Front Disc Brake Service
Contributed By: Dennis "Doc" Fariello
This is how one would go about re-lining front disc brakes ('74 and up 1/2 ton SJs - GW, Cherokees, Wagoneers, and J-10). I don't know if the 3/4 ton J-trucks' brakes are different.
Dennis M. "Doc" Fariello
- Pick a side to start on
- Chock the rear tire on the opposite side
- Place your jack of choice into position and lift it to make contact, but do not lift vehicle yet. You can either use a floor jack under the axle (recommended) or a hi-lift jack, or (shudder) a bumper jack, or the factory screw-type jack.
- Loosen the lug nuts on that wheel approx 1 turn each.
- Jack vehicle up till tire is off the ground.
- Place jack stands in place either under axle or under frame
- Lower jack till vehicle weight is on jack stands
- Remove lug nuts
- Remove wheel
- Locate caliper floating pins / retaining bolts. Use a 3/8" allen wrench to remove both bolts.
- Remove caliper.
- Remove pads from caliper by pulling off.
- Remove anti-rattle spring from inboard shoe by prying off one end with a screw driver.
- Use a C-clamp or something similar to push piston back into caliper all the way. You shouldn't need to open the bleeder or remove the master cylinder cover, it should go back in no problem. If it doesn't go right in, you may need to rebuild the caliper. This will be covered in a later article at a future date.
- Place caliper out of the way, say on the leaf spring, being careful not to kink or stretch the brake line.
- Inspect brake line. If it's got major cracks or dry rot in it, you'll probably want to replace it. Same thing if there is any swelling, or if you can crush it between your fingers. You may even want to consider braided steel lines, they're not that much more expensive than the stock hose.
- Place anti-rattle spring on new inboard pad
- Place new inboard pad into caliper, being sure to seat the spring all the way into the piston
- Place new outboard pad into caliper. You will probably notice quite a bit of play in the pad, between the "ears" and the caliper itself. If the thought of rattling brakes bothers you, then take a big pair of channel locks and compress the ears on the pad till they are tight against the caliper. I'd recommend you temporarily insert the floating pins so that you keep the pad lined up.
- It is recommend you service your wheel bearings at this time. See "How to Service Manual Hubs and Wheel Bearings", by Mark Wallace.
- Inspect the disc surface. If it's warped or discolored, or has minor grooves, you should have it turned. Most auto parts store can do this for you, they typically charge about five dollars per is all. If the disc has cracks, or has worn too thin, then it will need to be replaced.
- Install caliper into place. Insert the rear of the caliper first, sliding the outboard shoe anti-rattle clip in between the mounting ear and the disc.
- Insert floating pins into place. Do NOT lubricate.
- Tighten floating pins all the way. They should seat fully against the caliper housing. There are metal bushing in there, make sure they are seated properly and don't get lost. The pins should be seated fully against these, no gaps.
- You shouldn't need to bleed the brakes unless you've rebuilt the caliper or replaced the brake line.
- Install wheel.
- Install lug nuts, hand-tight
- Tighten lug nuts best you can with lug wrench.
- Jack vehicle up to remove weight from jack stands.
- Remove jack stands.
- Lower vehicle.
- Tighten lug nuts all the way, in a criss-cross pattern, to 100 ft. lbs. Or "star torque" them. This means torque them till you see stars. Repeat pattern as necessary till they all are fully tight.
- Repeat procedure for the other side.
- Test drive vehicle carefully.
- Re-torque lug nuts after 50 miles or so, especially if you have aluminum wheels.
13 February 1997