[E-Type] Brake lag

Any thoughts on cause of slow response of full braking and release on
Series 3? I notice when I brake that the grab goes from an unassited
power feel to full braking. When I release the pedal, I notice the pads
hold momentarily, and then release…this is only noticed at a stop on an
incline. I feel the brakes release and then it begins to roll. I’m sure
the same effect occurs at speed but would not be evident as it is not a
strong hold. I don’t think it’s the master, but may be the unit in front
of the master?
thanks, max

Search the archives & forums - http://search.jag-lovers.org/
Subscription changes - http://www.jag-lovers.com/cgi-bin/majordomo

On 19/09/2003, max azevedo told us:

Any thoughts on cause of slow response of full braking and release on
Series 3? I notice when I brake that the grab goes from an unassited
power feel to full braking. When I release the pedal, I notice the pads
hold momentarily, and then release…this is only noticed at a stop on an
incline. I feel the brakes release and then it begins to roll. I’m sure
the same effect occurs at speed but would not be evident as it is not a
strong hold. I don’t think it’s the master, but may be the unit in front
of the master?

This is a common problem, but there seems to be a bit of doubt about the
causes.

I think it is usually caused by the reaction valve on the end of the master
cylinder. On my car, after I had the cylinder sleeved, the little reaction
piston was a rather tight fit in the bore, and I think this caused the
delay on releasing the brake. It seemed to fix itself after about 5000
miles use.

I only noticed that it was ‘fixed’ after bleeding the rear brakes with a
power bleeder, which firmed up the pedal, so maybe having a little air in
the rear circuit makes the problem worse?

regards,
Mike Morrin

Search the archives & forums - http://search.jag-lovers.org/
Subscription changes - http://www.jag-lovers.com/cgi-bin/majordomo

In reply to a message from max azevedo sent Fri 19 Sep 2003:

Max,
Since it’s apparently reacting slowly on both application and
release, I’d be suspicious of something binding in the booster.
Other candidates are a collapsed vacuum hose, the little piston in
the nose of the master cylinder that drives the reaction valve is
sticking, or a sticky caliper. I think a master cylinder problem
is unlikely, as that most commonly shows up as a slow release only.
You should be able to determine if it’s the little piston or
not by putting a vacuum gauge on the hose from the reaction valve
to the back side of the booster. As soon as you press the brake,
that pressure should rise immediately. As soon as you release the
pedal, it should drop immediately. The hose feeding the front side
of the booster should have full manifold vacuum at all times.
Any time the pedal is released, the pressure on both sides of the
booster should be identical. If there’s a delay in either, or the
pressures front and back do not match when the pedal is released,
then it’s either the little piston or the reaction valve itself.
Otherwise, it’s the booster, servo cylinder, or a wheel cylinder.–
Ray Livingston
Santa Cruz, CA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

Search the archives & forums - http://search.jag-lovers.org/
Subscription changes - http://www.jag-lovers.com/cgi-bin/majordomo

ray, thanks for the pointers,
max

Search the archives & forums - http://search.jag-lovers.org/
Subscription changes - http://www.jag-lovers.com/cgi-bin/majordomo

In reply to a message from max azevedo sent Fri 19 Sep 2003:

That’s probably caused by air in the system. Needs more bleeding.
several times after some driving.
Walter Schuster–
Walter Schuster 69E/78XJ6
Albuquerque/New Mexico, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

Search the archives & forums - http://search.jag-lovers.org/
Subscription changes - http://www.jag-lovers.com/cgi-bin/majordomo

In reply to a message from max azevedo sent Fri 19 Sep 2003:

Max,
Since it’s apparently reacting slowly on both application and
release, I’d be suspicious of something binding in the booster.
Other candidates are a collapsed vacuum hose, the little piston in
the nose of the master cylinder that drives the reaction valve is
sticking, or a sticky caliper. I think a master cylinder problem
is unlikely, as that most commonly shows up as a slow release only.

My master cylinder is new (2 years) but I have slow releasing brakes. When
the pedal is released, the brakes remain engaged for 2 - 3 seconds. Very
irritating.
I’m going to replace the vaccum lines today and see if that helps.
Is it likely I have to do something to the master cylinder???
I sure hope not.— Ray Livingston rayl@atc.creative.com wrote:


Do you Yahoo!?
Yahoo! SiteBuilder - Free, easy-to-use web site design software
http://sitebuilder.yahoo.com

Search the archives & forums - http://search.jag-lovers.org/
Subscription changes - http://www.jag-lovers.com/cgi-bin/majordomo

In reply to a message from Paul Ward sent Sun 21 Sep 2003:

Paul,
My message to Max outlined the most likely causes. You should
perform the same test on the vacuum system I outlined there. That
will tell you if it’s the master cylinder or not. Unfortunately,
that little bitty piston in the nose of the master cylinder seems
to be somewhat problematic at times…–
The original message included these comments:

Is it likely I have to do something to the master cylinder???
I sure hope not.


Ray Livingston
Santa Cruz, CA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

Search the archives & forums - http://search.jag-lovers.org/
Subscription changes - http://www.jag-lovers.com/cgi-bin/majordomo

Any thoughts on cause of slow response of full braking and release on
Series 3? I notice when I brake that the grab goes from an unassited
power feel to full braking. When I release the pedal, I notice the pads
hold momentarily, and then release…

My series 2 showed the same symptoms, only worse. My brakes would stay
engaged for two, maybe three seconds before releasing. After driving it
last Friday, I decided not to drive it until I fixed the problem. It seemed
to be getting worse with time and it was no good to have to wait for the
brakes to release before leaving a stop light.

Since replacing the vacuum hoses was easiest, I did that first.
I was using clear vinyl hose that was reinforced with nylon thread. Its the
same stuff you see in any good hardware store.
One or two sections of it appeared to be pretty flat. After replacing all
the hoses with 3/8 rubber vacuum hose (it looks like regular gas line to me)
the problem is completely gone!!
The brakes work perfectly now.
If any of your hoses look like they might be getting sucked flat by the
vacuum, replace them.
I suppose some hoses might be going flat under full vacuum when the engine
is running but might look fine when the engine is off.
I sure am happy that was it and I don’t have to pull the master cylinder.
Paul Ward
69 FHC— max azevedo maze87@juno.com wrote:


Do you Yahoo!?
Yahoo! SiteBuilder - Free, easy-to-use web site design software
http://sitebuilder.yahoo.com

Search the archives & forums - http://search.jag-lovers.org/
Subscription changes - http://www.jag-lovers.com/cgi-bin/majordomo

In reply to a message from Paul Ward sent Mon 22 Sep 2003:

Vacuum hose is to normal hose as arteries are to veins - i.e. much
more muscular and less floppy. They may look the same from the
outside on casual inspection but they are not the same at all and
not interchangeable. Easy mistake to make I suppose, but I don’t
think I’ve ever seen clear vacuum hose. I could be wrong.–
Peter Crespin 94 X300 Daimler / 67 2+2 ‘E’
Buxton, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

Search the archives & forums - http://search.jag-lovers.org/
Subscription changes - http://www.jag-lovers.com/cgi-bin/majordomo

Vacuum hose is to normal hose as arteries are to veins - i.e. much
more muscular and less floppy.

I agree totally. If you examine the vinyl reinforced hose, it seems pretty
stout. It is hard to squeeze and surely seems like it would take the
vacuum. I think when it heated up in the engine compartment, much of it’s
strength was lost.
Also, not all rubber hose is created equal. I have had some of those that
were too light and too flexible to be used for vacuum service.

Paul Ward
69 FHC— Peter Crespin jag@thewritersbureau.com wrote:


Do you Yahoo!?
Yahoo! SiteBuilder - Free, easy-to-use web site design software
http://sitebuilder.yahoo.com

Search the archives & forums - http://search.jag-lovers.org/
Subscription changes - http://www.jag-lovers.com/cgi-bin/majordomo

In reply to a message from Paul Ward sent Mon 22 Sep 2003:

You should assume NO rubber hose is suitable, unless it is
specifically sold as vacuum hose. That stuff is constructed quite
differently from fuel line, vent hose etc etc. The nearest you
would come in terms of wall/lumen proprtions would be flexible
rubber brake hose, but stick to vacuum hose and if it’s not that,
then expect trouble at some point. I don’t remember exactly but
doesn’t vacuum hose have some kind of a colour stripe or visible
external ID on it, or am I getting mixed up with my welding hoses?–
Peter Crespin 94 X300 Daimler / 67 2+2 ‘E’
Buxton, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

Search the archives & forums - http://search.jag-lovers.org/
Subscription changes - http://www.jag-lovers.com/cgi-bin/majordomo