If the plates are still there, pull the bastards and throw them in the nearest trash can.

If they are not there it is possible for the brake pad to or the piston to hang on something.

You said the pins were rusted. Make sure they are smooth because it is possible for the pads to hang up on one and get crossways to the piston.

Pins are brand new. I replaced the when I rebuilt the caliper. I’ll try to remove those plates and see what happens. Just trying to figure this out since the rear caliper rebuild parts are going to get here next week. I like to think I know how to bleed brakes and clutches, but this is kicking my ass.

One other thing sometimes is if you are still using the old pads and put them in the wrong way round (IE: on the other side) then the wear on the pads does not match the grooves in the disc and this can make the brake feel spongy until they bed back in.

hillsy wrote: ↑

Wed Apr 27, 2022 6:25 pm

One other thing sometimes is if you are still using the old pads and put them in the wrong way round (IE: on the other side) then the wear on the pads does not match the grooves in the disc and this can make the brake feel spongy until they bed back in.

I swapped them and they felt the same. Out of frustration I bled them some more the old school manual way. I feel like the lever tightened up a bit even though I didn’t see any air bubbles come out. I’m going to give it a short, slow ride tomorrow and see what it feels like on the road and maybe try to re-bed the pads. At this point I have to squeeze the lever pretty hard to get it to touch the bars.

00Vs1400GLP wrote: ↑

Wed Apr 27, 2022 8:18 pm

hillsy wrote: ↑

Wed Apr 27, 2022 6:25 pm

One other thing sometimes is if you are still using the old pads and put them in the wrong way round (IE: on the other side) then the wear on the pads does not match the grooves in the disc and this can make the brake feel spongy until they bed back in.

I swapped them and they felt the same. Out of frustration I bled them some more the old school manual way. I feel like the lever tightened up a bit even though I didn’t see any air bubbles come out. I’m going to give it a short, slow ride tomorrow and see what it feels like on the road and maybe try to re-bed the pads. At this point I have to squeeze the lever pretty hard to get it to touch the bars.

Strap the lever back to the bars and leave it overnight. Turn the bars to the left so the MC is the highest point and (if you can) have the MC banjo bolt slightly lower than the MC bore. Next morning, release the lever and "jiggle" it a few times to move any air bubbles into the reservoir. If it's just a matter of a little air still in the line you should notice a big difference after this.

Try this. Remove the caliper and pads (do not disconnect the hose), crack open the bleeder, now push the pistons all the way back into the bores inbound first, re-assemble and bleed using the ball of a finger to act as a non return valve initially until you get fluid passing then close the bleeder, check. if needed bleed some more conventionally. Turn the bars so that the banjo bolt is pointing upwards, wrap a rag around it, crack the bolt. pull and hold the lever, re-tighten the bolt.
Did you replace the O-ring between the 2 halves of the calipers?

hillsy wrote: ↑

Wed Apr 27, 2022 9:48 pm

00Vs1400GLP wrote: ↑

Wed Apr 27, 2022 8:18 pm

hillsy wrote: ↑

Wed Apr 27, 2022 6:25 pm

One other thing sometimes is if you are still using the old pads and put them in the wrong way round (IE: on the other side) then the wear on the pads does not match the grooves in the disc and this can make the brake feel spongy until they bed back in.

I swapped them and they felt the same. Out of frustration I bled them some more the old school manual way. I feel like the lever tightened up a bit even though I didn’t see any air bubbles come out. I’m going to give it a short, slow ride tomorrow and see what it feels like on the road and maybe try to re-bed the pads. At this point I have to squeeze the lever pretty hard to get it to touch the bars.

Strap the lever back to the bars and leave it overnight. Turn the bars to the left so the MC is the highest point and (if you can) have the MC banjo bolt slightly lower than the MC bore. Next morning, release the lever and "jiggle" it a few times to move any air bubbles into the reservoir. If it's just a matter of a little air still in the line you should notice a big difference after this.

This seemed to make it even better. It’s doing much better now. Thanks for all the suggestions.

00Vs1400GLP wrote: ↑

Thu Apr 28, 2022 4:16 am

This seemed to make it even better. It’s doing much better now. Thanks for all the suggestions.

I can attest that this idea does help. however, I found that this method is the sure-fire way to get all the tiny Micro-bubbles out of the Hydraulic system;

http://intruders-alert.com/viewtopic.php?f=10&t=4

Back to a squishy lever again. Looked at the front disk and it has some fluid on it. Got to take apart the caliper again, most likely, to see where I screwed up.

00Vs1400GLP wrote: ↑

Sat Jun 04, 2022 3:12 am

Back to a squishy lever again. Looked at the front disk and it has some fluid on it. Got to take apart the caliper again, most likely, to see where I screwed up.

Did the pistons have any corrosion on them when you rebuilt the caliper beforehand? They may be pitted which would be the cause of the leaks.

No corrosion on the pistons. Pulled the caliper off today. A little wetness, but couldn’t tell where it was coming from. Didn’t see anything running from around the pistons, the bleeder valve, brake line. The only weird thing I saw was when I took the top caliper mount bolt out, there was some type of fluid on it. That didn’t make any sense to me thou because that bolt doesn’t hold back any fluid. Unless it’s not brake fluid but something else??

Fork oil perhaps?

I thought I had a leaking caliper on my old Divvy once - had some strange fluid over it and some on the disc....ended up being a tom cat had sprayed on it

There may be two issues here. But it seems remote that both the Fork Oil Seal starts leaking at the same time as the Lever gets,...."squishy".

Since the Fluid was found up by the upper Caliper Mounting Bolt, might there be some sort of leaking at the Caliper Banjo Fitting/Bleeder Screw when under pressure?

hillsy wrote: ↑

Sat Jun 04, 2022 8:36 pm

Fork oil perhaps?

I thought I had a leaking caliper on my old Divvy once - had some strange fluid over it and some on the disc....ended up being a tom cat had sprayed on it

I have a background as an aviation mechanic so my first instinct when I see a leak is to smell it to try to identify the fluid. It is definitely not cat pee.

Designer wrote: ↑

Sun Jun 05, 2022 5:25 am

There may be two issues here. But it seems remote that both the Fork Oil Seal starts leaking at the same time as the Lever gets,...."squishy".

Since the Fluid was found up by the upper Caliper Mounting Bolt, might there be some sort of leaking at the Caliper Banjo Fitting/Bleeder Screw when under pressure?

I check those both under pressure. No signs or trace of fluid. I cleaned everything off and I’m going to take an easy ride today to try to see if I can identify where the fluid is coming from.