Hello every1.
so here is my problem: Almost all the time when i am stopped at a red light for a more then 30 seconds , I feel a knocking on my brake pedal. Any1 has an idea of what this issue might be. Then when i putt it to neutral ( most times when stopped i have this habit of putting car on neutral) knocking goes away.

thank you for all your knowledge and replies

 

So you're saying that when you're sitting still with your foot on the pedal you can feel a pulsation through the pedal?

 

yes exactly that is what i mean

 

Are your windshield wipers on?

If putting it in neutral does make the "knocking" go away then the most likely culprit is your rear motor mount.

 

If it was moving I would say that it was an ABS problem. But since it is sitting still my insticts suggest a hydraulic problem. You might want to get your brake booster checked out. I googled it and I found this little blurp...

http://answers.yahoo.com/question/in...4011450AAsjNws

 

If it's brake booster related and if stopping efficiency hasn't changed than more than likely it's on the intake side. Might want to clean up the throttle body and possibly deep creep / seafoam the booster line.

 

i appreciate all your helps .
one guy ; Are your windshield wipers on? no they are not but sometimes when it rains and they are on i feel them knocking in the pedal as well.

so guys what do i do to fix this issue bring it to stealer or locale mec. or is it somehting i can fix muyself am sure it is brake booster at this point

 

You can seafoam the booster line yourself.

 

when I get home I'll check my manual and see if it has any procedures for checking the brake booster. If there is anything promising I'll post the pages here.

 

Does the pedal move at all when you feel the knocking? Is it a constant knock or random? When AC compressor kicks off, more vaccum is sent to the booster and the pedal will sink just a little along with a very slight knock.

I agree with others, check the mounts first.

 

Usually booster testing involves testing with the engine off and how long it will hold vacuum, assuming pedal pressure is normal.

 

I am guessing you have a AT. I had a very similar issue with a 95 Intrepid. It was the torque converter. The torque converter is still trying to push you forward even though your foot is on the brake, it stops when you are in neutral because the trans is no longer engaged. Number one thing to do is check the trans fluid level. If it is OK take it to a tans shop and have them check it out. PS the Intrepid when another 6000Km after that, and then the trans locked up. Thankfully I sold it before the lock up.

 

As promised, here are the scans for the testing procedure of the brake booster. It seems pretty easy to do and shouldn't really take up much of your time.

 

on that ck valve in the booster line--iirc you can remove that and deep creep/seafoam it
if its not working

but dont do a seafoam engine vac port treatment thru the booster line, due to that ck valve
Use TB master vac port, or thru tb throat itself with deep creep aerosol

IHC can you verify that?

 

broken front/rear motor mounts that are vac assisted will cause other vac related problems

 

I will try the testing later tonight and keep you guys posted

 

I never thought of that. Good point. If the booster checks out then checking the rear mount, as others have said, would also be a good idea. As far as I can recall the rear mount is the only one that is vacuum assisted.

 

OK EVERYBODY SORRY FOR THE DELAY BUSSY WEEK.
So i tried all the above and non of them are making fault and the freaken brake pedal heartbeat thing seems to have gone away. One strange thing though when i turn the winshield washers on i get that heartbeat thing to what causes that .....

 

Just vibration from the wipers down the firewall to the pedal. I believe there's a tsb for it somewhere in the garage. I just learned to live with it.