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Pulsing brake pedal, part deux #282846
04/09/09 06:10 PM
04/09/09 06:10 PM
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central PA
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mopartial Offline OP
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I followed the other thread closely. 99 Dakota 4WD. My pedal pulses vigorously and brakes can shake vehicle to a stop. I do not think warped rotor(s): 1)I do not unevenly or over torque rotors. 2)I do not feel any shimmy in steering wheel upon braking. 3)And with a bad rotor, if you turn wheel by hand you can feel it grab-go, grab-go, grab-go...

So I looked to rear. Put rear axle on jackstands, truck in gear, apply brake, NO pulsation at all. I was thinking if its a drum, I will still have it applying rear brakes like this...

Where is my pulsing pedal coming from?

Last edited by mopartial; 04/09/09 06:12 PM.

If it aint broke, dont break it.
Re: Pulsing brake pedal, part deux [Re: mopartial] #282847
04/09/09 06:40 PM
04/09/09 06:40 PM
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Lincoln Nebraska
RapidRobert Offline
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This is not ABS right? I'd go back to the front rotors & recheck them (runout)


live every 24 hour block of time like it's your last day on earth
Re: Pulsing brake pedal, part deux [Re: RapidRobert] #282848
04/10/09 12:08 PM
04/10/09 12:08 PM
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mopartial Offline OP
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When its a bad rotor, I always feel it in the steering wheel when braking. But not now, its only at the pedal...


If it aint broke, dont break it.
Re: Pulsing brake pedal, part deux [Re: mopartial] #282849
04/10/09 12:20 PM
04/10/09 12:20 PM
Joined: Dec 2007
Posts: 7,759
So Cal
HealthServices Offline
Why would you even post that?
HealthServices  Offline
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If it is pulsating pedal it is most likely the rear brakes. Is it disc in the rear? What is the run out? Note grease/oil on shoes will have a affect on brakes as well. The axle seals ok?


Allen Here's a novel idea, let's not throw a bunch of parts at the car hoping it will fix the problem and instead spend a little time diagnosing it first. Life was a little easier when I was just a wrench.
Re: Pulsing brake pedal, part deux [Re: HealthServices] #282850
04/10/09 12:40 PM
04/10/09 12:40 PM
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central PA
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mopartial Offline OP
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Rear drums. I could replace em but I hate changing parts without knowing whats wrong. When I jacked up rear I couldnt feel it which is why Im not so sure...


If it aint broke, dont break it.
Re: Pulsing brake pedal, part deux [Re: mopartial] #282851
04/10/09 12:46 PM
04/10/09 12:46 PM
Joined: Dec 2007
Posts: 7,759
So Cal
HealthServices Offline
Why would you even post that?
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Unless you have a brake lathe there is no easy way to check runnout.


Allen Here's a novel idea, let's not throw a bunch of parts at the car hoping it will fix the problem and instead spend a little time diagnosing it first. Life was a little easier when I was just a wrench.
Re: Pulsing brake pedal, part deux [Re: mopartial] #282852
04/10/09 12:47 PM
04/10/09 12:47 PM
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Hummelstown, PA
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AINTNRT Offline
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If you think it's in the rear brakes, try applying the emergency brake while driving. Just make sure to have your hand on the release handle and the release pulled so as soon as you take your foot off the e-brake pedal the e-brake releases. Also don't do it in traffic, use common sense! Although I'd bet it is in the front.

Re: Pulsing brake pedal, part deux [Re: AINTNRT] #282853
04/10/09 02:45 PM
04/10/09 02:45 PM
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Chino Valley
RodStRace Offline
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You think it's not a lot of things but don't know what it is?
This is the dirtball way to check when you are SURE it's not the rotors but don't know what it is...
Find a SAFE place to do the following:
Take a pair of vice grips and pinch off the rear brake hose. Test drive it. Remove the vice grips and pinch off the right front brake hose. Test it. Now move them to the LF. At this point, you should have a good idea where it's coming from.
BTW, you also have to replace the hoses you just crimped!

Re: Pulsing brake pedal, part deux [Re: RodStRace] #282854
04/10/09 03:07 PM
04/10/09 03:07 PM
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mopartial Offline OP
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Thats a great method except for the ruined hoses part...

If I had a brake lathe I wouldnt be asking for advice here. Maybe the mechanic I know will check em for me. I dont usually have em turned anymore cause labor cost = price of new. And if I just start replacing things, then Im a "parts changer".

Last edited by mopartial; 04/10/09 03:08 PM.
Re: Pulsing brake pedal, part deux [Re: mopartial] #282855
04/10/09 03:19 PM
04/10/09 03:19 PM
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So Cal
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Since it is a 99 you should be able to use a tool made for the factory soft hoses and get away with it. Just don't over tighten.

5155886-DSC04234.JPG (38 downloads)

Allen Here's a novel idea, let's not throw a bunch of parts at the car hoping it will fix the problem and instead spend a little time diagnosing it first. Life was a little easier when I was just a wrench.
Re: Pulsing brake pedal, part deux [Re: RodStRace] #282856
04/10/09 03:22 PM
04/10/09 03:22 PM
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Lincoln Nebraska
RapidRobert Offline
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or cap each hard line with several cheap brass fittings but no mas, I got $5 that says it is the fronts


live every 24 hour block of time like it's your last day on earth
Re: Pulsing brake pedal, part deux [Re: RapidRobert] #282857
04/10/09 05:12 PM
04/10/09 05:12 PM
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mopartial Offline OP
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Thanks RR. I will try to get my rotors checked. But if it is the front, how come no transmission to steering column?


If it aint broke, dont break it.
Re: Pulsing brake pedal, part deux [Re: mopartial] #282858
04/10/09 05:34 PM
04/10/09 05:34 PM
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Lincoln Nebraska
RapidRobert Offline
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How about clamping the rear brake hose w some vice grips with something in the teeth to protect the hose & take her out for a quick(but safe) spin. Or clamp the fronts.


live every 24 hour block of time like it's your last day on earth
Re: Pulsing brake pedal, part deux [Re: mopartial] #282859
04/10/09 05:40 PM
04/10/09 05:40 PM
Joined: Dec 2007
Posts: 10,542
BROOK PARK, OH
WILD BILL Offline
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A pulsation due to bad front rotors will not always be felt in the steering wheel. There are 3 reasons rotors pulsate.

1. Excessive runout. This can be checked by bolting the rotor to the hub and placing a dial indicator on the surface and watch the needle move as you gently rotate the rotor. It's best to have the caliper off during this check.

2. Parellel variation. This is checked by using a micrometer and measuring the thicknes at multiple points around the rotor. Think of the rotor as a clock face and measure the thickness at each hour mark. This is the most common cuase of a pulsation. The rotor gets thin and thick spots causing the pads to went to travel in and out as the rotor turns. The pulstion gets transmitted back to your foot as the thick point of the rotor comes back around to the pads and pushes them back against the fluid pressure.

3. Badly rusted surfaces. Basicaly the same as #2 but easily seen with no reason to look into the rotor any further.

Warped rear drum brakes will generaly not be felt in the peadal and usually cuases the whole car to feel like it's surging while coming to a stop.

Hope this helps.


I'ld put my $$$ on the rotors.

Re: Pulsing brake pedal, part deux [Re: RapidRobert] #282860
04/10/09 05:42 PM
04/10/09 05:42 PM
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mopartial Offline OP
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Hoses are old. I think Id hafta squeeze it mighty tight to occlude psi generated in line. If I ruin hose Ill have another problem on top of the one I have now...


If it aint broke, dont break it.
Re: Pulsing brake pedal, part deux [Re: mopartial] #282861
04/10/09 05:45 PM
04/10/09 05:45 PM
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
RapidRobert Offline
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We sure dont want to ruin any hoses as we'd be going in the wrong direction here. stay in touch & holler when you find it. If it ain't broke we dont need to be breaking it.

Last edited by RapidRobert; 04/10/09 05:47 PM.

live every 24 hour block of time like it's your last day on earth
Re: Pulsing brake pedal, part deux [Re: WILD BILL] #282862
04/10/09 06:09 PM
04/10/09 06:09 PM
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Posts: 7,759
So Cal
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Quote:

A pulsation due to bad front rotors will not always be felt in the steering wheel. There are 3 reasons rotors pulsate.

1. Excessive runout. This can be checked by bolting the rotor to the hub and placing a dial indicator on the surface and watch the needle move as you gently rotate the rotor. It's best to have the caliper off during this check.

2. Parellel variation. This is checked by using a micrometer and measuring the thicknes at multiple points around the rotor. Think of the rotor as a clock face and measure the thickness at each hour mark. This is the most common cuase of a pulsation. The rotor gets thin and thick spots causing the pads to went to travel in and out as the rotor turns. The pulstion gets transmitted back to your foot as the thick point of the rotor comes back around to the pads and pushes them back against the fluid pressure.

3. Badly rusted surfaces. Basicaly the same as #2 but easily seen with no reason to look into the rotor any further.

Warped rear drum brakes will generaly not be felt in the peadal and usually causes the whole car to feel like it's surging while coming to a stop.

Hope this helps.


I'ld put my $$$ on the rotors.





You forgot hot spots (hard spots on the rotor) that do not wear down evenly with the rest of the drum or rotor as it wears over time. Throw away the rotor if you have these as they cannot be cut out easily and will come back. Most of the time you can see the hard spots on the surface as discolorations that appear to be on the surface, but in some cases you can actually feel them when you run your hand across them.

Re: Pulsing brake pedal, part deux [Re: HealthServices] #282863
04/10/09 06:26 PM
04/10/09 06:26 PM
Joined: Dec 2007
Posts: 10,542
BROOK PARK, OH
WILD BILL Offline
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Quote:

Quote:

A pulsation due to bad front rotors will not always be felt in the steering wheel. There are 3 reasons rotors pulsate.

1. Excessive runout. This can be checked by bolting the rotor to the hub and placing a dial indicator on the surface and watch the needle move as you gently rotate the rotor. It's best to have the caliper off during this check.

2. Parellel variation. This is checked by using a micrometer and measuring the thicknes at multiple points around the rotor. Think of the rotor as a clock face and measure the thickness at each hour mark. This is the most common cuase of a pulsation. The rotor gets thin and thick spots causing the pads to went to travel in and out as the rotor turns. The pulstion gets transmitted back to your foot as the thick point of the rotor comes back around to the pads and pushes them back against the fluid pressure.

3. Badly rusted surfaces. Basicaly the same as #2 but easily seen with no reason to look into the rotor any further.

Warped rear drum brakes will generaly not be felt in the peadal and usually causes the whole car to feel like it's surging while coming to a stop.

Hope this helps.


I'ld put my $$$ on the rotors.





You forgot hot spots (hard spots on the rotor) that do not wear down evenly with the rest of the drum or rotor as it wears over time. Throw away the rotor if you have these as they cannot be cut out easily and will come back. Most of the time you can see the hard spots on the surface as discolorations that appear to be on the surface, but in some cases you can actually feel them when you run your hand across them.





Those would be covered under parallel variation.

Re: Pulsing brake pedal, part deux [Re: WILD BILL] #282864
04/10/09 06:35 PM
04/10/09 06:35 PM
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mopartial Offline OP
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Thanks Bill.

So far theres $5 + $$$ riding on my bad rotors...
I will probably replace them and pads tomorrow.

...and forever wonder why sometimes a bad rotor makes your steering wheel shimmy and sometimes it doesnt...


If it aint broke, dont break it.
Re: Pulsing brake pedal, part deux [Re: mopartial] #282865
04/10/09 06:41 PM
04/10/09 06:41 PM
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Posts: 10,542
BROOK PARK, OH
WILD BILL Offline
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Quote:

Thanks Bill.


...and forever wonder why sometimes a bad rotor makes your steering wheel shimmy and sometimes it doesnt...





I used to wonder about that sort of thing but it started keeping me up at night so I cut it out.

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