mlevk

My 91 has 140K, and I replaced the pads about 36K ago, however
my brakes are getting mushy and slighty pulls to one side at highway speeds.
If I pump it , the brake pressure stiffens quite a bit.
My diagnosis would be the MASTER BRAKE cylinder, any one else had this
symptom or problem ? I'll check the pads as soon as I can as well since
36K is normal wear for a BOSTON stop and go traffic.

spxChrome

How long has it been since you flushed the brake fluid? Mushy brakes can be the result of contanimated fluild. If it is dark I would get it changed.

I do it the simply way. Go to Lexus and buy 2 bottles of OEM Brake Fluid. $6.32

Buy a turkey baster and suck the old fluid out of the resivor. Refill it. Drive it around 5-10 miles and repeat the steps. Do this like once a week for about a month or until the fluid is clear.

Be carefull not to spill any brake fluid. It is toxic and will eat through near about anything especially your paint.

Some people will actually bleed the brakes but this is to time consuming and it is easy to get air caught in the lines and then it becomes a real pain.

seanl

IMO changing the brake fluid with the above turkey baster method won't help much with spongy/soft brakes.

You need to bleed the air out of the brakes. If you are not familiar with the process of 'bleeding brakes' then I would recommend you have it done professionally. Have them run a quart of fluid through the system, all 4 corners should be clear by then. Changing the fluid this way will also remove the trapped air and should result in a firmer pedal.

A proper bleeding will eliminate trapped air, not cause it.

Good Luck.

ATSOU

My LS too...........When I step on the brake, the car pull to the right (very right.)

additude

Bleed the brakes to start. You have air in the lines.

Check master cylinder if the problem persists.

If the fluid is dark in color, replace all fluid when bleeding.

mlevk

Okay, I bleed the lines with the vacuum brake bleed kit I see
all the time , but my question is how did I get air in the lines
if that is the case. Other than checking the brake fluid thru
the reservoir cap, it really shouldn't get air in the lines.

The other thing I haven't considered in the rubber brake lines
themselves, but I see this weekend , Thanks everyone.
.

additude

Air in the lines either came from a low reservoir situation where air was allowed to get in that way or a poor seal on a brake cylinder or the master cylinder itself. If you are not loosing fluid then I doubt it's a hole or cracked hose, etc.

mlevk

Well , the brake pedal finally sank all the way down to the floor
yesterday, and I cannot find a leak anywhere, the fluid is full as always
and the color is normal. So , I ordered a OEM rebuild kit from my dealer
and will rebuild and bleed the system this weekend .

Any tips for me ? and I'll also post the pics when I'm done.

Slexus

How to know if Air is in your brake system??
-Push on your brake few times (perhaps 5 to 7 times) and you can feel if your foot being pushed back toward your body; that mean there is air in the braking system (Air being compressed by pushing on the brake and air is expanding). If you don't feel your foot being pushed back then there is no air in your braking system.

How to release Air in your braking system??
-This requires two persons.
- Inspect your braking system (master cylinder, calipers etc...) to see if any wet spot cause by brake fluid.
- Refill your brake fluid.
- Inspect where are the bleeding screws (perhaps 4 bleeding screws, one for each wheel), and prepare for wrench size (best use boxed wrench).
- Inspect and find the way to catch the brake fluid.
- Wear goggles

-Bleeding Air out: Ask your helper push on the brake pedal; say 6 times then ask him keep pushing on the pedal (Ask him not to release his foot until you say so, keep his foot pushing on the pedal) while you start unscrew the bleeding screw you might see brake fluid escaping out, then tighten the screw back (when you unscrew the bleeding screw, you might see the brake fluid + Air bubble flushing out ). Repeat Bleeding Air out step a few times on each brake till you see only fluid come out (not bubble fluid). Your helper only release or pump when the bleeding screw is tight and being told by you, if he release or pump while bleeding screw is open the air might get in to brake system.

- Frequent refill brake fluid. Empty brake reservoir will let the air in to braking system.
- Recheck if Air still in the braking system by using How to know if Air is in your brake system?? above.
- If you still feel there is air on the braking system, you might try Bleeding Air out again; if it's not helps your master cylinder or other braking component is bad.

Please add your comments.

mlevk

Here's the low down,

The Master Cylinder is fine , the rear pads and left front were worn pretty much down to
nothing ! Probably causing the caliper piston to travel a little too far causing the
lose in brake pressure , though I didn't see any seepage at the piston seals.
So all changed with PADS from Tire Rack , I bought the ceramic fronts and rears.
I bleed all the lines with a bleeder kit , it takes too long in my opinion. And now the
brakes are firm and quick though not as quick as my friends MAXIMA's those are
really quick reacting.

The front are dual piston calipers if anyone is not sure , but not CLAMPING dual pistons
like my Datsun 280Z !. The rears are single piston.