2nd Gen Non-Engine/Transmission brake problem, it's a good one

[MarkMiller]

So I have now replaced the hard lines from the MC to the axles and the rubber lines with braided stainless. New calipers on the front, rear wheel cylinders are not leaking. New hydroboost unit, new MC, new proportioning valve.



Pedal is firm/hard with engine off. Soon as it is running the pedal goes to the floor with little effort. Bled the system both forwards and back with vacuum bleeder. Bled all the fittings from MC to PRO, PRO to ABS manually.



Rear wheel ABS only. No rear load sensing valve. 1999 2500 4wd.



Been fiddling with this for weeks and either going to burn the truck or sell it.



Any ideas?

 

[mickeyblueyes]

Where these parts made in China? That would be my first guess.


There is a sequence for bleeding,I do not remember but it makes a difference.

 

[fest3er]

According to a recent thread, you probably need to cycle the ABS under program control to purge the air out of it.

If you do decide to burn it, let me know first. I'll take it off your hands. It's the very least I could do to keep you out of stir for maliciously pollutin' the environment.

 

[B.G. Smith]

You need to power bleed, start with the right rear, start with the MC full, have someone pump up the pedal, bleed only till pedal goes about half way down, continue on this until you are sure no air or bubbles are coming from that wheel. Best way to do that is to use a length of clear tubing over the bleeder screw and the open end in a clear sontainer under the fluid level, keep MC full. Do the other rerar same way the move to fronts, you may need as much as a quart of fluid to get results. Also make sure the bleeder screws on the front calipers are at the top of the cylinder, i have seen them installed on opposit sides with the bleeders down, wont work like that. bg

 

[budnate]

pull the fuse to the abs, my truck was doing weird stuff like this last summer, did everthing you did chasing it, I found my abs unit off the master cyl was unloading for a lack of better explanation and letting fluid short cycle, I run with my fuse out for now strong pedal at the top and the truck stops nice when you have to hop on the brakes hard, I also stuck in the oversize rear wheel cyls.



I second a good power bleed job, after I did mine trying figure out what was going on the brakes were more solid.



peace,B.

 

[MarkMiller]

Bled in sequence. Most people do both rears then both fronts. The correct sequence is RR, LF, LR, RF. That is according to ASE and SAE anyhow. Right now I am wishing this thing had air brakes.

I use a a professional, air operated vacuum pump and have never had it not entirely evacuate the system. I have pulled multiple full systems worth of fluid through the lines. MC was bench bled before install. The MC, PRO, and ABS were all power or manually bled.

The problem persists with the ABS motors unhooked from the computer (no power to them).

I will try a manual bleed at all four corners today and make a line to bypass the entire ABS system. More info this evening when I am done. Or I may be drinking beer watching a fire.

Thanks guys.

If your serious about buying it PM me. 1999 QC LB SLT 4wd, II phat shaft turbo, F1 mach 4 sticks, O-ringed and studded head, F1 Helix 2 cam, TST power max 3, Edge EZ, South Bend full ceramic dual disk clutch, 5 speed ditched for 6 speed. 5 inch lift with 35 in tires, Fox and bilstien shocks, 4. 30 gears FR RR, and a Detroit in rear. Front axle has 35 spline CM shafts all the way out, manual hub conversion. Power leather seating, Alpine stereo system with Focal highs and MTX subs under rear seat. Tinted windows, gooseneck hitch. Was planning on selling, just wanted to fix brakes first.