1986 Nissan 300ZX BLEEDING BRAKES

MCGM

MEMBER
1986 NISSAN 300ZX

Brakes problem
1986 Nissan 300ZX 6 cyl Two Wheel Drive Manual 132K miles

I have replaced the Master Cylinder with a re-manufactured one and tried to bleed the brakes.
i could not get the brake peddle to stay firm when you released it. I had the taken to an auto shop, they tried to bleed the brakes and got the same results. They recommended to bay a new Master cylinder, which I did, but I got the same results. When I pump the brake peddle to get it firm, bleed all 4 wheels, but the peddled goes soft after a few seconds. I am totally baffled.

3 Replies

MERLIN2021

MECHANIC
17,250 POSTS

First step is to bench bleed the master off or on the car, then bleed at the lines that connect to the master, then LR, RR, RF, LF. Why did you change the master out? Was the rubber swollen? If so, it was contaminated with a petroleum fluid, or in other words, all rubber parts would need to be replaced, oil or tranny fluid in the brake system is real bad! If this is not the problem, perhaps you have a bad caliper.

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Tuesday, March 17th, 2009 AT 1:35 PM

MCGM

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2 POSTS

[quote="merlin2021"]First step is to bench bleed the master off or on the car, then bleed at the lines that connect to the master, then LR, RR, RF, LF. Why did you change the master out? Was the rubber swollen? If so, it was contaminated with a petroleum fluid, or in other words, all rubber parts would need to be replaced, oil or tranny fluid in the brake system is real bad! If this is not the problem, perhaps you have a bad caliper.

[/quote

Thank You for the information... I had to replace the Master because it was leaking inside the car. No foriegn fluid was intorduced into the brake system. I found that the left front caliper would not bleed... just air no fluid. Bench blead the Master again and the same thing, no fluid would come out the left caliper. I used a vacuum pump to check it, all three other wheels were OK.

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Tuesday, March 17th, 2009 AT 6:48 PM

MERLIN2021

MECHANIC
17,250 POSTS

Remove the flex hose from the caliper, will fluid run out of if? Dont pump it just see if it runs freely. Any cracks or kinks in the hose? If hose is good, replace the bleeder screw on the cal, and rebleed.

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Wednesday, March 18th, 2009 AT 7:36 AM