Hydroboost diagnois
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Laughing Gas
Joined: Jan 2017
Posts: 1,221
Likes: 94
Hydroboost diagnois
When I press the brake pedal down at idle there is some rumbling in the pedal and some noise comming from under the hood. I did the “hydro boost test” where you depress the pedal several times than start the truck and wait for the pedal to press back on your foot. My truck did nothing but the brakes seem to be working fine. Once RPMs increase 100 over idle the sound dissapears. Also have a new power steering pump vacuum bled just installed thought that was the problem but was only part of it.( One of the mounting bolts backed out and was messing w the system so I just swapped it given I didn’t know the history on it. )Definite improvement but not a total solution.
Hotshot
Joined: Nov 2006
Posts: 11,286
Likes: 263
From: North of Greenville
Well, I've been through both the MC and Booster replacement processes, and each time, I was fortunate to have taken the correct route in diagnosing, and each component was a 100% fix at the time. You've sort of gone further down the process than I ever did, so I don't think I can offer much more than a bump for the thread.
FTE Leadership Emeritus
Joined: May 2014
Posts: 27,351
Likes: 5,945
From: Lake Hartwell, GA
I had a similar problem this winter and did not present itself until a few months after replacing the steering gear. Turns out the problem was air or moisture in the hydroboost and power steering system. It took nearly a gallon of Valvoline synthetic ATF in order to get the pedal vibration out. My wife was pumping the pedal and turning the wheel while I monitored the fluid evacuation from under the hood. After about the 6th session of pumping the pedal, she said that the pedal was getting better. We pushed nearly a gallon of fluid through the system, and all has been well since.
Again, this problem did not present itself until months after the system was exposed to air and bled out before.
This is a video of the problem I was having.
Again, this problem did not present itself until months after the system was exposed to air and bled out before.
This is a video of the problem I was having.
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Laughing Gas
Joined: Jan 2017
Posts: 1,221
Likes: 94
Ran some fluid through the top port today. Results after there was a deffinte increase in braking pressure and when I repeated the hydroboost test the brake pedal pressed back up on my foot in working order. Deffinetly some air in the system. However, the noise has persisted especially at around 1900-2100 on the highway or at idle speed. Over the past few days I’m at below 1900 or over 2100 because the sound is gone, it runs fine, and rolling without the noise should do me better. The truck does not make the noies at those rpm in other gears. Additionally, engine oil temp also has been a bit warm for the trucks usual operating numbers. Just loosened the belt to inspect to find a little movement forward to back when grabbing the fan.
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