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Brake question, WITH VIDEO

KingOfTheHill

KingOfTheHill

NAXJA Forum User
Location
Palmdale, Ca
My brakes are just not right and i need to get this sorted out.

I have bled the whole system and its clean coming out... Master cylinder does not leak externally, checkvalve on the booster works fine as well.

Im torn between the Booster or Master cylinder... 1 friend says Master cylinder, im leaning towards Booster..

Funds are tight and i don't feel like playing the guessing game so i took a video to hopefully get a good response from you guys.

What do ya think?

http://www.youtube.com/watch?v=9tFQ0ElTp4U
 
One easy way to see if your booster is leaking is to start the car, turn it off, let it sit for a minute or two, then pull the check valve out of the booster slow, do you hear vacuum releasing?
 
Tested it... Started the car up, brought up the idle, let it go back to idle and settle... shut off...waited 2 minutes and slowly pulled the check valve... heard a nice solid hiss... so it sounds like it may not be the booster?

But what gets me is that i hear that hiss/leak only at a certain part of the pedal throw 1/4-3/4 of travel.

JOe
 
Put the trans in neutral, stop the engine and apply the brakes 2-3 times to remove all vacum, appy the brakes and start the engine, the brake pedal will tend to move downward with consant foot pressure, if it does not move downward, the booster is junk.
 
FordGuy said:
What Are the brakes doing that you feel is wrong?
Click to expand...

I just don't have any stopping power... feels like on a scale of 1-100 im only reaching 50-60.... Ive had 2 other XJ's before this, 1 was even heavier with a 31" tire (current one is on 30's) and it would stop no problem at all.. this one just slowly comes to a stop...

If something were to jump out in the middle of the road id be screwed... I won't even take it offroad right now because i can not lock up the tires on a fairly mild descent... or if i have to back down a hill i can't lock my tires either, i just slide.

JOe
 
FordGuy said:
Put the trans in neutral, stop the engine and apply the brakes 2-3 times to remove all vacum, appy the brakes and start the engine, the brake pedal will tend to move downward with consant foot pressure, if it does not move downward, the booster is junk.
Click to expand...

Ok, tried this and it does move down...

pedal was SOLID then fired it up and the pedal dropped about 1/3 of its travel and held.

I just put a vacuum guage on there and i am losing vacuum when i just hold the pedal down about halfway... but when i mash on it, its not leaking or when its not being touched it isn't leaking either.

I just don't want to buy twice but it looks like im going to have to flip a coin.... damn

JOe
 
Do you have the rear drums adjusted right?? My brakes were terrible for a while and then I had everything apart to weld the diff. up and adjusted everything when I put it together and all of the sudden I had good brakes......:clap: Just a thought.....

Dane
 
I don't think it is your booster, I also asked my brake guys here at the Dealership, and think that if you checked it the way I suggested, its not the booster. The reason you loose vacuum and here the noise is when you first push on the booster, the pressure must equalize. I am thinking you have more of a brake pad/Shoe issue. It is possible your master is not working front or rear.
 
woh... since when do break boosters hiss?
#1. I can tell by your steering wheel that you have an old jeep. What year is it?
#2. I searched your thread history and it looks like you may have recently puton 32" tires? (pardon my snooping)
#3. IF you have an older jeep (like mines an 89), and IF you 32" tires the stopping power you describe is normal. I was rolling right through stop signs a couple of weeks ago.

Also, I do not think that hissing is normal. If you can hear it inside the cab like that... wtf...

I'd do a WJ booster/master cylinder swap. It will fix the problem no matter what it is. Search on car-part.com and sort by distance from your zipcode. Ask them to include the check valve, the breaklines and all the bolts and mounting hardware. Cost me $80 and I can now lock up 33's on dry pavement. It's pretty awsome.

Of course, if my guesses are all wrong, I appologise.
 
My bad for not clarifying..

Its a 1989 XJ 4.0 auto. Front pads are Hawk's mid quality pad and rotors were turned (less than 1,500 miles ago)... and rear drums were replaced about 2k ago... System has been blead about a month ago. and the tires are 30x9.5x15's on there right now.

The 32's i just bought aren't on yet and i was hoping to get a little more stopping power before i even put those on.
 
Youve got new pads, rotors and shoes. Did you seat them after you installed them?
I dont think its a booster issue. A bad booster shouldnt hamper the braking ability, just the amount of foot pressure it takes to brake.
Take your jeep out on an empty dry road and slam the brakes a few times. Dont over heat them by riding the brakes for an extended time, just hit them hard for shorter periods, what you are trying to do is wear or seat the pads with the rotors so they have better contact.
Are you sure theres no air in the system?
 
Ray H said:
Youve got new pads, rotors and shoes. Did you seat them after you installed them?
I dont think its a booster issue. A bad booster shouldnt hamper the braking ability, just the amount of foot pressure it takes to brake.
Take your jeep out on an empty dry road and slam the brakes a few times. Dont over heat them by riding the brakes for an extended time, just hit them hard for shorter periods, what you are trying to do is wear or seat the pads with the rotors so they have better contact.
Are you sure theres no air in the system?
Click to expand...


When my booster went, I had to put both feet on my brake pedal and push with all of my might to come to a slow stop. It may effect how hard you have to push, but it pushes hard enough that you may break your seat mount before stopping..
 
cal said:
When my booster went, I had to put both feet on my brake pedal and push with all of my might to come to a slow stop. It may effect how hard you have to push, but it pushes hard enough that you may break your seat mount before stopping..
Click to expand...

I guess its a matter of reference. I grew up on non powerbrake vehicles (no booster). The non power brake vehicles had longer brake pedal arms that allowed more mechanical advantage but other than that, they worked about the same as a vehicle with a bad booster. It took some effort but I could lock up the non boosted brakes on my 70 Camaro.
 
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