Thumping Brakes

Sure pull the wheel off and set up a gauge to measure surface variance...

Check brake pad wear for even or irregular patterns...

http://www.phoenixfriction.com/t-disc-brake-pad-wear-patterns.aspx

Bonus tips.....

But do check first if you have adjustable wheel bearings or not. This not a "given"...

If adjustable, use the service manual and set them up correctly.

Go for a drive, but DO brake a couple of times, with the motor running BEFORE driving off, just to make sure that the pads are on the disks. Till you get a "hard" pedal again!!

In a safe place try the brakes to see if they are any better or not. Maybe a couple of emergency stops and see if the problem is fixed.

Remember, the problem could get even worse if the disks were badly worn AND the wheel bearings were out of adjustment!! Possibly!

So be careful!!!

If still apparent, follow SolarEagles videos.

Usually today wheel bearings on the front (if front wheel drive) are not adjustable.

But they might be worn and have too much play. 12 year old car!!

Prise the pads away from the disks, both sides a few millimeters, and try rocking the disk holding the disk at the top and bottom, then left and right.

ANY discernible movement in the wheel bearing, simply change the bearings out with new disks, and follow SolarEagles videos.

Brake pads have a ‘tone pad’ built within the wear material, this located near the end of usable brake material.

When the pads wear enough, this tone material exposes and when rubbed on the rotors squeaks, squeals, They tell me, I can’t hear the pitch, so I don’t know. The idea is, this tells you that there is a limited amount of life left in the pads, and if you change ‘em out before the steel pad frame starts digging into the rotors you can save yourself some coin.

I do remember the sort of fading or thumping while braking you describe, so I suggest you cannot hear the tone either and the pads are about worn out.

Check the run-out with a dial indicator. .006 inch is the limit, they say. A brake shop can do this.

Mis-tightened lug nuts may be the culprit too, but I'd say hitting a puddle after heating the disks with a hard stop is the culprit.

I see SE has already posted.

Does the car pull slightly toward one side with the rythm of the thump?

Can you feel the thumping strongly through the steering wheel?

If you apply brakes lightly can you feel a difference in the thumping comparing cornering to the right vs cornering to a similar degree to the left?

Perhaps you could drive over a section of clay or sand while applying the brakes to the point the thumping is most noticeable and then examing the tire tracks for indication of periodic variation in braking.

Perhaps there will be significantly more brake dust schmoo on the thumping wheel as compared to its mirror image wheel.

The thumping has just started, but is soooo minor right now. Thing is, by the time it gets bad it will be winter. Thumping brakes on snow and Ice is not cool, and doing a brake job in the snow also is not cool. he he he Jan here can be below zero he he he

So the brake dust shmoo buildup rates are not showing a left right variation on at least one axle?

will look tomorrow, will let ya know.

I may be wrong, but I can't imagine you will see any difference.

I'll be a little surprised, but I can easily imagine it.

I have no knowledge of the Malibu breaking system, but could it be that your "mechanical" break pad wear indicator is engaging.

Brake Pad Wear Sensors (Mechanical) The mechanical brake pad wear sensors are small metal tabs on the backing plate of a brake pad. They are designed to contact the brake rotor surface and make a squealing or scraping noise when the brake pads have worn down to the point of needing replacement.

Brakes are still totally silent.

Just not smooth even braking action.

Well, your question was is there a way to tell which brake is giving this symptom, right?

8 years, there is a good chance the MTBF of the pads has been reached or will do so in the next couple of days. Every manual I have ever seen advises strongly to do the brake at both axle ends at the same time. Almost certainly time to refresh the brake oil as well.

I would say, take the car to a qualified Brake shop and have them inspect all the brakes and advise of repairs. They are the pros and safety is first.

The only issue with that is, if I do that I may as well just buy new rotors and pads and change them all out. cost would be almost the same

Have you pulled the front wheels and looked for any obvious damage?

Measured the pads?

Not yet, too hot out there gonna be a while.

That's my excuse.

Right now, in the shade, under the roof overhang, shaded by an Orange tree, it's 105°F at my house.

Can you top that?

Ahh put your straw hat on and wet yourself down with the hose every now and then, take breaks in the A/C when the heat gets to you, drink plenty of water....You'll be fine...it's about 95 here and the humidity is around 90%....I'm replacing all the mounting bolts (over 100 3.5" studs) for my hurricane shutters at about 2 hrs a day....sweating my balls off...still have about 2 or 3 more days...

Somebody installed galv steel studs and they rusted up....I'm replacing them with stainless steel....Then I need to test fit and label all of the panels....That should take about a week...

I HATE Stainless bolts.

I always seem to snug them just a bit too far and then that gall all up and more or less have to grind or cut them to get them off.

No A?C Here so in the house is even hotter!

Sometimes on real hot days we used to rig up a beach umbrella when working on a roof...it was a lifesaver....

This looks perfect...

Ahaa.... So you tried the search term "cantilever sunshade" to solve last weeks guess the architecture too.

Or is this just a coincidence?

Yeah brass is even worse....but these are attached using wing nuts and rubber washers...

I use a drop of WD-40 on stainless steel threads. It seems to work well. Unless you really do them up far too tight.....

Using it on non stainless seems to stop corrosion too....

On either, a torque wrench can help prevent over enthusiastic nut tightening.

Especially important on wheel nuts!!

Though any form of oil is probably not a good idea there IMHO, though I have used copper paste to good effect on corroding wheel lugs, after a good wire brushing....and I always torque them down correctly!

This is exactly it! Yes the car is outside, and can sit for days and not move. And after every rain, they are indeed "Crusty" you can hear them rubbing till a few applications of the brakes rubs off where they rusted. I guess it sucks not having a garage!

I've not got a garage, but if I did the car would not get in for the amount of 'useful items' I'd have just waiting for a new use. It can take half an hour to empty enough out my shed to get to that tool I've not use for a few months.

My brakes are on a four year cycle: front ones this year, rear in 2 years,.... Keeps costs & work spread out.

My brakes are on a "What's that noise" cycle.

Not really. I buy my tires from a local, family owned shop. I also have them rotated regularly and they check pad thickness for me each time.

We don't know what rust is here in Arizona.

When it's this hot and I feel the urge to go outside and work,......................... I don't.

Maybe an hour or two in the morning, while it's still under 100.

I jumped in the pool with my T shirt on about 6:00 PM and when I got out I nearly froze to death. Humidity, 10%.

Cutting and welding metal now, so that makes for short days.

NSS has no AC? That's a pity.

Some car designs, it seems the front rotors just weren't large enough to handle typical stopping duty, and a warped rotor seemed to be inevitable. Even for a careful New England Yankee driver (my father), 2001 Cadillac ?DeVille with multiple rotor sets under his belt. 2003 version of same vehicle, no problem....

I suspect there is a good degree of empirical engineering when it comes to rotor design for the driving habits of the general populace.

Very, very true!!

I wonder if I would drive it some and instead of applying the regular brake, I slowly apply the parking brake. if I feel the same thumping then I know it is the rear set, if none then it is in the front. Thoughts?

Joe

My parking brake is a drum/shoe affair, inside the rear disk.

I do not know if this is typical, or unique to pickups. (I'd guess they are all like this)

That's weird. Nope all 4 are the same on this. no drumness at all.

I drive a Citroen with hydropneumatic suspension. It has all round discs and parking brake in the front calliper. Earlier Citroen’s had a second, smaller pair of pads for the front parking brake. This setup is needed as the suspension drops when the engine is off, causing the wheelbase to lengthen.