Brake Servo Rebuild?

[tdanko]

Hello Everyone

I was wondering if anyone out there had a diagram of the innards of a brake
servo...I do not like the idea of taking one apart before I know that I can
get it back together. Perhaps someone sells such a diagram. In that case,
could some one point me in the correct direction to find this? Thank you.

Thank you

Todd
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[jensmartin]

Todd, try Paul Matty, if you are lucky they have some Breake servo
repair kits left, they are a litte hard to find nowdays. I that kit
You
get a diagram and a handful of spareparts: diaphragm, oilseals etc.
Non
return valves are available at www.rdent.com. This regards the
Girling
MK2b servo. If You're out of luck I could send you a copy of my
diagram. I just rebulit one of my boosters with a good result.

Leaking are they?

http://www.racecar.co.uk/pmattysportscars/

Jens Martin
+2 S130
Lund Sweden





--- In ***@***.***, "Todd Danko" <twdanko@h...> wrote:

[Stevie-Heathie]

Paul Matty does have some kits available ( I rang yesterday), but they do
not necessarily guarantee a fix for a leaking servo.

When my Plus 2 returns from the garage I am considering removing the leaky
servo altogether. I know that people out there have done it already. Has
anybody written up the procedure on a web page?

Cheers

Steve

-----Original Message-----
From: Jens Martin [mailto:***@***.***
Sent: 27 September 2000 11:49
To: ***@***.***
Subject: [LotusElan.net] Re: Brake Servo Rebuild?



Todd, try Paul Matty, if you are lucky they have some Breake servo
repair kits left, they are a litte hard to find nowdays. I that kit
You
get a diagram and a handful of spareparts: diaphragm, oilseals etc.
Non
return valves are available at www.rdent.com. This regards the
Girling
MK2b servo. If You're out of luck I could send you a copy of my
diagram. I just rebulit one of my boosters with a good result.

Leaking are they?

http://www.racecar.co.uk/pmattysportscars/

Jens Martin
+2 S130
Lund Sweden





--- In ***@***.***, "Todd Danko" <twdanko@h...> wrote:

[Foxie]

Steve,

To remove/isolate the brake servo from your brake sytem, all you have to do is make up a short length of brake line with a female union at each end, connect up the servo inlet and outlet brake lines, and bleed the system.

However, having driven on occasion with a non-operative servo, I certainly wouldn't recommend doing it out of choice.

Best wishes,

Sean Murray
1970+2S
----- Original Message -----
From: Steve Heath
To: ***@***.***
Sent: Wednesday, September 27, 2000 12:03 PM
Subject: [LotusElan.net] Brake Servo Rebuild?

When my Plus 2 returns from the garage I am considering removing the leaky
servo altogether. I know that people out there have done it already. Has
anybody written up the procedure on a web page?

Cheers

Steve

[Stevie-Heathie]

Hi Sean

Is the effort required at the pedal very much greater? (There must be a
reason Chapman whacked the servo on the car in the first case I s'pose.)

Steve

-----Original Message-----
From: Sean Murray [mailto:***@***.***

However, having driven on occasion with a non-operative servo, I certainly
wouldn't recommend doing it out of choice.

Best wishes,

Sean Murray
1970+2S

[melvinhecht]

Yes, you have to use more pressure. You still have power brakes, but now it
is the power of FEAR that works.

Goodluck,

Melvin 1971 Plus 2S 50/0216N



----- Original Message -----
From: Steve Heath <***@***.***>

Sent: Wednesday, September 27, 2000 9:40 AM
Subject: [LotusElan.net] Brake Servo Removal

[daves56]

Steve,
I second that. When I got the car I bought two rebuilding kits to do the
servos but decided to remove them altogether (still have the servos and
kits). I bought a new 0.700" dia. M/C from Tilton. This works pretty good
but does not feel anything like a power brake. It would require a lot of
force in a panic stop. Which makes me nervous because the pedal box is not
that strong. I believe the stock M/C size is 0.875". If you do remove the
servos, going to a smaller bore is a must.
Regards,
Dave Sutcliffe
69 +2

-----Original Message-----
From: Melvin Hecht [mailto:***@***.***
Sent: Wednesday, September 27, 2000 9:01 AM
To: ***@***.***
Subject: Re: [LotusElan.net] Brake Servo Removal


Yes, you have to use more pressure. You still have power brakes, but now it
is the power of FEAR that works.

Goodluck,

Melvin 1971 Plus 2S 50/0216N



----- Original Message -----
From: Steve Heath <***@***.***>

Sent: Wednesday, September 27, 2000 9:40 AM
Subject: [LotusElan.net] Brake Servo Removal

[Foxie]

Hi Steve,

If you want to check pedal pressure, just disconnect the vacuum line, (blank the end off), and take it for a drive. In my experience not only is it considerably greater, but more to the point, it is just not possible to get enough pressure on the brakes to make them work in any but the gentlest of stops. My servo failed while on the Norwich Union in 96, and for a few days I drove in pure terror on hills, circuits and traffic.

Regarding fitting a smaller dia master cylinder, this may be an option, but I find that I still have too much pedal travel with the standard master cylinder (servo in service), despite fiddling with pushrod legths and bleeding the system till the cows came home.
I would welcome any suggestions how to get an improvement here.

Dave Sutcliffe is right about the weakness of the pedal box mounting, I reinforced this some time ago and posted details on the list some time ago. Basically I ran the front and rear pedal box mounting flanges the full width of the driver side underdashboard area and tied them into the steering column mountings, which greatly stiffened up the steering column as well.

(BTW, I always thought Chapman must have been nodding the day they put in TWO servos)

best wishes,

Sean Murray
----- Original Message -----
From: Steve Heath
To: ***@***.***
Sent: Wednesday, September 27, 2000 2:40 PM
Subject: [LotusElan.net] Brake Servo Removal


Hi Sean

Is the effort required at the pedal very much greater? (There must be a
reason Chapman whacked the servo on the car in the first case I s'pose.)

[gobw2]

Sean - maybe it would be ok if he changed the pads to the softer ones
used by the cars made without servos like mine? George

On Wed, 27 Sep 2000 13:36:06 +0100 "Sean Murray" <***@***.***>
writes:

[gobw2]

Sean - I have a no servo car - was able to substantially cut pedal travel
and make the brakes feel firmer by replacing stock brake hoses with
reinforced ones. Seems stock hoses, although safe, swell slightly under
pressure, allowing some fluid to be displaced into them. this causes
more pedal travel and soft feel to brakes. I suspect the effect would be
more pronounced with the higher line pressures of servo brakes. Maybe
reinforced hoses would help? Just a thought.
Second thought - I have no experience with type of servo brakes on Elan,
but I had a ford where the vacuum diaphragm in the power brake unit
failed. On American Iron, it is between pedal and master cylinder -
different. BUT - with it inoperable and in place, the brakes were like
you said - didn't want to drive car. Removed unit and bolted master cyl
direct to firewall - without dead weight of servo, brakes were hard, but
operable - I could make hard stops with lot of leg pressure. Would the
dead weight of that servo make the brakes harder to operate than if it
was not in system?
George

On Wed, 27 Sep 2000 21:05:53 +0100 "Sean Murray" <***@***.***>
writes:

[davidcroft]

Sean Murray wrote:


Sean

Dear Sean

Does the pedal firm up if you give the pedal another pump?

The reason I ask is that my Plus2's brakes have a problem that I've never heard of before, and I've just found out what it is.

The symptoms were that on initially pressing the brakes, the pedal went a disconcertingly long way towards the floor before anything happened. The car stops perfectly well - locking up in the dry if you want to - it's just that the pedal moves a long way before anything happens.

If, however, I give the brakes a quick 'double-pump', the pedal is rock-hard, right at the top of it's movement.

Various very clever mechanics (not me, obviously) have tried all sorts of things. The brakes have been bled more times than Dracula's girlfriend - all to no avail.

What is actually happening is this - the brake pistons in the calipers are binding to the seals rather than sliding through them. This pulls the pistons too far back into the calipers, so the pistons are starting their movement from too far away from the discs. A second pump pushes the pistons that extra bit further, making contact with the discs, before the bindng seals have a chance to pull the pistons back inside the cylinders.

This explains how you can have excessive pedal movement (helped by a second pump) in a brake system that you know to be correctly bled.

The solution - reconditioned calipers with stainless innards. About ?100 per corner plus labour.

By the way, I was dead impressed with your European tour. I suppose your insurance isn't a limited mileage policy. And did you get extended super-duper AA euro-cover.

I would truly love to take my car on a trip like that, but sadly there is absolutely no way my wife would either come with me, or let me go without her (female logic...). Any drive longer than 10 minutes on the motorway she sticks tissue paper in her ears and sulks.


Regards

David

PS - I've got a sound file of the car, but I've completely failed to upload it anywhere. What do I do with it?

["Paul Savill"]

Melvyn wrote:



Nothing wrong with a bit of FEAR - helps keep the roads safe.

I found the remote servo to be an ongoing headache, and I don't think that
applies just to the +2. A lot of British stuff in the sixties used one.
Bit of a bodge really.

I took mine off and used the softest set of (front) pads that I happened to
have lying around. It's then just a matter of getting used to a stiffer
pedal (particularly first thing - when pads/discs are cold). I like the
improvement in pedal feel and the ability to use a bit of heel'n'toe without
wondering where the brake pedal will be when I most need it! It is still
possible to lock the wheels up without popping a vein and in that respect it
could be argued that it's safer than thye servoed system...

Anyway, as soon as these pads go home, I shall fit a set of EBC (Green)
Kevlar pads - I expect that will reduce pedal effort. A lister
contemplating buying a Servo repair kit might like to spend the money on the
Kevlar pads instead and let us know how they perform.

Paul Rightlegbiggerthanleft Savill

[Foxie]

George,

Sorry I didn't mention this, I replaced the standard flexible brake lines with SS braided Aeroquip type many years ago.

Regarding the effect of the deadweight of the servo, removing a 10lb servo from an approx 2,000 lb car would acheive an improvement in braking, but it would be so small as to be unnoticeable. If you noticed an improvement it was probably for other reasons, which is what we would like to identify.

Best wishes,

Sean Murray
----- Original Message -----
From: ***@***.***
To: ***@***.***
Cc: ***@***.***
Sent: Thursday, September 28, 2000 4:16 AM
Subject: Re: [LotusElan.net] Brake Servo Removal


Sean - I have a no servo car - was able to substantially cut pedal travel
and make the brakes feel firmer by replacing stock brake hoses with
reinforced ones.


Second thought - I have no experience with type of servo brakes on Elan,
but I had a ford where the vacuum diaphragm in the power brake unit
failed. On American Iron, it is between pedal and master cylinder -
different. BUT - with it inoperable and in place, the brakes were like
you said - didn't want to drive car. Removed unit and bolted master cyl
direct to firewall - without dead weight of servo, brakes were hard, but
operable - I could make hard stops with lot of leg pressure. Would the
dead weight of that servo make the brakes harder to operate than if it
was not in system?
George

[S3_SE/DHC]

David--That is the best explanation I have heard for my own
first-stroke-soft-brake-pedal issue. On the second stroke, the pedal firms
right up. It does not act like air in the system, since the system behaves
the same even if the first brake pedal push is very slow. I would think
that air in the system would need a rather vigorous pedal pump in order to
disperse the air bubbles into little ones. I have rebuilt my calipers twice
with sst pistons, new seals, etc. And have bled gallons of fluid through.
I have also fitted braided sst lines at all four corners, and tried with and
without the servo plumbed in. At one point I thought that a pair of
slightly flexed anti-squeal shims between the front pistons and the pads
were responsible for pushing the pistons back into the bores, resulting in a
long pedal travel after the first stroke. So I removed those, but again no
change. My final thought was possibly movement in the hard piping somewhere
along the chassis, or possibly ballooning and nearing failure, but that
seems a little far-fetched.

It seems amazing that the little rubber seals have enough grab and pull to
retract the pistons back into the bores. I'll have a close look with a
bright light while a friend pushes the pedal. When I rebuilt the calipers,
I simply used brake fluid as the initial lubricant on the seals. Is there
another type of grease or lubricant to use?

Gerry Snow
Spokane, Washington, USA
67 S3 DHC



cylinder (servo in service), despite fiddling with pushrod legths and
bleeding the system till the cows came home.


stops perfectly well - locking up in the dry if you want to - it's just that
the pedal moves a long way before anything happens.


to no avail.

pistons too far back into the calipers, so the pistons are starting their
movement from too far away from the discs. A second pump pushes the pistons
that extra bit further, making contact with the discs, before the bindng
seals have a chance to pull the pistons back inside the cylinders.



super-duper AA euro-cover.

her (female logic...). Any drive longer than 10 minutes on the motorway she
sticks tissue paper in her ears and sulks.

[type26owner]

No amount of pumping will reduce the pedal travel due to air bubbles.
Another myth is that boiling brake fluid causes fading. The fading is a
thermal effect of the rotor and pads heating to the point that the
outgassing of the materials causes a layer of gas to form between them
and it acts as a lubricant.

IIRC, the gaskets can be installed incorrectly. They have a slight wedge
shape if viewed in cross section. If you know what to look for the taper
on the seal surface is easy to see. A gasket installed backwards will
not slid on the piston but will tend to grip and roll. The thinnest side
should be contact the fluid.
--
Keith Franck

LBNL Engineering

***@***.***
http://xraysweb.lbl.gov/esg/