Questions and Answers

Bleeding Datsun 240-Z Brake System Q. We removed the front calipers. By the time we got new ones and installed them a lot of fluid drained out. Now when we are trying to bleed the system we can not get any pressure to pump in the fluid. The car is a 1973 Datsun 240Z. Do we have to have the engine running? How do you get the master cylinder to start pumping fluid?

A. If the master cylinder went dry, you will need to bleed the master first. Fill the master cylinder with brake fluid. Then crack the lines coming out of it and wait about ten minutes, or until you see brake fluid start to drip out. The older master cylinders may have bleeders on them. If yours does just crack them open instead of the brake lines. For the sake of this answer I'll just assume it doesn't.

Close off the lines and pump the pedal four or five times. Hold it down and crack the back line or bleeder first. Keep doing this until you get a good stream and no more bubbles. Make sure the master cylinder doesn't go dry or you will have to start all over.

Once the master cylinder is bled, crack open the bleeders on the brake calipers until brake fluid starts to drip. Once it does, close the bleeder and bleed as normal.

If you can not get a stream out of the master cylinder, it will need to be replaced. Most brake master cylinders fail during a brake job. The engine does not have to be running to bleed the brake hydraulic system.