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Symptoms of a bad brake booster?

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jblackburn
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Symptoms of a bad brake booster?

Postby jblackburn » Mon Mar 05, 2012 5:58 pm

Since Saturday, my brakes just feel like they're not grabbing. They still hit the ABS - albeit, just barely - a few pulses - if you smash your foot down on the pedal, but I feel like it just needs more effort in normal driving - almost like stopping with wet rotors, but the roads are dry. Bad vacuum line? Check valve maybe?

I had a bad booster once on my Saab (when I'd just started driving), and they were so bad I blew through an intersection when a light turned yellow pretty far before the intersection. The Volvo's are nowhere near that bad, but I did find myself having to mash on the pedal when it wasn't slowing enough.
'98 S70 T5
2012 Chevy Cruze LT 6MT


A learning experience is one of those things that says, "You know that thing you just did? Don't do that."

mercuic: Long live the tractor motor!

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regent
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Re: Symptoms of a bad brake booster?

Postby regent » Mon Mar 05, 2012 7:02 pm

If the membrane in the booster is ruptured you will loose the brake assist; without it you would need about a dozen times 'heavier foot' on the pedal to achieve the required breaking effort. If you are unprepared, it feels like you have no brakes. I have had that happen to me in the past on a different europen make. :o
Thanks for sharing
Example of Precision: Measure with a Micrometer, mark it with Chalk, and then cut it with an Axe.
Disclaimer: We (very) seldom do that

2002 S60 2.4 non-turbo - lovely!
1987 340 DL (with the 4-cyl N/A Renault Diesel engine, 5-speed manual, RWD) - sold (I wish I did not have to...)

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jblackburn
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Re: Symptoms of a bad brake booster?

Postby jblackburn » Mon Mar 05, 2012 7:05 pm

So it would really feel like I had nothing for stopping power if the booster itself went bad, right?

Did yours make any strange noises or anything?
'98 S70 T5
2012 Chevy Cruze LT 6MT


A learning experience is one of those things that says, "You know that thing you just did? Don't do that."

mercuic: Long live the tractor motor!

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regent
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Re: Symptoms of a bad brake booster?

Postby regent » Mon Mar 05, 2012 7:11 pm

It 'feels' like that because you expect it to behave differently.
If you had a bad check valve, your booster would still work, however it would lose vacuum as soon as the engine stops. With everything working 100%, you should have sufficient vacuum for 2-3 brake applications after you switch off the engine.
I would start by eliminating the vacuum lines first.

As far as noises, you may be able to hear a hissing sound from the booster if there is a small leak in it, but then you should have 'some" partial boost.
Example of Precision: Measure with a Micrometer, mark it with Chalk, and then cut it with an Axe.
Disclaimer: We (very) seldom do that

2002 S60 2.4 non-turbo - lovely!
1987 340 DL (with the 4-cyl N/A Renault Diesel engine, 5-speed manual, RWD) - sold (I wish I did not have to...)

User avatar
jblackburn
MVS Moderator
Posts: 13895
Joined: Sun Jun 08, 2008 9:54 pm
Year and Model: 1998 S70 T5
Location: Alexandria, VA
Contact:

Re: Symptoms of a bad brake booster?

Postby jblackburn » Mon Mar 05, 2012 7:16 pm

Makes sense! Thanks.
'98 S70 T5
2012 Chevy Cruze LT 6MT


A learning experience is one of those things that says, "You know that thing you just did? Don't do that."

mercuic: Long live the tractor motor!

User avatar
jblackburn
MVS Moderator
Posts: 13895
Joined: Sun Jun 08, 2008 9:54 pm
Year and Model: 1998 S70 T5
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Re: Symptoms of a bad brake booster?

Postby jblackburn » Mon Mar 05, 2012 10:11 pm

It is indeed a vacuum leak. That hose was replaced 3 years ago, but it ripped near the clamp.

Got a Check Engine light confirming that too...the first in 2 years :(

I got a piece of hose and will put it on tomorrow when it's not freaking 30 and snowing sideways at 20 mph.
'98 S70 T5
2012 Chevy Cruze LT 6MT


A learning experience is one of those things that says, "You know that thing you just did? Don't do that."

mercuic: Long live the tractor motor!

User avatar
regent
Posts: 1135
Joined: Tue Feb 23, 2010 1:34 am
Year and Model: 2002 S60 2.4
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Re: Symptoms of a bad brake booster?

Postby regent » Mon Mar 05, 2012 10:53 pm

Glad you sorted it.
What a great benefit it is having the luxury of choosing when to do a job...
:)
Example of Precision: Measure with a Micrometer, mark it with Chalk, and then cut it with an Axe.
Disclaimer: We (very) seldom do that

2002 S60 2.4 non-turbo - lovely!
1987 340 DL (with the 4-cyl N/A Renault Diesel engine, 5-speed manual, RWD) - sold (I wish I did not have to...)

User avatar
jblackburn
MVS Moderator
Posts: 13895
Joined: Sun Jun 08, 2008 9:54 pm
Year and Model: 1998 S70 T5
Location: Alexandria, VA
Contact:

Re: Symptoms of a bad brake booster?

Postby jblackburn » Wed Mar 07, 2012 5:24 pm

FIXED! I have good brakes again!!!

Too bad something simple like that won't un-warp my front rotors :(
'98 S70 T5
2012 Chevy Cruze LT 6MT


A learning experience is one of those things that says, "You know that thing you just did? Don't do that."

mercuic: Long live the tractor motor!

User avatar
regent
Posts: 1135
Joined: Tue Feb 23, 2010 1:34 am
Year and Model: 2002 S60 2.4
Location: USA
Flag: United States of America

Re: Symptoms of a bad brake booster?

Postby regent » Wed Mar 07, 2012 10:52 pm

I bought an unwarping kit for mine from FCP, and it worked right out of the box!
Example of Precision: Measure with a Micrometer, mark it with Chalk, and then cut it with an Axe.
Disclaimer: We (very) seldom do that

2002 S60 2.4 non-turbo - lovely!
1987 340 DL (with the 4-cyl N/A Renault Diesel engine, 5-speed manual, RWD) - sold (I wish I did not have to...)

User avatar
jblackburn
MVS Moderator
Posts: 13895
Joined: Sun Jun 08, 2008 9:54 pm
Year and Model: 1998 S70 T5
Location: Alexandria, VA
Contact:

Symptoms of a bad brake booster?

Postby jblackburn » Wed Mar 07, 2012 11:00 pm

I've heard people say changing their blinker fluid makes a huge difference as well ;)
'98 S70 T5
2012 Chevy Cruze LT 6MT


A learning experience is one of those things that says, "You know that thing you just did? Don't do that."

mercuic: Long live the tractor motor!


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