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Author Topic: Question about caliper piston and brake lines  (Read 2524 times)

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Offline BeSeeingYou

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Question about caliper piston and brake lines
« on: February 21, 2009, 01:18:08 PM »
I am working on the front brakes on my 76F and of course the piston and pad are stuck.  I have read some earlier posts about using air pressure to force them out.  What is the best way to plumb the compressor to the caliper?  I have tried using my rubber tipped nozzle stuck in the inlet port but the nozzle seems to have some type of pressure release valve so it won't build up any great amount of pressure.  Or it is just a #$%*ty Chinese made nozzle.  My other thought was to use the MC to push it out.  So I thought I would clean out the brake lines first.  The metal lines no problem but I can't blow any air through the rubber lines.  I tried to run a small wire through to clear out any obstruction.  I can get it in about 1/2-3/4 inch in on either end and then I am stopped cold.  I can't imagine any obstruction would be that solid.  How are these built?  Is their some type of check valve built into the connectors.  The lines themselves are in excellent condition and the fluid I was able to get out of the steel lines was fine.  This is all new territory for me even though I have run my XS650 for 29 years my only experience with the brakes was to periodically open up the bleeder screw to change fluid.  I have never had them apart.
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Offline Bill Vaughan

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Re: Question about caliper piston and brake lines
« Reply #1 on: February 21, 2009, 01:38:17 PM »
Several ways to do it and I'm sure others will post with their preferred methods, but I like to use a grease gun.  I just unstuck a 550 caliper piston that sat unused for the past 20 years.  Air, up to 120 lbs. wouldn't do it.  The hand grease gun got it out in 30 seconds.

Just remove the bleed fitting, install the threaded hose connection from the gun and pump away.  It's important to note that the threads won't be the same, so be careful here.  Thread the hose in lightly until you feel resistance.  You just want to get it to stay in place.

It should go without saying, but be sure to clean the caliper afterword.  No grease can remain in there.
« Last Edit: February 21, 2009, 10:58:48 PM by Bill Vaughan »
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Offline Bodi

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Re: Question about caliper piston and brake lines
« Reply #2 on: February 21, 2009, 01:43:46 PM »
The lines don't have any obstruction built in. Sounds like they're plugged with something nasty.
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Offline Bob Wessner

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Re: Question about caliper piston and brake lines
« Reply #3 on: February 21, 2009, 02:25:53 PM »
Quote
It's important to note that the threads won't be the same, so be careful here.  Thread the hose in lightly until you feel resistance.  You just want to get it to stay in place.

A bit of Teflon plumber's tape helps seal without having it be too tight.
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Offline moham

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Re: Question about caliper piston and brake lines
« Reply #4 on: February 21, 2009, 02:29:43 PM »
Quote from: Bob Wessner on February 21, 2009, 02:25:53 PM
Quote
It's important to note that the threads won't be the same, so be careful here.  Thread the hose in lightly until you feel resistance.  You just want to get it to stay in place.

A bit of Teflon plumber's tape helps seal without having it be too tight.

Nice tip.
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Offline Bido

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Re: Question about caliper piston and brake lines
« Reply #5 on: February 21, 2009, 03:24:04 PM »
I second the grease gun.

Bido
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Offline fmctm1sw

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Re: Question about caliper piston and brake lines
« Reply #6 on: February 21, 2009, 06:01:14 PM »
I've had success just using a good master cylinder and forcing the pistons out.  I salvaged a line once by running an old clutch (or was it a throttle) cable with the end snipped off through it...
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Offline fishman_Phil

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Re: Question about caliper piston and brake lines
« Reply #7 on: February 21, 2009, 09:13:51 PM »
Watch that compressor method. The piston can come out with a bang and fly across the garage and in the worse case do some damage to something else. Grease gun is the best method I have used and even if you do not have a good fitting nipple, it only needs to be bare started to enable this method to work.
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Offline Gamma

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Re: Question about caliper piston and brake lines
« Reply #8 on: February 22, 2009, 07:14:34 AM »
Got to agree. Just done 2 calipers that have been in a scrapyard for 20 years, using the grease gun method.

As usual, it took longer to bleed the grease gun than removing the pistons
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mutt

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Re: Question about caliper piston and brake lines
« Reply #9 on: February 22, 2009, 08:15:06 AM »
i put a piece of wood where the pads would go,then jam the rubber tip of the compressors blower attachement in the brake line hole. The woods eases the impact on the rapidly expelled puck, no grease to clean up. .....
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Offline ajinreno

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Re: Question about caliper piston and brake lines
« Reply #10 on: February 22, 2009, 07:54:13 PM »
I'm kind of in the same boat. I've never done more than bleed and change pads. Just bought a 78 750F this weekend and took rear and front calipers off because they were sticking. I should be able to just pull the caliper pistons about by hand correct? They don't seem to be budging so I'm guessing I need to use a grease gun. I'm a bit of dolt so if someone wouldn't mind verifying if this is correct I'd greatly appreciate it.
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Offline ajinreno

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Re: Question about caliper piston and brake lines
« Reply #11 on: February 23, 2009, 06:55:09 PM »
So I was assuming the MC works because the back wheel was free when I loaded it in my truck and then when I took it out and applied the rear brake is when it stuck. That's when I took it off and realized the piston seemed to be frozen. I hooked it up again, as recommended, to get the piston out. But it still didn't move. So I thought maybe I need to bleed the brakes first. I started bleeding and the air bubbles never stopped. I probably did it about 20-25 times and their was continously air bubbles. Does this mean something wrong with either the MC or the lines?
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Offline Jerry Rxman Griffin aka MuthaF'er

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Re: Question about caliper piston and brake lines
« Reply #12 on: February 23, 2009, 07:19:02 PM »
Grease gun has been the easiest and safest for me. IF an air compressor will work then it will create a high speed large projectile that WILL damage whatever it hits. You, your car's window, your dog, your kid, etc. A grease gun will ease it off. Rather than remove the bleeder valve why not just slightly open it and attach the grease gun nozzle to the bleed valve nipple! Put one of your other bolts into the other hole just don't screw it in so far as to damage the pieces inside. Worked for me plus no cross threading. If you don't have a grease gun, you need one for the swing arm anyway.
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Offline papp101

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Re: Question about caliper piston and brake lines
« Reply #13 on: February 23, 2009, 07:49:38 PM »
I wanted to thank you Srust for posting this, as I have some crazy similarities to your post:

1. My birthday is Feb 9th, the day you bought your CB750.
2. I live in Minneapolis.
3. I spent 2 hours today using various methods of abuse on a caliper that has not been used since 1975.
4. I tried plumbing my compressor to it.
5. I used my Harbor Freight (Cheap Chinese) rubber tip to press up against the steel tube, all to no avail.
6. I told myself to go search about it before breaking the thing into pieces.

Hopefully I can grab a grease gun to use on my caliper so it will release this week.

My master cylinder was missing all sorts of parts from the previous owner, so a replacement of sorts there will definitely be in order.

Thanks for posting it man! Maybe someday I can pimp you for ideas for my 1979 xs850 Triple I've got to fix and sell!

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Offline motorhead55

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Re: Question about caliper piston and brake lines
« Reply #14 on: February 23, 2009, 10:34:04 PM »
REPLACE the rubber hose! It has deteriorated inside. Rebuild the caliper and master cyl, replace the brake hose, clean out the steel line and THEN use SILICONE brake fluid. I have had that in my 550 for 15 years and in the Porsche drum brake system that I have on my '55 Vw for 18 years. I haven't had any leaks, stuck pistons, ect.
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Offline Jerry Rxman Griffin aka MuthaF'er

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Re: Question about caliper piston and brake lines
« Reply #15 on: February 24, 2009, 08:45:22 PM »
The front brake hoses are still available from Honda. I just got 1 in and the other is on the way from another supplier. Braided stainless is nice too. However, the rear is not available.

Motorhead is going to get some stink raised about SILICONE fluid as usually happens BUT I'm with him on that. I put silicone in the front after my rebuild and powder coating of the caliper, rotor, and front fork legs and it works just fine PLUS it won't eat the paint when the seal leaks again. FWIW I still have DOT4 in the rear and it works fine too but I will change that when I do the restore.
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As of today 3/13/2012 my original owner 75 CB750F has made it through 3 wives, er EX-wives. Free at last.  ;-)
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