Breaking problem

[Luke G]

I have a 2011 ram 1500 5.7 with 120,000 kilometers. Problem is brake pedal is firm and great when the engine is not running, but when the engine is started the pedal Is soft and spongy and will slowly drop to the floor. Have installed new pads and rotors Still had mushy pedal suspected master cylinder, remove master cylinder with no leaks replaced with new master cylinder, fully bled the system bled the abs and still have spongy pedal. No warning lights, No codes. Please help thanks.

 

[Racer9]

Check vacuum line

 

[ppine]

Braking problem because something is broken.

 

[Rlaf75]

A spongy brake pedal would indicate that there's air in the system somewhere. If there was a vacuum leak going to the brake booster then the pedal would be rock hard and you'd have to stand on the brake pedal to get it to stop. If you're confident there are no leaks in the system then I'd take it somewhere to see if they can pressure bleed the system. Also need to make sure there isn't a certain procedure to bleed the system. Certain vehicles require a scan tool to activate the ABS modules in order to properly bleed the entire system

 

[Burla]

Yeah you need to flash it now, or whatever word you want to put on the procedure to clear the abs system because at some point air got in there.

 

[StateOfMind]

Yeah you need to flash it now, or whatever word you want to put on the procedure to clear the abs system because at some point air got in there.

Agree with this

 

[Jeepwalker]

They're right. There's air in the ABS Valve assembly,

1) If you know a guy with a really good scan tool, or a OBDII scan tool which activate the brake bleed function, do that.

2) Tow it to any mechanic shop, or the dealer, who probably has a scan tool.

3) Buy a scan tool which DOES do brake bleeding (AlfaOBD & MX+)

The Scan tool opens the ABS brake valves and runs the brake pump and purges out the air. After that, you (or the shop) needs to re-bleed the air out of the brakes as per normal.

 

[StateOfMind]

They're right. There's air in the ABS Valve assembly,

1) If you know a guy with a really good scan tool, or a OBDII scan tool which activate the brake bleed function, do that.

2) Tow it to any mechanic shop, or the dealer, who probably has a scan tool.

3) Buy a scan tool which DOES do brake bleeding (AlfaOBD & MX+)

The Scan tool opens the ABS brake valves and runs the brake pump and purges out the air. After that, you (or the shop) needs to re-bleed the air out of the brakes as per normal.

I did not know my AlfaOBD has that function too. Thanks Jeepwalker!

 

[62Blazer]

What happens if you pump the brake pedal? If there is air in the system, typically if you pump the pedal several times right in a row it will firm up on the next pump.
Probably what you are feeling between the engine on and off is simply there is no power brake booster with the engine off, so the pedal will feel really hard. It's not that the problem goes away with the engine off or anything.....you just don't notice it.

 

[Jeepwalker]

If a guy can get 'firm pedal' drive the tk on a gravel lot (not on the road), get some speed and slam on (and ride) the brakes hard. It'll activate the ABS which will essentially articulate the ABS valves & do the same thing as the scan tool. Do a couple times. Then go back and bleed all the air out of your tk's brakes (again) like normal to get the rest of the air out. That should firm up the pedal.

Be sure to NOT let the reservoir run low. Sounds like a no-brainer, but new fluid is clear, easy to do (I've done it!).

 

[Tominator223]

If the air is all bled out. And stil mushy. If you hear air (leak) under dash. Booster could be bad.

 

[Marshall]

If my 2014 sits for a few days, before I start the truck , the peddle can be hard, but as soon as motor start , it goes back to normal, I presume the vacuum as leaked out.
I probably should get new fluid, but I am just about 80th km on the truck

I have not done any hard stops , should take a drive out a lonely road and nail the brakes, I have not really noticed any ABS when streets are slippery.
When I was still out in the country I had built a power brake breeder as I was have trouble with a couple old trucks . I think at one time I had 5 going, and a few old cars.

 

[Jeepwalker]

Probably a bad vacuum booster check-valve, or cracked hose-end, or plastic fitting...

 

[Marshall]

I wonder, can you use a I phone 8 as a mic pickup?
Guess I can check in settings.
I have hearing aids and phone plays in to them on blue tooth, could be handy in place of a rubber tub in the ear to pick up noise. Until you drop the damn phone.