[modern] Re: Brake pressure loss on XJR

Mike,

If you weren’t losing the fluid I would say it was an internal master
cylinder leak. Since you are losing fluid, well it’s got to go someplace.

There are really only three possibilities. First, it could be leaking
out of the master cylinder or reservoir. Check around the master cylinder
for any signs of it. Also check your carpet under the dash behind the
brake pedal. Second, it could be leaking along the brake lines or at one
of the wheel calipers. Work the brakes for several minutes with the car
running and parked, then move the car and look for drips. Third, and this
is a bit more difficult to see sometimes, your car has, I believe, a
vacuum operated booster and the there may be a hole in it. This can allow
brake fluid to be sucked into the engine via the vacuum line so you will
not see an external leak. However, you may see white smoke from the
exhaust.

I hope this helps. I would not drive the car like this. I would get it
to the dealer ASAP.

Mike wrote:> Starting the one day I drove it last week, my 2000 XJR evidences the

following brake problem. I will be taking it to the dealer for warranty
work; but would like some ideas before it goes.

On brake application, the pedal feels normal. But, if I hold constant
pressure on the pedal at stop, the car will begin to creep. Adding foot
pressure lowers the pedal and stops the car. If I apply heavy pressure to
the pedal, it will slowly drop from the normal travel stop to the floor over
about 30 seconds.

I added 6 oz. of DOT 4 on Sunday. I drove it for about 25 minutes in stop
and go this morning and it lost about 2 oz.

No warning or other lights. No obvious evidence of dripping or puddles
under the car or on the calipers even after running the pedal to the floor a
couple of times in a garage.

Idea, suggestions?

Michael
'00 XJR BRG
'00 XKR FHC BRG

Michael:

Unless there is something unique about the XJR master cylinder, the problem
is most likely fluid seeping by the main piston seal. (This usually happens
to older vehicles as the rubber parts wear & age). It may not leak out of the
system, just leak around the piston so that pressure is slowly released and
the pedal sinks. The harder you push, the faster it sinks. Pumping the pedal
at long lights is no fun if you get too close to a semi :wink:

I would suggest that you request that the dealer replace the master cylinder.
It is probably easier for them to do that than to rebuild the current one
(install a new seal which is what I would do on my out-of-warranty model).
You might make a note of the number on the existing cylinder (or mark it) to
keep track of what they really do.

Let us know what the “pros” do,
George BalthropOn 1/16/2001, Michael Brown wrote:

Starting the one day I drove it last week, my 2000 XJR
evidences the following brake problem. I will be taking
it to the dealer for warranty work; but would like some
ideas before it goes.

On brake application, the pedal feels normal. But, if I
hold constant pressure on the pedal at stop, the car will
begin to creep. Adding foot pressure lowers the pedal
and stops the car. If I apply heavy pressure to the pedal,
it will slowly drop from the normal travel stop to the floor
over about 30 seconds.

I added 6 oz. of DOT 4 on Sunday. I drove it for about
25 minutes in stop and go this morning and it lost about 2 oz.

No warning or other lights. No obvious evidence of dripping
or puddles under the car or on the calipers even after running
the pedal to the floor a couple of times in a garage.

Thanks, Pete, Gregory and George.

The cat is going to the dealer on Thursday; and I shall not drive it
tomorrow.

I looked again carefully tonight. No drips on the ground, on the carpet or
in the engine bay. Also all the brake line connectors at the calipers are
dry. I will be betting on the master cylinder. But, I will let the list
know.

Let’s see. A master cylinder at 6,800 miles and ten months. Over the next
20 years, that’s . . . .

Michael
'00 XJR BRG
'00 XKR FHC BRG----- Original Message -----
From: JagsXJ40XJSXKE@aol.com
To: modern@jag-lovers.org
Cc: MHB@GDM.com
Sent: Tuesday, January 16, 2001 6:29 PM
Subject: [modern] Re: Brake pressure loss on XJR

Michael:

Unless there is something unique about the XJR master cylinder, the
problem
is most likely fluid seeping by the main piston seal. (This usually
happens
to older vehicles as the rubber parts wear & age). It may not leak out of
the
system, just leak around the piston so that pressure is slowly released
and
the pedal sinks. The harder you push, the faster it sinks. Pumping the
pedal
at long lights is no fun if you get too close to a semi :wink:

I would suggest that you request that the dealer replace the master
cylinder.
It is probably easier for them to do that than to rebuild the current one
(install a new seal which is what I would do on my out-of-warranty model).
You might make a note of the number on the existing cylinder (or mark it)
to
keep track of what they really do.

Let us know what the “pros” do,
George Balthrop

On 1/16/2001, Michael Brown wrote:

Starting the one day I drove it last week, my 2000 XJR
evidences the following brake problem. I will be taking
it to the dealer for warranty work; but would like some
ideas before it goes.

On brake application, the pedal feels normal. But, if I
hold constant pressure on the pedal at stop, the car will
begin to creep. Adding foot pressure lowers the pedal
and stops the car. If I apply heavy pressure to the pedal,
it will slowly drop from the normal travel stop to the floor
over about 30 seconds.

I added 6 oz. of DOT 4 on Sunday. I drove it for about
25 minutes in stop and go this morning and it lost about 2 oz.

No warning or other lights. No obvious evidence of dripping
or puddles under the car or on the calipers even after running
the pedal to the floor a couple of times in a garage.

… that’s bad luck… the bad part in the batch…

It’s not something that comes up often on the list, even from early X300s

Pascal

Let’s see. A master cylinder at 6,800 miles and ten months. Over the
next----- Original Message -----
From: “Michael Brown” michaelbrown@fuse.net
20 years, that’s . . . .

Michael
'00 XJR BRG
'00 XKR FHC BRG

JagsXJ40XJSXKE@aol.com wrote:

Michael:

Unless there is something unique about the XJR master cylinder, the problem
is most likely fluid seeping by the main piston seal. (This usually happens
to older vehicles as the rubber parts wear & age). It may not leak out of the
system, just leak around the piston so that pressure is slowly released and
the pedal sinks. The harder you push, the faster it sinks.

George,

I have to disagree with you just a little. In my experience, if you push
harder on a master that’s going bad, the pedal firms up because the seal
flares out to seal against the bore. A master that’s worn and beginning
to fail almost always exhibits this behavior, that is, pedal falls to
the floor under light pressure but firms up and stops the car under hard
pressure. As time goes on, the pedal will drop under harder and harder
pressure until it won’t firm up at all, regardless of how hard one
pushes.

I did email Michael off-list to say that his problem sounds like a bad
master cylinder to me, too. But after considering that he seems to be
losing fluid, I’m not so certain about it, unless he finds fluid leaking
from the master. It will be interesting to see what the dealer
diagnoses, if Michael will let us know.

Best regards,

Gregory Wells
Coventry West, Inc., Atlanta, GA
New, Rebuilt, & Used Jaguar Parts
http://www.coventrywest.com
800-331-2193 x103

My brake problem was the master cylinder. Replaced on Friday. No details
yet; I did not get to pick her back up.----- Original Message -----
From: “Michael Brown” <@Michael_Brown>
To: JagsXJ40XJSXKE@aol.com; modern@jag-lovers.org
Cc: MHB@GDM.com
Sent: Tuesday, January 16, 2001 9:50 PM
Subject: Re: [modern] Re: Brake pressure loss on XJR

Thanks, Pete, Gregory and George.

The cat is going to the dealer on Thursday; and I shall not drive it
tomorrow.

I looked again carefully tonight. No drips on the ground, on the carpet
or
in the engine bay. Also all the brake line connectors at the calipers are
dry. I will be betting on the master cylinder. But, I will let the list
know.

Let’s see. A master cylinder at 6,800 miles and ten months. Over the
next
20 years, that’s . . . .

Michael
'00 XJR BRG
'00 XKR FHC BRG
----- Original Message -----
From: JagsXJ40XJSXKE@aol.com
To: modern@jag-lovers.org
Cc: MHB@GDM.com
Sent: Tuesday, January 16, 2001 6:29 PM
Subject: [modern] Re: Brake pressure loss on XJR

Michael:

Unless there is something unique about the XJR master cylinder, the
problem
is most likely fluid seeping by the main piston seal. (This usually
happens
to older vehicles as the rubber parts wear & age). It may not leak out
of
the
system, just leak around the piston so that pressure is slowly released
and
the pedal sinks. The harder you push, the faster it sinks. Pumping the
pedal
at long lights is no fun if you get too close to a semi :wink:

I would suggest that you request that the dealer replace the master
cylinder.
It is probably easier for them to do that than to rebuild the current
one
(install a new seal which is what I would do on my out-of-warranty
model).
You might make a note of the number on the existing cylinder (or mark
it)
to
keep track of what they really do.

Let us know what the “pros” do,
George Balthrop

On 1/16/2001, Michael Brown wrote:

Starting the one day I drove it last week, my 2000 XJR
evidences the following brake problem. I will be taking
it to the dealer for warranty work; but would like some
ideas before it goes.

On brake application, the pedal feels normal. But, if I
hold constant pressure on the pedal at stop, the car will
begin to creep. Adding foot pressure lowers the pedal
and stops the car. If I apply heavy pressure to the pedal,
it will slowly drop from the normal travel stop to the floor
over about 30 seconds.

I added 6 oz. of DOT 4 on Sunday. I drove it for about
25 minutes in stop and go this morning and it lost about 2 oz.

No warning or other lights. No obvious evidence of dripping
or puddles under the car or on the calipers even after running
the pedal to the floor a couple of times in a garage.