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2005 isuzu ascender
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Discussion Starter #1
'05 Isuzu Ascender: I was stopped on a steep hill waiting on traffic, facing uphill. I had eased off the brakes and rolled backwards a little bit. When I pressed on the brakes to stop again, there was a dull popping sound from under the hood in front of me, a noticable pulse in the brake pedal when the pop happened, then the pedal went almost all the way to the floor. However, I still had brakes.

Now the brake pedal travels easily almost all the way to the floor before the bakes engage, and the stopping pressure is no where near as firm as it used to be. Emergency braking is impossible, and just to be careful I downshift now when slowing down in addition to using the brakes. When I slam on the brakes hard, it usually locks up the wheels. Occasionally I will feel the brakes pulsing like the ABS is trying to work.

There are NO leaks in the system, fluid level has stayed full. Front calipers are brand new as are the pads. System was bled properly and functioned properly prior to this happening. Is this an issue with the ABS module? The vacuum boost? I do have an occasional audible vacuum leak at start-up, but it goes away quickly once there's a good vacuum pulled.
 

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Sounds like one hydraulic brake system has failed..... your vehicle has two... front and rear.

That you have a very low ... but working pedal.... in your case.... sounds like you lost the front brakes and are working on the rears only.

The "Pop" you heard may have been a piston in the caliper when it blew out or another vaguely remote possibly of a blown brake line...... your problem lies somewhere in between those two extremes.
 

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2005 isuzu ascender
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Discussion Starter #3
It's not the calipers. I've ruled that out. It happened again yesterday. Now there are no brakes at all. It has to either be the ABS block or the vacuum system. Since both parts are relatively pricey, does anyone know how to diagnose which is the issue??
 

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Rule out the vacuum booster... it won't give you NO BRAKES, just very hard to press.
Check the master cylinder reservoir.... if it has ZERO fluid in it.... you've got to find the leak.
Dual Brake Systems are designed to shut off one side that fails via the Proportional-Dual Purpose valve.

Realistically, it will keep fluid in either the front or rear brake system so you can still stop the vehicle..... although if the rear brakes are the survivors, you will require more brake pedal travel and reduced braking ability.

You'll get somewhat "decent braking" if the hydraulic failure is in the rears since you use the front brakes more so than the rears at almost all times.

For the brake system to totally fail..... as you describe ..... you've got to have either ignored an existing problem for a long time via the constantly ON brake warning light, or the bulb is burned out.... and has been so for a long time.....or someone put black tape over it.

There's always a possibility that your wife-girl friend or some jilted ex-spouse wants to kill you.

NO PEDAL AT ALL is not supposed to happen unless it's integrity is physically compromised somehow.

The "pop" you heard should have been checked INSTANTLY! Brakes don't make that kinda sound unless some catastrophic event has just happened. and.... a "To-the-floor" pedal is not a normal happening.

If you don't know what your doing or observing.... park this vehicle until someone better qualified checks into it.


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