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'Pulsating' Brake Pedal?

96Mystique

CEG'er
Joined
Oct 18, 2007
Messages
192
1996 Mercury Mystique
2.0L Zetec
Auto transmission

Here's the problem, I just installed my cold air intake last night. Got everything complete, put everything 'mechanical' back together as it should be. I left the aesthetic stuff off, just for the test run. I drove it around the block, and I noticed that the brake pedal is 'pulsating' for some odd reason. It wasn't doing this before I put the CAI on. I just replaced my rotors with OE rotors (were replaced before the CAI was installed, along with new pads.) It only happens whenever I'm accelerating. When keeping throttle at one point, it doesn't do it. When I start to brake it doesn't do it. I have good pressure on the pedal when braking, and I brake fine. I checked fluid level, and I could use some, but it's not necessary. I will buy some fluid whenever I go by the auto parts store. Any ideas what may have caused this, or what may be the problem? I did hit the master cylinder a few times while installing the CAI, but I don't think I hit it enough to cause this, as it was more like a tap coming from the intake tubing.
 
If the fluid level is less than it was before, you definitely have a leak somewhere. I'm assuming you have rear DRUM brakes? Might want to take a look there. The cylinders are prone to failure :(
 
Yes, I have rear drums for the time being, until I get around to the hassle of changing them to rear disk. The wheel cylinders are fine, I just replaced them less than 250 miles ago. The only thing is, is that I can't remember how much brake fluid I left in the reservoir when I redid the brakes. I had meant to buy more, but I had forgot to. I'm fairly sure I have the same amount, but I will check for any signs of leaks tomorrow.
 
Stupid question, but are your lugnuts on tight/torqued??? This will cause a vibration.
Been there, done that. :troutslap:

Chris :D

Yes, they are, I check them every 100+ miles, as I've had a very bad experience with loose lug nuts.
 
1996 Mercury Mystique
2.0L Zetec
Auto transmission

I drove it around the block, and I noticed that the brake pedal is 'pulsating' for some odd reason. It wasn't doing this before I put the CAI on. I just replaced my rotors with OE rotors (were replaced before the CAI was installed, along with new pads.) It only happens whenever I'm accelerating. When keeping throttle at one point, it doesn't do it. When I start to brake it doesn't do it. I have good pressure on the pedal when braking, and I brake fine. I checked fluid level, and I could use some, but it's not necessary. I will buy some fluid whenever I go by the auto parts store. Any ideas what may have caused this, or what may be the problem?
If you regularly ride the brake pedal any time other than when braking you are most likely overheating the rotors and warping them. That's the only thing that jumped out at me in your story. Either that or you knocked a vacuum line loose somewhere but still, only use the pedal when you're braking. Or was that a typo?
Karl
 
If you regularly ride the brake pedal any time other than when braking you are most likely overheating the rotors and warping them. That's the only thing that jumped out at me in your story. Either that or you knocked a vacuum line loose somewhere but still, only use the pedal when you're braking. Or was that a typo?
Karl

I drive 2 footed, so I rest my foot on the brake. When I do this, it does not engage the brakes. I did notice that my intake is sitting on the brake reservoir, so when I do accelerate, the vibrations from the intake it vibrates the whole setup. Could this be causing the problem I am seeing?
 
You drive two footed...stop it. You may not notice that the brakes are engaged but most likely they are "slightly" engaged thus causing heat build up and causing the rotors to warp. I used to see this all the time at the shop I was at, especially with cross drilled rotors.
 
Why do you drive with two feet? Besides the comments above about the warping of the rotors, you can easily boil the break fluid too and this can create a lethal situation.

If the CAI is touching parts of the break system, it will transmit the normal vibrations of the engine.
 
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