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Spongy brakes issue


96vteccd5
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Good Evening fellas,

 

I have a 05 1500 Silverado Ext Cab with rear drums (138,000) and I am having a braking issue that I am trying to diagnose. My current setup:

Power Slot Cyro treated Rotors

Hawk LT pads

SS brake lines.

 

I have bleed the system twice. First myself and then the 2nd time I took it to a shop. After each time, the brakes on the truck felt great for about a month or so but now the spongy brake issue has come back. With the truck off I can press the brake pedal and load of the lines and they will lock with no movement. When I do drive, I have to push the pedal father to the floor then before but the truck will stop. When I do press the brake pedal, I hear a loud hissing sound from under the dash when pressing the brake pedal. I have read that this trucks have rusty brake line issues and I am wondering that the rusted lines is introducing moisture to the brake system.

 

Had anyone ever experienced this or any thoughts on what it could be?

 

Sidenote: getting ready for GM nationals again :)

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The original steel lines on our, (and all GM trucks around these years), are known to corrode and go bad. If your lines were bad enough to let moisture in they would be leaking brake fluid out. Are you losing brake fluid? Have you checked your master cylinder for leaking? The fading brake pedal is a pretty good indicator of a leak somewhere in the system and if your not seeing an obvious leak at the wheels or lines I would suspect the master cylinder.

 

The loud hissing that you mention makes me suspect the vacuum booster. First thing that I would do is get someone to press the brake pedal while you listen to the brake booster from outside the cab with the hood open. I don't know that the hissing necessarily means that the booster is bad. If you had a vacuum leak in the booster the truck would run like poop.

 

Good luck and let us know what you find.

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The original steel lines on our, (and all GM trucks around these years), are known to corrode and go bad. If your lines were bad enough to let moisture in they would be leaking brake fluid out. Are you losing brake fluid? Have you checked your master cylinder for leaking? The fading brake pedal is a pretty good indicator of a leak somewhere in the system and if your not seeing an obvious leak at the wheels or lines I would suspect the master cylinder.

 

The loud hissing that you mention makes me suspect the vacuum booster. First thing that I would do is get someone to press the brake pedal while you listen to the brake booster from outside the cab with the hood open. I don't know that the hissing necessarily means that the booster is bad. If you had a vacuum leak in the booster the truck would run like poop.

 

Good luck and let us know what you find.

Thanks for the info. No noticeable leaking fluid and the reservoir stays full all the time. I will get under the truck to take a look but last I checked everything looked fine. I will keep you guys posted.

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Thanks for the info. No noticeable leaking fluid and the reservoir stays full all the time. I will get under the truck to take a look but last I checked everything looked fine. I will keep you guys posted.

 

I have seen master cylinder leaks that are pretty small leaks but will cause a spongy pedal. (Small enough leak that you may not notice reservoir level dropping. Sometimes you won't see evidence of the master cylinder leak until you take it off of the booster and look at it from the booster end of the cylinder.

 

Best luck.

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