# Brake pedal still spongy after multiple bleeds



## daveb1

Did you bench bleed your new master cylinder? Perhaps you finally got your system bled and then changed the master?


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## jpearson311

daveb1 said:


> Did you bench bleed your new master cylinder? Perhaps you finally got your system bled and then changed the master?


No we didn't bench bleed it, but the entire system has been bled twice since we've installed the new MC.

Jesse


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## christoff

Did you check to see if there is a bleeding sequence from one wheel to the other?


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## christoff

If you have Abs,it might also be a consideration when bleeding.


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## jpearson311

christoff said:


> Did you check to see if there is a bleeding sequence from one wheel to the other?


No. We bled them the "traditional" way. Rear passenger, rear driver, front passenger, front driver.

Jesse


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## christoff

Maybe it would be an idea to go to a nissan site to see if there is a special way to bleed. chris


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## Marqed97

If it has ABS, most scan tools provide a brake bleed function that cycles all the valves to move any air out of the valve body. I've had a few over the years that were just awful to bleed out. 

Also, you could try the bleed procedure for a diagonally split system (LR RF RR LF). Have seen them split this way on many imports and domestics over the years.


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## cjm94

Are you sure the rear brakes are adjusted properly? If they are to far out they will make the brakes feel spongy


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## rusty baker

jpearson311 said:


> No we didn't bench bleed it, but the entire system has been bled twice since we've installed the new MC.
> 
> Jesse


Master cylinders really need to be bench bled. That is most likely your problem.


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## jpearson311

Well, there is an update and it's not good. So I did a power booster test last night and it totally failed. Spent over $200 today and installed a new booster. The pedal was definitely harder, but still ultimately soft. I decided to remove the front wheels to inspect the brakes and what do you know? The pads on both sides were seized to the rotors, the rotors were rusty as hell, the passenger side caliper was seized, and the driver side caliper piston came clean out of the caliper when the brake pedal was pressed and spilled brake fluid all over the floor.

Now I have to return the brake booster and spend $160 for new calipers, pads, and rotors. Awesome, what an exciting day I had. What's the moral of the story? Don't ever listen to your lazy hippie neighbor when he tells you all it needs is the brakes to be bled. Thanks for your help you guys.

Jesse


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## 95PGTTech

jpearson311 said:


> Well, there is an update and it's not good. So I did a power booster test last night and it totally failed. Spent over $200 today and installed a new booster. The pedal was definitely harder, but still ultimately soft. I decided to remove the front wheels to inspect the brakes and what do you know? The pads on both sides were seized to the rotors, the rotors were rusty as hell, the passenger side caliper was seized, and the driver side caliper piston came clean out of the caliper when the brake pedal was pressed and spilled brake fluid all over the floor.
> 
> Now I have to return the brake booster and spend $160 for new calipers, pads, and rotors. Awesome, what an exciting day I had. What's the moral of the story? Don't ever listen to your lazy hippie neighbor when he tells you all it needs is the brakes to be bled. Thanks for your help you guys.
> 
> Jesse


Power booster should not impact pedal softness because you bleed with car not running (no boost assist). Power booster simply reduces the pressure the driver needs to apply to the pedal to get braking action (mechanical advantage).

Take off the rear wheels and get the brakes and hardware squared away before continuing.


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## jpearson311

95PGTTech said:


> Power booster should not impact pedal softness because you bleed with car not running (no boost assist). Power booster simply reduces the pressure the driver needs to apply to the pedal to get braking action (mechanical advantage).
> 
> Take off the rear wheels and get the brakes and hardware squared away before continuing.


If you run the engine for a minute or so, turn it off, and then pump the brake pedal, if the pedal doesn't incrementally get firmer, then a lot of the time, the booster is bad. It's bad because it's not holding it's vacuum pressure. Regardless, one of the rear wheel cylinders was leaking so we replaced both of them and the front break hoses. It stops now, but the pedal still goes really low. Thanks though. At this point, it's a mystery.

Jesse


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## 47_47

You need a direction to go.

Place trans in park or chock the wheels, e-brake off. Start engine. Rapidly press the brake pedal (release, press, release, press...). If you can pump it up, you have air and brakes need bleeding. If you can't basic brake problems.

For a power booster test, key off, depress brake pedal. You should get 2-3 hits of power assist. If you don't, either leaking booster or bad check valve. On the last hit keep your foot on the brake pedal. Start engine, pedal should fall slightly.


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## 95PGTTech

jpearson311 said:


> If you run the engine for a minute or so, turn it off, and then pump the brake pedal, if the pedal doesn't incrementally get firmer, then a lot of the time, the booster is bad. It's bad because it's not holding it's vacuum pressure. Regardless, one of the rear wheel cylinders was leaking so we replaced both of them and the front break hoses. It stops now, but the pedal still goes really low. Thanks though. At this point, it's a mystery.
> 
> Jesse


You're over-complicating it again. Base brake system, brake hydraulics, and vacuum or power assist are all completely separate systems and should be diagnosed and serviced separately.

Visual inspection of all base brake components - hardware, bolts, rotors, pads, soft and hard lines, shoes, drums, wheel cylinders, etc. Replace as necessary due to visual failure.

Hydraulics - now depress brake pedal with truck completely off - do all four wheels engage correctly? If not, address air in lines, master cylinder, proportioning valve, ABS pump, etc.

Vaccuum assist - now that all those are done, turn truck on and address this. Pedal should be high and hard if the top 2 system are addressed when completely off. When you run it, pedal should be softer as the booster is giving you assist. The booster is such a large vacuum demand most times it is diagnosed by customer first noticing engine running concerns.


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## Doc Holliday

you didn't listen to your brakes as they were crying for help as they wore out before listening to your hippie neighbor? come on...


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