Stiff Brakes, where to start?

[Valmunin]

I'm new to the forums and owning a jeep. I know I'll need to improve my mechanic abilities.

I recently got my '83 Scrambler. It starts right up and drives. It has a few issues, but the first one I want to address my extremely stiff brakes.

I am probably looking for a full on guide to troubleshoot it as I might not know my way around each component of the brake system.

To further describe the problem it is never easier or harder to brake, just always very hard to press the break pedal down. I can't seem to move the brake pedal very far down and the braking power seems insufficient.

Someone suggested I "bleed the lines" a little as perhaps there is too much brake fluid.

Reading Ogre's post (https://www.cj-8.com/threads/brake-issue-with-the-new-scram.49114/) I wonder if I too have some sort of vacuum problem.

Any ideas?

I really want to get out there and drive it around, but do you all think it's unsafe in it's current stiff brake condition?

Can anyone come up with a list of things I ought to check first? (...and maybe how to check them.)

Thanks in advance and please remember I'm most definitely not as skilled mechanically as many of you.

EDIT: I do have power Boosted brakes, Front disk brakes and rear drum brakes.

 

[93_Fummins]

Stiff brakes are generally a lack of power boosting (vacuum leak, bad diaphragm in booster, weak engine vacuum, weak power steering pump with hydroboost applications, or bad seals in hydrobooster), or deadheaded pressure caused by stuck pistons, clogged lines, or faulty proportioning valve. The suggestion "too much brake fluid" doesn't really make sense.... However, air in the lines is definitely an issue, but usually manifests as weak braking action or a "spongy" pedal.

I would start by inspecting the overall condition of your brakes. Are the pads in good condition? Are the rubber lines in good condition? Are all the components present in the rear drum assembly (assuming stock)? Are there any signs of leaks? Get a good idea of the condition and configuration of everything.

Next, I would inspect that each corner is properly clamping and releasing. You can jack up each wheel, one at a time (assuming hubs are unlocked and there are no locking differentials), have someone spin that wheel monitoring the drag on it, then push the brake pedal and monitor clamping force to ensure brakes are working at that wheel, also verifying brakes release when letting off the pedal. If any of the wheels does not stop or does not release, this identifies a specific local problem, generally either a stuck or unbled piston. If the piston is stuck, it's best to simply replace with a new or remanufactured caliper/slave cylinder. If there is air in the system, simply bleed it and recheck function.

To check the booster you will need a vacuum pump and gauge. Simple hand vacuums are generally available at parts stores. You can hook it up to the port on the vacuum booster and verify that vacuum pressure assists in pedal feel and also that the diaphragm will hold vacuum pressure. If it will not build or hold vacuum, then it is best to replace the booster with a new or remanufactured piece. Inspect the host going from the intake manifold to the booster to verify that it is in good condition, and replace if not.

That should at least get you started, if not help you find the culprit. I caution that I am NOT a professional mechanic, NOR a professional to-do writer. Best of luck.

 

[Valmunin]

I'll check back in when I've made progress on this list you wrote. Thank you!

 

[OGRES]

Valmunin,

I responded to your PM. I think the above information is similar to some of my suggestions.

Posting pictures of your setup can help some of the other gurus on this board to help figure things out as well.

 

[Valmunin]

So it does have power brakes and I have located the booster. It happens to have disk brakes up front and drum brakes in the rear nothing is obviously wrong with the lines Via a visual inspection.

 

[spankrjs]

The booster needs the vacuum line run to the intake manifold.

 

[spankrjs]

On this thread, a few pics down:

https://www.jeepforum.com/forum/f8/...j-doen-t-have-enough-power-brake-why-1296209/

 

[Valmunin]

Are you talking about this pic?

 

[spankrjs]

Are you talking about this pic?

Yes, the one that says brake booster. If you don't have the factory metal piece just find a hose Barb that will thread in, connect it to the black plastic elbow on the booster with appropriate sized vacuum hose

 

[tower210]

The vacuum from the intake manifold is what gives your brake booster it's power. You are currently driving with manual brakes....

How big are your tires?

 

[John N]

With, apparently, no hose connected to the booster, not only are the power brakes not going to work, but the hose that supposed to be going to the booster is probably just dangling around, causing a massive vacuum leak. Making the engine run rather poorly.

 

[spankrjs]

The proportioning valve hanging off the master cylinder is not stock, might be an issue. Is the stock valve still on the frame? Rear end looks like it has perches on top like it was spring over at some time.

 

[bigwalton]

The proportioning valve hanging off the master cylinder is not stock, might be an issue. Is the stock valve still on the frame? Rear end looks like it has perches on top like it was spring over at some time.

Interesting routing on the front brake line coming off the proportioning valve apparently as well (up over the top of the fender.)

 

[John N]

It’s a duel diaphragm set up...not stock, but good when they work.

 

[jammer1]

It's a aftermarket set-up. You can buy the set with a proportionate valve up on the fender. They use the chevy (corvette) MC. When I got mine I considered that design (make working on it easier) but I already had stainless steel lines. Didn't want to run steel lines to fill the gaps.

 

[Valmunin]

The vacuum from the intake manifold is what gives your brake booster it's power. You are currently driving with manual brakes....

How big are your tires?

31 inches tall.

 

[Valmunin]

The proportioning valve hanging off the master cylinder is not stock, might be an issue. Is the stock valve still on the frame? Rear end looks like it has perches on top like it was spring over at some time.

I don't think so...


Thanks for all the help guys! I'm gonna have a more experienced buddy help me with this, next Saturday hopefully. I'll keep you posted.

 

[Valmunin]

Thank you all very much. Bought a couple of hoses and hooked everything up correctly and now my brakes are working super well.

My next project will be to lower the brake pedal. The height difference between the brake and gas pedals is way too much.

 

[jmarston]

Thank you all very much. Bought a couple of hoses and hooked everything up correctly and now my brakes are working super well.

My next project will be to lower the brake pedal. The height difference between the brake and gas pedals is way too much.

Any update on your brake pedal? Mine is a bit high also.

 

[Valmunin]

Any update on your brake pedal? Mine is a bit high also.

No update yet. I am saving for an engine/transmission swap. After that is paid for I'll get back into other items on my jeep. You know how it is, you look at one item on the list and you find you need to add five more.

So, post here or send me a message if you figure yours out first.