Subie brake problem....

G

gearsoup

New member
So, my brakes suck. They are really soft, but they work. I've bled the bejezus out of them, and it hasn't improved. If I give it a few quick presses, it builds up pressure quite nicely. If I only hit it once, it's really soft. (the pedal travels quite a bit before it hooks up)

I've done:

rear disk swap

complete change of the fluids

Both front and rear rotors are heating up to about the same temp. Warm, but not hot. Could this be a possibility: Both front calipers have a lot of in and out play. I know that they are a free floating design, but I'm talking almost 3/16" of an inch! Hmmmm.....

 
Runnah

Runnah

New member
How do the rubber seals look like on the pistons, if they are cracked you need to be replaced. Dave (Rightseat) suggest getting piston rebuild kit when I was having trouble with mine.

Try some of the Super Blue Racing brake fluids. It will stiffen up pedal feel quite a bit.

 
ReZPunK

ReZPunK

New member
I'll take brake master cylinders for $1000 Alex.

if you have dropped it to the floor too hard while bleeding you can ruin the cups inside the brake master cylinder.

seen it happen on several different subies.

if you build up pressure, does the pressure hold if you hold on the pedaL?

if it feels like it slowly leaks, then its the brake master cylinder

 
G

gearsoup

New member
well, when the car is off and i pump the pedal, it builds up pressure and seems to hold it.

have not pulled off the front calipers. Am going out side now for more diagnosi....

 
W

WRXav8r

Member
sounds like a vac leak then.... how much does it help to have the engine running?

Shade tree tech advice (me).....

... take a propane torch (unlit) and with the engine running have someone apply the brake.... run the nozzle of the torch around the master cylinder... if the car rpm increases it is sucking in the propane from a vac leak...

Please not doing this for extended periods of time builds up propane in the engine compartment resulting in the instant Darwin Award for you...

 
G

gearsoup

New member
yep. It's looking to be a series of vacuum leaks. I went for a brisk drive, and I did a lot of left foot braking. When i was in the higher rpm's or gas pedal all the way down, I had wicked awesome brakes. If I let off the gas, and used my right foot to do the braking, I had a sponge. Kicked up the rev's and it firmed right up.

Got home and popped the hood. Definately hear vacuum leaks. How do I find them? I already found one at the throttle body, plugged that, and I still hear another.....

 
R

robu

New member
Mechanic's stethescope. You hold a piece of coolant line up to your ear and point it at vacuum lines until you hear one...

 
R

rallyXcramps

Guest
if you unplug the vacuum from the manifold to the booster(and plug the gaping hole of course) how are the brakes? Should be wicked hard pedal but work well. If not we'll have look into this issue closely.

I find vacuum leaks by spraying brake clean in the general direction of suspect areas(hoses, manifold gasket area, ect), and engine should bog down momentarily until it sucks that shot of brake clean all the way in and is breathing regular air again (1-3 seconds.)

If you have an internal booster leak you might not ever find the leak and might have to assume the booster is leaking internally and just replace it. More often than not booster hoses leak instead of boosters themselves. And intake manifold gaskets wrinkle up sometimes and cause vacuum leaks. Short shots of brake clean (with the straw attached) can find vacuum leaks lickidee Split.

 
R

rallyXcramps

Guest
make sure you plug the booster hose(from the manifold) so you don't have a huge vacuum leak. Dont breath the fumes. ;D

 
G

gearsoup

New member
Didn't have a chance to do the leak test. I did unplug the booster vacuum hose though. Wicked nice pedal feel. Can I just leave it like that until I get a replacement master cylinder?

 
Evan

Evan

Active member
told you those throttle body gaskets were not always reusable
default_smile.png


 
You must log in or register to reply here.

Latest posts

Back
Top