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GT 4.6 SOHC
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Discussion Starter · #1 · (Edited)
Whats up everyone.

So check it, here is my issue.

In the signature pic, its the 2001 Mustang GT with about 120K miles on it. I have fairly new KYB GR2's with supporting Eibach pro's on poly-u isolators. 15K ago, replaced all the brake rotors with drill slotted along with all new pads (ebay Powerstop brand, ya I know!) I think the issue was occuring even before then, but cannot recall.

~To the issue: I always feel this thunk under medium braking to hard braking. Once I pass a specific brake pedal press (about 50%), it will thunk once and can be felt more towards the front driver side, (according to driver and passenger suggestions) Once I come to a complete stop after making the initial thunk, it seems that that thunk will either (a.) thunk back in place or (b.) won't feel the secondary thunk until I begin to accelerate.

In a reverse manner, it seems like I can duplicate the noise much easier and quicker. Example, I would back out of a parking space and begin to press the brakes, this time around I only have to press the brake pedal (about 25%) and the thunk is there. If I am reversing out of a parking space and turning the wheels at the same time to the left, the thunk occurs the easiest (about 20% braking power).

When the thunk occurs, sometimes, I would here an immediate post-thunk like if what ever is shifting, is moving right back into its place. Other times, I would hear the post-thunk (back into place) when under light acceleration.

I do not hear the thunk when turning really hard to the left or right without brakes which leads me to belive the issue is the braking system and rather not the sway bar system...

I've read the following can be the issue:

-Could be a bad ball joint?

-I've heard that it could be the piston on the brake caliper that is sticking due to being dirt, or even that the brake pad is moving into a valley groved into the warped rotor?

-I have even heard that there is a possibility with the subframe bolts, or transmission bracket (or some thing like that)?

I can say that even after just 15K miles, the rotors feel prematurely warped after a short time and not even a year on it, the braking pulsation can be felt the most slow stops and even at 80 MPH with strong vibrations. There is very minor shaking at 15-65 MPH.

I can't tell if there is a reduction in braking power since I am generally trying to prevent this noise from reoccuring so I am light on the brakes all the time...
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Suggestions...!? As of this moment, I am open to checking all the necessary articles.

The wifey already said that we have plans to change the sway bar fronts and backs with Eibach to compliment the already in Eibach springs... Just don't want to fork out $300 if it wont fix the issue.

Eibach Mustang Anti-Roll Sway Bar Kit (94-04 excluding the 99-04 Cobra) 3518.320 - Free Shipping!

Gratci:dunce:
 

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I would check all bolts for anything that was just replaced. I had a thunk noise happening out of nowhere one day. It would only happen when I would be driving forward and stopping medium to hard. Found out one of the caliper bolts fell out on the driver front and the caliper was moving forward until it hit the bracket

Sent from my DROID RAZR
 

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I would check all bolts for anything that was just replaced. I had a thunk noise happening out of nowhere one day. It would only happen when I would be driving forward and stopping medium to hard. Found out one of the caliper bolts fell out on the driver front and the caliper was moving forward until it hit the bracket

Sent from my DROID RAZR
This^

I had this happen on a different car and one of the caliper bolts was completely gone. I think I must have forgotten to tighten it.

Also, if you feel pulsating while braking, your rotors are most likely warped and need to be resurfaced or replaced. If the noise wasn't present b4 the brake work then I would definately get the brakes checked asap.
 

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Control arm bushing can cause this.
 

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GT 4.6 SOHC
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270 Posts
Discussion Starter · #5 · (Edited)
I'll go ahead and open her up soon to determine the culprit. The reason why I am not as (WTF) as you would figure from the strange thunk is because it's been doing it for a pretty long time, just cannot put a time frame on it. I know I did my coil's then brakes, and the noise persisted throughout the entire process.

Could I be looking at the endlinks shifting slightly and knocking on the lower control arm due to worn out bushings on both the endlinks and on the sway bar support also? So in other words, the sway bar and endlinks are moving a bit under hard braking because it shifts forward?

And the noise doesn't occur while turning because it'll simply tighten the bushings from one side to the other...

Also, should the rotor be able to spin a tiny bit back and forth on the hub until stopped by the lugs or should it be completely stationary the moment you put it on the hub? I believe only the passenger side did that while the other rotor would simply stay in its place if you tried to spin it?

I will be going through the braking system again soon to see if I can determine culprit..
 

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GT 4.6 SOHC
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270 Posts
Discussion Starter · #6 ·
Control arm bushing can cause this.
Alright, I'll look into those also, you speak of the pressed in bushings on the control arms correct?
 

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Alright, I'll look into those also, you speak of the pressed in bushings on the control arms correct?
When the stock rubber bushings in the control arm (2 per side) wear, it can cause a clunk when braking. It did it on my car. Take some silicone based spray lubricant and spray the hell out of them. If it goes a way for a bit, that will help you identify the issue. It will come back then. If they are bad enough, that trick won't help. Good luck!
 

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GT 4.6 SOHC
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270 Posts
Discussion Starter · #8 ·
Nice, and thanks for the heads up. I was going to look into the issue over the weekend, but I got caught up doing other things. Will look into it first thing on Monday morning.

Feel free to continue to add your suggestions! Will be reviewing to look at it that day
 

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Like others have stated, check your brake caliper and caliper bracket bolts. Make sure your pads are not loose also, although you should get more of a clack then a clunk from rattling pads. Take a good look at your ball joints and control arm bushings. Jack up your front wheel under the spring perch on the front control arm. Do this enough to fit a pry bar or big azz screwdriver between the tire and the ground. Lift up on the pry bar while feeling for movement with your other hand. If any is felt, replace the bad or both ball joints. Good luck!
 

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GT 4.6 SOHC
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270 Posts
Discussion Starter · #10 ·
Finally got pictures posted!

Whats up all! Thanks for the responses.

As previously promised, I told you I will go ahead and get into the vehicle's front end and take some pictures that could help me get to the core of the issue. After taking a look at everything up front, I think I need to change all my bushings lol. You guys & gals take a look and let me know what you think.

I got pictures of the following: Sway Bar Bushings, End Link Bushings (top and bottom area), Ball Joint's, Upper Strut Area, & the Control Arm Bushings. Im sure you can tell when you look at them...

Driver side (Suspected area of noise)







Passenger Side










Haha, look at my control arms "Jonwrong", they look like flattened pancakes!
Will be waiting for the responses
 

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GT 4.6 SOHC
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270 Posts
Discussion Starter · #11 ·
Anyone view photos for the front end clunking issue?
 

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GT 4.6 SOHC
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270 Posts
Discussion Starter · #13 ·
LOL, thanks for the info. Yea, figured I would after taking all the pictures and blowing them up to check it out. I know by the pics I am looking at almost new bushings for everything and at least new ball joints!

-Considering going with the BBK balljoints from AM without the spacers so I get about a 0.5 inch drop in the front to get a nicer stance.

-Strenghtening the front and rear end with Eibach sway bars

Considering either getting just the bushings for control arm and having them pressed, or buying new control arms and balljoints to have them pressed without the need for removing and pressing again? What you think?
 

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GT 4.6 SOHC
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270 Posts
Discussion Starter · #14 ·
Upcoming purchase requirements?

Ok all, so check it. Im going to go ahead and look into the purchasing of new bushings for almost the entire front end.

After using the search forum (Woot Woot), I learned of a new website
Latemodel Restoration!

Things I am going to purchase soon are:

-New endlinks with bushings @ $20 usd: 1994-04 Mustang Prothane Front Sway Bar End Links, Black at LRS - Free Shipping!

-Upper strut mounts @ $25: 1994-04 Mustang Prothane Front Sway Bar End Links, Black at LRS - Free Shipping!

-Steering rack bushings @ $ 15: 1985-04 Mustang Prothane Offset Steering Rack Bushings at LRS - Free Shipping!

-Control arm bushings @ $40 (Unsure if I am standard or Hydro bushings) Either: 1996-04 Mustang Prothane Front Control Arm Bushings Without Metal Shells, Black, for Control Arms with Factory Hydro-Bushings at LRS - Free Shipping!
or
1994-04 Mustang Prothane Front Control Arm Bushings Without Metal Shells for Control Arms W/O Out Factory Hydro-Bushings at LRS - Free Shipping!

-BBK X2 Ball joints @ $140 (without plates for 0.5" front drop): 1994-04 Mustang Steeda X2 Ball Joints at LRS - Free Shipping!

About $240 usd... Hopefully I see good results.

Let me know if there is anything I should consider or am missing from the list!
Thanks
 

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I'm just gunna go ahead and point out that if you don't have the tools to change out the bushings, it is a BITCH lol. I've seen a buddy do his control arm bushings without a press and it took forever to wrestle the thing out
 

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GT 4.6 SOHC
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270 Posts
Discussion Starter · #16 ·
I was planning on taking the control arms off, and take it somewhere to get the old bushings pressed out along with the ball joints and have the new bushings and ball joints pressed in, then reinstall.

The only thing is that I do not know how much it will cost for shop to press out and press in...

If worse comes to worse, I am even considering these and rid of the trouble, only thing is. I am really afraid of the cup where the spring sits in and how there is the possiblilty of the welding to the a arm failing. What you think? Also, what if I have to replace the bushings on these???

1994-04 Mustang Front Mild Steel Tubular Control with Spring Cups at LRS - Free Shipping!

Hopefully someone from Latemodel Restoration can share some insight on this product!!!
 

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GT 4.6 SOHC
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270 Posts
Discussion Starter · #17 · (Edited)
Finally, An Update to this Problem! But Not Fixed Yet...

Whats up everyone,

So I have officially revived this thread!

I got to begin working on the vehicle since January and have some updates,

I went ahead and changed many components on the front end so far, with the same results; thunking under medium - hard braking while going forward and thunking while going in reverse under light - medium braking.

Both circumstances happen and seemingly as if something is getting out of its comfortable zone, then fall back into place.

I changed the following things on my vehicle thus far since the beginning.

-MM Caster / Camber Plates with Polyurethane Bumpstops
-Energy Suspension Sway Bar Endlinks - Polyurethane
-Sway Bar Bushings - Polyurethane
-Steeda X2 Ball Joints (Without the Spaces for .5 Inch Drop)
-OEM Used Control Arms W/ Rubber Bushings (Good Condition)
-Offset Steering Rack Bushings - Polyurethane (Bumpsteer is Minimal, I can live with it)
-Alignment settings to prevent tire wear
-Timken Hubs

And even new AM Rims & Tires and still the same results!

Here are the updated pictures:




I'm going to try and duplicate the issue in my driveway today to see if I can pinpoint the problem!

I think my next set of possibilities are:
Motor Mounts (Should have been replaced 25K ago with motor rebuild)
Brake Master Cylinder
Transmission Mounts
U-Joints on Drive Shaft

Share your thoughts again please!!!
 

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GT 4.6 SOHC
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270 Posts
Discussion Starter · #18 ·
Anyone at all...

Please
 

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This thunk your talking about can it be felt in the brake Pedal? I am really leaning towards a sticking caliper, or seized up slider pin, which may just be due to lack of lubrication or seizing . When you brake it applies pressure on the caliper then the pins freeze momentarily then release causing the clunk.
 

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GT 4.6 SOHC
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Discussion Starter · #20 ·
Hey SSG,

I appreciate the response.

When the issue occurs, I can feel it slightly in the brake pedal along with feeling it in the floorboard slightly. It is mostly heard rather than felt.

The thing is that I can jump on the brakes while in a stationary position, and I cannot make the issue re-occur.

I went ahead and began looking for the issue while I had the car parked in the driveway yesterday. I allowed the vehicle to roll backwards and got on the brakes quickly to hear the same issue occur. I then let off the brakes and allowed the vehicle to roll back again to get on the brakes again, though the issue did not re-occur (due to it already sticking, or moving into a position to make that thunk noise). I then drove forward at the same rate and got on the brakes and the noise occurred. I went ahead and did the same process and believe it is pointing towards the actual brake system, including the rotor, caliper, and / or brake pads.

As you mentioned, how would I go about checking on the seized up slider pin or sticking caliper? If so, re-lubing the location to prevent the noise / issue? It seems to only happen when there is movement in the wheels...
 
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