Dinner

Hello,

I've been trying to do some reading about front brakes sticking, and so far I've found information on the Calipers are toast, or perhaps it is a Power Steering/Hydroboost problem.

I replaced my front Calipers and Shoes yesterday hoping that would be the problem. Took it for a drive and my front brakes decide to slowly come back on while driving. I drained most of the fluid out of the front lines by filling the reservoir, pushing the brake pedal with the bleeders open on the front. Once the reservoir was low, I would add more fluid and repeat. I thought maybe there was bad fluid, however this did not fix the problem either.

I did read up on how to test your PS and Hydroboost, so I gave that a try. Running the truck and then shutting it off, the Brake Pedal is hard the first push. Starting the truck back up, I can push the pedal a good amount. If I have the truck running, turning the wheel back and forth..nothing changes. As soon as I shut the truck off my pedal is hard again.

I'm not sure if a bad HydroBoost/Master Cylinder would cause my front brakes to stick on however. When driving around I can smell the front brakes burning, I run about 900-1000 EGT just will cruising and I'm about 10PSI Boost will cruising. I can tell it's hard on the old girl since I'm running those temps and Boost.

Any help is greatly appreciated!!!

Dinner

I was out this morning and started opening brake lines here and there. I open the lines at the joint along the frame, wheels freed up. Moved up to around the ABS system, once opened there I could spin the wheels easier. So I opened the line which I'm assuming runs the front brakes off the master cylinder, this also freed up the wheels.

It is only the fronts that are locking, the rears release like normal

Is this pretty much telling me that my master cylinder has gone bad, that it's not allowing to relieve the pressure off the front brake lines? I just don't want to go and buy parts I do not need, been spending too much money lately.

Thanks!

98.5Hotrod

It may be the ABS unit gone bad. Check your truck for codes.

Dinner

Well my ABS hasn't worked for the past 6+ years, so I am running on regular style braking. What would happen is the ABS unit goes bad? It would still flow fluid right, just the electrical system is messed up?

I thought it might have been an ABS problem, then I got thinking that we haven't had ABS on this truck for a very long time, bah this is aggravating.

98.5Hotrod

Do trucks with ABS have proportioning valves, if so it could be bad.

j-fox

You may find the hoses going to the calipers are going bad. They swell and hold pressure, so it all doesn't blead off.
You may also find the pads are tapered front to back. Take then out and measure them with a dial caliper. If so and you are in a crunch, swap each pair to the oppsite wheel. If they are tapered, they allow the piston to **** in the bore and stick.

dozer12216

I believe you found your problem when releasing pressure at MC would release the front brakes. That says the problem was at MC. The compensating port on MC is not working properlly.
One moe test you might do! While front brakes are holding pressure as you did before, Loosen the bolts holding MC to hydroboost. This is tricky so don't condemn the hydro to quickly. More than likely it's MC. JMHO

nitrousn

I agree but he did not say where exactly he cracked the lines. He said around the ABS for the front brakes. He needs to try it at the master before he condems the wrong part. It could be in the abs valving esp since he has had a problem there he did not correct.

Dinner

Sorry I wasn't too clear earlier, I'm just trying to get the old girl back on the road.

After I cracked the lines right after the rubber meets the steel and the brakes released, I moved up to around the ABS stuff.

I pumped the brakes up(truck off) until they were locked. Cracked the line at the red square and the brakes released. So I moved to the fitting at the Master Cylinder, the orange square. After opening that fitting a little bit, the brakes would be released. With that being said, I figure that my lines and ABS valving are ok since they brakes would release all the way up to the MC.



Now both front brakes lock on, the rears are fine. I can pump the brakes to lock the fronts, crack the brake line for the rear wheels at the MC and no brake fluid will spurt out. Only the orange square fitting(which I'm guessing is the front brake feed) spurts fluid out.

Could this be only a bad Master Cylinder? I did the "tests" for testing out the Hydroboost and after shut off my pedal is always hard first push. Even sitting overnight the pedal is hard first push. I'm hoping (and thinking) that this isn't an ABS problem, but I could be wrong. Oh and my brake shoes are brand new, got them with my new Calipers. I may order a Master Cylinder and HydroBooster tomorrow just in case it is one or the other

Thanks so far guys

nitrousn

Just make sure your pedal is returning fully. If so it sure sounds like a bad master.

nitrousn

You also could loosen the master to hydro bolts and see if the brakes release. If so than the problem is in the hydro and not the master. Narrowing it down will save you money as each are available seperate.

Dinner

Nitrousn,

My pedal is returning fully, I can try to pull the pedal up with my hand and it doesn't go any farther. Heck I could only push the pedal down an inch it was so stiff.

I ended up ordering both Master Cylinder ($50) and Hydrobooster ($202). So I'll throw both the new pieces on once I get them in. If this doesn't fix the problem, then all I can see is bad brake lines, even though they seem to be ok, or it is my stupid ABS stuff. It didn't take me long to get the MC and HB off so this is how the truck sits right now,lol


Thanks!

maxpower

My '96 locked up the front brakes one day going down the interstate. Pulled over with smoke pouring from the front wheels. I was going to crack the bleeders on the front calipers to hopefully get me home, when for some reason I pulled the harness from the ABS. Problem solved, no more issues for the next 15,000 miles when I sold it.

dozer12216

Really believe problem is MC. Try it before replacing Hydroboost. Don't want you wasting 200 dollars.

Dinner

I will try just the MC and see where that gets me. If it still acts up then I'll throw the hydrobooster on there as well. Really hoping that either of these fixes the problem! Sucks not being able to drive my DD.

If the problem still occurs when MC and HB are changed, then I will look into the ABS, see if I can start pulling wires. Even though the ABS hasn't work for years, but anything could happen,lol