# Pulsing in Brake Pedal



## GMC Sierra (Nov 10, 2009)

I have a 1997 GMC Sierra 1500 4x4- 140K miles. When I hit the brake pedal, I feel pulsing through the pedal. If I really apply the force to the pedal, the pulsing diminishes (but is still there). New rotors up front and new drums in the back (with pads). No shaking or pull in the steering wheel whatsoever. When I apply the emergency brake and then use the brake pedal, stops smoothly with NO pulse. Seems clear to me it is coming from the rear brakes. 

I may have the "new" rear drums turned to see if I have an issue. Any thoughts....I like my stuff 100%. Any chance a wheel bearing issue in the rear? Air in the brake lines? Master cylinder? Any suggestions appreciated. Thanks.


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## JR Snow Removal (Jul 16, 2008)

My 97 1500 did that I pulled the ABS fuse and no more problem. Mine would pulse when i hit the brake but when i re-applied it went away.


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## GMC Sierra (Nov 10, 2009)

No- this is not the "ABS pulse" that is typical in these trucks (no ABS noise or rapid vibration). The ABS system is not engaging when this symptom occurs. Thanks for the reply.


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## sechracer (Nov 4, 2007)

Being that most of the stoping power is in the front brakes on these trucks, unless you are always really hard into the brakes, I would still look at the front. These trucks are known to have sticky calipers. I would look at the slide pins on the front and make sure they are lubed really well. If the pulsing stops when the ebrake is applied it may be the back drums but doubltful since it uses the same pads for the rear brakes.


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## Jgrub75 (Feb 16, 2006)

Sounds like warped rotors


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## grandview (Oct 9, 2005)

How old are your new rotors and were they after market rotors


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## GMC Sierra (Nov 10, 2009)

Yeah- I thought so too. I actually took the rotors off and had them turned to make sure they were true....no change. So, I am 99% confidnet it cannot be the actual rotor (new and turned). Thanks for the inquiry.


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## GMC Sierra (Nov 10, 2009)

Rotors are "new" and have been turned to ensure they are "true". They are aftermarket. I heard something about a lateral test...maybe this is what you are driving at. Not sure how to perform a lateral test on the rotor to ensure it is perfectly vertical as it runs through the caliper?


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## grandview (Oct 9, 2005)

Try and rotate the tires maybe you have a cord out and it's causing the problem .


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## GMC Sierra (Nov 10, 2009)

Yeah- could be....but I have absolutely no "feedback" through the steering wheel (tupical when a front end issue). With that said, I can turn either front wheel at will when up on the jack..would seem the caliper is "free". Thanks.


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## sechracer (Nov 4, 2007)

GMC Sierra;857180 said:


> Yeah- could be....but I have absolutely no "feedback" through the steering wheel (tupical when a front end issue). With that said, I can turn either front wheel at will when up on the jack..would seem the caliper is "free". Thanks.


might be free that way, but take the wheel off of both side, and see if you can slide the caliper on the slide pins. It wont move much since it squeezed already, but you should be able to tell if it is sliding freely on the pins. I hunted for the same problem with my truck when I first got it.


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## 2COR517 (Oct 23, 2008)

I have a similar situation. Where did you buy your drums? I bet that's the problem. I put some cheapie Autozone's on, I think they are no good. Actually, I'm quite sure they are no good. I noticed when adjusting the rear shoes, The drum would "catch" at one point, not even make a peep a quarter turn away. I should have bought the good ones from Napa I guess. I might just get them turned and see what happens.


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## Bruce'sEx (Sep 16, 2006)

If it is doing it more at very slow speeds, i.e just before you come to a stop. then it's likely the speed sensor in the hub. the ring gets some play in it. we have replaced several over the years

This is from a different year range, so might be wrong in your case but ours was not from corrosion, just wear.

Condition
General Motors has decided that a defect, which relates to motor vehicle safety, exists in certain 1999-2002 Chevrolet Silverado, 2000-2002 Chevrolet Tahoe, Suburban, 2002 Chevrolet Avalanche, 1999-2002 GMC Sierra, 2000-2002 GMC Yukon, Yukon XL vehicles located in the areas listed below. These vehicles may have a condition permitting corrosion to occur between the front hub/bearing assembly and the wheel speed sensor. If the brakes are applied while the vehicle is traveling at a speed of greater than 6 km/h (3.7 mph) but less than 16 km/h (10 mph), the corrosion may cause an unwanted anti-lock brake system (ABS) activation. If this condition occurred where stopping distance is limited, a crash could occur.


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## 2COR517 (Oct 23, 2008)

He clearly stated this is not an ABS issue.


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## Newdude (Dec 4, 2006)

When you changed the rotors, did you change the pads as well?


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## naturalgreen (Dec 6, 2008)

Had same prob on 93 and it was from impact wrenching lugs so warped rotors. Exact same prob but you say your rotors are fine so you got me. I would def say rotate tires and see what happens.


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## GMC Sierra (Nov 10, 2009)

Funny you say the Drums from Autozone....That is where I got them. I think I bought the mid grade....but I had the same experience adjsuting the shoes. Weird. I am going to look into that.


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## 2COR517 (Oct 23, 2008)

I'm pretty much all Napa at this point.


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## B&B (Nov 4, 2006)

Very simple. You're bargain basment brake drums were out of spec when you installed them....as many are. You get what you pay for.


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## grandview (Oct 9, 2005)

God has spoken on this matter. Please close this thread!


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## 2COR517 (Oct 23, 2008)

B&B;857646 said:


> Very simple. You're bargain basment brake drums were out of spec when you installed them....as many are. You get what you pay for.


Are they worth turning, or just take my lumps and head to the Napa?


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## B&B (Nov 4, 2006)

You can turn them but you'll be right back where you started within a 1000 miles. Except then they'll be even closer to minimum thickness than they were when new. Which isn't much on the aftermarket stuff.


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## 2COR517 (Oct 23, 2008)

You're just a party pooper tonight.

I actualy got AZ to give me my money back on an Idler arm after replacing it three times. Went to Napa with the cash, threw in the difference. Think I woulda learned back then, eh?


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## B&B (Nov 4, 2006)

Sometimes the truth isn't what some want to hear.


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## overtime (Nov 5, 2009)

When you wheel vibrats its the front brakes if you feel it only while braking. Sence you feel in pedel its the brakes in rear. If it was tired you would feel it when not braking.


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## RichG53 (Sep 16, 2008)

My 01 has been doing this when I brake,but only occasionally..(Shakes pretty good )...I was wondering if it is Rotors or front end Steering components ????

Any suggestions. ???????


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## haejinjoe (Nov 13, 2003)

As several have pointed out, you have a runout (rotors) or out of round (drum) issue or combination of both. Either or both can be felt in the brake pedal. It is possible to see if the drums are out of round by applying the parking brake while driving like the service brake while holding the release handle out. Obviously some care must be exercised when doing this and the parking brake cables must be freely operating. This test can tell you if the drums are out of round, but won't tell you if the front rotors are ok. Once eliminating the rear drums from the equation, then problem solved or go back to suspecting a runout problem in front.

AverageJoe


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## RichG53 (Sep 16, 2008)

RichG53;861235 said:


> My 01 has been doing this when I brake,but only occasionally..(Shakes pretty good )...I was wondering if it is Rotors or front end Steering components ????
> 
> Any suggestions. ???????


 NEED Help !!!!!!


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## B&B (Nov 4, 2006)

Probably rotors.


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## RichG53 (Sep 16, 2008)

Thanks B&B I was waiting for your response .......


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## jb1390 (Sep 23, 2008)

Rotors in combination with worn out front end components will make it shake pretty bad. I just did the front end on my 98, and the tie rods, pitman arm, etc were ALL junk. I am surprised, because it didn't feel loose in the steering before, but there was a lot of play when I got underneath it. A little shaking from the rotors will become much worse with worn out tie rods or ball joints. Quick and easy to check too.


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## RichG53 (Sep 16, 2008)

OK!!! what is the best way to check Idler & Pitman ??? On or off the ground ??? Same with tie rods ...


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## jb1390 (Sep 23, 2008)

Raise the vehicle and put it on jackstands so the wheels are about an inch off the ground. It may be easier with two people, but put a prybar underneath the tire, and pry lightly so the wheel is forced upward. Check the ball joints as you do that to see if there is any play. A slight amount of movement fromt he suspension is normal, but there should be no play in the ball joints themselves. 

Tie rods-with the vehicle still raised, try to turn the wheel (tire, not steering wheel) left and right with your hands. Because many of the joints are hidden under the truck, it is probably easier to have someone under the truck while you are wiggling the wheel (or have someone else turn it back and forth while you are underneath), and again there should be NO play in the tie rods. You could also do this by having someone turn the steering wheel and check for play in the joints.


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## 2COR517 (Oct 23, 2008)

I wish we had the banging head against the wall thingie....


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