jeepfan777

I've got a strange issue I hope someone can help me with. I can't find anything on it anywhere. We've got a 90 XJ pioneer that when I am going forward I have brakes and nice solid petal. If I put it in reverse and back up a little ways the pedal goes to the floor. No brakes, Not just soft. If I put it back and drive and pump the petal It gets firm again and will stop all day until I put it in reverse and the same problem happens again. I bled the brakes all the way, changed the wheel cyliders and shoes. I checked the entire system for leaks. I just don't get it. I don't understand why the direction would have an effect on the system. I'm missing something. Any comments would be greatly appreciated. Thanks for looking.

mdcmn7

I am curious

trans_am7935

it is your brake boster, it is not holding vacumme while you are in reverse, i assume you have an auto, just replace it with a later (92-96 2 stage brake booster) one and you will be fine. it is easy and you can pick one of these 2 stage ones up for like 20-30 bucks in the junkyard

Jamie57

Why would it only lose vacuum in reverse? This just doesn't make any sense. there is NO connection anywhere between the transmission and the brake system.

My guess is that something in your rear brakes is missing allowing the shoes to rotate in the drum. If the puck inside the wheel cylinder moves too far out of it's bore it will allow a long pedal travel.

Makes sure that you have both pins that hold the shoes to the backing plate and that the ebrake cables are attached.
Also make sure that the star wheel is properly adjusted and working.
If the rear drum brakes are not adjusted properly you will get a low pedal when braking.

Jamie57

here is a Youtube series on brakes.
Very informative.

Gee oh Dee

That makes no sense.

He's got 4 wheel drums? I doubt it. The fronts would still stop the truck.

Jamie57

Ummm so what? by your reasoning you really don't need rear brakes if your only going to use the front.

Do you really think thats good advice to be telling someone worried about their brakes?

Your brake system should ALWAYS be working properly if your going to drive on any public road.
The OP wants his vehicle to work right.
He wants Good advice.

Jamie57

Do you hear any clunk or something from the front end when you do that?

I've seen where the calipers were not seated properly and moved allowing the puck to almost come out of the bore.

The hard pedal then the soft pedal means that the brake fluid is going somewhere. It's a closed system and if there are no leaks something is moving past it's design limits only when you're in reverse.

storm101

listen to jamie, he knows what he's talking about, and just so you know booster issues have a symptom of a hard pedal, not soft. Soft is too much movement of brake pistons (due to many reasons) or air in the lines, yours seems like something is moving outta place while braking in reverse, I agree on checking all mount points for everything.

Willys55

bad booster equals rock hard pedal.

are the shoes on backward or are both primarys on one side and the secondaries on the other side

johns91xj

sounds like something wrong or backwards like previous mentioned with the drums mechanics check it out

Jamie57

Good one! Forgot about that. Haven't made that mistake in over 30 years.
The primary shoe should always be the the front, facing the front of the vehicle

Gee oh Dee

Excuse me? What advice did I give?

I told you that what you stated made no sense, that is all. If it were JUST back brakes, the fronts would still aid in stopping the vehilce, so there is possibly a bigger issue than just back brakes. The OP stated he has NO brakes.

Never once did I suggest driving the vehicle, let alone on public roads. Never once did I suggest his brake system is "OK" if not working properly.

There was no reasoning given on my end, you put TONS of words in my mouth.

With that reasoning, if the OP wants good advice, he should ignore you, who obviously doesn't read everything posted. Or doesn't pay attention to what he reads.

Now, let me clearify my post for you, since you have NO clue what I intended to convey...

What I meant was that the fronts should still help stop the truck somewhat, unless there is indeed something else wrong with the system other than rear brakes.

Better for ya Jamie?

2Evil4U

I'd put my money on drum setup as has already been covered.

One quirk about these brakes that even surprised me when I discovered it.

I lost the rear brakes on my 97 at work when a rusted line blew out. I drove the 45 miles home by downshifting and using the ebrake. The front brakes would supply a little stopping power, but not enough to amount to much when going forward.

I got home and prepped to back the truck into my parking spot and out of habit, tried to stop the truck with the brake pedal. NADA. Absolutely nothing. Luckily I was able to slap it into neutral and grab the ebrake before I smashed into my garage.

I have no idea why, but if you have no rear brakes, the design of the master cylinder and proportioning valve doesn't let the fronts do diddly squat in reverse.

I did a how-to here: Maybe some of the pictures might help to sort out the mechanical stuff?

https://www.cherokeeforum.com/f51/ho...-8-25-a-58947/

Gee oh Dee

Very nice!

I may have been a little harsh with my last post, but I just HATE it when someone puts words in my mouth in an attempt to make me look bad/foolish.