i had removed the front calipers when i rebuilt my front suspension this month. in the process i cracked the passengers side caliper, requiring me to replace the o-ring. i used a pipe wrench to compress the pistons on both sides. last week a friend and i bleed the system (all four corners). now the front calipers are not releasing. There is plenty of pressure. as an experiment, i pulled the pads on the drivers side caliper, and compressed the pistons again. then i reinstalled the pads, pressed the brake pedal, and they locked again. is there an easy, fast fix to this? http://www.mgexp.com/phorum/read.php?1,2065520,2065520#msg-2065520 Wed, 19 Jun 2013 18:14:01 -0500 Phorum 5.2.15a http://www.mgexp.com/phorum/read.php?1,2065520,2181040#msg-2181040 http://www.mgexp.com/phorum/read.php?1,2065520,2181040#msg-2181040 pumper MGB & GT Forum Thu, 27 Sep 2012 16:24:14 -0500 http://www.mgexp.com/phorum/read.php?1,2065520,2068817#msg-2068817 http://www.mgexp.com/phorum/read.php?1,2065520,2068817#msg-2068817
Dan]]> DanN1DLH MGB & GT Forum Tue, 15 May 2012 20:19:08 -0500 http://www.mgexp.com/phorum/read.php?1,2065520,2066740#msg-2066740 http://www.mgexp.com/phorum/read.php?1,2065520,2066740#msg-2066740
Now I have three new rubber hoses, 2 replaced (rebuilt from O'Reilly's) calipers and, oh yes, the PO also put in a rebuilt MC recently.

As apparantly is Adam, I am also stumped and trying to come up with the solution to this mystery. Again, brakes bled fine but when I apply foot pressure, the pads don't retract and the front wheels, expecially the left, won't turn, unless I pry the pads apart. And the brake switch is pulled:S back sufficiently. I think I sort of "hi-jacked" Adam's thread, so apologies up front!!

Best,

Dan]]> DanN1DLH MGB & GT Forum Sun, 13 May 2012 20:14:42 -0500 http://www.mgexp.com/phorum/read.php?1,2065520,2066538#msg-2066538 http://www.mgexp.com/phorum/read.php?1,2065520,2066538#msg-2066538 In reply to # 2066322 by tomkatb
The tool to compress the pistons is a C clamp, not a pipe wrench. The piston is a delicate/machined item and a pipe wrench is a crude tool. A screwdriver is another not so good tool for this.

When changing pads I use two carpenter shims or a piece of hardwood to push the pistons out.
In the B the caliper pistons move on both sides of the caliper so it actually DOES squeeze the rotor. On most cars the disc brake caliper has a piston on one side and the caliper slides on a pin pressing tone pad against the rotor and a stationary outer pad.
For this reason a C-clamp is inadequate, compressing one piston only actuates the other rather than returning fluid to the reservoir.]]> spikemichael MGB & GT Forum Sun, 13 May 2012 16:19:46 -0500 http://www.mgexp.com/phorum/read.php?1,2065520,2066459#msg-2066459 http://www.mgexp.com/phorum/read.php?1,2065520,2066459#msg-2066459 tomkatb MGB & GT Forum Sun, 13 May 2012 14:41:12 -0500 http://www.mgexp.com/phorum/read.php?1,2065520,2066325#msg-2066325 http://www.mgexp.com/phorum/read.php?1,2065520,2066325#msg-2066325 gooser MGB & GT Forum Sun, 13 May 2012 11:31:55 -0500 http://www.mgexp.com/phorum/read.php?1,2065520,2066322#msg-2066322 http://www.mgexp.com/phorum/read.php?1,2065520,2066322#msg-2066322 I had the same issue last year.

I had replaced a leaking master. Bleeding was easy. However, the caliper would not release, If I cracked a bleed screw they would release. Not retract.

In this case logic wise it is an issue that plagues both calipers. Thus you have to address issues where the hydraulic system is joined to one. I.E the valve/switch then the line to the master and the master. Your master has two circuits, front and back.

Item one. The brake light switch must not be restricting the pedal.

Item two. The spring must be on the pedal. Grab the pedal and see if it pulls up at all.

One and two ok then it is the switch or the master.

The rear brake has a set of springs that moves the pads away from the shoes. The front does not. Therefore the banging of the pads on the disc is what moves the pistons out. Thus the fronts will always be hotter than the rears. 30-40 degrees. They will not move out much on a stationary car.

It takes more fluid volume to move the front calipers than the drums. The rears start doing something first. If hydraulic fluid cannot get back to the master the brakes in front do not move.

I have not messed with the cars with the switch. As I recall the switch has to be moved out to bleed the front brakes. As I remember they can lock up in a position that causes this issue.

On our ford we fixed recently you had to alternate bleeding in a special way to reset the switch. Otherwise one circuit was a mess. Some kind of a safety issue. I use a power bleeder and for some reason it resets the switch. (on our ford and Chevrolet).

When you mess with an old car other stuff expires sometimes.

The tool to compress the pistons is a C clamp, not a pipe wrench. The piston is a delicate/machined item and a pipe wrench is a crude tool. A screwdriver is another not so good tool for this.

When changing pads I use two carpenter shims or a piece of hardwood to push the pistons out.

I am dyslexic and writing is a chore.

Call me for any questions. (937)885-3090 This is not hard. You got the hard part done already. I think it could be a bleeding issue. Look up the switch thing. Bleeding only take s few minutes. A dinner out will get my wife to help me bleed the car. She bought me a Motive power bleeder.

I cannot imagine two calipers failing in the same way at one time. Illogical. They do this but, not two at a time. You did not change brake fluids recently?

Last year I chased my tail for a week. I had a defective new master, Who would have thought it.]]> tomkatb MGB & GT Forum Sun, 13 May 2012 11:28:20 -0500 http://www.mgexp.com/phorum/read.php?1,2065520,2066065#msg-2066065 http://www.mgexp.com/phorum/read.php?1,2065520,2066065#msg-2066065 mjamgb MGB & GT Forum Sun, 13 May 2012 01:57:13 -0500 http://www.mgexp.com/phorum/read.php?1,2065520,2066025#msg-2066025 http://www.mgexp.com/phorum/read.php?1,2065520,2066025#msg-2066025 melbaver MGB & GT Forum Sun, 13 May 2012 00:32:53 -0500 http://www.mgexp.com/phorum/read.php?1,2065520,2066014#msg-2066014 http://www.mgexp.com/phorum/read.php?1,2065520,2066014#msg-2066014 spikemichael MGB & GT Forum Sat, 12 May 2012 23:55:02 -0500 http://www.mgexp.com/phorum/read.php?1,2065520,2065638#msg-2065638 http://www.mgexp.com/phorum/read.php?1,2065520,2065638#msg-2065638
very, very many times.]]> mac townsend MGB & GT Forum Sat, 12 May 2012 15:12:27 -0500 http://www.mgexp.com/phorum/read.php?1,2065520,2065599#msg-2065599 http://www.mgexp.com/phorum/read.php?1,2065520,2065599#msg-2065599 balloonfoot MGB & GT Forum Sat, 12 May 2012 14:09:44 -0500 http://www.mgexp.com/phorum/read.php?1,2065520,2065572#msg-2065572 http://www.mgexp.com/phorum/read.php?1,2065520,2065572#msg-2065572
would it be safe to assume the calipers need replacement now?

don't understand what i could have done to ruin them when i took them off. they were removed from the hubs gently, and support under the car on paint cans (no tension on the hoses).

beginning to feel like i am doing more damage to the car than good... kind of discouraged :(]]> DiBiaso MGB & GT Forum Sat, 12 May 2012 13:10:12 -0500 http://www.mgexp.com/phorum/read.php?1,2065520,2065526#msg-2065526 http://www.mgexp.com/phorum/read.php?1,2065520,2065526#msg-2065526
If it is assembled correctly the calipers are just a cylinder full of fluid. press the pedal more fluid goes in release the pedal that extra fluid comes out.

If they do not release on their own and you can release them by using a clamp, lever or whatever then you have one of two problems, the caliper is not releasing and needs rebuilding, or the flex hose is acting as a one way valve and the fluid cannot go back out the hose.

Test:
Press the pedal hard so the brakes clamp down.
go to your caliper and release the bleeder screw.
If the caliper releases right away (squirt of fluid maybe?)
The caliper is OK and the problem is likely the flex hose.

If the caliper does not release the caliper is bad... Did you perhaps get the O ring off center and it is blocking the passage?]]> spikemichael MGB & GT Forum Sat, 12 May 2012 12:00:03 -0500 http://www.mgexp.com/phorum/read.php?1,2065520,2065520#msg-2065520 http://www.mgexp.com/phorum/read.php?1,2065520,2065520#msg-2065520
last week a friend and i bleed the system (all four corners). now the front calipers are not releasing. There is plenty of pressure.

as an experiment, i pulled the pads on the drivers side caliper, and compressed the pistons again. then i reinstalled the pads, pressed the brake pedal, and they locked again.

is there an easy, fast fix to this?]]> DiBiaso MGB & GT Forum Sat, 12 May 2012 11:49:12 -0500