Back brakes are really wonky.

Hmm where do I start. Heres the situation.

My brake pedal goes almost to the floor, as the truck does almost no slowing down. At the last little bit of pedal, it gets harder and the truck stops much better. If I pump my brakes it gets harder a little sooner.

Here the thing. Whenever the pedal is soft and goes near to the floor, the little (!) brake light comes on, on the dash right before the pedal reaches that 'harder' spot, and will stay on until I pump my brakes up. I've checked both wheel cylinders as I did my shoes last night, and they're not leaking.

I just bled 3/4 wheels(bleeder valve snapped off of a caliper) recently and the back brakes are well fully adjusted. When I bled them, fluid SHOT out, not dribbled.

Winter's coming up so I'm trying to get the things fixed that keep it drivable. This seems to be the major problem right now next to tires

Any information is appreciated, and sorry if this has been discussed but all I seemed to have been able to find was people with bad ABS systems.

Try an new master cylinder and get back to us. When was the last time it was replaced?

yep just replaced mine twice. first one was bad too.

I don't know if it's ever been replaced...I've only owned the truck since February. Also its a 90.

make sure the wheel cyls. or any lines are leaking also

Being as it's a '90 I would look into replacing anything that has been moving brake fluid for nearly 17 years. The master cylinder is what the primary problem sounds like to me, but since I would wager large sums of money that the brake fluid has NEVER been flushed, your whole problem is bound to continue down stream.

Start with what you can afford and tackle yourelf. Rear wheel cylinder are cheap ('round $12 new, not reman), front calipers (less likely to still be original, but you never know) and the master cylinder. Don't forget new soft lines at the front wheels and the rear end.

Flush the whole system out with fresh fluid (or if it's really bad denature alchohol first) and bleed, bleed, bleed.

It's a good bit of work, but if you get a vacuum tester/brake bleeder, available at Sears for not too much $ it makes the job a lot easier. As well as making the subsequent annual changing of the fluid a much simpler chore.

I tend not to fool around whrn it comes to brake problems. It is a system, and if one part is compromised it isn't much longer before the rest of it begins to go too.

Besides, it might be a good opportunity to upgrade to the '95 booster and MC .

Good luck.

im going to replace the back lines on my 90 i blew 1 line. and broke another. really rusty.

If your brakes are adjusted, and you are not losing fluid, but your pedal goes down to the floor, it is, as others have said, almost certainly the master cylinder. Dual master cylinders of this sort are designed so that when one circuit fails, the pedal will sink quite far until the last moment, when it engages the one that has not failed. If you can, get on some sand or gravel, get up to a few miles an hour, and jam down the pedal. You should be able to determine which circuit has failed. If you bled one caliper but not the other, and if the problem is there, then it should pull pretty badly. If it stops evenly with both front wheels skidding, we're back to suspecting a master cylinder failure. A bad master cylinder will also often (though not always) be firmer if you hit the brakes hard and fast, but sink slowly under steady lighter pressure. If that happens, it really is the M.C. without a doubt.

There is no major pull when breaking. I bled both calipers when I put YJ lines on. It was the second time the bleeder F'd off. Also I was doing the gravel trick today. The front will lock up but the back wont do anything, unless I pump the brakes first.

Vanquish said:

There is no major pull when breaking. I bled both calipers when I put YJ lines on. It was the second time the bleeder F'd off. Also I was doing the gravel trick today. The front will lock up but the back wont do anything, unless I pump the brakes first.

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12GaugeXJ said:

Try an new master cylinder and get back to us. When was the last time it was replaced?

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