QX4 Vibrates when braking even after installing new brakes

[gordon.su]

Hey NICO,

I hope everyone is doing well!

I have an 2001 Infiniti QX4 with just over 220,000 km.

I am also experiencing a vibration problem when applying my brakes, it gets very obvious when braking around 60 km/h and worsens when you get faster especially on the highway.

I have changed both the front rotars and rear drums, but this problem still appears to be evident. I actually changed the front disc rotars last week thinking the old ones were warped, but it still did not solve the problem so assumed it was from the rear drums, but after changing the drums yesterday it did not make a difference.

The vibration can be felt on the brake pedal, floorboards, and steering wheel, seems to be coming from the front end of the car.

I have a few assumptions which I am hoping if anyone has experience or would know a solution to share some insights please =D!

my assumptions:
- front rotars were defective, as vibrations existed even after new disc rotars were replaced
- suspension
- tires unbalanced
- a buddy mentioned it could be something from the bushings?

Please let me know if you would need any more information to give a more accurate diagnosis

[Towncivilian]

Flush the brake system. There may be air in the system. Be sure to follow the bleed order listed in the pinned FAQ thread linked in my signature.

[gordon.su]

Hey Towncivilian, thanks for the quick reply!

I flushed/bled the brakes a bout a year ago in feb 2012, could this still be the root cause?

[Towncivilian]

Another flush in the correct bleed order would ensure there's no air anywhere in the system. Did you follow the correct bleed order when you flushed the fluid last?

[Buzzman]

Probably a dumb question, but nowhere did you mention that you replaced the front pads as well.
I'm assuming new pads as well as new rotors?

Also, to help isolate the front from the back, take it down a (quiet, no traffic) road, and pull hard on the emergency brake.
This will activate your rear shoes and leaves the front brakes alone.
If there is no vibration, then you can assume it's the front brakes that are the problem.

Good luck.

[gordon.su]

Thank you again for the explanation Towncivilian I believe it was done correctly the first time, I know the flush order is on the FAQ page of the forum (love the resources here ! ). In my next flush I'll make sure my mechanic follows it.

Buzzman yes I changed everything, pads for the front, shoes in the back + brake kit, springs, etc, I'll definitely try the hand brake test to be sure, will update everyone thanks for your advice

[Towncivilian]

This whitepaper is a good read and may provide some insight into your issue if it turns out to be the front brakes.

[smancer]

I'm having the same issues on my 01 Pathy. Except when I changed my rotors and pads out the vibration was fixed for a while now it's back and even worse. If I get to work on mine and find something out that helps I'll let you know.

I know how frustrating it is especially when slowing down from higher speeds feels so unsafe.

[gordon.su]

@ Towncivilian appreciate the extra resources, I'll take a look at the white pages about my brakes

@Buzzman I did the hand brake test and found no vibrations

@Smancer I hope we both resolve this issue together, you're right this can get very frustrating especially when guest are in the car and I always have to explain where the vibrations are coming from


Action plan:

1) brake flush

2) if problem is unresolved will get new front rotars under warranty

3) hopefully this step will not exist

[Slumpert]

I belive your going to need to address this by addressing the rotors. Either they are warped, or they glazed resulting in uneven resistance to the brake pads.

#1 Brake fluid is very hydroscopic and any "old" fluid left in the system will allow moisture to re-contaminate the whole system so you relly need to flush it all out. While this is not usually a issue right away, under the heat of the braking system this water can "boil" into microscopic steam which then puts the system under pressure. So even though you released the brake pedal, the system is still pushing on the rotors causing them to warp/glaze in short order.

Also a sticking caliper can cause the same result.

[gordon.su]

@ Slumpert thanks for your contribution.

I did not consider the caliper, now that you mentioned it it may be the issue.

Is there any way to determine whether or not it is stick by a physical inspection?

[gordon.su]

I actually verified with my mechanic over the phone and they mentioned that when they put in the rotars the other week, they lubercated the caliper piston, so it shouldn't be sticking/seizing.

My mechanic asked me if i noticed any uneven braking (loping left/right) that may be cause from the sticking rotars - i do not seem to have that problem.

[Buzzman]

I've been thinking about this a little more, and it may not necessarily be a rotor problem.
I would go a little further and start by checking the wheel bearings and other front end components.
If the bearings were not installed properly, or not adjusted properly, then the wheels will move/shimmy/vibrate under braking.
BTW (don't take this personally), but it's rotor, not rotar.
Cheers.

[gordon.su]

@Buzzman

Thank you for further brainstorming more ideas!

I think this is probably the most probable cause... this is my 2nd set of "rotOrs" having the same problem, perhaps you are right and it is not the actual brakes themselves...

when i bring in my car to the shop what should i look for to find out whether or not the bearings are the issue? (what are signs)

Maintenance around the front:
- Replaced Front stabilizer Link
02/01/11
175,000 km

- replaced front ball joints
2007

[gordon.su]

also:

Inspected front strut housing recall campaign (dealer said i passed)

06/21/11

182,000 km

[qx4dude]

Sounds like you have a bad U Joint on your front drive shaft. Lay under the truck and locate the front drive shaft. Try wiggling it to see if there is any play or if anything it broken.

I just went through this with my truck. Had a bad front end vibration start at 60km and was worse around 70-80 but smoothed out at 110. The vibration got worse when breaking between these speeds. I even had a mechanical clicking sound when driving at parking speeds. One of my U-joint had completly let go.
Even in 2 wheel drive the front drive shaft will spin because it is connected to the front wheels. If either of those U Joints is bad it will cause a bad front end vibration that can be felt exactly as you mentioned.

You can also double check your wheel bearing but jacking up the truck, grabbing onto the wheel and try pushing in and out to see if there is any play.

[gordon.su]

Hey everyone I wanted to update everyone.

It turns out the problem was coming from my new rear drums, I didnt suspect them because my front rotors were installed seperately from my rear drums.

week 1 - installed new rotors (still noticed vibrations)
week 2 - installed new drums (still noticed vibrations)
week 3 - removed new drums off, machined old drums (no more vibrations!)

We took my old OEM drums and machined them downm and removed the new drums off and SURPRISINGLY the vibrations magically disapeared =D.

[Carlsbad]

I'm having the same problems on my 2003 QX4 with 135,000 miles on it and I'm skeptical that the rear drums were the problem. Before reading all of this I basically discounted it being a brake problem because it is not very repeatable. I've had warped rotors before and know what that feels like. I don't think that is what the problem is. It varies from time to time and seems to be worse at warmer temperatures. It also varies with tire pressure. If my tire pressure gets lower it happens. I'm thinking it is a looseness in the front suspension that is most likely the lower ball joint. i jacked it up tonight and there was a small amount of play in the wheel in the top/bottom axis, none in the side to side direction. Ball joints are cheap and probably a good thing to do at 135k miles so I think I'll try that first. I'm not totally ruling out the brakes. I plan to do front pads, turn the rotors, and flush the system. I'd like to do it at the same time as I do the ball joints but then I won't know for sure what fixed the problem (assuming it fixes). --Jerry

[Carlsbad]

Update 2 days later: I rotated tires (5000 miles on new coopers) and raised pressure to 42 from 34 and no wobble. I'm still planning to replace ball joints. Lots of choices on ball joints. Just at pep boys getting a battery (old battery fine but dated 2008 so I replaced it while batteries are 20% off) and they had generic ball joints for $19.99. I think I'll go with Raybestos, Beck Arnley, or some similar known aftermarket brand for around $40. I want this SUV to keep driving like new for another 100000 miles. --Jerry