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sticking front brake  Rating:  Rating
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 Posted: 08-09-2006 02:52 am
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10dtom
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Greg,

I have been a member since day one, thanks for the great job.

After a brake job I have foung that my left front brake will not release. I have bleed the brakes several times, released them with the bleeder pumped them up, bled them. Compressed the pistons completely in to make sure they were not binding. All seems well.

Delta suggests that it could be the master cylinder, but it seems to me that would effect both sides.

Any thoughts or ideas would be greatly appreciated.

tom in NC

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 Posted: 08-09-2006 03:55 am
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Mark Rosenbaum
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The most likely cause is a defective brake hose with a deteriorated lining that acts as a one-way valve and won't let brake fluid return to the master cylinder.  As an alternative, there might be debris in the caliper's internal passageway performing the same undesired function to one or both pistons.

Given the work you've described in regard to moving the pistons, it seems fairly unlikely that one of these would be sticking.  Still, there's no piston return mechanism other than the wobble of the brake disk and a slight suction when the brake pedal is released, so with suitable rust in place, it's possible for a piston to stick in the 'brakes applied' position.

I agree with you that a defective master cylinder seems very unlikely.

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 Posted: 08-09-2006 05:55 pm
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Brett Gibson JH5 20497
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Tom, the front calipers are a totally simple single piston design on either side of the rotor, push the pedal and they squeeze it, over time the pistons develope rust and start binding against the sealing o-ring, I think that's your problem.

Two choices, take the caliper off and pull the piston's out and see if you can clean them up, a little fine steel wool, put them back on and hope they don't leak, or get a couple of rebuild kits from Delta along with new pistons, do both side's so you wont have to visit this issue again, and as Mark mentions, those hose's should probably be replaced as well, you cant beat the new stainless hoses, if I remember correctly they sell all three (rear one also) for the price of what a rubber one would go.

Brett.

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 Posted: 08-09-2006 08:37 pm
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Jim Sohl
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Hi Tom,
Let me first say that the advice given so far is quite good and very well may get you going.  I write to relate my past experience with the Girling units.  Specifically, the pistons are chrome plated and upon disassembly, the chrome was found to be literally peeling off.  Also, the edges of the peeled up chrome was tearing at the seals from the inside.  And finally, the pistons had started to rust where the chrome had lifted up.  All of the above was going on completely out of sight and for the most part, without symptoms.  As I was new to British cars at the time, it provided a good starting point to suspect that there are always problems, somewhere, just waiting to be found!  Did I say that I enjoy fixing things?  Good luck!
Jim in Chandler AZ, sn11210

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 Posted: 08-09-2006 11:31 pm
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10dtom
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I did a disassemble and clean on both front calipers, both had slight rust on the pistons, but the seals were good and there was no indication of a problem.

Also, with the bleed valve open the brake pad can be moved easily on both sides of the rotor.

I suspect there is a problem in the pressure diffirential warning actuator. I will try am going to try and bleed pressure back up to it next weekend

will post whatever I find out.

thanks,

tom

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 Posted: 08-11-2006 02:38 am
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Tom Thomson
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Tom

  I believe that Mark has the answer on your brake problem.  After my daughter-in- law came back trailing smoke from the rear brakes, I changed the hose and all was well.  As Mark said, the hose liner swells up and acts as a restriction to fluid flow.  The pressure developed by your foot and the booster can overcome this resistance but the return springs (rear) or the elasticity of the caliper seals cannot.  The problem first shows itself by the brakes not releasing immediately but dragging for a second after release of the pedal.  After a second - or two - or ten everything seems fine but don't be deceived; the car is just messing with you.

                                                 Tom 13753  

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 Posted: 08-13-2006 12:27 am
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10dtom
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thanks to all,

I am ordering the hoses from Delta (as they are wonderful). Will post my findings.

tom

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 Posted: 08-24-2006 07:46 pm
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Ron Earp
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Another option you have, and it is cheap, is all brand new calipers.

Triumph TR7 two piston calipers bolt right on, and, offer a larger pad area to boot.  They are are really inexpensive. I use them on my car and bought spares for the race kit too.

Typically you'll find them for $99.99 new from Victoria British and other places. However, on occasion, VB and another place, might be Moss, will sell them for $79.99 complete. Coupled with a TR7 Master Cylinder for $99 you can have a basically new system for $300.

http://www.victoriabritish.com/icatalog/tr/0102.html

The big reason I went down that route (didn't know they were so cheap) was that lots of race pad compounds are available from Brake Girl in the TR7 size while nothing other than stock was available for the JH.

Rebuild kits for the JH are cheap though, and as long as you don't suspect bore issues or piston issues you should be good to go.

Ron

Last edited on 08-24-2006 07:49 pm by Ron Earp

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 Posted: 08-25-2006 02:21 am
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Jensen Healey
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The Hawk street pads I use are from the Spitfire and are a little smaller than the JH.  They work great for 'normal' street driving. ;-)

Kurt

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 Posted: 08-28-2006 05:24 pm
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10dtom
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mark,

you were completely correct, the only problem was the hoses. I replaced them and the problem went away.

thanks for the very good advice.

tom

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 Posted: 08-28-2006 06:59 pm
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Mark Rosenbaum
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Tom,
Glad to hear your problem has been resolved without too much time, trouble, and expense.  Have fun with the car!

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 Posted: 09-22-2006 07:29 pm
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Delta Motorsports
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Greg,

I have followed the recent discussionon the sticking, front caliper with a fair bit of interest and would like to add my comments.

First. I did not mean to infer that the master cylinder was the culprit, but rather the booster push rod was in need of adjustment. With time the necessary clearance between the push rod and the rear piston of the master cylinder decreases until the piston can no longer fully return to its fully relaxed position. As a result the cylinder does not release hydraulic pressure, and the brakes remain lightly applied. You will note a threaded sdjustment on the push rod. Screw this a turn or two inward (shorter) and most non-release problems will be cured. Why this affects one wheel only I don't know. It just does.

Second. Collapsed hose linings are a possible cause, but relatively rare.

Third. I'm not sure where the chromed pistons came from. Most are billet steel (ours are now black anodized) and some are stainless. Stainless are nice, but expensive. Since most steel one shave lasted thirty years, I can't justify the extra cost. I would never remove and refit pistons without replacing the seals. Do not split the caliper halves as the sealing O rings are not included in the kits.

Fourth. Just to satisfy my own curiosity. I compared the Jensen Healey pads with the TR 7's. Although close, it appears the J/H pads are slightly larger. The currently available pads are state of the art ceramic, although we do have rivited.

I hope this helps sort out some of the confusion. If not, please don't hesitate to phone.

Jim Medland

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 Posted: 09-23-2006 10:52 pm
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Tom Thomson
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Jim

  I am reluctant to disagree with the expert but a defective hose may not be as rare as you think.  I have experienced this twice - on the JH and a Chevy Luv.  Also a Triumph (motorcycle) forum which I read recently ran a thread on the subject and 5 respondents had the same story.

                           Tom 13753

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 Posted: 09-24-2006 06:56 pm
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Greg Fletcher
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Clearly brake problems can have many sources and definitely worth the time to check that pesky push rod as I've had trouble with that before also, and collapsing rubber hoses.

I've experienced pulling to one side and after a complete caliper rebuild on both sides, the problem seemed just as bad afterward. Not to give up easily, as I was sure the caliper was the problem and I removed them once again, split the calipers (not recommended by the manufacturer as Jim notes), and gave them a very detailed cleaning in a bead blast cabinet. Parts dip was enough for my calipers. Once assembled with new seals and o-rings, they worked perfectly, no pulling, and stopped straight as an arrow. Those calipers can get pretty messed up over the years and passages can get blocked, at least that was the problem in my case.

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