Home » Public Forums » GMCnet » Brakes Help Needed (GM (not so much C) related)
| Brakes Help Needed [message #247241] |
Sat, 12 April 2014 13:15  |
Gary Mau
Messages: 152
Registered: February 2004
Location: Davenport, Iowa
Karma: 0
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Senior Member |
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Brakes on my 98 Chevy Blazer seemed to be getting softer over time. Pedal with engine not running was pretty solid but with engine running sank to where I didn't feel comfortable. Double checked the non running pedal and over several seconds it would slowly sink toward the floor so I decided to replace the master cylinder as they are not expensive and not tough to replace.
I bench bled per the instructions, and installed the NEW (not rebuilt or remanned) master cylinder. Checked the pedal with the engine not running and it felt good and didn't seem to sink over time. Started the engine and the pedal essentially went to the floor. I then bled the brakes at all four wheels and saw no improvement in the pedal essentially going to the floor. I did not replace all the fluid in the lines, only looked for bubbles at the wheel cylinders. Also, this is an ABS system.
All help will be much appreciated.
Gary Mau
Former 76 Royale owner
Davenport, IA
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| Re: Brakes Help Needed [message #247242 is a reply to message #247241] |
Sat, 12 April 2014 14:01  |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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Senior Member |
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| Gary Mau wrote on Sat, 12 April 2014 12:15 |
Brakes on my 98 Chevy Blazer seemed to be getting softer over time. Pedal with engine not running was pretty solid but with engine running sank to where I didn't feel comfortable. Double checked the non running pedal and over several seconds it would slowly sink toward the floor so I decided to replace the master cylinder as they are not expensive and not tough to replace.
I bench bled per the instructions, and installed the NEW (not rebuilt or remanned) master cylinder. Checked the pedal with the engine not running and it felt good and didn't seem to sink over time. Started the engine and the pedal essentially went to the floor. I then bled the brakes at all four wheels and saw no improvement in the pedal essentially going to the floor. I did not replace all the fluid in the lines, only looked for bubbles at the wheel cylinders. Also, this is an ABS system.
All help will be much appreciated.
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Gary, it sounds like you may have a leak in the system--either in a line or wheelcylinder (rear). Are you seeing any fluid on the ground after repeated cycles? It's possible that the new master cylinder is not completely bled--it takes a lot of pumps to really bleed it. If the pedal slowly sinks with applied force, then it most likely is a leak. Is the reservoir losing fluid after repeated pumps?
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] Brakes Help Needed [message #247251 is a reply to message #247241] |
Sat, 12 April 2014 14:39 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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Gary, had a similar issue with a Chevrolet S-10 P.U. Turned out to be the
ABS unit had some air in it from when we replaced the M.C. A local G.M.
tech hooked up his computer interface to it and it whirled a bit and then
quit altogether. New ABS unit was crazy money, so we made a trip to pick a
part and salvaged one from another S-10. Back to the tech guy, this time
success. I hate stuff that I have to trust to others for repairs. But as
the instructions say, "No user serviceable parts inside. "
Just what I encountered, your experience might be different.
Jim Hupy
Salem, Or
78 GMC ROYALE 403
On Apr 12, 2014 11:16 AM, "Gary Mau" <garyemau@aol.com> wrote:
>
>
> Brakes on my 98 Chevy Blazer seemed to be getting softer over time.
> Pedal with engine not running was pretty solid but with engine running
> sank to where I didn't feel comfortable. Double checked the non running
> pedal and over several seconds it would slowly sink toward the floor so I
> decided to replace the master cylinder as they are not expensive and not
> tough to replace.
> I bench bled per the instructions, and installed the NEW (not rebuilt or
> remanned) master cylinder. Checked the pedal with the engine not running
> and it felt good and didn't seem to sink over time. Started the engine
> and the pedal essentially went to the floor. I then bled the brakes at all
> four wheels and saw no improvement in the pedal essentially going to the
> floor. I did not replace all the fluid in the lines, only looked for
> bubbles at the wheel cylinders. Also, this is an ABS system.
>
> All help will be much appreciated.
> --
> Gary Mau
> 76 Royale
> Davenport, IA
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
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| Re: Brakes Help Needed [message #247256 is a reply to message #247241] |
Sat, 12 April 2014 15:18 |
Gary Mau
Messages: 152
Registered: February 2004
Location: Davenport, Iowa
Karma: 0
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Bob,
Pretty sure the new master cylinder was thoroughly bled, no bubbles, etc. I don't seem to have any leaks. The pedal is nice and solid until I start the engine, then I drops drastically. Same problem I started out with only worse after the new master.
Jim,
This is an S10 Blazer. I'm hoping you are not on the money and someone else will have something easier/cheaper. To get this to a GM tech means a tow and a big bill on top of that. I'm like you, I hate things I have to trust to others for repairs. Could be the ABS, as I had somewhat the same problem before the new master only now it's worse (not driveable).
Thanks guys!
Gary Mau
Former 76 Royale owner
Davenport, IA
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| Re: Brakes Help Needed [message #247259 is a reply to message #247256] |
Sat, 12 April 2014 15:40 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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Senior Member |
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| Gary Mau wrote on Sat, 12 April 2014 14:18 |
Bob,
Pretty sure the new master cylinder was thoroughly bled, no bubbles, etc. I don't seem to have any leaks. The pedal is nice and solid until I start the engine, then I drops drastically. Same problem I started out with only worse after the new master.
Jim,
This is an S10 Blazer. I'm hoping you are not on the money and someone else will have something easier/cheaper. To get this to a GM tech means a tow and a big bill on top of that. I'm like you, I hate things I have to trust to others for repairs. Could be the ABS, as I had somewhat the same problem before the new master only now it's worse (not driveable).
Thanks guys!
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The fact that the pedal drops upon starting is due to the extra assist when the booster gets vacuum. It still suggests air, external leakage, or internal leakage. Jim H may be right.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] Brakes Help Needed [message #247261 is a reply to message #247256] |
Sat, 12 April 2014 15:44 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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Gary, if you look at the top of the ABS box, you will find some bleeder
screws. The tech activated the ABS through the
obd ll connector and opened those bleeder screws with a bleeder line and
catch can attached. As I recall, fluid came out in pulses or squirts. There
are either solenoid plungers or pistons or similar devices inside that
rapidly pulse your brakes when front and rear wheel rotation is enough
different to trigger the system. The brake guys I know, replace, not repair
the whole ABS device when bad stuff happens to them. If you really want a
shock, price them out. Scary, but that is why these modern braking systems
work so much better than early models without it.
Jim Hupy
Salem, Or.
78 GMC ROYALE 403
On Apr 12, 2014 1:18 PM, "Gary Mau" <garyemau@aol.com> wrote:
>
>
> Bob,
> Pretty sure the new master cylinder was thoroughly bled, no bubbles,
> etc. I don't seem to have any leaks. The pedal is nice and solid until I
> start the engine, then I drops drastically. Same problem I started out
> with only worse after the new master.
>
> Jim,
>
> This is an S10 Blazer. I'm hoping you are not on the money and someone
> else will have something easier/cheaper. To get this to a GM tech means a
> tow and a big bill on top of that. I'm like you, I hate things I have to
> trust to others for repairs. Could be the ABS, as I had somewhat the same
> problem before the new master only now it's worse (not driveable).
>
> Thanks guys!
> --
> Gary Mau
> 76 Royale
> Davenport, IA
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
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