No brake pressure after changing brake pads (Problem solved)

[johnnyredbone]

I've searched all over for my specific problem but can't find anything similar. This is in the front brakes. I changed the left side pads. Afterwards, I checked for brake pressure and everything was aok. I then changed the right side and checked for pressure again and nothing. Just feels like there is no fluid in there at all. I even bled that caliper with a mityvac and no difference. The only thing I can think of is that I may have pushed the pistons in a little further than I did on the left caliper. Anyone ever had a similar problem or any ideas? Thanks in advance.

 

[Fire-medic]

Try pumping the brake lever repeatedly and see if that moves the pads in.

SImple things, check for the master cyl fluid level.

Using the Mityvac should have fixed 'pushing in the pads too-far.' I think this is a good case for doing a reverse-bleed. Directions here:

https://www.vmaxforum.net/threads/clutch-slave-cylinder-replacement.45011/

 

[johnnyredbone]

Thank you for the response, Fire-medic.

Try pumping the brake lever repeatedly and see if that moves the pads in.

SImple things, check for the master cyl fluid level.

Using the Mityvac should have fixed 'pushing in the pads too-far.' I think this is a good case for doing a reverse-bleed. Directions here:

https://www.vmaxforum.net/threads/clutch-slave-cylinder-replacement.45011/

Thank you for the response. That's what I was trying to say in my original post. I pumped the lever when I changed the left side pads and it built up pressure. But when I changed the right side, there was no pressure at all on the lever no matter what. And there was plenty of fluid still in the master. I even bled the right side caliper and still no difference. I will look into the reverse bleed but my brakes were fine before I changed the pads.

When I changed the pads, I never took the master cylinder cover off nor cracked open any brake lines. Not sure how air could have gotten in the system

 

[one2dmax]

You may not have air in the system but rather a situation where the pads are too far retracted and can't move back to where you can feel the pressure feeback. You need to look in at the calipers and see if one set is not contacting the rotors (and you may be able to see them flexing in and out with your movement of the hand lever).

Did you clean off the pistons before pushing them back in for the new pads?

 

[Fire-medic]

Did you clean off the pistons before pushing them back in for the new pads?

Yes another thing to do in a pad swap, if you aren't going to remove/clean the caliper pistons and the bores. Yes to watching the pads move slightly with pressure. If you can't see that, you likely need to remove the caliper and remove the pistons, and give everything a good sanding. If there are visible deposits, I'll use a brass bristle wheel on the pistons, and the same in a Dremel for the bores. Wear eye protection for the Dremel. A mechanic's bib is a good thing to prevent you from becoming a human pincushion in the chest and arms from errant flying bristles. Harbor Freight has packages of assorted brass Dremel-style wheels.

A tip for the smallest one which resembles a paintbrush: use a piece of heat-shrink tubing and place it halfway-up the bristles. The brass brush will work in nooks and crannies like the bottom corner of a caliper, or the corners of a master cyl. better, w/o spreading-out.



I like Weiler wire wheels, they have better balance, and seem to stay together better. They are more-expensive.
Power Mini Brushes | Weiler Abrasives

The product catalog: Power Brushes | Weiler Abrasives

This is the $10 HFT 8" brass wheel.

• 1-1/4 in., 1 in., 7/8 in., 3/4 in., 5/8 in., 1/2 in. arbor with ten inserts for most grinders: 1 in., 7/8 in., 3/4 in., 5/8 in. and 1/2 in.
• 4500 RPM maximum speed

https://www.harborfreight.com/8-inch-crimped-brass-wire-wheel-93467.html
They have a 6" wheel too, 5/8" arbor w/a 1/2" adaptor.

For these, I recommend a full-face NIOSH/OSHA rated faceshield.

 

[johnnyredbone]

You may not have air in the system but rather a situation where the pads are too far retracted and can't move back to where you can feel the pressure feeback. You need to look in at the calipers and see if one set is not contacting the rotors (and you may be able to see them flexing in and out with your movement of the hand lever).

Did you clean off the pistons before pushing them back in for the new pads?

Thanks for the reply! I kind of feel like that may be the problem. Except that I did have pressure when I changed the left side. I'm not sure why the right side would affect the pressure I had on the left side. I did not clean of the pistons. Do you think that they are stuck in the calipers? But I would still think that I would get some pressure on lever.

 

[johnnyredbone]

Yes another thing to do in a pad swap, if you aren't going to remove/clean the caliper pistons and the bores. Yes to watching the pads move slightly with pressure. If you can't see that, you likely need to remove the caliper and remove the pistons, and give everything a good sanding. If there are visible deposits, I'll use a brass bristle wheel on the pistons, and the same in a Dremel for the bores. Wear eye protection for the Dremel. A mechanic's bib is a good thing to prevent you from becoming a human pincushion in the chest and arms from errant flying bristles. Harbor Freight has packages of assorted brass Dremel-style wheels.

A tip for the smallest one which resembles a paintbrush: use a piece of heat-shrink tubing and place it halfway-up the bristles. The brass brush will work in nooks and crannies like the bottom corner of a caliper, or the corners of a master cyl. better, w/o spreading-out.
View attachment 91173


I like Weiler wire wheels, they have better balance, and seem to stay together better. They are more-expensive.
Power Mini Brushes | Weiler Abrasives

The product catalog: Power Brushes | Weiler Abrasives

This is the $10 HFT 8" brass wheel.

• 1-1/4 in., 1 in., 7/8 in., 3/4 in., 5/8 in., 1/2 in. arbor with ten inserts for most grinders: 1 in., 7/8 in., 3/4 in., 5/8 in. and 1/2 in.
• 4500 RPM maximum speed

View attachment 91174
https://www.harborfreight.com/8-inch-crimped-brass-wire-wheel-93467.html
They have a 6" wheel too, 5/8" arbor w/a 1/2" adaptor.

For these, I recommend a full-face NIOSH/OSHA rated faceshield.

Great advice, Fire-medic! I didn't realize I needed to clean the pistons but I think that may be the problem. If the pistons are stuck in, would the fluid somehow not build up pressure though? I think I have some brass bristle wheels somewhere but if I can't find them, I will probably get some from harbor freight since it is only about 20 minutes away from me.

 

[MaxMidnight]

Assuming that you have removed all of the air then I would still expect to get a firm lever feel regardless of the pistons being stuck or not?
If they are stuck the pads wouldn't move but you should still have a firm feel to the lever.
As you don't have any feel then either there is still air in the system, possibly being sucked pass the calliper piston seals if they are too far back(?) or there is a problem with the m/c seals (unlikely?).
Reverse bleeding may displace the air and give a lever sufficient to push the pistons further out.

I would only clean the piston bores if there is a build-up of crud and only use the least abrasive method to do so. Unless there is any plating or hard anodising the aluminium could be easily be damaged or scratched which could lead to further aggravation.
The pistons will take more abuse but if you use a wire wheel I'd be inclined to remove the seals if the wheel is likely to go anywhere near them...you know the inevitable will happen...

 

[Jack Hammer]

I would use the finest Scotch-Brite on the bores to clean them out. Same on the pistons. No machines, by hand.

I just don't think this is the problem. Johnnyredbone clearly stated that there was never any leaks, if I got it right. I'm just quessing here but what if there was an air bubble in the system to begin with? And while pushing the pistons in for new pads, the bubble moved up right into the pressure face in the master cylinder.

I'd keep on bleeding it. It's a pity, and frustrating but it will bleed out. What I've done is open both bleeds in the caliper, have the top off from master and keep pumping slowly. Adding fluid. The bubble wants to go up so it will eventually come through the bore in the master while the piston in the master moves. Then the caliper bleeds start to run and your system is free of bubbles.

If even this is unsuccessful, then do it the traditional way, pump pressure like 10-20 times on the handle, loosen the bleed, see that fluid moves even small amount and while movement of fluid stops, tighten bleed while lever is still pulled in. Release lever and do it again.

When I rebuilt my clutch hydro side, it was a pain to bleed it, took many tries but I got it done.

 

[Fire-medic]

Reverse-bleeding has for me been the fastest, most effective method of bleeding the Gen. 1 VMax hydraulic systems.

When you can build your own reverse-bleeder for the price of a lunch meal, and solve your issues in minutes, once you begin the reverse-bleed, that sounds like a winner to me!

 

[johnnyredbone]

Thanks for all of the responses. I'm not working on my bike today, but I will this week. For whatever reason, this issue happened when I changed the right side pads and not the left. I think that's where I'm going to concentrate first. As soon as I find something out, I will let you guys know.

 

[one2dmax]

When the pistons are extended from worn pads they build up a layer of crud on them. When you push them back in without cleaning they pusht that crud in and behind/under the seals. That isn't helping the situation. On a car there is usually a rubber diapragm that covers up the pistons so that this doesn't happen. On the bikes they usually don't have that protection.

 

[johnnyredbone]

When the pistons are extended from worn pads they build up a layer of crud on them. When you push them back in without cleaning they pusht that crud in and behind/under the seals. That isn't helping the situation. On a car there is usually a rubber diapragm that covers up the pistons so that this doesn't happen. On the bikes they usually don't have that protection.

I appreciate the info. Yeah, I've done brakes on cars hundreds of times. This is my first time doing it on a motorcycle.

 

[Bad Max]

I've searched all over for my specific problem but can't find anything similar. This is in the front brakes. I changed the left side pads. Afterwards, I checked for brake pressure and everything was aok. I then changed the right side and checked for pressure again and nothing. Just feels like there is no fluid in there at all. I even bled that caliper with a mityvac and no difference. The only thing I can think of is that I may have pushed the pistons in a little further than I did on the left caliper. Anyone ever had a similar problem or any ideas? Thanks in advance.

I had a similar problem with my front brake . The problem turned out to be a tiny bubble behind the billet lining at the very top. With a bit of tapping and squeezing of the lever, it finally cleared . Best of luck.

 

[johnnyredbone]

I had a similar problem with my front brake . The problem turned out to be a tiny bubble behind the billet lining at the very top. With a bit of tapping and squeezing of the lever, it finally cleared . Best of luck.

I guess I'm not sure what you mean by billet lining. Where did you tap at? The top of the master cylinder? That could be the problem. Thanks for the suggestion!

 

[Fire-medic]

A question: What happens to the carbonation in your Coke when you pour a glass? It rises to the top.

Try reverse-bleeding. Bubbles rise. When you push brake fluid into the system from the bleeder valve, any bubbles get pushed upwards and into the master cylinder. It's a Bubble Eliminator. When you get a solid geyser of brake fluid from the master cylinder floor hole, as you push on the reverse-bleeder syringe plunger, you got all the bubbles.

 

[johnnyredbone]

Thank you, Fire-medic. I will try to do that today. I understand the principle and it makes sense.

 

[johnnyredbone]

Problem solved! I started working on the bike earlier tonight and just kept thinking the brake lever is just way too easy to pull, like there is no resistance on it whatsoever. So I looked where the lever pushes against the plunger on the master cylinder and noticed the plunger was stuck all of the way in. I removed the brake line from the master cylinder and I could see the spring in there compressed. I took a small screwdriver and pushed back on the spring and the plunger popped back out. I worked the lever a few more times gently and the plunger got stuck one more time, but just barely. I tapped on the master cylinder and it popped back out and I just kept pumping the lever further and further and the plunger/piston never got stuck again. Not sure how it got stuck in the first place, maybe a little piece of dirt or something. Anyways, I just bled the brakes and everything is good now.

I just want to say thank you to everyone for the suggestions. This is a great community and I'm glad to be part of it!

 

[Fire-medic]

Good on-ya, for keeping at it. Something simple.

Are you gonna use some WD-40 on that plunger outside where it contacts the lever? Might as well use some on the other side as well, and the sidestand switch, push it in a few times after lubrication until it becomes noticeably easier to operate.

 

[johnnyredbone]

Good on-ya, for keeping at it. Something simple.

Are you gonna use some WD-40 on that plunger outside where it contacts the lever? Might as well use some on the other side as well, and the sidestand switch, push it in a few times after lubrication until it becomes noticeably easier to operate.

Good ideas! Thanks and will do.