Brake problem! Pedal gets very hard to depress and pushes back against my foot. (1 Viewer)

[AdventureBuddies]

97 FZJ80

Brake pads are good. Fluid is new and topped off and recently bled. Fluid level hasn't gone down so I don't suspect a fluid leak.

Last night on the trail in Anza Borrego, my brake pedal got rock hard and it took a lot of foot pressure to stop the truck. Can't find anything about this when searching.

Symptoms: When driving, at first the brake pedal behaves normally as I start braking (ie for a stoplight). Then, while I'm still slowing down, the pedal gets very stiff and i have to push on it very hard to get the truck to stop. Once stopped, with my foot still on the pedal, the pedal starts pushing out against my foot to the point where it takes a lot of pressure on the pedal to stay stopped at the stoplight against just the normal idling.

Once I start driving again, the brakes are normal at first and then the symptoms repeat. Once the hard pedal thing happens, and I press harder on the pedal to try to stop, there is an audible sound of air releasing somewhere around the foot pedal.

When the pedal first get's hard and I give it a firm push, it feels almost as if I've "pushed through" the stiffness and then it gets a little easier to press until I've stopped at which point the pedal pushes back against my foot as described earlier.

Recent work on the truck: replaced brake fluid 2 weeks ago with synthetic - no brake issues after. Also new springs but little change in lift amount (about 3"). Had the stealership attempt a front end alignment, but they supposedly were unable to break the adjustment loose. I doubt this is relevant but thought I should mention it.

Brakes were fine on the way out to the desert. problem occured after easy trail driving.

Any help is much appreciated.

 

[Brian894X4]

That sounds like a vacuum boost problem. You'd be surprised at how much brake pressure would be required to give the same braking with and without vacuum boost. Sounds like your boost is going in and out. When it goes out, the pedal will become harder to push. If it goes out when you've got pressure on the pedal, I can see the pedal firming up and pushing back at you, because without vacuum boost, you need more foot pressure to apply the same braking forces.

The first thing I'd check is the easiest. Check your vacuum line to to the brake booster, make sure it doesn't have any leaks or cracks or didn't rub up against something. These don't normally wear out, but if you have something mounted on the firewall it might have gotted damaged or come partly loose if engine work was done in that area.

Beyond that, the vacuum booster may need to be replaced, which can be a bit involved.

That's my best guess.

 

[Michael Hanson]

vacuum booster or hose to it. Mike

 

[AdventureBuddies]

Thanks. i will check the hose first. make's sense that there might be aleak there since I hear air releasing around the pedal area.

 

[lt403]

if i remember correctly that a text book symptom from the maint manual for a new booooster

 

[SMG1]

I've got the same problem with my LX450. I found a brake booster at O'Reillys for $239 but I wanted to try to make sure this is the problem before I start throwing money into it. If you guys think it's the brake booster, should I buy OEM or is re-manufactured okay?

Thanks for any help

 

[Michael Hanson]

My 2 cents, booster, MIke

 

[Ozdunc]

I'd go booster as well, but its worth looking at the brake lines from the axle to the calipers. When they age, they can swell under pressure, giving a hard pedal feel but no increase in braking resistance.
Changing the those lines on my 94 transformed the braking and pedal feel is now nice and progressive.

 

[Sc0-]

I think a test for the vacuum booster was to turn the truck off and step on the pedal a few times, it should gradually get harder with each press.

I have a similar problem, have power brakes but panic or emergency stops and it's not gonna happen. I do have old brake lines, autozone pads, and a system that needs to be bled REALLY good. Next step is to put the truck under some jackstands and carefully put it in drive with observers to check for a sticking caliper/piston ordeal. If the calipers are good i'll throw in the new brakelines and rebleed properly then look at the MC/booster for further issues.

 

[SMG1]

I'm planning to work on it this weekend and I'll let you know what I find out. Thanks for the advise.

 

[46/71 Hybrid]

I'm planning to work on it this weekend and I'll let you know what I find out. Thanks for the advise.

So what'd you find? I'm looking at the same symptoms as well. My guess is the brake booster but swelled hoses would be alot easier.

 

[scottlindner]

I know this is a very old thread but I wanted to post my solution to this problem in case others are searching for a solution. I had the exact problem as described. I found the caliper slides were not greased. I got some break slide grease (high temp grease) and greased the caliper slides and the problem was solved. The slides appeared to be complete dry. My guess is they were binding and that's what we were feeling on the pedal.

 

[unklwedy]

Also check out vacuum fitting on intake manifold, they get glombed up.

 

[Manuelsv]

Had the same exact symptoms couple of years ago.. It was the brake booster.. Replaced it and it's been now over 40K miles no issues..
I went cheap with a reman from Vatozone.. Yes I know should have put an OEM one in but budget was tight at the time..
IF you put a reman or el cheapo in they are not painted or rust proofed mine is rust color in Arizona where we don't have rust.. So I don't know if it's advisable to paint them but if you can I would. it looks like the oldest component under the hood and it's only 2 years old!