[RESOLVED] Why do I have spongy brakes?

[tsunari]

Ok, here's the situation: Installing new pads & rotors all-around. Decided to remove the calipers and paint them while I was at it. So of course all of the brake fluid drained/leaked out of the unhooked lines. Reinstalled everything and bled the system roughly 5-7 times, yet the pedal still goes to the floor when depressed. I even went as far as to bleed the master cylinder and then re-bleed the calipers to no avail.

I've checked the operation of the brake booster and it appears to be working fine. I do have SOME braking power, but the pedal is still extremely mushy and pretty much better off how it was before I started all of this last weekend.

The troubleshooting chart in the FSM suggests the following:

Air in brake system -- I've bled the HELL out of it
Worn lining or pad -- Uhm . . . these are new pads
Broken vacuum hose -- Brake booster tested just fine, and all was working before
Faulty master cylinder -- How would this happen all-of-the-sudden?? I never touched it
Brake fuid leaks -- Dont see any
Auto adjuster malfunction -- There's an auto adjuster for disc brakes??
Excessive push rod to master cylinder clearance -- It was fine before . . .

So any ideas? Or something I'm missing??

 

[BUCK]

You have air in the Brake System.
I take it your checking for leaks.
Never let the Master Cylinder go dry.
Is the car level? Or are you "bleeding" with Back of car jacked up & front down?
Are you starting at the farthest Wheel Cylinder & ending at the Front Drivers Side?
It's a 2 man job - do you have decent help?

 

[tsunari]

You have air in the Brake System.
I take it your checking for leaks.
Never let the Master Cylinder go dry.
Is the car level? Or are you "bleeding" with Back of car jacked up & front down?
Are you starting at the farthest Wheel Cylinder & ending at the Front Drivers Side?
It's a 2 man job - do you have decent help?

Hey Buck . . . Here's a bit more detail on what's going on:

The only time the reservoire went try was when I pulled the calipers off and the fluid dripped out of the lines, so I guess the master cylinder might've lost some fluid then too. But my assistant and I later bled the master cylinder by:

+removing the output lines
+slowly depressing the brake pedal to the floor and holding
+coverd the output lines with my fingers
+slowly raised the pedal up from the floor so as to draw fluid in from the reservoire

Did that 3 or 4 times and never saw any bubbles come out of the master cylinder.

We then proceeded to bleed the calipers on level ground in the following order:

+Passenger-side Rear
+Driver-side Front
+Driver-side Rear
+Passenger-side Front

The initial caliper bleeding yielded air and old fluid (the fluid is now crystal clear). As for how we bled it, we pretty much:

+Had the car running @ idle
+Opened the bleeder valve ~1/8 turn or less
+Slowly depressed the pedal to the floor and held
+Closed the bleeder valve
+Released the pedal
+Repeat

That should've done it - ya?

 

[tsunari]

Have you checked your brake booster?
Have you checked your brake check valve ?

Yeah, checked the brake booster and it passed all of the tests. Haven't checked the brake booster check valve though.

Would that give a mushy pedal? If so . . . how could it just die like that when I didn't even touch it changing out pads and rotors?

 

[BUCK]

Your Order & Procedure suck-

The CORRECT Order & Procedure to Bleed:

+Passenger-side Rear

+Driver-side Rear

+Passenger-side Front

+Driver-side Front

NO NEED whatsoever to have car runnning - NONE - ZERO.

WITH BLEEDER VALVE CLOSED - Pump Pedal a few strokes.

With Pedal slowly IN MOTION toward the Floorboard -Crack bleeder & bleed air & Fuid - BEFORE PEDAL HITS FLOOR CLOSE THE BLEEDER (takes some teamwork & communication here).

Then...

WITH BLEEDER VALVE CLOSED - Pump Pedal a few strokes.

With Pedal slowly IN MOTION toward the Floorboard -Crack bleeder & bleed air & Fuid - BEFORE PEDAL HITS FLOOR CLOSE THE BLEEDER (takes some teamwork & communication here).

Then...

WITH BLEEDER VALVE CLOSED - Pump Pedal a few strokes.

With Pedal slowly IN MOTION toward the Floorboard -Crack bleeder & bleed air & Fuid - BEFORE PEDAL HITS FLOOR CLOSE THE BLEEDER (takes some teamwork & communication here).

+Repeat till you get no air from that Wheel Cylinder - it's a LONG WAY for a bubble to travel from Master Cylinder to the first Rear Caliper so don't be in a hurry.

Go to next Wheel Cylinder in order & Repeat.

Keep a close eye on Reservoir so it does NOT run dry.

You may find it necessary to go around twice thru the order.

Have Plenty of Fluid handy.

 

[tsunari]

Your Order & Procedure suck-

The CORRECT Order & Procedure to Bleed:

I'd like to clarify that it's not MY procedure that was followed but that which was stated in the Mitsu FSM. I personally have never had the engine running while bleeding brakes up until this point . . .

 

[dont need 8]

WITH BLEEDER VALVE CLOSED - Pump Pedal a few strokes.

I am upgrading my drums to discs on Saturday and want to make sure I bleed correctly. I have read that pumping the brakes with air can cause the fluid to become frothy if there is air in the system. This would make it that much harder to bleed, right.

 

[tsunari]

I am upgrading my drums to discs on Saturday and want to make sure I bleed correctly. I have read that pumping the brakes with air can cause the fluid to become frothy if there is air in the system. This would make it that much harder to bleed, right.

I too have read this in several places, but this is supposed to happen mainly if you depress the pedal to the floor rapidly . . .

 

[Denji]

Haynes manual recommends leaving the car on. I'm not saying conclusively that this is the correct way to do it, but its true.. IF anyone denies it you will be seeing a picture of my haynes service manual with the procedure specifically saying that you bleed the lines with the vehicle on.

 

[turboholic]

Haynes manual recommends leaving the car on. I'm not saying conclusively that this is the correct way to do it, but its true.. IF anyone denies it you will be seeing a picture of my haynes service manual with the procedure specifically saying that you bleed the lines with the vehicle on.

-With the motor running, it'll reduce the padel effort, but that's not a must.

 

[BUCK]

I was Bleeding brakes BEFORE the guy who wrote that Manual was BORN!

BTW I have a Factory Manual Set too & IMO in some areas a LOT was lost in translation from Japanese to English.

My way works.

 

[RamenPride]

I've heard you can damage the seal in the master cylinder by pushing the pedal all the way to the floor (not sure if this is true).

I've never bled the master cylinder, but if it does go dry then you're going to have a lot of bleeding to do. I don't really know exactly what's involved, but plugging a hose with your finger doesn't make for an airtight seal either.

 

[Mike1992]

Listen to Buck, I bled them as he says a few months back while I put my Stainless Lines on and I got awesome pedal feel and excellant stopping.

 

[tsunari]

Well, just got my system power bled from the mitsu dealership last night and everything seemed to come out clean. Pedal is still as mushy as before

Any other ideas / suggestions? Think the only thing I have to go on at this point is:

+Master Cylinder died when it went dry ?
+Air in the master cylinder ?
+Something wrong with the calipers??

I'd really hate to replace the master cylinder only to find out that it was perfectly fine to begin with . . .

 

[tsunari]

Usually mashy brakes have to do with the booster... Pull it apart check it out.

Well I was actually trying to figure the problem out WITHOUT having to drain and remove the master cylinder / brake booster, etc . . .

 

[Otis]

Are all the pads in right? I've seen that cause a mushy pedal many times. Also did you try to gravity bleed em? Crack the bleeders and let em sit for a while until fluid comes out steaily. Keep the cap off the master and keep it full.

 

[tsunari]

Are all the pads in right? I've seen that cause a mushy pedal many times. Also did you try to gravity bleed em? Crack the bleeders and let em sit for a while until fluid comes out steaily. Keep the cap off the master and keep it full.

Never gravity bled em . . . after bleeding them for like the 8th time, I got tired of not getting anymore air out of the system and still having spongy brakes. So I took the car to the mitsu dealership and hooked it up to their power bleeder machine (forces fluid in at the reservoire and vacuum at the calipers). But that didn't help the situation any either . . .

 

[tsunari]

Have you tried a brand new booster? Its about the only thing left now :thumbdown

Actually, I was about to try a new master cylinder. I *think* the brake booster is fine. The FSM has like 3 or 4 tests you can perform to check the operation of the booster. If it fails any of them, then there is supposed to be something wrong with it, but mine passed with flying colors . . .

 

[Knoob]

i am having brake problems as well.... but mine is on the interstate... if i touch the brakes my steering wheel goes crazy.... i am thinking a roter is bent.....

sorry to hi jack your thread...

 

[tsunari]

i am having brake problems as well.... but mine is on the interstate... if i touch the brakes my steering wheel goes crazy.... i am thinking a roter is bent.....

sorry to hi jack your thread...

If your steering wheel vibrates- it's most likely this:
http://www.stoptech.com/whitepapers/warped_rotors_myth.htm

 

[BUCK]

i am having brake problems as well.... but mine is on the interstate... if i touch the brakes my steering wheel goes crazy....

^THAT^ sounds like a Tie Rod End - not a Rotor - VERY dangerous - get it looked at immediately!

 

[Knoob]

really what can go wrong???

how do i check this.. never looked at it before???

it only does it when i hit the brakes... thats it.

i was doing around 95 going around a curve the other day... and tapped the brakes a lil and it felt like i lost full control over the car... sucked bad. i thought i was gonna die.

 

[tsunari]

Okay . . . I sprung for a new master cylinder and installed it today. Bled the master cylinder, then bled the brakes. While everything was out, I also checked to make sure the check valve in the brake booster line was working. So here's what all has been done:

+New Pads
+New Rotors
+Calipers were removed, painted, and re-installed (brake lines ran dry because of this)
+Rebuilt Master Cylinder
+Brake booster is functioning properly
+Brake booster check valve is functioning properly
+Master cylinder has been bled
+Entire brake system has been bled both manualy & power bled

and STILL . . . the pedal is mushy- just like it was with the original master cylinder after I installed the new pads and rotors. I'm completely out of ideas

 

[tsunari]

Ok, just closing this thread . . . think I've FINALLY gotten my problem solved after about a month of troubleshooting.

For those who are having brake problems, I suggest going over to www.mpbrakes.com and check out their tech articles -- VERY helpful.

Turns out I had air somewhere in the system that just did NOT want to come out.