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Old 10-31-2012, 06:14 AM
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Crunchy brake after hard acceleration

Truck is a 2008 F250 4x4, all stock except for H&S and straight pipe. 160k miles, stock size tires, no known mechanical issues.

If I romp on it from 1-3rd gear and let off, my brake pedal will feel "crunchy" for about 5-10 seconds. The brakes still work, the pedal just feels terrible.

Is this just the ABS engaging? Or maybe a potential issue with my booster?

thanks!
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Old 10-31-2012, 06:15 AM
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sounds like ABS for some reason. you may have a bad ABS sensor
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Old 10-31-2012, 06:53 AM
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Check your fluid level, and also test it for water/moisture.
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Old 10-31-2012, 06:59 AM
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Forgot to mention, the brakes work perfectly outside of this happening. If i'm just cruising along and have to slam the brakes, they work flawlessly with no odd behavior.
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Old 10-31-2012, 07:03 AM
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Quote:
Originally Posted by Rubenk View Post
Forgot to mention, the brakes work perfectly outside of this happening. If i'm just cruising along and have to slam the brakes, they work flawlessly with no odd behavior.
Check your hydroboost lines lines for leaks too, as well as power steering fluid level. You may be low on power steering fluid ( which is what is creating the hydroboost pressure ) so when you accelerate its making the fluid in the reservoir shift enough for the pump to draw in air.
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Old 10-31-2012, 07:07 AM
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I've checked all the fluids, but will doublecheck the powersteering, I know the brake fluid level is good and all the lines in that area look fine.

I will visually doublecheck everything I can, thanks!
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Old 10-31-2012, 07:11 AM
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Originally Posted by Rubenk View Post
I've checked all the fluids, but will doublecheck the powersteering, I know the brake fluid level is good and all the lines in that area look fine.

I will visually doublecheck everything I can, thanks!
If you look to the right of the master cylinder closest to the fender there are two hard steel lines going towards the firewall, the one closest to the master cylinder should have a light blue colored tape going around both sides of the connection point. if these have a leak that will also cause weird braking issues.
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Old 10-31-2012, 05:20 PM
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Forgot to check things after work, but I did run an errand and had it happen again.

Mild acceleration, just barely slipped a tire and started cruising once I hit around 45mph...touched the brake pedal lightly and there was a constant buzzing through the pedal, it slowly went away till it stopped about 8-10 seconds later.

Seems like the ABS acting up when I spin a tire.
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Old 11-14-2012, 07:15 PM
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Mine does the exact same thing
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Old 11-15-2012, 06:01 AM
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Did a visual inspection yesterday and it all looks ok. The part with the reservoir and the hard brake lines going into it does look new compared to the rest of the stuff attached to the firewall. No visible fluid leaks. Brake fluid is full.

I forgot to check the power steering, will do that later today.

Any other ideas? Is it normal? Maybe a bad sensor?
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