Pulsating brake pedal when stopped at traffic light

[ovexi]

I am having this issue that hopefully somebody here can give me some clues as to where it is coming from. My car drives fine in general but when the engine is fully warmed, I feel the brake pedal pulsating when I am stopped at a traffic light. This happens in particular when the auto transmission is in “Drive“ mode. If I switch to “Neutral” I can still fell slight vibration but it is not as bad.
My 2008 Mazda 3 has almost 90k kilometers and there is only powertrain warranty left. The dealer is asking for almost $100 for diagnostic and I most likely have to pay if the issue is not covered under powertrain warranty.
Thanks for any input

[trulankan]

So it pulsates while you are idling or as you are braking?

[sarujo]

I would PM your VIN to Booter22 (he works at Budd's Mazda) and he could look it up to see if your vehicle is part of the power steering recall.


I am having this issue that hopefully somebody here can give me some clues as to where it is coming from. My car drives fine in general but when the engine is fully warmed, I feel the brake pedal pulsating when I am stopped at a traffic light. This happens in particular when the auto transmission is in “Drive“ mode. If I switch to “Neutral” I can still fell slight vibration but it is not as bad.
My 2008 Mazda 3 has almost 90k kilometers and there is only powertrain warranty left. The dealer is asking for almost $100 for diagnostic and I most likely have to pay if the issue is not covered under powertrain warranty.
Thanks for any input

[ovexi]

So, is just me having this problem?

[ovexi]

Oops, I just noticed that I had a few replies

[ovexi]

I would PM your VIN to Booter22 (he works at Budd's Mazda) and he could look it up to see if your vehicle is part of the power steering recall.
I had the recall for the power steering done last year

So it pulsates while you are idling or as you are braking?
It pulsates when I am braking only

[DanScarps]

If it's pulsing while you are slowing down, then I'd look at replacing your rotors.

If it's pulsing while you're at a standstill, I'd look into a couple things... Check your vacuum hoses on your break booster(do you have a check engine light for vacuum leak?). If you have had a caliper changed or a line repaired, I'd look into power bleeding your brakes as your ABS unit could be confused by air trapped in it.

But if you come to a complete stop, and have your foot on the brake pedal and it drops on you, this is normal. Your brake booster works best when you're at idle, or when you foot is off of the gas pedal. Sometimes it's just settling, as the vacuum increases, so does it's braking power.

But honestly, as long as you car stops well every time, I'd just leave it until it causes a problem. I'm leaning towards a brake booster problem.

[krimsalt]

Soudns liek a warped rotor. I would change it.

[trulankan]

yeah its definately a warped rotor. I have the same problem and for me the car actually starts moving to the right if I brake hard and dont hold the steering wheel straight lol

[trulankan]

i think JR Automotive (sponsor) has a deal on a complete brake job plus caliper painting for $400 which I need to inquire about when I go see them

[ovexi]

Sorry to bump this old thread now but after watching the car for a while I kinda figured out what the problem may be. I noticed that when the engine is warm, the rpm drops to close to about 500 rpm and the brake pedal starts to shake, it's like the car is almost stalling. This happens when the car is stopped and AT in drive. When the engine is cold the rpm is higher and I don't have this issue.
Thanks for any help again