Front brakes pulsate when braking?

[Risen]

So I haven't driven my NSX in half a year and the ABS and TCS light both turn on as soon as I drive. Before, it was just the ABS. When I hit the brakes (even if I lightly push it down), the brakes in the front slowly pulsate. It's not fast pulsating like when braking on gravel or a wet / slippery road. The car drives fine though, it's only when I brake. The rotors are not warped and the brake pads look good. I also have a Check Engine Light, which I have to check, but I had that CEL before and it did not effect the brakes. Has anyone else had this issue?

Thanks.

 

[JMChristopher]

Just a shot in the dark, but could there be a problem with the ABS computer? Maybe a fuse blew or something?

 

[shawn110975]

its been sitting you need to go exercise the ABS system........

go drive it get up to about 45mph try and lock them up, pretend a small child has walked in your path... the ABS will kick in and do what its made for..... do this 5-6 times you will start to smell rubber that's when you stop.

then report back.. Not kidding this is real advice

 

[NSXGB]

Wheel sensor?

 

[NSXonwheels]

Shawn, when exercising the abs brakes the old fashion way like you said do you reccomend sucking out a little bit of the old brake fluid and adding new clean fluid and keep checking it after every abs exercising stop?

 

[nsxtasy]

Shawn, when exercising the abs brakes the old fashion way like you said do you reccomend sucking out a little bit of the old brake fluid and adding new clean fluid and keep checking it after every abs exercising stop?

"Exercising the ABS" usually means going out in a parking lot or other vacant road, taking the car up to at least 40-50 mph, and then slamming on the brakes (REALLY REALLY HARD) so the ABS activates and the pedal pulses. That's all you need to do. But if the ABS doesn't activate and the pedal doesn't pulse, then you can start checking fluid and using electrical means to activate the ABS solenoid.

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The most common reason for front brakes to pulsate is due to uneven deposits of brake pad material on the surface of the rotors. There are several ways to deal with it, some involving more expense and effort than others: "bedding" the brakes (taking them through progressively harder braking, then NOT using them on the way home and letting them cool overnight), and/or turning the rotors, and/or replacing the rotors.

You can read more about this phenomenon, and about how to bed brakes, in the technical white papers on the Stoptech website:

• The "Warped" Brake Disc and Other Myths of the Braking System
• Pad and Rotor Bed-In Theory, Definitions and Procedures

 

[warrenw]

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The most common reason for front brakes to pulsate is due to uneven deposits of brake pad material on the surface of the rotors. There are several ways to deal with it, some involving more expense and effort than others: "bedding" the brakes (taking them through progressively harder braking, then NOT using them on the way home and letting them cool overnight), and/or turning the rotors, and/or replacing the rotors.

You can read more about this phenomenon, and about how to bed brakes, in the technical white papers on the Stoptech website:

• The "Warped" Brake Disc and Other Myths of the Braking System
• Pad and Rotor Bed-In Theory, Definitions and Procedures

Nailed it!

I had this exact issue with OEM brakes after a couple of track days. What ever was on my rotors attracted brake pad material in a couple of spots and I had the exact same symptom. Bedding may work, but you need to get what ever is on your rotors off. The true way is to turn the rotors, then bed the brakes again. you could try a harder racing pad tpo clean the rotors for a while then go back to OEM pads and bed them back in.

It is remote, but check that your pads are installed properly and actually float on either side of the rotor. Grease the pad pins as per the manual. This can cause brakes to pulse as well, as they do not applying even pressure on either side of the rotor, but not as common.

 

[nsxtasy]

The true way is to turn the rotors, then bed the brakes again.

Yes, I should have mentioned, if you turn the rotors OR if you get new rotors, it's a good idea to bed them afterwards, to prevent the same thing from occurring.

Also note that you will need to bed (at a minimum) or turn or replace the rotors any time you switch from one brand/type of brake pad to another. It's not needed when you replace worn pads with new ones of the same brand and type.

This problem is most likely to occur with those tracking their NSXs, or those driving them really hard. The remaining 3 percent of NSX owners shouldn't need to worry about it. :biggrin:

 

[Briank]

The OP said the car was not driven for half a year, its likely the rotors have rust spots on them.

 

[Risen]

Hey guys! So I checked the codes:

https://youtu.be/8_YDvXM0dAs

And it appears that it is the Front Left Speed sensor that is causing the TCS light, possibly making the brakes pulsate when I brake? Can you guys confirm that this is the error code? 4 Long and 2 short = Code 42 = Left Front? And for the Check Engine Light, it appears as if it is also 42 as well, the Rear Primary O2 sensor? Wanted to confirm before I spend some big bucks to get these sensors replaced.

 

[Larry Bastanza]

Your interpretation of the codes is correct.

However these issues are not related to your brake pulsing.

And the pulsing has nothing to do with the ABS.

JMO.....

HTH,
LarryB

 

[tof]

How can you tell that the rotors are not warped. While the most likely culprit is the deposit issue first mentioned by nsxtasy, warped rotors can't be ruled out unless you have measured the run-out on them and it is within spec. I also like the possibility that the floating calipers might not be floating as mentioned by Warren.

 

[Hapa88]

How can you tell that the rotors are not warped. While the most likely culprit is the deposit issue first mentioned by nsxtasy, warped rotors can't be ruled out unless you have measured the run-out on them and it is within spec. I also like the possibility that the floating calipers might not be floating as mentioned by Warren.

Stoptech says "warped discs" are a myth.
http://www.stoptech.com/technical-support/technical-white-papers/-warped-brake-disc-and-other-myths

 

[tof]

Stoptech has an ox to gore. And just because they make brake systems doesn't mean the copy writer in the marketing department knows what he is talking about. I offer the last sentence on the page as a quick example:

"If the brake fluid is topped up the first warning of warn out pads will be the screech of steel backing plate against iron disc. This will be both annoying and expensive."

First off, you don't get "warn out" pads, you get wOrn out pads. Second, long before a brake pad is worn down to the backing plate, a built in noise maker will contact the disk and make a scraping sound that is designed to let you know its time to install new pads. The result is not any more expensive than changing the pads at a certain pad thickness. Of course maybe Stoptech pads don't have noise-makers.

Disks DO warp. It's just that way more often braking vibration that most people (and far too many mechanics) attribute to warped disks is, in fact, something else.

 

[Risen]

Your interpretation of the codes is correct.

However these issues are not related to your brake pulsing.

And the pulsing has nothing to do with the ABS.

JMO.....

HTH,
LarryB

I found the issue. I removed the front rotors and there was a nice "rust patch" the size of the brake pads on the back side. I replaced all four rotors and pads and the car brakes fine now.