The TJ specs DOT 3, but DOT 4 is a smart upgrade for any rig that sees mountain descents or heavy towing. Plan on 32oz of fluid and a one-person gravity bleed or a two-person pedal bleed — both work.
Brake fluid is hygroscopic, which is a fancy way of saying it sucks water out of the air. Wet fluid boils at a lower temperature than dry fluid, and the moment your fluid boils mid-pedal, you have no brakes. The factory recommends flushing every two years — almost nobody does, and almost nobody should be surprised when their pedal goes soft on a long descent down Schnebly Hill. If your fluid in the reservoir looks dark amber or coffee-colored, you're overdue.
Start by sucking the old fluid out of the master cylinder reservoir with a turkey baster. Get every drop you can without dragging the screen at the bottom. Refill with fresh fluid to the MAX line. This step alone replaces about 30% of the system's volume and is worth doing on its own if you're short on time.
For the actual flush, the TJ bleed sequence is rear passenger → rear driver → front passenger → front driver. Furthest from the master cylinder first, closest last. Pop a 10mm box wrench on the bleeder, slide a piece of clear 1/4" vinyl tubing over the nipple, and run the tubing into a bottle with about an inch of fresh fluid in the bottom (the fluid in the bottle keeps air from sucking back in).
Two-person method: helper presses the pedal slowly to the floor, you crack the bleeder, fluid pushes out, you close the bleeder, helper releases. Repeat five or six times per wheel until clear fluid runs through the tubing. Critical rule — never let the master cylinder run dry. Top it off after every wheel. A dry master cylinder pulls air into the ABS module on later TJs and turns a 90-minute job into a several-hour ordeal.
Plan on about a quart of fluid total for a proper flush. Buy two quarts so you're never tempted to skimp. If you're switching from DOT 3 to DOT 4, flush thoroughly — they're chemically compatible. Do not mix DOT 5 (silicone) with anything; that's a full rebuild conversation.
| Part | Vendor | Est. price |
|---|---|---|
| Valvoline DOT 3/4 Brake Fluid (32oz) | Valvoline | ~$8 |
| Mopar DOT 3 Brake Fluid (12oz) | Mopar | ~$7 |
| ATE Type 200 (amber, German spec) — for DOT 4 upgrade | ATE | ~$18 |
Written and maintained by an AZ wheeler and driveway wrencher. Always cross-reference your factory service manual — modifications affect vehicle safety and warranty. Work at your own risk.