Sticky front brakes

[MOSHO92]

Iv'e been having a problem with my front brakes making noise while driving. The rotors and pads are about 10,000 miles old and are still in good condition so today i took off the wheels to see what was up.

What i found was that the caliper was holding the pads onto the rotors pretty tight. It takes effort for me to spin the wheels while on jackstands and in neutral, and then as soon as i stop spinning them they stop very quickly. It is like someone is just resting their foot on the brake pedal.

This is happening with both of my front wheels. Could this be a failing brake booster, or 2 rusty calipers?

What is the actual clearance SUPPOSED to be between the pads and the rotor. Should they be touching??? I felt up my brake pedal to see if it was staying down when i let my foot off...its not. What do you all think?

 

[rangerj]

MOSHO92,

A couple of thoughts come to mind, given the symptoms.

1. Siezed caliper pistons, or pistons cocked in the bore. (both at the same time? unlikely

2. Rubber brake hose swolen on the inside and restricting the flow of brake fluid back toward the master cylinder. (both at the same time? unlikely)

3. Slider pins rusted and stuck. (both? )maybe!

The brake pads ride a against the disk with the small amount of "static" pressure on the brake fluid. In the front and/or rear master cylinder resivoir openings, where the brake fluid gets into the mastercylinder, there is a small hole that allows the fluid to flow back into the resivoir.

If this hole gets blocked with "crap" it will prevent the fluid from flowing back to the master cylinder, and effectively maintain pressure on the brakes. ("Like someone holding their foot on the brakes")

The fact that both side are doing the same thing tells me that this is the first place I'd look for the problem. Make sure the hole is clear of crap that might be blocking it. Use a piece of thin wire to clear the hole.

When the brake peddal is pressed and released, by a "lovely assistant", you should see fluid "squirt" up from the little hole uppon release of the peddal.

Let us know what you find please. rangerj

 

[MOSHO92]

Thanks alot rangerj. I will try that idea using the master cylinder.

Just to clarify: There should be some "static" pressure maintained on the pads?

 

[MOSHO92]

Ok, one more thing. Where is this fluid return hole. I took off the brake fluid resevoir cap and everything is pretty dark. Is is in the brake fluid resevoir? Do i need to disassemble something to find it?

 

[rangerj]

MOSHO92,

The small hole is in the master cylinder itself. The resivoir is just that, a holding tank. If the fluid is that dark it is time for fresh fluid! doh But that can be addressed later.

That having been said, stir up the fluid in the resivoir and siphon the "dark" fluid out of the resivoir.

I once used my wifes turkey baster for this purpose and she still has not forgiven me for that! So, I got one of those "Mitey Vac" pumps.
You can get a cheap "bulb suringe" from an auto parts store, like Auto Zone, for a few dollars. (Maybe even at Wall-mart)

Anyway, find a way to siphon out the dark fluid and get a look in the top of the master cylinder for the small hole by each of the holes where the resivoir goes into the master cylinder.

DO NOT SYPHON OUT FLUID BELOW THE LEVEL OF THE BOTTOM OF THE RESIVOIR. You could get air in the system if you do. Once you have located the holes clean them out with a piece of thin wire.

Then add some fresh brake fluid (DOT4). About an inch over the top of the master cylinder should be enough to test and see if the fluid squirts up through the holes when the brake peddal is released.

If everthing works right, fill the resivoir to the desired limit (with clean fresh brake fluid).

As for the static pressure, it is held in the lines by a small valve that is in the master cylinder where the brake lines screw into the master cylinder.

The little valves will hold 4 to 6 lbs psi of static pressure on the fluid in the lines. Pressure in excess of that is allowed to flow back into the master cylinder.

It is enough pressure to hold the brake pads against the disk, i.e. no clearance.

Once you get everything working right again, a complete flush and fill of fresh brake fluid is overdue! DOT 4 Castrol GT LMA (Low Moisture Activity), ATE Blue OR ATE Gold (BMW uses it), Valvoline (the new stuff), or Ford has a high performance brake fluid.

If this is not the problem, we'll go back to square one! thumb rangerj