02 Liberty 3.7L Sudden Loss of Brake Pressure

[darkxfire]

Me and a friend were working on his liberty. We changed a wheel hub, and I took the front calipers off to spray some permatex disc brake quiet on it. The drivers side caliper was replaced a few weeks ago with a new one, and the pads and rotors are mostly new for the most part.

After we put everything together, we noticed that there was almost no brake pressure, even after stomping on it for a while. It did get better with many hard brakes, adjustment, and even bleeding each wheel around 5-10times. We dont notice any fluid loss anywhere. The pedal builds up pressure when the car is off, but falls when started. Its at an acceptable level now, you can actually stomp on the brakes and lock up the wheels, but its still spongy, compared to before.

I was baffled. I couldnt think of anything either then maybe a pinched brake line, or leak, but I didnt find anything. I'm thinking to replace the master cylinder tommorow. Its just odd that it happened suddenly.

 

[M38 Bob]

It didn't "happen suddenly ". Y'all managed to screw something up on the way back together. This is the voice of experience here, if it can be screwed I've done it at least once. Go back and disassemble it slowly and look for something out of place.

I'll never understand how the thought process can decide bleeding is necessary when the system has never been opened to allow air in?

Bob


Sent from my iPad using Tapatalk

 

[darkxfire]

The only thing I could think of was maybe the caliper pinched off the rubber side of the line and got air or blockage in the system. We looked and didnt find this the case. So we bled it. I will have to bench bleed the system tommorow, and the lines again

 

[LibertyTC]

:shrug:
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:fish_h4h:

 

[Billwill]

Check your vacuum on the brake Servo.
With the engine OFF press ******* the brake bad...should be firm.

Start the engine and you should feel the brake pedal move down a bit under your foot...this means the Brake Servo is doing its job!

 

[tommudd]

Me and a friend were working on his liberty. We changed a wheel hub, and I took the front calipers off to spray some permatex disc brake quiet on it. The drivers side caliper was replaced a few weeks ago with a new one, and the pads and rotors are mostly new for the most part.

After we put everything together, we noticed that there was almost no brake pressure, even after stomping on it for a while. It did get better with many hard brakes, adjustment, and even bleeding each wheel around 5-10times. We dont notice any fluid loss anywhere. The pedal builds up pressure when the car is off, but falls when started. Its at an acceptable level now, you can actually stomp on the brakes and lock up the wheels, but its still spongy, compared to before.

I was baffled. I couldnt think of anything either then maybe a pinched brake line, or leak, but I didnt find anything. I'm thinking to replace the master cylinder tommorow. Its just odd that it happened suddenly.

When you remove the calipers and push the piston back in , you will feel no pedal at first that is normal
Also when you pump it up with the engine off it will pump up and feel hard
Then when you start it the pedal of course will go down some, thats all just how it works
As far as spongy, are you sure or now playing mind games with yourself ?
Without opening up the system ( i.e. installing new caliper say) there would be no way for air to enter the system unless you broke a line or???

 

[CactusJacked]

Also check the caliper brake hose. Those can crack (mine did) where the steel line meets the fitting for the rubber portion. When mine went, the brake fluid would leak when the wheels were turned left, but tension on it made it hold pressure when the wheels were turned right. Look for wet spots (insert joke here).

 

[belvedere]

Sorry, I gotta ask: you sprayed this on the BACK of the pads, right?

 

[ltd02]

Sorry, I gotta ask: you sprayed this on the BACK of the pads, right?

(yeahthat)

I know of someone else who sprayed the front. Not good for performance. :gr_grin:

 

[tommudd]

Common sense , but then I have to remember some just never got their cup of it from the get go:shrug::icon_lol:

 

[darkxfire]

Thank you for the replies.

I believe the problem lied between the brake lines. I guess somehow air got into the system, and the right passenger calipers pins were sized solid, and we got that taken care of. The rear drums were recently replaced and noticed they were also not adjusted at all. I think that all might've contributed to it, and a twisted line. One of the brakes lines that had a caliper recently replaced was rusted, and the nut was not 100% tight. Also bled the master cylinder and took care of the other problems. Feels 100x better. Before, you would push it all the way to the floor and it felt like you were coasting.

On some cars, the pedal feels fairly loose. I have a small toyota yaris, the pedal always felt spongy from when I got it, even after adjusting the shoes, bleeding and a new master cylinder, it still feels spongy. I guess it could be that it is mostly rubber lines, but it stops fairly well.

You never know with cars. Sometimes they like to cooperate, other times no. After we put everything back today, we went for a test spin, came back, restarted the car and it kept dying. Cleaned the IAC, throttlebody, and tps sensor, and it starts no problems now. Geez lol It's almost like the car is cursed. Now to clean the map sensor

 

[JasonJ]

You never know with cars. Sometimes they like to cooperate, other times no. After we put everything back today, we went for a test spin, came back, restarted the car and it kept dying. Cleaned the IAC, throttlebody, and tps sensor, and it starts no problems now. Geez lol It's almost like the car is cursed. Now to clean the map sensor

Sounds more like piss poor maintenance over the years. Perhaps starting with Owner #1.

Glad you got it sorted.

 

[metalmoto]

Spongy brakes means there is still air in the lines. You didn't let the master cylinder run dry when you blead the brakes, did you? Otherwise, I am thinking your master cylinder is on it's way out. Also check carefully "everywhere" for a leak at the fittings and lines, both the rubber and steel lines. And if yours is a 02-05, there is another rubber line connected to the rear axle. It's hard to see, unless you climb under and look for it. I just replaced all 3 of my rubber lines, rear cylinders and some rusted lines for the rear brakes. They are attached to the axle.