Another Brake Thump Question
Thread Starter
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4wd Low
Joined: Aug 2024
Posts: 10
Likes: 0
From: Georgia
Another Brake Thump Question
Okay to lay the ground work, 2015 F250 King Ranch 6.7 Diesel Crew Cab 161000 miles, this occurred before and after replacing the front brakes/pads/rotors etc. This is reproducible. When pressing the brake peddle multiple times in succession either sitting still or going down the highway, eventually apply the brakes will cause a loud thumping to occur coming from the center front firewall area and through the floor and into the brake peddle. If you don't apply the brakes for a short period of time, you can press the peddle without the thumping re-occurring. It only occurs after pressing the peddle several times. For instance, sitting at a red light, I press the peddle 5 times, then let the truck roll a foot or two and press the peddle again and the thumping occurs for a brief period.with a rhythm I cannot tie to anything like the wheel speed. .The thumping stops and light turns green, I let up on the brakes go down the road a bit and apply the brakes without the thumping occurring. As stated it seems to only occur after apply the brakes multiple times in a short time span.
Any thoughts would be most appreciated. Thinking its a booster/vacuum issue somewhere.
Thank you.
Any thoughts would be most appreciated. Thinking its a booster/vacuum issue somewhere.
Thank you.
Thread Starter
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4wd Low
Joined: Aug 2024
Posts: 10
Likes: 0
From: Georgia
Thanks for the suggestion but no change in behavior ... was making a gradual turn to the right and left on an express highway the last time it happened. I can say that at highway speeds, the thump is a little louder.
Was reading about how pumping the brakes help relieve pressure on the system and started wondering if this is a feature gone wild.
Was reading about how pumping the brakes help relieve pressure on the system and started wondering if this is a feature gone wild.
Thread Starter
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4wd Low
Joined: Aug 2024
Posts: 10
Likes: 0
From: Georgia
Keep the suggestions coming please .... No codes are thrown to show ABS issues, vacuum pressure is good to the booster but I am still leaning in the direction of the booster as the sound is pretty loud. All fluid levels are good and hoses are good not showing any signs of leaking fluid. Going to have a friend come over and listen as I can reproduce it just by pumping the brakes and then ease off and re-apply the brakes to make the thump occur.
Hotshot
Joined: Oct 2015
Posts: 19,722
Likes: 12,865
From: Wyoming
I read your description with a mechanical issue in mind. I'm not sure that it's a mechanical issue, but it still could be. When you say pumping the brakes either while still or going down the highway, do you mean that the vehicle is in park when it's "sitting still"?
If it does it in park, then I don't think it's a mechanical issue such as the calipers being loose, allowing the calipers to rotate (a small amount) in the same direction the rotor is going. If the calipers are loose but not allowed to rotate I could see the calipers getting pressed back and forth by the action of the cylinder at the wheel.
Once you narrow the noise down to one of the front brakes, take the wheel off and have your assistant watch what the brakes are doing.
Could you have a loose brake hose?
If it does it in park, then I don't think it's a mechanical issue such as the calipers being loose, allowing the calipers to rotate (a small amount) in the same direction the rotor is going. If the calipers are loose but not allowed to rotate I could see the calipers getting pressed back and forth by the action of the cylinder at the wheel.
Once you narrow the noise down to one of the front brakes, take the wheel off and have your assistant watch what the brakes are doing.
Could you have a loose brake hose?
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Thread Starter
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4wd Low
Joined: Aug 2024
Posts: 10
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From: Georgia
Thank you for the questions ....
"When you say pumping the brakes either while still or going down the highway, do you mean that the vehicle is in park when it's "sitting still"?"
Yes ... both ... going down the highway and tapping the brakes to slow down (a little harder then needed to release the cruise control) or sitting at a red light, not moving, press the brake pedal 5 times, checked on the 5 times and verified, then let the truck roll forward a little and apply the brakes and the thumping occurs.
"Once you narrow the noise down to one of the front brakes, take the wheel off and have your assistant watch what the brakes are doing."
This thumping has occurred with the old brakes and new brakes, with new meaning rotors/pads/return clips/guide pins, and I went ahead and replaced the bolts for the caliper bracket as well all torqued to spec.
"Could you have a loose brake hose? "
Thought the same and checked, no fluid loss in the reservoir.
My son "the assistant in training" will be home this evening to help with locating the noise which is reproducible.
"When you say pumping the brakes either while still or going down the highway, do you mean that the vehicle is in park when it's "sitting still"?"
Yes ... both ... going down the highway and tapping the brakes to slow down (a little harder then needed to release the cruise control) or sitting at a red light, not moving, press the brake pedal 5 times, checked on the 5 times and verified, then let the truck roll forward a little and apply the brakes and the thumping occurs.
"Once you narrow the noise down to one of the front brakes, take the wheel off and have your assistant watch what the brakes are doing."
This thumping has occurred with the old brakes and new brakes, with new meaning rotors/pads/return clips/guide pins, and I went ahead and replaced the bolts for the caliper bracket as well all torqued to spec.
"Could you have a loose brake hose? "
Thought the same and checked, no fluid loss in the reservoir.
My son "the assistant in training" will be home this evening to help with locating the noise which is reproducible.
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Thread Starter
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4wd Low
Joined: Aug 2024
Posts: 10
Likes: 0
From: Georgia
Thank you ... the hoses look good and connected ..... The thump is strong enough to be felt through the dash and through the brake pedal and steering wheel. I will try and make a video recording this evening.
Logistics Pro
Joined: Mar 2005
Posts: 3,549
Likes: 2,510
From: West Michigan
Is the thumping at a repeating rhythmn? Or something without repeating duration? If repeating, it has to be mechanical. you may not get a code out of the ABS, but to me it seems like it could be a stuck valve? Is the thumping at the same speed as when ABS is active on slippery road?
Thread Starter
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4wd Low
Joined: Aug 2024
Posts: 10
Likes: 0
From: Georgia
Thank you for the questions ... yes, it has a rhythm of sorts for a brief moment not related to the speed of the vehicle. I have only experienced ABS on slick roads with the truck once and could feel the ABS working but not hear it. As for speeds, as indicated above, its reproducible at any speed including a brief roll from a dead stop after pumping the brakes 5 or more times. It doesn't happen all the time and after it happens, I can drive for a short distance and brake without the thumping occurring. The key seems to be in the multiple application of the brake pedal triggering the thump.
pedal press,
pedal press,
pedal press,
pedal press,
pedal press,
pedal press + thumping ...
drive short distance, press the brakes and no thump.
Thanks again for the thoughts ...
pedal press,
pedal press,
pedal press,
pedal press,
pedal press,
pedal press + thumping ...
drive short distance, press the brakes and no thump.
Thanks again for the thoughts ...