[xj] Odd sound from brake pedal

I step on the brake pedal and all is normal. When I let up on the
brake pedal it sounds like I just stepped on an frog. I hope this
description makes sense to someone.–
John: 87 XJ6
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In reply to a message from Neatherd sent Sat 26 Jan 2008:

Sometimes springs or the cover boot make some noise.

                                   Walter--

The original message included these comments:

I step on the brake pedal and all is normal. When I let up on the
brake pedal it sounds like I just stepped on an frog. I hope this
description makes sense to someone.


Walter Schuster 78XJ6L FI Ser.II, 69E Ser.II 2+2original
Albuquerque/New Mexico, United States
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I’ll throw this in for what it’s worth…I got that syndrom on the S3
comming up the Alcan in winter…also felt like the pedal was coming
up against a restriction.
The brakes worked fine,except for that.
Then i noticed the fluid was way low…when i added fluid everything
was normal.
My guess was that the brake fluid had ice crystals in it and it was
bypassing the brake cup in the master cyl., “or something”
Or it was jammed a little and getting air around the cup.The groan
was air coming in or fluid going out.
How’s the fluid level in both resevoirs (front and back)?
None of this makes sense to me…but that’s what happened.
No more trouble ever since, even at below zero Far.
Are you, your children, or your neighbors missing any frogs?
Bill
'86 v12 vdp
AlaskaOn Jan 25, 2008, at 3:41 PM, Neatherd wrote:

I step on the brake pedal and all is normal. When I let up on the
brake pedal it sounds like I just stepped on an frog. I hope this
description makes sense to someone.


John: 87 XJ6

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Neatherd wrote:

I step on the brake pedal and all is normal. When I let up on the
brake pedal it sounds like I just stepped on an frog. I hope this
description makes sense to someone.

Not me, John - I never stepped on one…:slight_smile:

There should be a hiss of air as the pedal is depressed, but nothing as
it is released. Nothing for it but stopping the engine for a better
listen while operating the pedal. It’s essential to first locate the
noise to either underdash or in the engine compartment. It may be
something rubbing, or noise of vacuum extracted from servo - or possibly
reservoir noise. But it shoudn’ be there - and nor should a frog…:slight_smile:

I’d dearly love to get the answer to this one, John…:slight_smile:

Frank
xj6 85 Sov Eirope (UK/NZ)===================================================
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In reply to a message from Frank Andersen sent Sat 26 Jan 2008:

It started back when I had a leaky rear caliper. So the air in the
system thing makes some sense. However I used a bleeding pump and
pulled brake fluid through the system until I got fresh clean
fluid. It was better after the brake work but with the very cold
weather it is now more pronounced.

Could the master cylinder have gotten air caught in it and a system
bleed from the calipers would not have gotten it out? Or could have
the air damaged an O-ring or packing?

I have heard there is a brake booster somewhere. My main concerns
is that it may be going bad. That is not a friendly thought. But,
in both the manual and parts book I cannot find a brake booster and
bellows anywhere.–
John: 87 XJ6
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I have heard there is a brake booster somewhere. My main concerns
is that it may be going bad. That is not a friendly thought. But,
in both the manual and parts book I cannot find a brake booster and
bellows anywhere.


John: 87 XJ6

G’day John,
Jaguar call it a servo. In my CD-ROM version of the green book the test
procedure is operation no. 70.50.05 on page 70-7.
regards,
John Hudson
Brisbane Australia
71 SI XJ6, 85 SIII XJ6----- Original Message -----
From: “Neatherd” neatherd@yahoo.com
To: xj@jag-lovers.org
Sent: Saturday, January 26, 2008 11:31 PM
Subject: Re: [xj] Odd sound from brake pedal

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Neatherd wrote:

In reply to a message from Frank Andersen sent Sat 26 Jan 2008:

It started back when I had a leaky rear caliper. So the air in the
system thing makes some sense. However I used a bleeding pump and
pulled brake fluid through the system until I got fresh clean
fluid. It was better after the brake work but with the very cold
weather it is now more pronounced.

Could the master cylinder have gotten air caught in it and a system
bleed from the calipers would not have gotten it out? Or could have
the air damaged an O-ring or packing?

I have heard there is a brake booster somewhere. My main concerns
is that it may be going bad. That is not a friendly thought. But,
in both the manual and parts book I cannot find a brake booster and
bellows anywhere.

You can’t possibly miss the brake booster, John - it’s a huge round
thing immediately behind, and attached to, the master cylinder. And
listening there may, just may, tell something…:slight_smile:

Two things; with any air in the system the pedal will be so
characteristically spongy that it cannot be missed. And; the ms may leak
brake fkuid into the booster, and accumulated it may ‘slurp’ as the
liquid is drawn out when air is drawn out of the booster after braking.

Though; while such leaking is not unknown, noises like that is not - but
listening at the booster may tell. There is no sure-fire way of
detecting, and cure, such a leak except by dismantling - abnormal drop
in reservoir fluid level would be an indication, of course. And you can
disconnect the one-way valve (a possible noise source as well) in the
brake booster air line and see if it is drenched in brake fluid…

If the brakes are otherwise working well, it’s unlikely to cause a
sudden collapse, but on the other hand; any brake anomaly should be
treated with respect. Like an effort to precisely locate the place of
the noise, if not the cause. Also; if the noise is always there, or only
with the engine running or while car is moving - and permutations…?

Frank
xj6 85 Sov Europe (UK/NZ)===================================================
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In reply to a message from Frank Andersen sent Sun 27 Jan 2008:

We had nice weather today, up to 45F. So, I got out and took a
look. I noticed some loose clamps on the vac sys and tightened
those. When compressing the brake pedal, fluid bubbles up in the
rear of the reservoir. Is this normal, I have not noticed it before.

The fluid is full, so no leaks and no fluid in the vac sys
connections. The sound is far less than it was at 0F so cold may be
a major factor. The sound is still there but not really noticeable
unless listening for it. So maybe just something rubbing a bit.
Sounds like a spring todo list item.–
John: 87 XJ6
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Neatherd wrote:

In reply to a message from Frank Andersen sent Sun 27 Jan 2008:

We had nice weather today, up to 45F. So, I got out and took a
look. I noticed some loose clamps on the vac sys and tightened
those. When compressing the brake pedal, fluid bubbles up in the
rear of the reservoir. Is this normal, I have not noticed it before.

The fluid is full, so no leaks and no fluid in the vac sys
connections. The sound is far less than it was at 0F so cold may be
a major factor. The sound is still there but not really noticeable
unless listening for it. So maybe just something rubbing a bit.
Sounds like a spring todo list item.

It doesn’t sound like like it requires immediate action, John - drive
on…:slight_smile:

And some activity in the brake fluid reservoir while pedal is moving is
perfectly normal…

Frank
xj6 85 Sov Europe (UK/NZ)===================================================
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