Brake Battle -- Mushy-No brakes
- Thread starter Bear80
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With the wheel on I hope? As well, after you adjust the drums, are you going back and pressing down on the brakes to set the shoes? You cannot tell the correct drag by adjusting with the wheel/tire off. A correctly adjusted drum will "drag" the wheel so that it should only turn a couple of times when turned/spun by hand. Drive and check again.
The 40% deal makes me think you are only using your front brakes. Just a thought.
The 40% deal makes me think you are only using your front brakes. Just a thought.
Dan:
The drum brakes, counter to what most folks think, should (if done right) provide more braking power due to the surface area of the braking components. The disks on the minis are VERY small-much like the 40's. So, a good drum system i.e. turned drums, adjusted pads should lock that rear up in a heartbeat.
The drum brakes, counter to what most folks think, should (if done right) provide more braking power due to the surface area of the braking components. The disks on the minis are VERY small-much like the 40's. So, a good drum system i.e. turned drums, adjusted pads should lock that rear up in a heartbeat.
Jukelemon said:
However, the proportioning valve on the rear of the truck (LSPV) should make sure that most of the power is going to the front because you can get more stopping power from the front without locking up. I agree that drum brakes are much more effficient. I have drums all the way around on my 63 mercury and it will lock them up if even think about touching the pedal.
Also the physics favor the pushing out of drums over the squeezing of disc.Dan
Hmm, I would think the opposite actually. It takes more pressure, friction, to provide equal stopping power on the front. Stopping power is a matter of heat dissipation and surface area. In other words, I would think the LSPV is compensating for the inefficiency of the disk brakes. Good question.
A well adjusted 4 drum brake system stops very well minus in an environment where the drum is soaked in water. One could have a very efficient disk set up, as in an m3, but that is costly and requires large rotors and calipers-almost three times theh size of the mini's set up.
So, it would be interesting to find out the proportioning %'s on a stock system. That should be the tell all.
A well adjusted 4 drum brake system stops very well minus in an environment where the drum is soaked in water. One could have a very efficient disk set up, as in an m3, but that is costly and requires large rotors and calipers-almost three times theh size of the mini's set up.
So, it would be interesting to find out the proportioning %'s on a stock system. That should be the tell all.
- Thread starter
- #27
Well the LSVP is what first came to mind when my problem started. However neither the front nor the back brakes lock up, or even get close to lock up. I went out and adjusted the rear brakes to the point that I could barely turn the wheels-tires on. And it made absolutly no difference. I can't figure this out, I have a mushy pedel that does not pump up and goes to the floor while providing no aditional braking.
I still vote for master cylinder, or possibly bad calipers...
By stopping power, I meant that the friction coefficient is greater on the front tires during braking due to the weight distribution changes that occur during braking, the majority of the weight is shifted forward, so the front brakes are designed to provide more braking force. If the force to front and rears was equal, the rears would immediately lock up, and the fronts would have to do ALL the work.
By stopping power, I meant that the friction coefficient is greater on the front tires during braking due to the weight distribution changes that occur during braking, the majority of the weight is shifted forward, so the front brakes are designed to provide more braking force. If the force to front and rears was equal, the rears would immediately lock up, and the fronts would have to do ALL the work.
- Thread starter
- #29
The only case of bad calipers would be a sticky or one that is leaking correct. I've check both calipers and neither seems to leak and the pistons move in without problem. I did put these on five years ago and the calipers are the only things I haven't changed since the problem started.
If all things are operating coorrectly i.e. MC, valve and calipers/drum pistons, then you have an obstruction in your line and maybe a crack. I have had cracks in the line that would allow for a bleed but not full braking power. That is all that is left I think.
Well, theoretically no BUT you could have a crack in a line that is not easily noticed i.e. obscured. It is enough to decrease the psi in the system but not big enough to leak out the fluid in any time soon. As well, you can an obstruction in your line i.e. rust and s*** that would show a good bleed but, like a clogged artery, would not allow for the full stopping power due to fluid restriction.
It has to be one of those if ALL the other components have been replaced. You might try to take off the lines at the calipers, rear cylinders and MC and blow some compressed air through the lines. See what comes out . Hopefully, if it is an obstruction, you can push it out/though the lines.
It has to be one of those if ALL the other components have been replaced. You might try to take off the lines at the calipers, rear cylinders and MC and blow some compressed air through the lines. See what comes out . Hopefully, if it is an obstruction, you can push it out/though the lines.
On my '91 runner it supposedly had a new master on it when I bought it. Same problem you describe. The PO went round and round bleeding the brakes, replacing bleed screws and other to no avail. I replaced the front calipers as the pistons were frozen and that helped, but still had the mushy pedal and no engagement. I looked at the back of the piston where the pedal engages (from inside the cab) and sure enough, leaky master. Ordered a new one from CDan, bled it according to the FSM procedure, works great.
Are you sure the piston diameter is correct? Assuming no leaks, and if you can't build up pressure by pumping it (indicating air in the lines) maybe you're not moving enough fluid? Didn't first gens have a smaller bore diameter than second gens or V-6 rigs? The bore size is cast on the side of the OEM MC's....I'm sure Pirate has it in the FAQ.
Do you get air out of the lines when you bleed the system?
Are you sure the piston diameter is correct? Assuming no leaks, and if you can't build up pressure by pumping it (indicating air in the lines) maybe you're not moving enough fluid? Didn't first gens have a smaller bore diameter than second gens or V-6 rigs? The bore size is cast on the side of the OEM MC's....I'm sure Pirate has it in the FAQ.
Do you get air out of the lines when you bleed the system?
Did you ever solve this problem? My 93 fjz has the same problem and it's driving me crazy as well.
Any news????
It's been a few months, have you had any revelations?
My 89 pickup is sitting up on jackstands in the garage right now with the same problem.
What tees me off is that a friend helped me bleed the brakes and they worked find for a couple months and I drove the crap out of it. Then they went out again, and I can't get them back.
It's been a few months, have you had any revelations?
My 89 pickup is sitting up on jackstands in the garage right now with the same problem.
What tees me off is that a friend helped me bleed the brakes and they worked find for a couple months and I drove the crap out of it. Then they went out again, and I can't get them back.
- Thread starter
- #40
Not yet, but since my last post I found that when I replaced the LSPV years ago the front line and front return line was swaped. This did improve the brakes but they still won't lock up except on a very wet road. I also put a tundra booster/master and new Napa rear wheel cylinders. I highly recommend the Napa rear cylinders over anything else, they are also priced the same as the crap you get at autozone etc. I have zero leaks and never lose fluid, and the system has been bleed probably 50 times, with a helper pumping, power bleeder and a combo of each, I just cannot belive there is any air in there. I also replaced the front rotors and right now I'm left with putting new callipers on to see what happens. I'm going with the larger v6 ones.
Oh and even with the "new" booster and cylinder the pedel feels as soft and easly pressed to the floor as it did before. If I have issues with the front calipers, I don't see why he pedal would still be mussy and go to the floor. I could see that they could be part of my issue with no lockup.
Oh and even with the "new" booster and cylinder the pedel feels as soft and easly pressed to the floor as it did before. If I have issues with the front calipers, I don't see why he pedal would still be mussy and go to the floor. I could see that they could be part of my issue with no lockup.
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