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Soft Brake Pedel  Rating:  Rating
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 Posted: 11-10-2006 05:31 pm
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Jay
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My JH brakes seem to work pretty well in general. If you apply them at a somewhat normal speed (that is to say, the speed at which you move the pedel), or if you apply them quick and hard, the seem okay, maybe not great but okay. If I sort of sneak up on the pedel and apply the movement very slowly, the pedel will continue move to what I think is the end of its' available travel (just about to the floor), and no noticable amount of brake pressure seems to be applied. This seems to happen wether the engine is running or not. I am suspecting some sort of leaking past the piston in the master cylinder, but wondered if there might be some other cause. I have not seen any fluid on the pedels' arm or anywhere else for that matter. I have not yet opened the rear brakes to look more closely. I was wondering if fluid were baypassing in the master cylinder would it stay in the cylinder/system, or would it leak out somewhere? Any advise to futher diagnose would be most welcome. Are rebuild kits available?
Thanks,
Jay

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 Posted: 11-10-2006 08:53 pm
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Greg Fletcher
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It's most likely leaking past the seals in the master. You don't need fluid pouring out to have a bad seal, it often starts out gradually as you describe it. I always recommend a new master cylinder, but reseal kits from Delta are around $54, I think. If you don't drive the car much and you just want it safer than it is now, a reseal might work depending on the condition of the bore. I've had resealed and resleeved master cylinders suffer catastrophic failure, so I stay away from those.

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 Posted: 11-11-2006 04:56 pm
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Ron Earp
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Ditto what Greg said, skip the rebuild kit and go for a new TR6 master. It bolts straight up, works great, and you can get them on sale from Victoria British for $99 sometimes - completely new unit too. I think the JH Club Store has new stock JH units if you want that one.

I have two TR6 units, one on the car and one in the race spares box. Thus far not had any issues with it and the pedal is much better than I ever got out of the old JH unit I rebuilt. The stock JH one worked after being rebuilt, but just didn't provide the firm pedal I like as the new one does.

R


Last edited on 11-11-2006 04:56 pm by Ron Earp

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 Posted: 11-11-2006 06:11 pm
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Mark Rosenbaum
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I concur with Greg and Ron.  From what I've heard and read, only about one in six to one in eight dual-circuit master cylinders can be rebuilt successfully.   The TR6 part is a true bolt-in replacement.  Some time ago I posted my experiences with installing one in my car, and the writeup should still be available in the old site's archives.  (Seem to have lost my link to that site, alas.)

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 Posted: 11-11-2006 06:50 pm
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Jensen Healey
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http://www.jensenhealey.com/msgboard.mv?parm_func=showmain+parm_starting_root=1

The old message board is still up!

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 Posted: 11-14-2006 08:02 pm
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Jay
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Mark,

I believe I found your writr-up on the old board. Is the Roadster Factory part number(s) that you quoted, GI64068822 - "T56 Master Cylinder Assy, Brake" (should this have been "TR6"?) the part that I should be looking for. I was wondering if different model years of the TR6 and the JH would have any bearing on which part number I need for my JH. I will check the numbers on my M/C and compare to those that you quoted from your original JH M/C.

Thanks for the write-up.
Jay

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 Posted: 11-14-2006 09:03 pm
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Mark Rosenbaum
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Jay, to answer your questions:

As far as I know all JHs and GTs used the same master cylinder and fluid reservoir.

The Roadster Factory designation T56 refers to parts used on both the TR5 and TR6 (IIRC their catalog explains all that, somewhere).  Don't know whether the TRF has any in stock right now, nor whether their price will be lower than the JHPS price.

All part numbers in that post were taken directly from actual parts in hand, or from online catalogs, as appropriate.  I think everything is accurate -- certainly I never found any typos or errors, and no one else has drawn my attention to one.

You may also wish to read a followup post I wrote, relating to a transient failure of the new master cylinder's tipping valve, which resulted in a lack of front brakes.  The cause for this was pretty positively identified as the presence of barely visible debris in the brake fluid.  Bleeding the car's brakes got rid of the both the debris, and the problem.

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 Posted: 12-09-2006 06:57 pm
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edward_davis
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Out of curiosity, is the TR6 servo unit a drop-in replacement as well?  My JH has a TR6 M/C already, but I've discovered it's leaking fluid from the connection between the M/C and the servo - time to get another TR6 unit...  I'm curious about the servo, though, and whether I should think about replacing it as well.  Can I test its function if the M/C is leaking? 

I'd never felt like I have a difficult car to stop, so I'm guessing that I'm getting a vacuum assist.  My clue something was wrong this time was that the pedal traveled almost all the way to the floor, but I still had no trouble stopping, and I didn't feel like I needed much more pressure than I usually do.  I discovered that the M/C reservoir was almost empty, and when I topped it up, I got some of my pedal height back.  And it still wasn't hard to stop the car.  I don't want to drive her until I get the M/C replaced, and I figured that since I was going to be in there anyway, I should think about the vacuum assist unit as well.

Thanks,

Edward

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 Posted: 12-09-2006 10:24 pm
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Jensen Healey
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oops

Last edited on 12-10-2006 01:24 pm by Jensen Healey

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 Posted: 12-10-2006 11:36 am
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edward_davis
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I see now that Mark has already answered my question in a previous posting on this thread:

http://www.jensenhealey.com/forums/view_topic.php?id=20&forum_id=6&page=1

Thanks, folks!

Edward

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