soft brakes

[Blaine B.]

Interesting, not an XJ but we have a 1980 Oldsmobile Royale Brougham with 56,000 miles on it.

Brakes are awesome but you do get a "whoose" noise when pressing the brake pedal.

 

[Shorty]

If you have pressure before you turn the ignition, then the pedal sinks to the floor after you start it, thats a bad booster.

that is the sign of a functioning booster (with the exception of going all the way to the floor)

a firm pedal before starting the vehicle that drops with engine vacuum is how it's supposed to respond. The engine vacuum pulls on the internal diaphragm and provides some assistance to the mechanical input (your foot on the pedal)

 

[xj88superjeep]

that is the sign of a functioning booster (with the exception of going all the way to the floor)

What part of "then the pedal sinks to the floor when you start it" did you misunderstand?

 

[Shorty]

What part of "then the pedal sinks to the floor when you start it" did you misunderstand?

I think it was the part where the OP said "almost"

 

[xj88superjeep]

I think it was the part where the OP said "almost"

LOL, well then don't disagree with my true statement... I said "to the floor" But at any rate, if the pedal is anywhere NEAR the floor, and it's still not a firm feedback that IS a sign of a bad booster... as stated above, a good booster engages high and firm, a bad booster engages low and soft... sorry you feel the need to disagree.

 

[dbxtr3]

I have a 89 xj with the the same problem. My pedal almost goes to the floor before I get brakes and their is no way I could ever get the tires to lock up I am running 31x10.50. I was getting very low fluid flow to the rear wheel cylinders.

Luckly I have a spare parts 89 XJ in my garage that has a ton of brake pedal pressure.

I changed the proportion valve it help a increase fluid flow to the rear wheels and a little better pedal pressure. I also installed brand new rear wheel cylinders and rear hose and both front hoses. I still am not happy with the pedal.

Last night night I took the brake booster and master cylinder off the parts jeep and installed on my Jeep I will bleed the brakes sometime this weekend and report back to tell if it has fixed my problem.

 

[ehall]

dbxtr3, check the manifold vacuum pressure

low vacuum==low boost

 

[xj88superjeep]

dbxtr3, check the manifold vacuum pressure

low vacuum==low boost

Do you know what the manifold pressure is supposed to be? How do you increase the manifold vacuum pressure if it is low? I ask because I wonder if a few of my beloved gremlins are camping out and feeding off of this.

 

[ehall]

Acceptable vacuum pressure for cars is 15-22 hg inches. You want to be close to 20.

If it's low, look for leaks. The lines usually either stretch out or get brittle at the connectors. I was able to boost vaccum on my XJ by 3 or 4 hg just by replacing connectors.

If the brakes are whooshing then the leak is in the booster itself

 

[xj88superjeep]

Hmmmmmmmmmmmm! I swear, as much as I love my jeep, she is a million piece puzzle! She just loves my attention, and loves to keep me thinking about her! UGH! But still the best vehicle I have ever owned!

 

[dbxtr3]

I have a 89 xj with the the same problem. My pedal almost goes to the floor before I get brakes and their is no way I could ever get the tires to lock up I am running 31x10.50. I was getting very low fluid flow to the rear wheel cylinders.

Luckly I have a spare parts 89 XJ in my garage that has a ton of brake pedal pressure.

I changed the proportion valve it help a increase fluid flow to the rear wheels and a little better pedal pressure. I also installed brand new rear wheel cylinders and rear hose and both front hoses. I still am not happy with the pedal.

Last night night I took the brake booster and master cylinder off the parts jeep and installed on my Jeep I will bleed the brakes sometime this weekend and report back to tell if it has fixed my problem.

It was a bad master cylinder. The one off my parts Jeep gave it the pedal firmness I was looking for but it was leaking at the booster. So I went to Orielly's auto part and got a reman master cyl for $23 it fix the problem. I don't have to stand on the pedal to get it to stop.