'87 K7s - can't get brakes to bleed

[kentuvman]

When I returned from the Sedalia, MO rally, I decided to overhaul the calipers up front and try EBC HH pads as I've got some brake shutter & pulsing again. I'd installed the EBC floating rotors @ 15k miles ago but then used a new set of CL A3 pads I happened to have on hand. The new rotors helped a lot.

Prior to removing the calipers, I drained the brake lines. The fluid was very dark - definitely time for a change. When I popped out the pistons, there was some contamination inside. So it was a good move to get in and clean things up.

I have Spiegler S/S lines front & rear and believe the front master cylinder to be in good shape.

Spent the better part of this evening w/out success! Read on a previous thread about pushing the caliper pucks in - what's throwing me off is when I re-assembled them I did push them down all the way. I put all the seals where they're supposed to go. I installed the new pads & mounted the calipers over the rotors.

The Clymer manual mentions bleeding the master cylinder - not sure if they mean to put my thumb over the big hole inside the plastic reservoir or over the hole where the banjo bolt goes in - tried it both ways and I basically wound up with dribbles of brake fluid over a piece of plastic I'm using to protect the bike from brake fluid - nasty stuff!

I used my US General Brake Bleeder to pull the brake fluid through the lines without success. Also used an oil can to push the fluid the other way. I've read a windshield washer pump connected to a 12v battery makes a good vacuum for pulling the fluid through the lines.

If pushing in the pucks means removing the calipers and new brake pads, I'll take them off. This task is more complicated than I figured!

It could be the m/c needs to be bled but I really don't get the concept - I read and re-read the Clymer book last night - just not getting it.

Appreciate any suggestions!

 

[42906]

When I returned from the Sedalia, MO rally, I decided to overhaul the calipers up front and try EBC HH pads as I've got some brake shutter & pulsing again. I'd installed the EBC floating rotors @ 15k miles ago but then used a new set of CL A3 pads I happened to have on hand. The new rotors helped a lot.

Prior to removing the calipers, I drained the brake lines. The fluid was very dark - definitely time for a change. When I popped out the pistons, there was some contamination inside. So it was a good move to get in and clean things up.

I have Spiegler S/S lines front & rear and believe the front master cylinder to be in good shape.

Spent the better part of this evening w/out success! Read on a previous thread about pushing the caliper pucks in - what's throwing me off is when I re-assembled them I did push them down all the way. I put all the seals where they're supposed to go. I installed the new pads & mounted the calipers over the rotors.

The Clymer manual mentions bleeding the master cylinder - not sure if they mean to put my thumb over the big hole inside the plastic reservoir or over the hole where the banjo bolt goes in - tried it both ways and I basically wound up with dribbles of brake fluid over a piece of plastic I'm using to protect the bike from brake fluid - nasty stuff!

I used my US General Brake Bleeder to pull the brake fluid through the lines without success. Also used an oil can to push the fluid the other way. I've read a windshield washer pump connected to a 12v battery makes a good vacuum for pulling the fluid through the lines.

If pushing in the pucks means removing the calipers and new brake pads, I'll take them off. This task is more complicated than I figured!

It could be the m/c needs to be bled but I really don't get the concept - I read and re-read the Clymer book last night - just not getting it.

Appreciate any suggestions!

My first question is, when you tried the US General Brake Bleeder, did you get brake fluid to flow out of the bleeder fitting and did the level in the master cylinder reservoir fall as a result? I am trying to determine if you have a blockage somewhere.

Second, does you bike have ABS?

You are going to laugh at how I bleed front brakes on non-ABS bikes. I simply fill the master cylinder reservoir and operate the brake lever repeatedly until bubbles stop coming up out of the hole in the bottom of the reservoir. It usually takes about 10 - 15 minutes of operating the brake lever, topping it with fresh fluid as the level falls, to get some resistance in the lever. About that time you get a little geyser of brake fluid coming out of the hole in the bottom of the reservoir. When this happens you are very close to having bled the system. I never operate the bleed fittings on the calipers to do this. I ususally turn the forks left and right several times so any trapped bubbles can work free, and I tap on the brake hoses too. I find this bleeds the brakes as effectively as any other method I have tried with less effort and mess.

 

[kentuvman]

My first question is, when you tried the US General Brake Bleeder, did you get brake fluid to flow out of the bleeder fitting and did the level in the master cylinder reservoir fall as a result? I am trying to determine if you have a blockage somewhere.

Fluid was not flowing out of the bleeder fitting.

Second, does you bike have ABS?

Non ABS

You are going to laugh at how I bleed front brakes on non-ABS bikes. I simply fill the master cylinder reservoir and operate the brake lever repeatedly until bubbles stop coming up out of the hole in the bottom of the reservoir. It usually takes about 10 - 15 minutes of operating the brake lever, topping it with fresh fluid as the level falls, to get some resistance in the lever. About that time you get a little geyser of brake fluid coming out of the hole in the bottom of the reservoir. When this happens you are very close to having bled the system. I never operate the bleed fittings on the calipers to do this. I ususally turn the forks left and right several times so any trapped bubbles can work free, and I tap on the brake hoses too. I find this bleeds the brakes as effectively as any other method I have tried with less effort and mess.

I've bled the brakes as you've described - I think the biggest variables could be the I R&R of the calipers or the m/c needs to be bled. When I reassembled the calipers, I pushed the pucks in as far as I could. With the caliper mounted on the forks, I also pushed against each brake pad with my finger do make sure they were still pushed in all the way - not sure I achieved that with the brake pads on and not sure how critical either. The other possiblity is the front m/c needs to be bled but I can't quite make sense of the technique described in the Clymer book. A friend suggests I block the handlebar & secure the handle pulled in 1/2 way with a rubber band and let it sit overnight.

Thanks much!

 

[98lee]

Remove calipers from forks. Put wood blocks between pads to keep pistons all the way retracted.

Turn handlebars ALL the way to the left. Leaving the bars straight ahead allows air to get trapped in the master cylinder and making it almost impossible to even start getting the master bled.

Bleed brakes.

If you are going to manually bleed it using the brake lever, put a 1/2" block between the lever and the grip so that you do not push the piston in the master cylinder into an area of the cylinder where it normally doesn't go. Any pitting in that area can cut the lip of the cylinder seal.

You can use suction at the caliper bleed screws or manually push it through the master using the lever and opening and closing the bleed screws.

 

[kentuvman]

Thanks, Lee

Is it that the caliper pucks are allowing air to enter thru the brake lines that's preventing the fluid from flowing? Haven't given this a go yet but plan to this weekend.

What kind of a wood jig are you using between the pads to keep the pistons retracted?

 

[98lee]

Just use blocks of wood or metal between the pads that will keep the pistons as deep in the calipers as you can.


The reason that I suggest blocking the pistons all the way back in the calipers is that, when initially filling them, it allows less room for air pockets to develop and you use less fluid to initially purge all the air from the system.

 

[kentuvman]

Brakes bled & working properly

Note to self: next time when working on a righty & lefty put parts in separate bins or mark them

Had the outside caliper covers mixed up -
Pleasee don't ask me to help you on your next brake job! I'm dyslexic.

Took a couple days for everything to sink in but intuition set in & my hunch went back to the calipers - like the bench wrenching article - look back at the last thing you did to your bike! And it pays to be patient - not one of my virtues.

 

[ghyber]

Just use blocks of wood or metal between the pads that will keep the pistons as deep in the calipers as you can.


The reason that I suggest blocking the pistons all the way back in the calipers is that, when initially filling them, it allows less room for air pockets to develop and you use less fluid to initially purge all the air from the system.

I like the idea of the wooden blocks.

However, is one able to push the pads fairly easily back into the callipers without having to pry? I am worried about damaging the opposite pads with that method. I ask the question as I am trying to avoid purchasing the $113 piston resetting tool sold by Max BMW. Or maybe, there is a cheaper non-BMW alternative tool for the job like those sold by Ken Lively?

 

[ted]

I picked up two cedar shims from Home Depot, sanded them smooth, and they work perfectly. Just slide them in on opposite ends and they evenly and smoothly push the pistons back in.

 

[ghyber]

I picked up two cedar shims from Home Depot, sanded them smooth, and they work perfectly. Just slide them in on opposite ends and they evenly and smoothly push the pistons back in.

Now that idea I like a lot. Thanks for sharing...