First I would like to say ‘‘Thank you’’ to all the wonderful Jag-
Lovers that have been so kind to offer advice to this poor boy.
I think I discovered something that may be of interest. I’m
looking for verification.
My saga has been in trying to bleed the brakes on my 69 XKE.
Not being able to get the brake pedal to firm up when bleeding the
brakes, I reluctantly once again removed both the master and the
Servo and took them appart for inspection. The master was put
together correctly, and at first look the Servo appeared to be
correct too. BUT upon further review, the instructions in the
Haynes service manual Chapter 9, Section 20, page 180, item 16
states ‘’…assembly the two rubber seals (23 and 25) to the piston
so that their concave faces oppose each other’’.
Eureka! They were previously, and by the previous owner, assembled
so they faced in opposite directions. AND the picture Fig.9.23
shows them facing opposite each other. Both the previous owner and
myself obviously followed the picture, not the written word. Now
the question becomes, which is correct?? Does anyone have a clear
understanding of the correct positioning of these seals??
I would love to know before I reassemble the entire works and find
it wrong again. Thank you again for your advice.–
Daglover
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
In reply to a message from David Glover sent Fri 18 Jul 2003:
Does ‘‘oppose each other’’ mean ‘‘facing each other’’ (towards each
other) or ‘‘facing away from each other’’?? (in opposite directions)–
Daglover
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
In reply to a message from David Glover sent Fri 18 Jul 2003:
David,
The book says, if I remember right, to have the concave faces
opposing each other. This would mean with the open side of
the ‘‘cups’’ facing towards each other, which kinda makes sense if
you look at what the purpose of those two seals appears to be. I
believe they provide a means of sealing between the two hydraulic
circuits when one has failed. So they need to be able to resist
pressure in both directions, depending on which circuit has
failed. I don’t have one to look at, but if you look at the parts,
and consider how it must work, I think the proper orientation
should become clear.–
The original message included these comments:
Does ‘‘oppose each other’’ mean ‘‘facing each other’’ (towards each
other) or ‘‘facing away from each other’’?? (in opposite directions)
Daglover
–
Ray Livingston
Santa Cruz, CA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
I did my brake servo a while ago. As I remember there was a discussion
about the seal
direction at that time also.
I did them per instructions of the leaflet that came with the rebuild set.
This matched excactly
how the slave piston sub-assembly came out of the servo.
The opening of both rubber seals facing forward!
I could mail you, off list a photo of the sub-assembly before renewal of
the components.
Jos Raven
1969 E 2+2
At 05:07 18-7-2003 +0200, you wrote:
First I would like to say ‘‘Thank you’’ to all the wonderful Jag-
Lovers that have been so kind to offer advice to this poor boy.
I think I discovered something that may be of interest. I’m
looking for verification.
My saga has been in trying to bleed the brakes on my 69 XKE.
Not being able to get the brake pedal to firm up when bleeding the
brakes, I reluctantly once again removed both the master and the
Servo and took them appart for inspection. The master was put
together correctly, and at first look the Servo appeared to be
correct too. BUT upon further review, the instructions in the
Haynes service manual Chapter 9, Section 20, page 180, item 16
states ‘’…assembly the two rubber seals (23 and 25) to the piston
so that their concave faces oppose each other’'.
Eureka! They were previously, and by the previous owner, assembled
so they faced in opposite directions. AND the picture Fig.9.23
shows them facing opposite each other. Both the previous owner and
myself obviously followed the picture, not the written word. Now
the question becomes, which is correct?? Does anyone have a clear
understanding of the correct positioning of these seals??
I would love to know before I reassemble the entire works and find
it wrong again. Thank you again for your advice.
In reply to a message from Jos Raven sent Fri 18 Jul 2003:
Jos,
I’ve never taken one of those apart, but that makes no sense to
me, from what I can see in the manual. Aren’t those seals
separating the two circuits, specifically to deal with failure of
one circuit? If so, it seems to me they must point in opposite
directions (I believe with the concave sides pointing away from
each other) to provide the necessary isolation when one circuit
fails. Otherwise, it will work fine as long as both circuits are
intact, but when one of the circuits fails (the one on the concave
side of both seals), fluid will be able to push past both seals,
and you’ll lose both sets of brakes. Am I mis-reading this?–
The original message included these comments:
I did them per instructions of the leaflet that came with the rebuild set.
This matched excactly
how the slave piston sub-assembly came out of the servo.
The opening of both rubber seals facing forward!
Jos Raven
–
Ray Livingston
Santa Cruz, CA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
In reply to a message from Jos Raven sent Fri 18 Jul 2003:
In fact, this would explain the problem someone noted of having
fluid pump from one reservoir to the other when bleeding the
brakes. That would make perfect sense to me, if these seals are
installed incorrectly. I certainly see no other way fluid could
move in that way.–
The original message included these comments:
This matched excactly
how the slave piston sub-assembly came out of the servo.
The opening of both rubber seals facing forward!
Jos Raven
–
Ray Livingston
Santa Cruz, CA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
First I would like to say ‘‘Thank you’’ to all the wonderful Jag-
Lovers that have been so kind to offer advice to this poor boy.
I think I discovered something that may be of interest. I’m
looking for verification.
My saga has been in trying to bleed the brakes on my 69 XKE.
Not being able to get the brake pedal to firm up when bleeding the
brakes, I reluctantly once again removed both the master and the
Servo and took them appart for inspection. The master was put
together correctly, and at first look the Servo appeared to be
correct too. BUT upon further review, the instructions in the
Haynes service manual Chapter 9, Section 20, page 180, item 16
states ‘’…assembly the two rubber seals (23 and 25) to the piston
so that their concave faces oppose each other’'.
Eureka! They were previously, and by the previous owner, assembled
so they faced in opposite directions. AND the picture Fig.9.23
shows them facing opposite each other. Both the previous owner and
myself obviously followed the picture, not the written word. Now
the question becomes, which is correct?? Does anyone have a clear
understanding of the correct positioning of these seals??
I would love to know before I reassemble the entire works and find
it wrong again. Thank you again for your advice.
this is one instance where the book may be incorrect.
Find the instructions that came with the seals and follow them.
bentley’s is wrong and haynes may just be a copy from the Bentley in this
respect.
Hi David,
I have looked at 3 different manuals and they all have the seals as shown in
the picture as in the Haynes manual. I have a Bentley’s for the Series 1,
the Haynes for the Series 1&2 and a Series 3 manual (I think that the master
cylinders are the same with the exception of the early series 1’s). When I
look at the flow diagram it looks to me that the seals should be placed
facing opposite directions with the seal for the front brakes (25) facing
concave surface forward (to the front of the car) and the other seal (23)
facing with the concave (sealing aspect) surface to the rear.
I hate to say this but I am still suspicious of your master cylinder, could
you be missing the piston washer(23 on page 182) something like this could
allow the fluid to sidestep so to speak and prevent you from having any
pedal pressure.
Sorry I can’t be of anymore help,
best wishes.
Lynn G
Oh Boy, I’m getting really confused now! The Parts manual I have for the '73
has a exploded view that has them facing the same way with the sealing
surface towards the front. I agree that Haynes is a copy of the Bentley
however the manual I have for the Series 3 is not,needless to say, the parts
manual seems to be at odds with the repair manual (go figure!). Sorry David.
Lynn G
this is one instance where the book may be incorrect.
Find the instructions that came with the seals and follow them.
bentley’s is wrong and haynes may just be a copy from the Bentley in this
respect.
In reply to a message from David Glover sent Fri 18 Jul 2003:
Ok, I do feel better now. I was concerned that I might get
austricized from Jag-lovers for asking such a stupid question, but
now I’m confused. We have differing opinions. I’m tempted to put
it together and try it ‘‘concave sides facing each other’’. Is there
any concensus?–
Daglover
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
In reply to a message from David Glover sent Sat 19 Jul 2003:
Dave,
Not from me. My guess is just the opposite…–
The original message included these comments:
Ok, I do feel better now. I was concerned that I might get
austricized from Jag-lovers for asking such a stupid question, but
now I’m confused. We have differing opinions. I’m tempted to put
it together and try it ‘‘concave sides facing each other’’. Is there
any concensus?
Daglover
–
Ray Livingston
Santa Cruz, CA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
have a look, it is exactly as depicted in the leaflet that came with the
rebuild kit.
I have no problems with the brakes at the moment and they were tested at
the MOT / DOT
and found more than required.
Jos
At 18:18 18-7-2003 +0200, you wrote:
In reply to a message from Jos Raven sent Fri 18 Jul 2003:
Jos,
I’ve never taken one of those apart, but that makes no sense to
me, from what I can see in the manual. Aren’t those seals
separating the two circuits, specifically to deal with failure of
one circuit? If so, it seems to me they must point in opposite
directions (I believe with the concave sides pointing away from
each other) to provide the necessary isolation when one circuit
fails. Otherwise, it will work fine as long as both circuits are
intact, but when one of the circuits fails (the one on the concave
side of both seals), fluid will be able to push past both seals,
and you’ll lose both sets of brakes. Am I mis-reading this?
The original message included these comments:
I did them per instructions of the leaflet that came with the rebuild set.
This matched excactly
how the slave piston sub-assembly came out of the servo.
The opening of both rubber seals facing forward!
Jos Raven
–
Ray Livingston
Santa Cruz, CA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
David, I agree that this is very confusing but I still stand by my belief
the seals have to face opposite each other with #25 facing forward and #23
facing backwards. On page 178 of the Haynes manual there is a flow diagram
that I think supports my view. As pressure builds up in the master cylinder
the fluid is pushed into the servo ‘A’ where it ‘pushes’ against the
secondary piston and to the front calipers. If this seal were facing the
other way I believe that the brake fluid would be pumped into the secondary
reservoir. The only difference that I can see between the early 4.2 and the
late is that they switched the lines from front to rear on the servo master
cylinder. I think that the effect of the booster can be ignored for the sake
of this discussion as it would act in the same fashion as increasing the
fluid pressure on the secondary piston.
It sure makes you wonder why they came up with this incredibly complicated
arrangement, it seems like if they had a choice between a simple system or a
complicated one they always choose the more complicated;)
Good Luck,
Lynn G
In reply to a message from Jos Raven sent Sat 19 Jul 2003:
Jos,
Again, I’ve never taken one of these apart, so I could be
completely full of you-know-what, but…
These seals are between the two hydraulic circuits, so you
could put them in in any orientation, and everything would likely
work just fine. It’s only when one circuit fails that you’ll be in
trouble if they’re not put in correctly.
If you look at the cutaway system diagram on page 178 of the
Haynes book, you can see the front seal (#25) of the central piston
is exposed to one circuit on it’s front side, the rear seal (#23)
is exposed to the other circuit on it’s rear side. In all cases,
the cup must open to the high pressure side, so the fluid pressure
acts to expand the cup against the cylinder wall. Unless I’m
reading this all wrong, it seems very clear to me that the front
seal, #25, must open to the front, and the rear seal must open to
the rear.
Again, if they’re installed wrong, the brakes will still work
perfectly until one circuit fails. If the seals are installed
incorrectly, a failure in one circuit will cause total loss of
brakes. Which circuit will cause the total loss is a function of
exactly how the seals are installed. Like I said, I’ve never
worked on one of these myself, but the more I study the manual, the
more convinced I am that I am correct, so please give it careful
thought and, I hope, find a flaw in my logic.
BTW - This is one bizarre brake system!–
The original message included these comments:
Ray,
I posted the photo on my web-site; http://www.mraven.com/e-type-project-own-page13.htm
have a look, it is exactly as depicted in the leaflet that came with the
rebuild kit.
I have no problems with the brakes at the moment and they were tested at
the MOT / DOT
and found more than required.
Jos
–
Ray Livingston
Santa Cruz, CA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
In reply to a message from Ray Livingston sent Sat 19 Jul 2003:
The front seal faces forward and the rear seal faces back as ray
has stated—this is definatly correct, if the front seal is
installed facing back fluid would collapse it as the piston moves
forward and those brakes (front on early cars, rear on later cars)
would be inoperative, If the rear seal is installed facing
forward,fluid under pressure from the master cylinder( acting thru
the primary piston) would collapse it and the fluid would be fed
into the resovoir bottle----Peter–
The original message included these comments:
reading this all wrong, it seems very clear to me that the front
seal, #25, must open to the front, and the rear seal must open to
the rear.
Again, if they’re installed wrong, the brakes will still work
perfectly until one circuit fails. If the seals are installed
incorrectly, a failure in one circuit will cause total loss of
brakes. Which circuit will cause the total loss is a function of
–
Peter Conway 69 2+2
Georgetown Ontario, Canada
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
In reply to a message from Ray Livingston sent Sat 19 Jul 2003:
FWIW - I'm now positively convinced these two seals *must* be
installed with their concave sides facing away from each other -
that is, the front seal opens to the front (away from the booster)
while the rear one opens to the rear (towards the booster). Other
configrations may appear to work, depending on how tightly the
seals fit the cylinder, but run the risk of total failure of both
systems when one fails, and can also result in fluid being pumped
from the ‘‘primary’’ reservoir (on the ‘‘master’’ master cylinder) into
the secondary reservoir (on ‘‘slave’’ master cylinder).–
Ray Livingston
Santa Cruz, CA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
In reply to a message from Ray Livingston sent Sat 19 Jul 2003:
Ray, a hydraulic ‘v’’ seal will not hold pressure in the reverse
direction no matter how well it fits in the bore. If you look at
the hydraulic diagram for the braking system you will see that
there is only a hydraulic ‘link’ between the servo main piston and
the secondary piston. If the seal is installed in reverse on the
secondary piston it will not move ( with much force ) under the
fluid pressure from the primary piston and the fluid will definatly
pass the seal and end up in the other reservoir Comments?—Peter–
The original message included these comments:
In reply to a message from Ray Livingston sent Sat 19 Jul 2003:
FWIW - I’m now positively convinced these two seals must be
installed with their concave sides facing away from each other -
that is, the front seal opens to the front (away from the booster)
while the rear one opens to the rear (towards the booster). Other
configrations may appear to work, depending on how tightly the
seals fit the cylinder, but run the risk of total failure of both
systems when one fails, and can also result in fluid being pumped
from the ‘‘primary’’ reservoir (on the ‘‘master’’ master cylinder) into
the secondary reservoir (on ‘‘slave’’ master cylinder).
Ray Livingston
–
Peter Conway 69 2+2
Georgetown Ontario, Canada
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
In reply to a message from Peter Conway sent Sat 19 Jul 2003:
Peter,
I can see your logic, but consider the fact that caliper seals
are normally a rectangular cross section, and they seem to hold
pressure just fine. There’s no reason a tightly fitting V seal
couldn’t achieve a tight seal (at least for a while). It all
depends on the dimensions, the fit, and the material. I would
certainly expect a reversed seal to leak, but Jos seems quite
certain he installed his both pointing the same direction, and
seems just as certain his brakes are working properly. If he’s
right about how he assembled his master cylinder, and I have no
reason to doubt him, then I see no other explanation than the seal
is somehow holding pressure despite being installed backwards.
(However, if I were him, I know what I’d be doing first thing
tomorrow morning…)–
The original message included these comments:
Ray, a hydraulic ‘v’’ seal will not hold pressure in the reverse
direction no matter how well it fits in the bore. If you look at
the hydraulic diagram for the braking system you will see that
there is only a hydraulic ‘link’ between the servo main piston and
the secondary piston. If the seal is installed in reverse on the
secondary piston it will not move ( with much force ) under the
fluid pressure from the primary piston and the fluid will definatly
pass the seal and end up in the other reservoir Comments?—Peter
Peter Conway 69 2+2
–
Ray Livingston
Santa Cruz, CA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
I have put a exploded picture of brake master cylinder with the aircontrol
valve
on my web-site and also a link to a .pdf of the brake servo repair kit.
(4.4 Mb)
Look at figs # 7,8 and 9.
Take in mind this is for my 1969 2+2.
I hope that there is no confusion for earlier models.
Jos Raven
At 05:25 19-7-2003 +0200, you wrote:
In reply to a message from Peter Conway sent Sat 19 Jul 2003:
I would certainly expect a reversed seal to leak, but Jos seems quite
certain he installed his both pointing the same direction, and
seems just as certain his brakes are working properly.
This is in the Servo unit, not the master.
If he’s
right about how he assembled his master cylinder, and I have no
reason to doubt him, then I see no other explanation than the seal
is somehow holding pressure despite being installed backwards.
(However, if I were him, I know what I’d be doing first thing
tomorrow morning…)
In reply to a message from Ray Livingston sent Sat 19 Jul 2003:
Ray, perhaps the confusion is that jos is talking about the master
cylinder and we are concerned with the servo cylinder. In the
master cylinder the seals both face forward as one is the piston
seal and the other is the piston to body (stationary) seal. Peter–
The original message included these comments:
certainly expect a reversed seal to leak, but Jos seems quite
certain he installed his both pointing the same direction, and
seems just as certain his brakes are working properly. If he’s
right about how he assembled his master cylinder, and I have no
reason to doubt him, then I see no other explanation than the seal
is somehow holding pressure despite being installed backwards.
(However, if I were him, I know what I’d be doing first thing
tomorrow morning…)
–
Peter Conway 69 2+2
Georgetown Ontario, Canada
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–