Hi

I have a 91 vert and a couple weeks ago coming downhill the brakes got really hot and the pedal went to the floor, then it became rock solid and then worked fine. Later that evening when I got into the car to drive, the brakes were acting very strange, the pedal could be pushed down easily, but when it got halfway through the normal range it was very stiff, and it took a lot of effort to stop the car.

so i took the car in to get serviced, and saw that a caliper had seized. I had them rebuild the calipers and replace the master cylinder, bled the system, turn the rotors, and put new brake pads on.

After all of this, i got back in the car, and the brake pedal travels as far as it used to but it feels like its not going far enough, and is getting too hard thus it is very hard to stop the car..

I was reading about the abs system being clogged, could this have something to do with anything, or could it be the brake booster?

cheers

 

mine did the same thing...weird...i replaced the booster.. didnt hold a vacume..got another one..didnt hold a vaucme after i put it in but did befor...i must have broke something...

anyways you can test the booster to see if it holds a vacume...try that and if it doesnt thats what it is..

 

............i think your brake booster took a dump..........check your booster check valve and your vacuum connection to the block.......

 

The master if bad could allow your foot to go to the floor. With the new master the pedal might be higher due to the better pressure it would develop.

As for the booster, a leak in it would cause a hard pedal. But could also cause varying symptoms if the lead was not consistent. If it was not giving you full power you could not push the pedal as far down as if it was working properly. Shut the engine off a and pump pedal 3 times, it should get progressively harder by the third time. Then do it again but after engine shutdown but wait 5 minutes and do it. The booster should hold vacuum that long and the test results should be the same

ABS units do clog which might not allow the brake pressure to reach a specific wheel causing no braking to that wheel. Have read you your ABS information on the Forum or internet or elsewhere?

 

Thanks for the responses,
I havent been able to find too much on the abs clogging, only that it can get clogged..
how would you check that?

Also, for the booster, I took the car for a drive again today, and its a wierd feeling, the booster pumps 3-4 times before getting hard when the car is off, and it does hold its vacuum. but it feels like the pedal is not travelling enough to stop the car... its quite loose at first then it gets really stiff at the point which you need to push it harder to stop...

then when I was going downhill, i pushed quite hard and it seems like it went past that point, and the wheel suddenly pulled to the left... no idea whats going on..

 

i have a slightly similar problem with my brakes. they appear to be fine with really no hard pedal or long pedal travel. i keep comparing the pedal feel to that of my toyota. my brakes suck to say the least and like another florida member, have changed, checked, or flushed the obvious. soon as i get a chance, will replace the booster to se if any difference although i doubt it very much. funny thing, it holds vacuum fine, both engine vacuum and from an external source. i don't think you could really check the abs for a clog and all the info i read says to replace it as an entire unit. it would be my opinion that if you flush the brake system, there should be no "clogs". ya think ya have any calipers/pads hanging up?

 

If your pulling to the left, the right caliper might not be working correctly. (But I would definitely check both wheels (all) wheels). The piston could be hung up or sized in the caliper. Jack up the car and step on the brake to locate the wheel (could possibly be rear) that has no braking power.

Then you can try to bleed that caliper to see if any fluid comes out. If no pressure you need to work your way backwards. Disconnect the brake line from caliper and check, remove line from car and check. Check by gently depressing brake to see if fluid comes out. If no fluid comes out of hard line then ABS probably is clogged. If you can bleed the caliper, then the caliper itself is the problem and it may have been cooked.

This is a general procedure and results might not take you exactly down this path. Offhand it sounds like your booster is OK. First locate the bad wheel and your on your way. If you find a bad caliper, then you may need to rebuild it.

If the piston in the caliper is frozen and does not move it could cause the pedal to have a higher feel because when you push down that amount of fluid is not displaced to move the piston and the system will reach brake pressure sooner hense less fluid moving thru the system.

 

From the symptoms, sounds like you need to replace the brake master cylinder AND the booster. Before replacing both, check booster for vacuum leak and make sure you check your master cylinder. Do a complete bleed and flush and replace with a good synthetic.

 

i tend to agree....your choice of brake fluid though.....

 

Interesting discussion as I have the same problem but intermittently. Sometimes the brake pressure is as it would be if the car was not running (very hard peddle). The difference in pressure when the car is not running is because of no booster pressure therefore I'm surmising its probably the booster.
I don't see how a hung up caliper would cause a hard peddle but it would cause that left dive.

 

I actually already changed the master cylinder and brake fluid, flushed out the system etc...
what is this about turning the booster piston to change the range I was reading about that in another post.
I dont know why the booster could be bad, its only a year old..
very strange.
Ill check the vacuum tomorrow and post back.

thanks

 

Your brakes were working correctly and something changed, and that’s what has to be fixed. If the booster screw adjustment was OK, it is probably fine and would not change on its own. It is a sensitive adjustment and if adjusted out to far, it could cause the brakes to drag. To far in will cause the pedal to drop to far before it contacts the master’s piston.

Before you dive into this area or take things apart, do the basics first. Jack the car up, spin the wheel and step on the brake for starters. Check to see if one of the wheels has a specific problem. If you find something that will lead you the root cause of the problem sooner. If you find nothing, then you can move to the next higher level.