Intermittent Vibration Help

[LoSt180]

Technical question for an intermittent problem, I'm a bit stumped. After driving on the interstate a while, the car starts shaking and steering wheel will vibrate like a tire is out of balance. It's not tires because it would be constant. Also while this is going on, I've noticed the brakes are hard, like tapping them is like slamming the brakes, pretty much an on/off switch. While cold, they feel fine, and not every time either. Yesterday going to work was crazy, coming home was fine.

Front suspension has been replaced, including shocks, outer tie rods and ball joints. I've triple checked lug nuts. I'm suspecting inner tie rods, some bushings, or something is up with the brakes. This is an S14 with Z32 brakes all around.

[lunchmeat]

I've had tie rods do that. And it would be more noticeable at interstate speeds. Under 50 I couldn't feel it.

[jedi03]

alignment, worn ball joints, tie rods bushings, tires rotting internally...many things could be goin on...

[anti tyler]

So it sounds like you've done just about everything with exception to your bearings.

Have you had the front end in the air to check them?

[S14AZ]

Check your brake lines sounds like you have a line that has a pinch.

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[S14AZ]

Also were the z32 calipers new or used?
Did you change out the master cylinder to z32?

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[LoSt180]

Originally Posted by S14AZ

Also were the z32 calipers new or used?
Did you change out the master cylinder to z32?

Used. I rebuilt them before installing about 3.5 years ago. But I did have to rebuild the front right this winter because it seemed to be frozen (pulling and rotor radiating serious heat after a short drive). Rotors don't seem warped because it doesn't vibrate while braking all the time. Shaking is only at highway speeds, and only sometimes. Entirely possible I have to rebuild the other side.

Still have stock S14 15/16 master cylinder. Have a brand new 1" Z32 MC, just haven't installed it in the 3 years it's been sitting in my garage, lol.

I hate intermittent issues.

[1on1]

From my understanding about the z32 brakes, you need to change out the BMC since you're running all 4. Stock MC is fine if you had front z32 only; if the car was changed from auto to manual, the auto brake booster will make your brakes very sensitive compared to 5-speed factory (auto brake booster is larger than manual).

I understand you said that tires cannot be an issue but if your wheel is not balanced, this will also cause your wheel to shake at "certain" speeds.

Here's the info about the brake booster/Master cylinder I am referring to:

http://importnut.net/300zxbrakeswap.htm#MC (old)
http://importnut.net/the-definitive-...cylinder-swap/ (New Version)

Lastly, inner tie rods fail and in order for you check is it jack up your car, remove the other tie rod from the knuckle and see if there's play when you push/pull the tie rod (best way is to get the steering to lock if you're working by yourself).

[S14AZ]

I wonder if the calipers might be sticking......

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[brndck]

[QUOTE=1on1;6215235]From my understanding about the z32 brakes, you need to change out the BMC since you're running all 4. Stock MC is fine if you had front z32 only; if the car was changed from auto to manual, the auto brake booster will make your brakes very sensitive compared to 5-speed factory (auto brake booster is larger than manual).

QUOTE]

you don't HAVE to change to z32 master, but its an improvement, since the z32 master is sized for those calipers. Running a 240 master with z32 calipers works just fine, but the pedal feel is better with z32 master.

OP, does your car have ABS? is the ABS light on?

[LoSt180]

Originally Posted by brndck

you don't HAVE to change to z32 master, but its an improvement, since the z32 master is sized for those calipers. Running a 240 master with z32 calipers works just fine, but the pedal feel is better with z32 master.

OP, does your car have ABS? is the ABS light on?

No ABS currently. Was an auto to manual conversion. Pedal feels okay normally.

I'll inspect brake lines and try to check for play in the tie rods tonight. Also check for uneven pad wear in case brakes are messed up.

[brndck]

check all tires for feathering or signs of flat spots or tread separation or bubble in the sidewall

[1on1]

Originally Posted by brndck

you don't HAVE to change to z32 master, but its an improvement, since the z32 master is sized for those calipers. Running a 240 master with z32 calipers works just fine, but the pedal feel is better with z32 master.

OP, does your car have ABS? is the ABS light on?

Ahh ok, I must've read it wrong but thanks for correcting me.

[kyral]

My car shook like hell 40-45 mph and only in that speed range. got my front tires balanced and that was the end of it.

id highly recommend checking your wheel bearings and chassis components for play. this is likely and alignment/tire balancing issue