2001 Toyota Sienna knocking noise from rear break

Tiny
WAMUK2
  • MEMBER
  • 2001 TOYOTA SIENNA
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 60,000 MILES
My 2001 Toyota Sienna makes knocking noise from the rear brake area when it approaches the stop bar at the intersection at a low speed. I wonder where the problem is.
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Monday, February 11th, 2008 AT 3:20 PM

6 Replies

Tiny
NAYBORBOB
  • MEMBER
My 2000 Sienna is also making a thumping noise that kind of feels like 2 per rev. My wife thinks she can feel pulsing in the brake pedal. It occurs on hard braking, with more passengers and especially at low speeds. I have replaced a brake drum which did not seem to help. I have swapped the bearing hubs which eliminated a bearing problem. I took it to the dealer today and they said the problem was drums were out of round. There is 120,000 on the original drums. They also wanted to get me for new brake cylinders (the hydraulic pistons that actuate brakes when you push on the pedal) because they said they were leaking (although I could find no evidence outside the rubber boot ends, and they told me the backing plates were beginning to rust and separate. They want $675 to repair all three items for both rear wheels. I am having a hard time buying the drum issue because I replaced one and the problem did not improve. So I took the car back from the dealer and am going to have the drums checked and turned tomorrow. Will replace the cylinders myself, and the backing plates look fine to me, and I am an engineer.
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Thursday, March 13th, 2008 AT 7:45 PM
Tiny
MELTILLIS
  • MEMBER
I keep having noise with my Sienna. I could take the drums off and clean the brake dust off of all internal parts. The noise would go away for a while then return. The brake shoes still looked good, but still kept making this noise. I finally bought new, (after market) shoes, and installed them, the noise has not returned almost an entire year later. I believe something was wrong with the original shoes that came new on the van. Again try some new after market shoes, this is the cheaper way out. Be sure to clean out all old brake dust
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Saturday, December 6th, 2008 AT 11:43 PM
Tiny
KRINIZA
  • MEMBER
I had the same issue on my 2002 Sienna. Annoying knocking sound when braking at low speeds. Yesterday I took off the rear drums and found huge amount of rusty dust and dirt inside one of the the drums. I cleaned it all by using my garden blower and the noise went away. The brakes looked fine otherwise. Need to wait and see if/when the noise will come back.
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Monday, January 16th, 2017 AT 7:13 AM
Tiny
KEN
  • ADMIN
Hey KRINIZA,

thanks for the addition to the thread, please add information to 2CarPros anytime.

Best, Ken
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Saturday, January 21st, 2017 AT 1:17 AM
Tiny
KRINIZA
  • MEMBER
More on my previous post. The real reason why the brakes were knocking and were so rusty and dirty turned out to be a leaking wheel cylinder. Replacing the wheel cylinder spilled into a big pain because as soon as I tried to unscrew it the brake line just snapped and broke. :(. I tried to replace the whole line, but due to inexperience and poor knowledge of how to deal with the rusty nuts as well as lack of time I took the car to a mechanic who used a torch to extract the old brake line. He replaced the wheel cylinder as well. The whole job with the two wheel cylinders and the brake line cost $300. What a shame just because of the rusty nut. I learned one lesson though. To deal with the rusty nuts one must have a torch and vise-grips. A sharpened, nail-like piece of metal with a hammer to help the nut to move after it is heated would also help. The mechanic did a poor job on bleeding the brakes. I will probably need to re-bleed them now.
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Monday, January 23rd, 2017 AT 2:49 PM
Tiny
CARADIODOC
  • EXPERT
Welcome to our world! Mechanics run into rusted parts all the time, and we often break off brake lines. We can't plan for all of those things, but customers aren't so understanding when it's "our fault".

For future reference, there are better ways to do this yourself. When the soft metal nut is rusted to the steel line, you can still loosen it from the wheel cylinder, then unbolt the wheel cylinder and rotate that to unscrew it from the line.

Under no circumstances use any penetrating oil or other petroleum-based lubricant to try to free up the nut. If even one drop mixes with the brake fluid, the entire hydraulic system can be contaminated. The only proper repair for that is to remove every part that has a rubber part in it that contacts the fluid, flush and dry the steel lines, then install all new parts. That is a very expensive repair, and even worse if the vehicle has anti-lock brakes. If any rubber part is not replaced, the contamination will leach out of it and recontaminate all of the new parts. This includes rubber flex hoses, wheel cylinders, calipers, master cylinder, combination valve, height-sensing proportioning valve, the ABS hydraulic controller, and the reservoir and the rubber seal under its cap.

Another alternative is to rebuild the old wheel cylinders right on the vehicle. As late as the 1980s that was a standard part of many brake jobs. Today the cost of new wheel cylinders is very low, so we just replace them, but I still required my students to know how to do it for exactly the reason you ran into. The kits cost about five dollars, and the job takes 15 to 20 minutes per cylinder. Those on '80s Ford Escorts and Tempos usually had areas corroded away that caused the leakage, so they couldn't be rebuilt. You have to check for that on all other brands, but it's not real common. Use brake fluid or brake assembly lube to lubricate the new lip seals. Professionals even wash their hands with soap and water first to avoid contaminating the rubber parts with fingerprint grease.

As for bleeding, you want to avoid pedal-bleeding with a helper. Running the brake pedal more than half way to the floor can damage the master cylinder. The resulting internal leakage will cause a slowly-sinking pedal, but that often doesn't show up until two or three days later. Gravity-bleeding is sufficient to bleed the wheel cylinder and that line. You'll make a lot more work and frustration if you allow the master cylinder to run empty while the wheel cylinders are apart. If the van has anti-lock brakes, and air gets into the hydraulic controller, you may need a scanner to command the computer to open the valves so air can be expelled from some of the chambers.

A simple way to stop the reservoir from running empty is to use a stick between the brake pedal and seat to hold the pedal down about an inch or two. The lip seals will move past the "replenishing" ports and block fluid flow. Remove the stick when you're ready to bleed. When fluid comes out, close that bleeder screw and wait for the next one to flow. When all the bleeder screws are closed, "irritate" the brake pedal a little, by hand. That will wash any remaining trapped air bubbles into the wheel cylinders and calipers. Open each bleeder once more for a couple of seconds to expel those last few bubbles.

If you catch the reservoir just as it's running empty, (or you're replacing the master cylinder), there is no need to bleed at the wheels. Add fluid to the reservoir, push the brake pedal slowly so it takes about 20 seconds to go half way to the floor. Release the pedal quickly, then repeat that a few times. Pushing it slowly will push fluid down the lines while giving the air bubbles time to float back up. Releasing the pedal quickly washes the air bubbles into the reservoir with the fluid that's rushing back.

The knocking noise you had could indeed be caused by an out-of-round brake drum, but there has to be more to the story. Shoes are expected to slide back and forth on the backing plates as they're applied and released. The rust your mechanic was referring to are grooves worn into the six "lands" the shoes ride on. Those are raised spots that tabs on the shoe frames rest on. A standard part of a drum brake job is to clean those lands, then lubricate them with a special high-temperature brake grease. That step is overlooked by even the most conscientious do-it-yourselfers. In normal to light braking, a shoe can catch on a groove and fail to apply. After hard braking, a shoe can catch and fail to release. With a warped drum, the shoes will slide back and forth over those grooves and cause a knocking noise once or twice per wheel revolution. Your mechanic was right to want to replace the backing plates if he had your best interest at heart. The knocking noise may be gone now with the new drum, but it wouldn't have occurred if those grooves hadn't developed. You can't see those grooves with a simple inspection. You have to remove the shoes or pull them away from the backing plates, then peek behind them.

Some people will try to grind or file those lands until the grooves disappear, but that is not acceptable. All three have to be the same height so the shoe is supported evenly on all three points. Removing material lowers their height and adversely affects where the lining contacts the drum, and the angle of contact between the lining and drum.

An additional clue that might be observed when there's no brake grease on those lands is a squeak from the rear shoes when the brake pedal is released. The lack of lubrication causes the noise that you hear, but it also causes the grooves that will cause a problem later.

Auto parts stores sell the brake grease. It contains molybdenum disulfide which prevents it from spreading over time. Most of the brands are black, but the one I'm most familiar with is copper-colored. It's called "Rusty Lube".
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Monday, January 23rd, 2017 AT 7:05 PM

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