2nd Gen Non-Engine/Transmission OK, I need some real help with brakes

[Lightfoot]

My '96 stopped great but pulled and pulsed to the right a little with a warped rotor. I tore the thing apart, threw in a set of drilled,vented rotors with ceramic pads from Napa and replaced the brake hoses. Bled the system and buttoned the wheels back on. Took it out for a spin and it stopped beautifully. No pulse, no pull. Hit them binders and it hauled right down on wet pavement, no skid. But the pedal wants to sink slowly to the floorboards at a stop sign. All the lines are bled right. I took it to a friends repair shop. He said "new master cylinder. " One new master cyl. later still the same problem. He called another shop that specializes in diesel trucks. They say it's the ABS electronic apportioning valve just below the master cyl. The truck has all wheel ABS. All this stuff worked great before the operation. Man I could use some help. I have to go down to Oregon to pick up a trailer in a couple of days. I'm prayin about this one. Anyone?



'96 4x4 quad cab,AT,354 gears,PowerLoc rear,4" exhaust with high flow

muffler,PacBrake,Long Bed

 

[Rescue Ram]

I would have a hard look at the ABS system. This sounds exactly like what occured in my 96 when my ABS computer said "adios".

 

[Lightfoot]

Rescue Ram, what was the remidy with your ABS system. New computer? The wiring from my ABS modules disappears under my relay,fuse box located next to the battery. But I didn't know the '96 used a computer. I just thought the wires ran to a relay. Theres a computer module in that relay box?

Thanks for the response.



'96 4x4, rebuilt AT, 354 gears, Power Loc rear diff. ,PAC brake, 4" exhaust from turbo to tail pipe,high flow muffler

 

[clinebarger]

Did you open the bleeder screws when you pushed the caliper pistons in? If you did not, its possible that debris from caliper was forced through the abs hydraulic control unit when you pushed the piston in. You can have it pressure bleed and try to get the trash out of the control unit. if that does not work you might have to replace the entire unit. I do not think that it is sevicable. Hope this helps.

 

[I-6DZL]

try bleeding like this



put a person in the truck with the engine off, pump the pedal about 6 to 7 times, hold down on last pump, while they're holding down, open the bleeder.



Do this 2 times per wheel starting with RR, LR, RF, LF



It is definite that you still have air trapped in the system. Usually when a master goes bad, all you have to do is push really hard really fast on the pedal and it'll be hard as a rock for a second then fade off. If that happens it's a bad master.



Did you guys bench bleed the master before installation. It's tough to get all of the air out, takes patience.



Curtis

 

[Lightfoot]

Clinebarger; thanks for the comeback, yeah the caliper assembly was disconnected from the brake hoses when the pistons were pressed in. In fact the assembly was prepped on my work bench. The master cyl. and lines did run dry but we refilled, thoroughly bled and re-bled.

 

[Lightfoot]

1-6DZL thanks for the help. Yeah the lines were bled from a corner to corner sequence. I passed the truck on to Midway for the second round. They installed the new master cyl. , and I'm sure they bled and re-bled it. The origional master cyl. did act like you said, but so does the new one. The shop I passed it on to is pretty thorough. Between my work and their work you'd think we managed to squeeze the air out of the lines. I'll shoot your comments back to them tomorrow though. From the comments recieved so far it's looking like an ABS quirk. Anyone else ? Any help is very much appreciated.

 

[jtwcummins]

There should be a blue can by your MC, looks like a frozen OJ can. I know of 2 96-97 RAMS that had to replace it to get brakes right. On mine I had the system power flushed and the problem was gone. I also had issues with variation in pedal pressure. Using a turkey baster I flushed out the power steering then added lubeguard. Used Valvoline synthetic fluid. Fixed noise in steering when cold and brake pedal pressue is always the same.

 

[Lightfoot]

jtcummins- come back if you catch the question. I am having trouble making the connection between power brakes an power steering. Can you explain what you mean ?

 

[vssman]

97+ used hydraulic assisted brakes. Ours are vacuum assisted. Do you have 4wheel abs or rear wheel only?

 

[twopipes]

Do a search and find "Brakes!!!" by TSterken. Evidently the recommendation from Bloomy works for the condition you're having - at least for him.

 

[jtwcummins]

The 97 has hydra boost using the PS pump. Since mine was built jan 9, 1997 the engine is tagged as a 96 so I don't always remember when the vac booster was replaced. A little problem with pwr steering can cause big problems with brakes

 

[Dave M]

Hydroboost or not?

jtcummins- come back if you catch the question. I am having trouble making the connection between power brakes an power steering. Can you explain what you mean ?

I just replaced the hydroboost unit in my 97. If you have hydroboost assisted brakes then the hydroboost unit will be mounted directly behind the brake master cylinder and you will be able to trace power steering lines from the hydroboost unit to your power steering pump. The master cylinder is mounted to the hydroboost unit and the hydroboost unit is mounted to the firewall.



The power steering pump provides boost for your brakes using the power steering fluid from the pump to your hydrboost unit on the firewall. Your brake pedal is connected to the hydroboost unit and a rod comes out the the hydroboost unit into the master cylinder to activate the brakes. There is no fluid connection between the hydroboost and the master cylinder... its all mechanical. If instead, you have vacuum boost then, I assume, you will see the 9 inch or so round vacuuum boost unit on the firewall instead of the hydroboost unit. By the way, my original hydroboost unit had a blue canister on it but the new one I got from www.hydroboost.com is gold anodized as you can see from my pics.



Here are some pics of my 97 and the seperate hydroboost unit.



Dave