Knock Knock - What is it?

**Blown97** · 05-03-2008

Alright folks, I have a 97 GTP and when I go to brake with medium to hard it makes a knocking sound. Then after I start moving again I hear the same knock sound. If I accelerate and or brake like a grandma there is no knocking sound. But if I drive normal I hear this knocking sound when I brake and then again when I accelerate. To further describe this sound if I brake (lets say medium hard) it makes the sound but lets say after I have started braking and it made the sound I decide to brake harder, it will knock again. The same goes for when I accelerate.
Today I put it up on the lift and checked everything I could think of and nothing seemed loose or bad except the CV axle, which I thought had some play in it so I replaced it. But with no luck as it still has the same knocking sound. I have in the last year put on KYB struts and mounts all the way around as well as the GM suspension upgrade, along with the HD 12" brake upgrade. And have not had this sound until last week.

I sure would love to hear what you guys think on this. Thanks in advance.

**archemedes** · 05-05-2008

check the pads, if they move at all in the caliper they will knock

**Andrew_99GTP** · 05-07-2008

check to see if your dp is hitting your sway bar. I had to flip my GMPP's front sway bar because my dp hit it.

**Blown97** · 05-07-2008

Hmmm.....thats a good one....I forgot about that. I thought there was a lot of room there but I didn't check it...thanks

**Andrew_99GTP** · 05-07-2008

If you are running stock upper mount the engine moves quite a bit.

**Blown97** · 05-07-2008

It's worth a check!!! Thanks for the suggestion, and keep them coming guys.

**Blown97** · 05-10-2008

Well I put it up on the lift again and checked for the down pipe hitting the sway bar (no evidence or marks that would show positive results), checked the engine mounts, grabbed a hold of the caliper and tried to shake it, tried looking again at the control arm bushings (they look normal). None of these things show any wear or evidence of any kind of movement. Just an update folks. Still looking for suggestions. And believe me I know how easy it is to diagnose on the net........NOT!! So thank all who have tried to help.

I will be sure to let you all know what it was when I figure it out.

**Sabrewings** · 05-10-2008

Did you actually check the tightness of the cradle bolts? Should be 118ft-lbs for front and 122ft-lbs for the rear. Mine were loose (only about 80ft-lbs) when I checked, and they have never been messed with. Really tightened up the front of the car.

**Blown97** · 05-10-2008

I heard about that....I did check them but I didn't know what the toque was for those bolts. I can definitely see how that could be a problem to, it would make sense to move under braking and under acceleration. Thanks for the info!!

**archemedes** · 05-12-2008

if the pads are moving, you aren't going to shake them and cause it (unless you can bench about 1000 pounds)

**Blown97** · 05-12-2008

Originally Posted by archemedes

if the pads are moving, you aren't going to shake them and cause it (unless you can bench about 1000 pounds)

Alright, I'm with ya.....how do you propose I check the pads to see if they are moving in the caliper like you had advised before? I mean I tried moving them but they don't.

Thanks

**archemedes** · 05-12-2008

only way is to pull the caliper, also look at the rotor and see what the wear looks like, if any grooves then you have a problem

**siverio** · 06-16-2009

I have a 2000 GTP, same problem. hard breaking I hear the pop on both sides (twice) and also sometime if the car bounces on the hwy too. it's beem to the dealer and to aamco. this has existed for at least three years and no solution.

Hint, in the cold of winter is almost absent, it's almost impossible to reproduce below 40 degrees. also the hotter it is outside the louder and easier it is to reproduce (i drive with the AC in the summer and windows rolled up) it's scary to my passengers who think thet car is going to fall appart.

ammco has had the car 3 times for it, replaced tie rods motormounts and some bushing over the years but problem remains.

The dealer thinks the strutmounts are shot. (PEP Boys checked them and said they were fine).

HELP!!!!!

**sandite5** · 06-21-2009

Originally Posted by siverio

I have a 2000 GTP, same problem. hard breaking I hear the pop on both sides (twice) and also sometime if the car bounces on the hwy too. it's beem to the dealer and to aamco. this has existed for at least three years and no solution.

Hint, in the cold of winter is almost absent, it's almost impossible to reproduce below 40 degrees. also the hotter it is outside the louder and easier it is to reproduce (i drive with the AC in the summer and windows rolled up) it's scary to my passengers who think thet car is going to fall appart.

ammco has had the car 3 times for it, replaced tie rods motormounts and some bushing over the years but problem remains.

The dealer thinks the strutmounts are shot. (PEP Boys checked them and said they were fine).

HELP!!!!!

You know I've got nearly the damn thing happening. I've got the EXACT same results as you (hotter is louder, colder is quieter). My wife had the strut mount replaced (took it to a mechanic...). Though this didn't do anything for it.

What I DID notice was that if I was moving at a slow pace over a speed bump, with no gas or brake applied, it *creaked* pretty loud as the car bounded and rebounded. So my first thought is that it's the suspension, (IE. friction causing it). I then parked the car and verified it was suspension by sitting on the front left part of the hood (noise was only coming from the front left) and bounced up and down. Sure enough *creak creak creak*.

Using my awesome redneck problem solving abilities, I sprayed some WD40 all over the top part the spring, and the sound went away... Though since WD40 isn't permanent, then rain and outside elements washed it away and it the creak came back. I figure that if I just though some grease on the top part of the spring, it should go away.

I'll let you all know what I find out.

**siverio** · 06-22-2009

Funny you mention WD-40, It's been raining like crazy here the last few weeks and I notice the car behaves so much better when the suspension is wet, I hear the knock but I have to work harder to make it happen, so it occurred to me that I should try some WD-40 but I had no idea where.

PS: My car does not creak when I bounce the suspension or when going over bumps.

**yedi** · 10-23-2009

Same problem here..driving me nuts.

Only hear a click/popping sound when brakes are lightly applied, and hitting sharp bumps, coming from right front. Checked everything out (new struts/bearing 30,000 miles ago, new sway bar and end links 2 months ago, bushings look fine, cradle bolts are tight, and all plastic shields have been fastened tight, still have the noise.)

Everyone keeps telling me sway bar end links, I tell them their new..

I'm looking into this brake issue w/ the pads being loose. GM Part #18046457 might give these a try, not a big fan for buying parts I dont need, and still have the problem.

If anyone can comment on this, go for it....

**97gtsc** · 10-23-2009

Well id say drive it till it breaks then u will know what the problem was!

hehe

**yedi** · 10-24-2009

right....as my car just suddenly falls apart one day.

I'm installing a Napa Brake hardware kit today, has different style bolts and bushings for the caliper, I really hope this works...

**JDCMoney** · 10-24-2009

How about the sway bar to frame bushings? or the control arm bushings?

**minichopper6hp** · 10-25-2009

Check the front bolt on the lower control arms. Can make the noise if its loose.

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