Hey guys,

I thought I'd finally post a thread seperate from my long build page but I'm having a brake issue that is driving me insane. To put it simple the front brakes on my Blue truck suck. I can't lock them up on dirt, but I can lock the rears up under hard braking with 4500lbs of pin weight on asphalt.

Front has new slotted rotors and hawk pads
I replaced both front calipers with no change
Rear has new shoes properly adjusted with no change
New OE zero loss booster with no change
new master cylinder bench bled properly with no change

Pedal feels great. The front brakes simply are not where they need to be. I have chased this for some time and am about to loose it as there is almost 1000+ in the brakes now and they still suck azz. Yes I know how to do a hydroboost conversion, but am a bit past that point with money wasted. I always wwas happy with the braking of 94-97s for what they were. The brakes on the other two OBS trucks are night and day better and have 10 fold the front braking power. I have thrown enough parts at it and hate to even admit to it, as I have not been able to solved the issue over a couple years. Its fine unloaded but not ok when towing heavy. Like I mentioned the other two trucks will lock the fronts up on dry asphalt with ease. This truck will barely lock them up on a dirt road.

Can the RABS cause issue with this? I doubt it to this extreme extent. Bench bleeding the flow seemed terrific. Open to suggestions as I have never seen this before nordo I know where to go with it.

I assure you the master is bled properly, all air is out of the system, terrific vacuum on a new pump as well, its the same as day one minus 1k in parts


All components are OE FYI

 

The only thing I can think of that MIGHT have something to do with you braking problem, is the rubber brake lines to the calipers. You did not say if they have been replaced. I have not had any problems with mine, but have read where they can cause problems, usually from deterioration on the inside of the hose not letting the fluid to release.

 

I know what your saying but don't have any solutions. The OX is my third and by far the best braking and I don't know why?

 

I'd be happy to replace them as well however my gut tells me this is not the issue and I will be dropping more money into the pit without clear troubleshooting.I swear it has to be the proportioning valve or RABS

 

Can you bypass the RABS? When I made all new lines for the truck I did not find a proportioning valve. Is it the large nut on the side of the master cylinder the hard line thread into?

 

 

Nick.

I read back in your thread. If the RABS light is not on I would leave it alone. It sounds like your proportioning valve has crap stuck in it or something. I am no expert but the symptoms you describe lead me to believe the valve to be stuck open ie bypass. I bypassed my RABS because it was so rusty when I tried to pull the lines everything broke. I left it in there plugged in so I don't have an abs light in the dash. I believe the valve to be stuck in a position that doesn't trip the dash light.

ON another note. Have you done valve springs on these engines with the head on? If so what tooling did you use?

 

Same here. subscribed.

 

You would be sirprise what a collapsing soft brake line does, in my case in my work truck (00f250) the caliper would hang up and wouldn't allow the fluid to return fast enough and the truck felt like it was draging 20k for a couple of seconds, new lines problem solved. Also check if your hard lines are not smashed.

 

Just make sure the piston is TDC so the valve doesn't fall. Valve spring compressor.

 

I ordered a new proportioning valve, I don't know what else it is.... Just leaves lines and the RABS

Yes its fairly simple, spring compressor tool or make your own... motor can be in truck, just make sure that cylinder is at TDC and don't drop the valve. Use a guide rod through the glow plug hole if need be.

 

Brakes are not dragging, everything is new outside of the lines. I'll look closer at the hard lines but doubt that is the issue. I guess it could be, i just don't know what would have caused it....

 

I have a 96 4x4 that I converted to hydroboost and have similar issue. Rears lock before front when slippery. Makes slowing or stopping in corners real interesting. I even plumbed in a brake proportioning valve which seemed to help some. I plan to rebuild the back brakes, maybe are adjusting up too much?

 

I know hydroboost will overpower the rear cylinders in that situation and I'd dial back the rear if you can... Issue I'm running into is the fronts just are plain horrible in comparison to my other trucks.