BJ60 Brake Bleed

Have had truck for more than two years now. Changed the oil, nasty. Changed the transmission and diff fluids, nasty. Birfields empty. Changed the coolant – it was sure nasty. Replaced thermostat, replaced coolant lines. Changed the clutch master and slave, and the fluid in there was nasty too. Hmm. I’m seeing a trend.

So… How come I never touch the brakes? No even once? Wonder how that brake fluid is doing?

First I notice that the e-brake isn’t really working. I have to pull it harder and harder. After a few months I look in the manual and see there’s a simple adjusting knob and bolt to tighten at the handle. The bolt moves the pull point on the handle, means the cable to the e-brake is pulled further. Don’t make it too tight or the e-brake will be on all the time. The manual says 7-9 clicks to reach 20kg (44.1 lbs) of force.This is a simple 1 minute job.

On to the brakes. While there was no problem with the brakes, I felt it was time to maintain them.

While the e-brake is cable actuated, the car’s brakes are hydraulic: the brake pedal presses the master cylinder, the master cylinder compresses the brake fluid and the pressure goes through the entire system. Brakes on each wheel, also a proportioning valve in the middle of the car. Each of these points has seals and wipers and cylinders that move. Each point should be bled, meaning letting fluid out along with any accumulated air bubbles (if there is air that’s bad, a seal is leaking, but air can be introduced by the bleeding procedure if done incorrectly.)

I read the manual, there is a bleed nipple for each wheel, also a bleed nipple for the proportioning valve. To flush the brake system you have an assistant apply pressure to the brake, you crack open the bleed nipple, allow some fluid to exit, close the nipple. The assistant must not lift before the nipple is closed, otherwise air will be drawn back into the brake.

IMPORTANT STUFF ABOUT BLEEDING OLD MASTER CYLINDERS:

• Takeaway is: if you use the pedal method to bleed an old truck, be careful to keep the pedal in the normal range of travel. Don’t push the pedal to the floor as you may destroy the mc seals.

Explanation:

• An old doubtfully maintained car will not have had frequent brake fluid flushes.
• Old brake fluid absorbs water, meaning that any iron in contact with the fluid will corrode and rust.
• Master cylinders are usually made of iron.
• Your brake master brake master cylinder may be heavily corroded, but the corrosion will only be in the part of the bore that is never used. The sweeping of the seal on the used part of the travel means it will be like new there.
• WHEN YOU BLEED BRAKES WITH BRAKE PEDAL: its possible for the master cylinder to cross into the corroded region. When that happens the seals will be destroyed. You’ll have nice firm brakes but they will slowly fade. Bummer.
• It is possible to re-sleeve a MC, but it costs $400+. You could just rebuild with new seals, but remember these are brakes and they’re very very important.
• Bottom line: if you ruin the MC seals you need a new MC.

IMPORTANT POINT NUMBER 2:

• Use the precise recommended torque when tightening brake bleed nipples. Factory spec is 11N-m. Caliberate your hand using a torque wrench so you understand how little force that is. Pretty much if you feel any pressure then stop torqueing!
• Brakes are precise. It might be an old truck and the brakes are exposed to horrible road conditions, but remember that brakes are precision items, so treat them with care.
• Bleed nipples are made from soft brass:
  • the threads are easy to deform
  • the cone that closes the valve is easy to deform
  • the hex head used to open and close is easy to deform

The most excellent tool for gently breaking loose a stuck brake bleed nipple: 10mm Kobalt Impact Socket. Very hard steel and a nice long wrench so pressure is precise and gentle.

IMPORTANT POINT NUMBER 3:

• Use a high quality six point socket to first loosen the bleed nipple.
• When first opening a bleed nipple the metals may have welded themselves. The nipple may not want to move. If you use an open end wrench you can easily strip the hex head before the nipple comes loose.
• I have a set of hardened impact-wrench safe hex sockets. Six Point, not 12 point. These are extremely hard and fit precisely so when torque is applied it is even across the head. Use a 12-18 inch socket wrench and apply pressure very gradually. You want to use the min torque to get the bleed nipple free. Eventually you’ll hear a “crack” or a “creek” and the nipple will start to rotate. You use the socket just to get the bleed nipple a little loose, then use an open ended wrench (remember it only needs very little torque.)

With those important tips behind us, here is how to bleed a brake (on a bj60 but same applies to an air-cooled porsche 911.)

My Kobalt (lowes brand) metric impact sockets. The hard steel is very positive, you don’t realize how bad bad sockets are until you use some hard precise ones. Also my craftsman wrench that I got at a garage sale, its nothing special but I like the button socket release.

Toyota Shop manual instructions for brake bleed.

1. Get on the good side of your assistant. Bring her flowers the day before. Cook breakfast. Be charming and agreeable. This is important because you want this to be fun. It is pretty awful to mess this up, tip over the jar of brake fluid, have the assistant push the pedal to the floor, etc. It is just much easier if you start with a cooperative partner.
2. Put on your nitrile gloves
   1. Brake fluid is:
      1. Bad and poisonous
      2. Is neutralized by water, so clean it up with water right away
      3. Is metabolized by your body as alcohol, yes it makes you drunk, except that it also kills your liver (and you.)
      4. Eats paint like there’s no tomorrow. Be very careful not to spill it on anything (like, even paint and coatings in the engine bay.)
3. Do wheels in order of hydraulic line length from master cylinder:
   1. right rear
   2. left rear
   3. right front
   4. left front
   5. proportion valve

You’ll find the first bleed in the rear takes forever, the second in the rear is very quick. Ditto for the front.

1. Put clear tubing on nipple, other end runs into a jar.
2. Yell (pressure?) Have assistant apply stead pressure to the brake pedal (with CLEAR understanding that they aren’t to push it more than 2 inches or so.)
3. Assistant yells (ok!)
4. Open bleed nipple, let fluid run into tube “for a bit”, then close nipple.
5. Yell “reset!”
6. Assistant lifts foot off pedal, then reapplies pressure
7. Every 10 opens or so, get up and check the brake reservoir, fill back to top.
   1. DO NOT LET RESERVOIR RUN DRY, you’ll push air into the system and need to re-bleed it all over again.
8. Goto 5 until fluid runs clean (generally for the longest lines it took 30-40 small pedal pumps.)
9. Using a small torque wrench apply factor torque to brake nipple (11 N-m)

Until fluid runs clean:

For nasty old fluid it will first come out black but eventually it will come out the color of honey. Easy to tell when new fluid is flowing. This is much more difficult to determine if you bleed brakes after only 2 years. An old trick, I had 500ml of “ATE Super Blue” brake fluid. ATE used to make the same excellent brake fluid in two colors so you could tell when the new fluid was flowing. The blue is no longer legal in the US because of some federal brake fluid color law. I used the old blue fluid to bleed, once system was bled I ran the new stuff (because it was an old bottle that had been opened.)

ATE Super 200 (this stuff is gold, used to also be available in blue. :()