Front brakes lock on first press - Nissan 350Z Forum, Nissan 370Z Tech Forums
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post #1 of 6 (permalink) Old 10-31-2016, 08:38 AM Thread Starter
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Front brakes lock on first press

I just had my 2003 350Z Base model overhauled: JWP clutch and flywheel, OEM rear main seal, Wilwood clutch master cylinder with braided line, OEM clutch slave cylinder, Super Blue clutch fluid, Gates engine timing belt, both OEM tensioner pulleys, OEM fan pulley, OEM valve covers and gaskets, Z1 silicone PVC hose kit, OEM knock sensor, NGK 6240 Laser Platinum spark plugs, CZP Brake Kit Centric Rotors / Hawk Brake Pads and SS brake lines, Berk resonated test pipes and HKS replica true dual exhaust. I also had the injecters cleaned and flow tested.

Having that information should help you find my *new* problem...

My front brakes are locking up. At first I thought it was only after a short drive but right now I have the car on towers with the front wheels off.

If I turn on the car without touching the brakes, I can move the front rotors by hand. As soon as I press the brake pedal, the front calipers lock up. I go the the rotor and it's hard to move if at all.

If I pull the hose off of the brake booster, the caliper retracts and I can move the rotor by hand again. I covered the open end of the hose with my thumb and had my son press the brake pedal which is hard without the booster assist. As soon as he lets off I can move the rotors.

So my testing up to now is that the brakes lock up with the booster connected. My mechanic, who I consider extremely knowledgeble (BMWs and Mercedes his specialty), did all the work in the 1st paragraph and suggests I replace the ABS box, part number 47600-AM400. He thinks the brake lines had moisture and possibly damaged the valves in this module during the 2-3 months it took to complete the work.

I texted him with tmy test results to see if he still thinks its the module but he hasn't responded yet so I thought I'd throw this out there. Tomorrow I'll be testing the brake booster per the service manual to make sure it's operating correctly.

What do you guys think?

Update:

I pulled the brake vacuum hose out and noticed it has a bump like a valve inside (see pic)

Is this a one-way check valve? If so, if I blow into it shouldn't it only pass air in one direction?

I can blow from both ends without a restriction so if it's supposed to be a one-way check valve, it's toast...
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post #2 of 6 (permalink) Old 10-31-2016, 08:54 AM
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Originally Posted by 7rrivera7 View Post
Wilwood clutch master cylinder
1) Check the brake pedal spring is pulling the pedal back to it's normal return (off) position

2) Check the rod between the pedal and the master cylinder has been (length) adjusted correctly
If there is any tension at all (with the pedal in the normal return position) it will cause the pads to rub against the rotors
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post #3 of 6 (permalink) Old 10-31-2016, 03:24 PM Thread Starter
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Quote:
Originally Posted by MartinZ View Post
1) Check the brake pedal spring is pulling the pedal back to it's normal return (off) position

2) Check the rod between the pedal and the master cylinder has been (length) adjusted correctly
If there is any tension at all (with the pedal in the normal return position) it will cause the pads to rub against the rotors
Will check asap - thanks!
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post #4 of 6 (permalink) Old 11-13-2016, 02:34 PM Thread Starter
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Update: The problem turned out to be that the brake pedal needed reajusting (looser) after swapping in the new Hawk Pads
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post #5 of 6 (permalink) Old 11-14-2016, 02:02 PM
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Congrats to MartinZ for developing the correct solution.
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post #6 of 6 (permalink) Old 11-16-2016, 10:14 AM
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Glad to help a fellow Z owner...
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