91 TT brake issues

[Bobbymudd]

Hello new to the forums. today I got my Z out for the first time since it had been stored away for the winter. Started up great however after driving I started to feel like something wasn't right with the brakes. I feel like the My pedal is harder than it normally is and my stopping power is decreased, not to a dangerous level but definitely decreased. I'm assuming my brake booster is bad. However I'm in college (low low funds) and before I go buying a remanufactured booster I would like to just ensure this is what is wrong and it's not something else. I've heard of a check valve for the booster but I'm not sure how to check that. Over all my question to you guys is, what could cause my problem? If it is the booster how can I check and make sure. If it is the check valve how can I make sure? Thank you in advance for any help.

[Bobbymudd]

Any info helps, I'm new to the 300zx brake system.

[raremotive]

As a start of your diagnoses... buy $5 bottle of brake fluid and bleed your brakes. If problems persist then you can start looking at the mechanical stuffs.

You should bleed your brakes at least once to twice a year... especially after sitting around. Brake fluid is hygroscopic..which decreases your brake performance ...

At this time it's also good to check your pad thicknesses .. and verify even wear..

[itsa300zx]

This is copy and pasted from the internet; nothing special about the 300zx brakes. It is a standard vacuum assisted power brakes. Here's how to check the booster for air tight system:

If the pedal feels "hard" while the engine is running, the booster isn't operating correctly.

Test 1
With the engine off, pump the brake pedal to remove any residual vacuum in the booster.
Hold pressure on the pedal while you start the engine. When the engine starts, the pedal should drop about a 1/4", this indicates that the booster is working properly.


Test 2
Run the engine a couple of minutes.
Turn the engine off and press the pedal several times slowly. The first pump should be fairly low. The second and third should become slightly firmer. This indicates an airtight booster.

Test 3
Start the engine and press the brake pedal, then stop the engine with the pedal still pressed. If the pedal does not drop after holding the pressure on the pedal for 30 seconds, the booster is airtight.


Inspect the Check Valve
Disconnect the vacuum hose where it connects to the intake manifold. Do not disconnect the vacuum line from the booster. Air should not flow when pressure is applied, but should flow when suction is applied. If air flows in both directions or there is no air flow, the valve needs to be replaced.

Hope this helps.

[Bobbymudd]

Thank you both very much! I am currently at college however when I go home for the summer in two weeks I will do both of these things. Raremotive, Are there any tricks to bleeding the 300zx brake system or is it pretty straight forward? All 4 corners and the abs acutuator?

[raremotive]

1) Make or buy your own brake bleeder catch can. See below awesome image.

2) Open your brake reservoir, top it off.. and keep topping it off as you drain the fluid. Typically don't exceed max line.

3)Pump the brakes at the driver seat to try to distribute any air in the brake lines.

4) Start with the furthermost wheel from the brake reservoir, attach your catch can hose to the nipple.

5) Crack open the nipple and hold the hose such that it has a vertical up slope from the nipple(see below image). The goal is you want to watch the fluid climb up the tube. It also help reverse seals the nipple from bleeding air. Gravity will move the fluid for you. And with the tube vertical you can watch both the color and air bubbles;)

6) If changing fluid drain until you see a noticeable color change and you have at least 100 to 200 ml of brake fluid in the bottle. Or if you are just bleeding air, just stop when you think the air bubbles stopped.

7) Do step 3 .. 5.. 6.. again. And as much it takes until you feel you bled the air.

8) Remember to fill the reservoir.

9) Move to the next furthest wheel and repeat 3, 5, 6 and 7.

10) Repeat step 9 until you run out of wheels.

[Bobbymudd]

Thank you very much, So no need to bleed the abs actuator behind the passenger seat?

[raremotive]

Blah 95 and newer don't have those nipples =P

You can, it's mostly to get air out. It will help with a firmer pedal feel. You need a buddy to press the brake pedal. And you put your hose on front nipple and crack it open.. then close it before the pedal hits the floor. Release pedal and repeat bleed until you feel air is bleed. Then move to the back nipple to bleed.

[Bobbymudd]

Thank you guys for your help, it ended up being an unusual problem. Checked the bake booster and it was good. Opened up the brake master cylinder and fluid looked very fresh, flushed anyways which didn't help. It ended up being my brakes rotors had developed a glaze from sitting so long and me babying it when I first got it out. Took it on a long deserted road and stomped on the brake a few times and cleaned the glaze off. Thanks again for the help