| [GMCnet] Brake light on and off [message #69074] |
Thu, 31 December 2009 09:56  |
gmc gmc
Messages: 69
Registered: May 2009
Karma: 0
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Good morning again all... Brake fluid is full. When I start and drive brake
light is off, but when I apply brakes at a good or hard stop the brake light
comes on, stays on then... So back in 78 did they put sensors on brakes?
brake pads? or what might it be sensing or complaining about?
thanks
Miek in Houston about to head north! :)
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| Re: [GMCnet] Brake light on and off [message #69076 is a reply to message #69074] |
Thu, 31 December 2009 10:05  |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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| gmc gmc wrote on Thu, 31 December 2009 08:56 |
Good morning again all... Brake fluid is full. When I start and drive brake
light is off, but when I apply brakes at a good or hard stop the brake light
comes on, stays on then... So back in 78 did they put sensors on brakes?
brake pads? or what might it be sensing or complaining about?
thanks
Miek in Houston about to head north! 
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That means you have an issue between front and rear pressures--possibly because of a leak or defective master cylinder. The proportioning valve (which in this case is not a proportioning valve but a differential pressure and hold-off valve)is setting the light indicating a problem.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] Brake light on and off [message #69095 is a reply to message #69084] |
Thu, 31 December 2009 12:31 |
gmc gmc
Messages: 69
Registered: May 2009
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can we drive home TX to WI tomorrow, alto of highway Interstate driving you
all feel?
On Thu, Dec 31, 2009 at 11:45 AM, John Wright <powwerjon@gmail.com> wrote:
> Bob is correct, you have a real issue with your braking system.
>
> The combination valve which is located in the drivers side front wheel well
> is setting the brake alarm because of an imbalance between the front and
> rear brakes. This can be caused by the failure of the master cylinder, or
> a
> leak in the rear braking system, either a leaking cylinder or line leaking
> or a leak in the front braking system. My first opinion is that you
> probably have a bad master cylinder seeing you say the fluid level is not
> changing. Have you added any fluid lately?
>
> If you can find an Autozone you can get a master cylinder part# nm1730 it
> is listed for a 74 chevy C30 PU 2WD 5.7 eng. It is a new piece made by
> Fernco. If other have a better part# for the 78 coach please list.
>
> J.R. Wright
>
> On Thu, Dec 31, 2009 at 10:56 AM, gmc gmc <gmc@derr.ws> wrote:
>
> > Good morning again all... Brake fluid is full. When I start and drive
> brake
> > light is off, but when I apply brakes at a good or hard stop the brake
> > light
> > comes on, stays on then... So back in 78 did they put sensors on brakes?
> > brake pads? or what might it be sensing or complaining about?
> >
> > thanks
> >
> > Miek in Houston about to head north! :)
> > _______________________________________________
> > GMCnet mailing list
> > List Information and Subscription Options:
> > http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
> >
> _______________________________________________
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| Re: [GMCnet] Brake light on and off [message #69107 is a reply to message #69095] |
Thu, 31 December 2009 14:25 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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""can we drive home TX to WI tomorrow, alto of highway Interstate driving you
all feel?""
It doesn't take much to activate the light. How do the brakes feel? If they feel OK, then you're probably OK
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] Brake light on and off [message #69108 is a reply to message #69095] |
Thu, 31 December 2009 14:50 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Mike,
Here's what GMC had to say about the light in the Operating Manual.
QUOTE:
BRAKE SYSTEM WARNING LIGHT
The service brake system is a dual system designed so that one part will
provide some braking action in the event of loss of hydraulic pressure in
the other part of the system. If the red warning light labeled "BRAKE"
located to the left of the oil pressure gauge, comes on and stays on when
the ignition is on and after the brakes have been firmly applied, it may
indicate that there is a malfunction in one part of the brake system.
* The light is designed to come on during engine starting to verify that the
bulb is operating properly.
* Have the system repaired if the light does not come on during check.
* The warning light is not a substitute for the visual check of brake fluid
level required as part of normal maintenance.
IF THE LIGHT COMES ON:
1) Pull off the road and stop, carefully - remembering that:
* Stopping distance may be greater
* Grater pedal effort may be required.
* Pedal travel may be greater.
2) Try out brake operation by starting and stopping on the shoulder of the
road - then:
* If you judge such operation to be safe, proceed cautiously at a safe speed
to the nearest service outlet for repair, or
* Have vehicle towed to dealer for repair
Continued operation of the vehicle in this condition is dangerous.
UNQUOTE
It's your call if you want to risk it!
Good luck,
Rob Mueller
Sydney, Australia
AUS '75 Avion-The Blue Streak TZE365V100428
USA '75 Avion-Double Trouble TZE365V100426
-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org
[mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of gmc gmc
Sent: Friday, 1 January 2010 5:31 AM
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] Brake light on and off
can we drive home TX to WI tomorrow, alto of highway Interstate driving you
all feel?
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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