Today my husband replaced the rear brake pads on my 2004 XJ8. (The brakes were working without any problems, but the pads were down to about 10%.) We read all of the information we could find on the forums to be sure it was done correctly. Replacing the pads went smoothly, bled the brakes as directed in several posts here (twice).

Here are the issues we're having now:
1. The brake pedal goes easily straight down to the floor when you first press it and barely stops the car. If you press the pedal again right away, it gets harder and will stop the car well. Wait 5+ seconds and the pedal will go too easily to the floor again.

2. About half the time when you brake, there's a PSSSHHHH sound that comes from the driver's side front, sounds like pressure being released.

The new brake pads are Duralast CMAX purchased from AutoZone. The rotors appear to be fine. We reset the parking brake as directed in a post here. My husband did the front brakes a year or so ago with no issues at all. We really need some expert help here. Any advice would be greatly appreciated.

Thanks,

Tracy

 

You are describing air in the line. You need to bleed the brakes again. Not being an expert, I would suggest the rears that you worked on first. Keep the fluid topped off, and have one person in the car slowly pushing the pedal to the floor as the bleeder is open, then hold the pedal there until the bleeder is closed and repeat until there is good pedal. This goes for both sides.

I'm sure a tech can add a much better method, but this always works for me.

 

Yeah its definitely air. The problem is caused because the hydraulic fluid (aka brake fluid) doesnt compress, which causes you to have a nice pedal feeling. When the pedal is spongy it is cause when air is in the lines (and air does compress).

There are little bleeder nipples on the brake calipers that you unscrew with a little wrench. I think its a 10mm, but I cant remember. Anyways you want to open the bleeder nipple while another person is pressing the brake pedal (to pump fluid through the system) making sure to close the bleeder nipple before the person releases the brake pedal to make sure no air is drawn in. You will also want to make sure that you continually top off your brake fluid in the reservoir, again to make sure you dont draw any air through. Also dont reuse the brake fluid. Its tempting to do so, but it isnt worth it. After a while the fluid starts to break down and lose some of its thermal properties.

It is best to start with the brake caliper furthest away from the master cylinder. Your master cylinder is on the driver side (left) so on your car you would want to bleed the right rear caliper first. Followed by the left rear, front right and ending with the front left.

You can buy a brake bleeder kit at a local autoparts store. They include a piece of clear tubing that fits over the bleeder nipple and then you can see when there is no more air in the line. Plus they usually include a little cup to collect the used fluid, and usually some instructions.

Something that might be helpful (since I am a visual learner) is to search for videos on youtube. I do this often just so I know what the part looks like and know hat to look for.

Good luck and keep us updated!

 

Agreed...it is air in the line. If not known already, always bleed the wheel farthest from the master cylinder 1st, then one wheel closer, one more closer and the closest wheel last.

It is also a good idea to use a hose on the bleeder valve with the open end in a small container with a bit of new brake fluid in it. The submerged hose will prevent air from being drawn back into the system. Keep the hose submerged and bleed as mentioned above except you should pump the pedal several times with the bleeder closed, hold down on the last pump and now bleed. Keep your foot on the pedal until the bleeder is closed again... repeat until no more bubbles come up in the container with the hose in it. Hope you get the PSSSHHH out!

 

Thank you. We'll try to bleed it again and use these tips.

Tracy

 

Can you go over in detail how you changed the pads and the process used to bleed? For instance, How did you retract the calipers?

I am a big fan of Autozone's ceramic pads and have used them sevral times on customers' cars. In fact, I just did brakes on an 04 X350 last week and used them.

Let's hear the whole process you used before I weigh in. Start from the top, until you reached the point where you are now, then we'll go from there.

 

I forgot to mention something...after bleeding the brakes, even when properly bled they may initially feel soft to non-existant. In that case, with the engine running, pump the brake pedal several times. You should feel the pedal stiffen up as you do. If not, and you're sure they are properly bled, look for a leak(s).

You'll get it!
Bob

 

Thank you! Thank you! Thank you! He wasn't bleeding them from the right place. The MityVac tool really helped too. Now my brakes are perfect and I love my Jag again. You guys rock!

Tracy

 

I'm glad to hear that you have gotten it all straightened out.

 

Excellent! Glad you have your brakes back. Nice feeling to have a problem gone. I just replaced some suspension parts and have a smooth, quiet ride again... much more enjoyable to drive!

 

On the road again!

 

Akebono’s were recommended on this forum and I put them all around last week.
They work great. No more sticky brakes. No more brake dust. Shorter pedal travel.

Note: The rear pads have a "guide" pin protruding from the back which line up the outside pads. This pin interferes with the inside pad where the caliper piston sits against the pad. This means that the piston presses on the pin and only the outside edge of the pad presses against the rotor. And since this distorts the pad and the whole setup, the outside edge ends up dragging on the rotor heavily without the brakes applied, and noticeably slows the car. It also produced a “burning brake” odor, and worst of all it resulted in generating a tremendous amount of heat. I was worried about warping my rotors.

I had to grind the pin down on each of the inside pads to get the piston to press uniformly on the back of the pad and for the pad to apply flat against the rotor.

I checked out the old pads and I could see the same issue there, with the caliper piston outline overlapping the pin. You could see that the pin got caught in one of the two groves of the piston that are used to turn the piston back into the caliper. The result seems to be that as the pads wear, the pistons cannot continue to slowly turn out, as they should in order to the take up growing gap between the pad and the rotor. This creates a gradual increase in brake pedal travel over time.

I assume I have the correct pads. They fit fine and they match the old ones.
Here is a picture of what I purchased from RockAuto. There is a guide pin on the back side, opposite the butterfly spring. Other brands appear to have the same pin.

Anyone else recognize this issue?

(PS - I accidentilly posted this to the X-Type forum)

 

the pins are supposed to fit into the holes/slots in the caliper pistons. the piston slots should line up at 6 and 12 oclock when retracted. adjusted slightly to fit the pins.