Bleeding brakes on a 98 3500

[aarcuda]

I need to bleed the brakes on a 98 3500 truck that has the power steering hydraulic power assist but the pump pump pump hold method isnt working too good. the pedal is still soft.

Will the pump pump pump hold method work on this vehicle? it has some funky module that I believe to be the antilock brakes on it (the module sits on the inner fenderwall, has brake lines going in an out, 3-4 electrical connectors and a black top that says Kelsey Hayes).

Will the pump pump pump hold method work? several lines were busted and the entire master cylinder/power assist unit was replaced (from a junk yard donor truck) so I expect there is a lot of air in the lines.

and I did bleed the master cylinder first. I also tried a mityvac setup and found LOTS of bubbles in the front lines.

Someone told me that I need a scan tool to do an automatic bleed on the abs unit first, then do the manual bleed. anyone know about this?

[SpitAndDirt]

Check out these sites......They are invaluable for our trucks and their brake systems. I don't think that your Hydro-Boost system should make a difference in the bleeding procedure, but you should understand what your ABS module/motor is doing when you are bleeding your brakes. From my service manual, it says that there are three bleeders, in addition to the wheel bleeders. The first one is located underneath a rubber cap that is directly next to the brake lines entering and exiting the abs module. It is not a typical bleeder in that you don't unscrew it. You push in on the gold looking pin about a 1/4 of an inch and hold, THEN have someone push on the brake pedal SLOWLY to expel air trapped in the proportioning valve. Once his foot reaches the floor, stop holding the pin, and take 15 seconds to bring the pedal back up. This is so you can draw fluid from the brake resivior and not from the lines you just bled. You won't be able to push in the pin with someone standing on the brake pedal as the pin gets forced out about 1/4 inch from the fluid pressure. The other two bleeders are the internal ABS bleeders, located on both sides the ABS module. They look like 3/8 hex plugs. All you need to do to bleed the motor is open them up 1/2 turn and then bleed everything normally, with the key OFF/engine off. If you bleed with the key on/engine off, you will most likely set a code in the ABS computer. After bleeding the system, close the 3/8 hex plugs to 10 ft/lbs (don't force the plugs in, just SNUG, plus a little oomph). Check out these websites for more than you ever wanted to know about ABS and GM brakes. Hope this helps -Chris 96 Z71 5.7L All stock http://www.babcox.com/editorial/bf/bf60133.htm http://www.babcox.com/editorial/bf/bf70142.htm http://www.babcox.com/editorial/bf/bf50434.htm http://www.babcox.com/editorial/bf/bf30414.htm http://www.babcox.com/editorial/bf/bf120312.htm http://www.babcox.com/editorial/bf/bf50230.htm

[SpitAndDirt]

http://www.babcox.com/editorial/bf/bf90420.htm Here is one more about Diagnosing Spongy Brake Pedals - Enjoy!

[aarcuda]

HOLY BRAKELINE BATMAN! I thought I knew how to bleed brakes but I guess I don't!! Thanks for the links! I printed out all that material and will read it. Excellent links!! thanks.

After I digest this, I will give it a try tonight and let you know how it went.

Thanks.

[aarcuda]

hmmm, tried it. didnt work. spent about $20 in brake fluid so far. After opening the two bleeders on the antilock brake unit, i bleed as normal using the pump pump hold method. is this right?

maybe the master cylinder is junk. I will put the original on and try it again after bench bleeding it.

[SpitAndDirt]

Did you try using the line locks to try and isolate the front and rear brake systems as suggested by the articles? Then you could tell if the master cylinder is bleeding down, the rear brakes are misadjusted, or if your front calipers are not self-adjusting properly. Did you try plugging the quick-take-up valve in the master cylinder to see if you could get the pedal to get any harder? There are only so many things that you can do to firm up your brake pedal. Hope you get it fixed. -Chris

[aarcuda]

still working on it. the pedal is a little firmer. tried gravity bleeding it for a couple of hours.

havent tried the line lock yet since I didnt have the right tools (ie something to connect to the lines to block them off) but I am still trying to find something to do it with. what do you use? a length of tube which is blocked at the end?? do they sell a cap for this?

[SpitAndDirt]

Lisle Tools, sold at Pep Boys and O'reilly Auto Parts stores. You can check www.lislecorp.com and run this part number thru to see what they look like. #22850 I bought mine for about $8 for a pair of them at Pep Boys. Good luck

[J-Ri]

vice grips work too, just put a couple pieces of plastic, rubber, or wood on each jaw to keep from damaging the brake line.