My car, early 260z is leaking brake fluid badly. It leaks all of the brake fluid from the reservoir when I top it off two days ago. I notice the leak is from the bottom of the brake booster, but my question is, isn't the brake booster only act as a pressure builder to assist braking? Why brake fluid will leak from the bottom of the brake booster??? Also, is the 260z and 280z brake booster interchangeable? Please advise, thanks.

Ed

Edited February 7, 201114 yr by TQs30z

The Master Cylinder piston seal is leaking. That causes it to leak at the interface with the Booster. A rebuild of the MC is in order. While you're at it, purge the fluid lines and rebuild the rear wheel cylinders and front calipers too.

I upgrade the MC to 15/16 from 280zx a while ago along with 4x4 caliper upgrade, so what now? Order the new brake booster? Thanks.

Ed

Unless you have a vacuum leak in the booster, there's no reason to replace it. It has nothing to do with brake fluid.

Was the 280ZX MC a used one, or a rebuilt/new unit?

It was refurbished unit and it doesn't leak after the MC is swap(it was done in July), I noticed there is small leak when the weather is getting colder and now it worst. So, where should I start???

Ed

It might be leaking from the base of the plastic reservoir itself and running down the MC to the booster. I had that happen when I replaced my MC, I had to readjust and retighten the clamp at the base of one of the reservoirs.

Is it coming out of the bottom of the booster, the base of the MC where it bolts to the booster, or the bottom of the reservoirs and running down the bottom of the MC to the booster?

If all of the fluid leaks out in two days, I would be surprised that your MC pistons and seals can still develop enough pressure to apply the brakes.

You could have a cracked reservoir also. Do you have two, front and back, or just one?

You put on a rebuilt MC correct. Any rebuilt unit should be opened up and washed out totally before installing. I have seen way to much left behind in the way of shavings and grit which can chew up seals in relatively short order.

The car has been parked for like 1 month now, so I'm not sure if it still has brake or not; but I don't think it has since all the brake fluid has leak already. I just check, the brake fluild actually leak from between the MC and the brake booster. So, I guess the fluid is then go down to the brake booster which I thought where it was leaking before. As I recall, there is no seal or gasket on the MC when I connected to the brake booster. What now? remove the 2 bolts and MC, clean it up and rebolt it back to the brake booster?? And bleed the brake again? Any brake bleeder you guys can recommend??? Those one man job brake bleeder. Please advise, thanks.

Ed

You need to rebuld or replace the master cylinder. The bad seal is inside the master cylinder, not between the master and the booster (Master Vac).

If your master was rebuilt/refurbished when you put it on it might still have a warranty.