Soft Brake Pedal after Brake Fluid Flush (non-ABS)

OxLibertySport

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2005 Liberty Limited 4x4 (non-ABS)

So I vacuum flushed my brake fluid yesterday ... I used the 'ole Harbor Freight Pneumatic Vacuum Bleeder. The fluid was dark - Coca-Cola for sure.

Anyway, all went reasonably well. With the engine off, I have a nice firm brake pedal - but, when I crank it up, the pedal is spongy & goes to the floor.

I think I'm going to order a Motive Power Bleeder (Pressure Bleeder) and bleed the system again - but, I wonder if something else is going on? Any other non-ABS folks have issues with the pedal when the engine is running??
 
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LibertyTC

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It sounds like air has entered the system, bleeding will be required.
I have not had any issues with my non ABS system.
Use regular DOT3 fluid.
My master cylinder fluid was a bit dirty & all I did was suction out the old fluid and re-fill to last position.
 

JeepJeepster

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No idea why this happens, but I did the same thing on my ZJ and the master cylinder went bad. I had a brake hose collapse on me and was causing the rear brakes to hang up. Got that replaced, vacuum bled the brakes, then suddenly the pedal went to the floor when the Jeep was running. Pedal would get hard as a rock with the Jeep off, I could push on it as hard as I could with two legs. Start it, right to the floor... Cant explain it.
 

BullDoggie

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2005 Liberty Limited 4x4 (non-ABS)

So I vacuum flushed my brake fluid yesterday ... I used the 'ole Harbor Freight Pneumatic Vacuum Bleeder. The fluid was dark - Coca-Cola for sure.

Anyway, all went reasonably well. With the engine off, I have a nice firm brake pedal - but, when I crank it up, the pedal is spongy & goes to the floor.

I think I'm going to order a Motive Power Bleeder (Pressure Bleeder) and bleed the system again - but, I wonder id something else is going on? Any other non-ABS folks have issues with the pedal when the engine is running??
Hey its is a vacuum assisted master cylinder? If so the problem IS the master cylinder. It ctuates when engine running and falls back to good old hydraulic when engine off. Sound like time to buy a new one.
 

Ksat

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In my experience, a failing master cylinder will usually be able to stop the vehicle fine at 1st but then cause the pedal slowly sink to the floor and then be unable to keep the vehicle from moving. Not too different than when you have a small fluid leak in the line. Air in the system either won't allow the brakes to be applied at all or will only partially engage them. There isn't usually a change in pedal feel like there is with the failed master cylinder, unless you pump the pedal.
 

Ronald

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2005 Liberty Limited 4x4 (non-ABS)

So I vacuum flushed my brake fluid yesterday ... I used the 'ole Harbor Freight Pneumatic Vacuum Bleeder. The fluid was dark - Coca-Cola for sure.

Anyway, all went reasonably well. With the engine off, I have a nice firm brake pedal - but, when I crank it up, the pedal is spongy & goes to the floor.

I think I'm going to order a Motive Power Bleeder (Pressure Bleeder) and bleed the system again - but, I wonder id something else is going on? Any other non-ABS folks have issues with the pedal when the engine is running??
Some times the rubber lines are overlooked and they ballon out under a hard stop ,
 

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