Hello everyone! I'm new to the forums, but I did just buy a nice opal frost 96 convertible mustang GT. She only has 60,000 miles, but she sat for long periods of time without being driven. I think thats what led to some of the problems I've been having lately. One of those problems is with the brakes. The front brakes pulsate for no reason. It does it when there cold and not to long after start-up. The idle of the car seems to change for the better after it happens. The brakes were changed before I bought the car and you can tell they have been bled. The fluid is very clean. Thanks in advance for any help!

John

 

Congrats on your new purchase. You should post pictures in the picture section!!

Anyway, I'm no mechanic but how brakes can affect idle (unless I'm reading that wrong) is way beyond me.....

Normally when brakes pulsate it's because the rotors are warped. I'd take it to a brake shop like Midas, NTB or one of those type places and have them do a free brake inspection. They should be able to tell you what's going on.

 

The rotors are not warped. I wish they were because it would be an easy fix. I was hoping to get some advice, so I might work on it myself. I'm a do it yourself type person and only really take my car to shop when I absolutely have to. I was thinking maybe one of the ABS sensors was going bad, but the ABS light hasn't come on.

John

 

no offense but how do you know the brakes aren't warped? did you have them inspected? just looking at them isnt enough to know (they may not be visibly warped but could be slightly off). might get the rotors turned (grinded down) makes a world of difference. or maybe the pads just need to break in if they were just changed.

 

Check your vacuum lines. Could explain erratic braking and your idle issue.

 

I'm sorry if I didn't say this before, but the problem is only intermittent. It happens when they are cold and right after start up. normal driving before my car is warmed up. If the rotors were warped wouldn't it be all the time and get worse as they heated up. When everything is warm the brakes are smooth as glass. No problems. I was thinking something was wrong with the ABS. I will look for vacuum leaks today.

John

 

I would check the connections to the abs wheel sensors, make sure they are not covered in crud (the sensor is behind the spindle hub). You could also pull the fuse feeding the abs pump (the computer is integrated in the pump) that would disable abs and prove if it is the cause. Vacuum would have no effect on abs. Since it goes away when things warm up I suspect a connector is dirty.

 

Thanks everyone for all the advice. I will let you know how it turns out.

John

 

check if your brake booster is a vacuum or hydraulic unit, it may be something in the hydraulics causing it since it is run off the power steering pump.

 

^^This. It could also be something related to the ABS motor.