Brake pedal hard spot

[tez]

Hi all,

This is driving me nuts and I dont know if this is normal operation or not?
Front pads and rear drums an shoes have been changed along with the brake fluid.

Thing is the car stops fine although when I apply pressure on the brake pedal, it hits what I can best describe as a hard spot (half pedal travel) and does not go down any further. It feels as though something is stopping the pedal from going down any further.

I know the pedal can go right to the floor because when I bled the brakes, it hit or came close to the floor. But with the car on and pressure applied to the pedal, it seems to hit this hard spot?

Booster and master cylinder seem to be working fine and there are no external leaks. Everything else in the brake system works as normal.

So is this just normal operation?

[RAY185]

Sounds perfectly normal to me. Pedal should never go to the floor when braking. It goes to the floor when you are bleeding because you have released the bleed nipple therefore removed the restriction of fluid. In normal operation you should have a hard pedal once the fluid pushes your front pads and rear shoes onto the discs/drums and has no where to go. If it goes soft or to the floor under braking, you have problems.

Have you driven other vehicles that have behaved differently?

[tez]

Other cars I have driven, the pedal firms up as the pads and shoes push out, but just on this occasion, it feels as though your pushing and its pushing the brake pads and shoes, but then all of a sudden hits this "hard" spot.

It doesnt go right to the floor like it would if the bleed nipple is opened.

[Shadow]

sounds like a good brake pedal to me.

have you driven a car before?

sorry had to ask

[macneil]

i rekon a stiff pedal is good.. trust me its scary coming into a town and your brakes goto the floor.. my brakes almost lock at 1/4 movement..

[Goatse.AJ]

I think what he's referring to is a pedal with a lack of feel???

I prefer a pedal where there is still a little left at the bottom.

[tez]

Well there is zero feel as it gets to this point and feels like its stuck, like a block of wood is sitting under the pedal. The brakes do not gradually firm up.

It firms up a little and then hits this hard spot. Its hard to explain.

[tweak'e]

sounds like the rears might be a little loose or have worn drums. combined with new pads which are not worn in fully. tends to make it go from no pedal to grab.
i'm picking that the pads are simply not gripping well intill you apply full pressure and then they are grabbing. i've driven a few vechiles like that, its either full brakes or no brakes.

what sort of pads have you fitted and how did you wear them in?

or you just got used to spongy brakes and now you have normal brakes.

[tez]

The brakes grab fine, although its just when the car is statoionary, I apply some more pressure and it hardens up but then the pedal comes to a dead hard stop, like a block of wood or something is under the pedal preventing it from firming up more?

Bendix pads up front and did some hard stops when bedding them in.

[thehanko]

The brakes grab fine, although its just when the car is statoionary, I apply some more pressure and it hardens up but then the pedal comes to a dead hard stop, like a block of wood or something is under the pedal preventing it from firming up more?

Bendix pads up front and did some hard stops when bedding them in.

from what i know running in new pads, is not hard or stops, its from 60 ks to slow but not stopping gradually getting a little quicker to 'bed' them in. but im opretty sure what ive read in the past is that you dont go too hard oor come to a complete stop.

but not sure this would be your problem.

my hilux exhibits i guess 'similar' feeling, i know what you mean by its fairly soft then hits like a hard bitand its as defined as if hitting a block of wood. but my front pads are 30,000k old and it hasnt changed even when i swapped over read diffs / brakes complete.

unless it feels 'wrong' it might just be normal.

[mike_nofx]

When driving, can you hit the brakes hard enough to lock up?

Have you had a look at the pedal linkages up under the dash? and is there anything that may be causing it to jam up? Is the master cylinder push rod (?) located correctly?

[GeneralFubashi]

sounds a lot like you are running out of vacuum Its good for a while braking, but when you put the foot down it creates a slight leak and suddenly you have to use some muscle. Feels like there is no more movement to be had, just like trying to work the brakes with the engine off after giving them a few pumps.

Have the same thing on my hj47. Does the pedal harden up pretty quickly with the engine just turned off? (ie without actually pressing the pedal repeatedly)

[tez]

sounds a lot like you are running out of vacuum Its good for a while braking, but when you put the foot down it creates a slight leak and suddenly you have to use some muscle. Feels like there is no more movement to be had, just like trying to work the brakes with the engine off after giving them a few pumps.

Have the same thing on my hj47. Does the pedal harden up pretty quickly with the engine just turned off? (ie without actually pressing the pedal repeatedly)

Could be a possbility that I didnt think of. How would I test that? Apply the brake and then turn the car off to see if the vacuum runs out pushing the pedal up?

[macca81]

sounds a lot like you are running out of vacuum Its good for a while braking, but when you put the foot down it creates a slight leak and suddenly you have to use some muscle. Feels like there is no more movement to be had, just like trying to work the brakes with the engine off after giving them a few pumps.

Have the same thing on my hj47. Does the pedal harden up pretty quickly with the engine just turned off? (ie without actually pressing the pedal repeatedly)

Could be a possbility that I didnt think of. How would I test that? Apply the brake and then turn the car off to see if the vacuum runs out pushing the pedal up?

pump the brakes a few times with the car off till there is no more vacuum.
stand on pedal as hard as you can.
turn on the engine.

if the pedal sinks further once the engine is on, then you are getting vacuum.

[tez]

pump the brakes a few times with the car off till there is no more vacuum.
stand on pedal as hard as you can.
turn on the engine.

if the pedal sinks further once the engine is on, then you are getting vacuum.

There is vacuum as the pedal sinks a bit when the car is turned on. I then press the brake say another 1-2cm and it hits a real "dead" spot like a something it blocking it going further.

It cant be anything blocking the pedal going down because when the brakes are bled, it travels to the floor.

Could incorrectly adjusted rear shoes etc be the problem? When I changed the wheel cylinders, shoes and drums, I adjusted the rear so there was slight drag on the wheels when you turn them

[Shadow]

pump the brakes a few times with the car off till there is no more vacuum.
stand on pedal as hard as you can.
turn on the engine.

if the pedal sinks further once the engine is on, then you are getting vacuum.

There is vacuum as the pedal sinks a bit when the car is turned on. I then press the brake say another 1-2cm and it hits a real "dead" spot like a something it blocking it going further.

It cant be anything blocking the pedal going down because when the brakes are bled, it travels to the floor.

Could incorrectly adjusted rear shoes etc be the problem? When I changed the wheel cylinders, shoes and drums, I adjusted the rear so there was slight drag on the wheels when you turn them

no.

the only problem can be either your pedal linkage binding up or something? or the master cylinder, if there is indeed a problem.

[its aford not a nissan]

i think it is your rear proportioning valve bottoming out and its normal

[tez]

i think it is your rear proportioning valve bottoming out and its normal

Now thats something I hadnt ever thought of. So its restricting brake travel so the rears dont lockup (due to being unladen?)

If I undid the rear proportioning valve to test, this should allow for more pedal travel?

[its aford not a nissan]

i think its the other way around

your pedal is pressed down really hard to the point where the proportioning valve is now allowing full force to the rear wheels

[tez]

Had the brakes checked out and they all check out fine.
The only thing in question now is the load sensing valve.

The ute has been lifted 2", so can you adjust the proportioning valve to compensate for this or do I need to make a bracket so it raises the vavle off the diff 2" to get the stock feel?

This is how the vavle looks now. I adjusted the valve up the rod a little bit although Im assuming its not what I need to adjust and I need to lift the valve up 2" off the diff mounting?



If I want to test if it is the valve causing the pedal issue, do I just disconnect it from the diff and tie it up to see if it gives me more rear braking?

[Jacked]

sounds normal to me.
But being brakes im not going to tell you that without diagnosing it myself Last thing i need is "some bloke on the net told me too"

only time you will really notice a stuffed proportioning valve is when it locks the rear up. Some people "trick" the valve to provide half load pressure to the rears at all time. This still wont change your pedal feel. Its not your master/booster binding up or the pedal to booster rod because it go's to the floor when bleeding. Its a 4wd thing that once you get to that hard point that it doesnt go any further and it wont stop you any faster, especially pushing bigger rubber i had found myself close to pushing the pedal through the floor.

[tez]

If I jump on the brakes, the front ever so slightly locks up but the rears dont at all. I would have thought with the vehicle unladen, the rear should lock up as well.

Can the load proportioning valve close off the rear brakes all together as this is what it feels like its doing, and since the suspension is raised 2", its giving even less braking to the rear because its thinking the rear has even a lighter load than stock (if that makes sense).

To rule out the proportioning valve, do I unbolt it from the diff and tie the arm up?

[RAY185]

If I jump on the brakes, the front ever so slightly locks up but the rears dont at all. I would have thought with the vehicle unladen, the rear should lock up as well.

Can the load proportioning valve close off the rear brakes all together as this is what it feels like its doing, and since the suspension is raised 2", its giving even less braking to the rear because its thinking the rear has even a lighter load than stock (if that makes sense).

To rule out the proportioning valve, do I unbolt it from the diff and tie the arm up?

Yes unbolt it from the diff and tie it up. That will give max flow to the rear brakes (simulating heavy load in tray), however I would be surprised if thats your problem. As others said before, it is sounding alot like a booster/vacuum problem. Also as said, its one of those things that is very hard to diagnose over the net.

[tez]

I'll tie up the load sensing valve to rule that out and keep looking. The load sensing spring is not straight and has a bend or two in it so Im not sure if this is causing the rear brake bias to be out as well.

I had a brake place have a look at it today and they didnt find anything wrong. Need to take it back for them to play around with the rear valve although he said to try tying it up and see if the brakes improve.

Can the load sensing valve prevent fluid from going to the rear competely or only a minute amount?

[Weiner]

I'll tie up the load sensing valve to rule that out and keep looking. The load sensing spring is not straight and has a bend or two in it so Im not sure if this is causing the rear brake bias to be out as well.

I had a brake place have a look at it today and they didnt find anything wrong. Need to take it back for them to play around with the rear valve although he said to try tying it up and see if the brakes improve.

Can the load sensing valve prevent fluid from going to the rear competely or only a minute amount?

Why would you want the pedal to go to the floor?

If it stops fine, and everything there would be nothing wrong with it.

Pretty sure pedals shouldn't go to the floor?

[tez]

Why would you want the pedal to go to the floor?

If it stops fine, and everything there would be nothing wrong with it.

Pretty sure pedals shouldn't go to the floor?

No I dont want it to go to the floor, but it feels as though there should be more pedal travel, the pedal is not going down enough to fully clamp the pads / shoes together to provide a good stop.

[tez]

Ok well I think Ive found the problem. Sticking pistons in the front calipers. After swapping master cylinders and brake boosters over to no avail, I pulled the front pads out of the calipers and while they were sitting there I tested each side.

Drivers side, one piston comes out as the brake is applied but all other 3 sit there. Passenger side, two come out and two sit there. I didnt think there was anything wrong with them because they push in ok, although dont come off.

So hopefully this will solve my brake dramas. Im going to drop it off and get them rebuilt tomorrow.

[beinthemud]

The brakes grab fine, although its just when the car is statoionary, I apply some more pressure and it hardens up but then the pedal comes to a dead hard stop, like a block of wood or something is under the pedal preventing it from firming up more?

Bendix pads up front and did some hard stops when bedding them in.

from what i know running in new pads, is not hard or stops, its from 60 ks to slow but not stopping gradually getting a little quicker to 'bed' them in. but im opretty sure what ive read in the past is that you dont go too hard oor come to a complete stop.

but not sure this would be your problem.

my hilux exhibits i guess 'similar' feeling, i know what you mean by its fairly soft then hits like a hard bitand its as defined as if hitting a block of wood. but my front pads are 30,000k old and it hasnt changed even when i swapped over read diffs / brakes complete.

unless it feels 'wrong' it might just be normal.

x2
welcome to drum brakes on the rear
also check your brake bias to the rear mine wasent adjusted with the raised suspension after it was it made a big difference

[tez]

x2
welcome to drum brakes on the rear
also check your brake bias to the rear mine wasent adjusted with the raised suspension after it was it made a big difference

Calipers are getting rebuilt now and Ive ordered a bracket to raise the proportioning valve higher off the diff.

[thehanko]

x2
welcome to drum brakes on the rear
also check your brake bias to the rear mine wasent adjusted with the raised suspension after it was it made a big difference

Calipers are getting rebuilt now and Ive ordered a bracket to raise the proportioning valve higher off the diff.

you have inspired me to check my calipers... damn it pretty much like yours, only one piston working properly, the others limited or seized.

mine are costing $110 each to rebuild as long as the pistons are ok, what did yours cost?

im looking forward to having a bit more bight in the front end