is it the ABS sensor issue?

[hangout]

I have the 91 TT with 82k miles. 5spd
in the morning, when I pulled out the car go work, I found the ABS is so easy to kick in.

the car was not fast, just like rolling to a stop sign. turn the wheel a little to left or right, when the car almost fully stop, I felt the ABS kike kicking in. also hear some sound like the string from the Passenger side. and some sound like the balloon blowing air behind the passenger side seat.
if I step on the brake few times before I drive the car out, then I don't see these came up that easy.

is it the ABS sensor issue? how to fix it?
I found some listings on ebay for the used sensor, around $50 (brand new OEM $400)..
will those part can fix issue?

please give me some advice

Thanks

[DCaff300ZX]

It's hard to really truly understand what you are saying here as English obviously isn't your first language, but let's give this a try.
First, check your brake master cylinder inside the car under the dash and also outside under the hood, and all four brake calipers, wheels and tires for signs of brake fluid leaking. If you find fluid leaks, this is your problem and repairing the leaking item (caliper, brake line, etc.) is your path to solve your problem. If this was your problem, what you are hearing is the fact that there is air in the brake system, and that air making noise in the brake lines and ABS module behind your passenger seat.
If the above leak check fails and you find no leaks, then your best bet would be to take the car in to a Nissan dealer or a trusted Nissan repair specialist for a checkup of the ABS system and it's sensors. Just buying any old sensor on e-bay is a recipe for disaster unless you know for SURE that it's the part you need, and that you know it's part number in order to get the right part.
If you are able to do mechanical work and diagnostics, then look at the online service manual in the "everything you need to know about the Z32" sticky at the top of the Z32 General page for that info.
Good Luck!

[hangout]

Thanks DCaff300zx
the brake line and caliper are all new, and I don't see any leaking around.
so the chance might be the ABS module or the ABS sensor.
the OEM abs sensor is so expensive, is there any other alternate brand ?
is it a hard work to get done?

[DCaff300ZX]

I've not dealt with the ABS beyond bleeding it when bleeding brakes so I can't comment from experience, but I would DEFINITELY stay with Nissan components in this case because any error or otherwise will have catastrophic results most likely, with even possibly having problems being bad enough.
You can shop our better vendors (CZP, Z1, Specialty Z)in hopes of a deal better than a dealer would charge, but I also would not be purchasing parts on chance...meaning I would be sure that any parts I buy are necessary either by tests/diagnosis, or by a repair shops' advise.
This isn't an area to mess around with and especially in our cars which are under-braked already IMO.