[Z06] Audible "Thunk" Upon Braking
Thread Starter
Melting Slicks
Joined: Apr 2009
Posts: 3,333
Likes: 0
From: DFW TX
Audible "Thunk" Upon Braking
Need some help guys.
There is a moderately loud "thunk" that happens only sometimes when I brake. I did some basic diagnostics and found out that it is not caused by extreme acceleration or deceleration. Instead, I am fairly sure it is from going over road obstructions (manhole covers, small holes, etc.).
The strange part is that the "thunk" resets itself every time I brake. For instance, say I run over a manhole cover, the next time I brake, guaranteed, the noise occurs. From then on, however, there will be no noise until I jossle the rear end around again. Wash, rinse, repeat....
It sounds like it is happening directly to the rear of the driver's seat, but I can't tell exactly how far back....
Any known culprits?????
There is a moderately loud "thunk" that happens only sometimes when I brake. I did some basic diagnostics and found out that it is not caused by extreme acceleration or deceleration. Instead, I am fairly sure it is from going over road obstructions (manhole covers, small holes, etc.).
The strange part is that the "thunk" resets itself every time I brake. For instance, say I run over a manhole cover, the next time I brake, guaranteed, the noise occurs. From then on, however, there will be no noise until I jossle the rear end around again. Wash, rinse, repeat....
It sounds like it is happening directly to the rear of the driver's seat, but I can't tell exactly how far back....
Any known culprits?????
Thread Starter
Melting Slicks
Joined: Apr 2009
Posts: 3,333
Likes: 0
From: DFW TX
Took the rear wheels off... to my dismay, no loose bolts or fasteners. The shocks are definitely not causing it. I did a full undercarriage inspection, no foreign objects. I'm gonna take it out for a spin later tonight, you know how sometimes these things just kinda fix themselves randomly.
Le Mans Master
Joined: Jan 2004
Posts: 6,801
Likes: 13
From: Anywhere where Cones need hit
Cruise-In 9-10 Veteran
CI-X Auto-X Champ (race tires)
St. Jude Donor '07-'09
I've been getting a random sound that sounds SIMILAR to this... but mine sounds more like a caliper hanging up and not releasing the pads when I let off the pedal on the front.
During a few autocrosses, I got a random thunk as well but wouldn't always do it on back to back runs.
The front end is getting gone over this weekend now that the season is over. Checking the sway bar end links ( HD heim joint style ) and also checking for binding of the swaybar itself.
Checking all the brake caliper bolts, connections...
Have to look at the shock mounts as well and double check those. Although the car will be getting new shocks in the coming months and it's about done driving for the winter.
Let us know what you find out!
During a few autocrosses, I got a random thunk as well but wouldn't always do it on back to back runs.
The front end is getting gone over this weekend now that the season is over. Checking the sway bar end links ( HD heim joint style ) and also checking for binding of the swaybar itself.
Checking all the brake caliper bolts, connections...
Have to look at the shock mounts as well and double check those. Although the car will be getting new shocks in the coming months and it's about done driving for the winter.
Let us know what you find out!
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Thread Starter
Melting Slicks
Joined: Apr 2009
Posts: 3,333
Likes: 0
From: DFW TX
You think a caliper could be hanging up in the rear? The car only has 30K miles on it, so I don't think the calipers should be shot yet...
Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
I have exactly this same issue and haven't had time to look yet - this weekend.
Another suggestion was lubricating the outer splines on the half-shafts; search will turn up a bunch of stuff on this and I plan to do it this weekend as well.
Another suggestion was lubricating the outer splines on the half-shafts; search will turn up a bunch of stuff on this and I plan to do it this weekend as well.
Le Mans Master
Joined: Jan 2004
Posts: 6,801
Likes: 13
From: Anywhere where Cones need hit
Cruise-In 9-10 Veteran
CI-X Auto-X Champ (race tires)
St. Jude Donor '07-'09
I originally didn't see that you stated that your thunk was from the rear. My apologies.
Advanced
Joined: Mar 2008
Posts: 70
Likes: 0
From: Thornhill Ontario
had something similar..
I had a clunk originating from a rear caliper. The noise would occur time to time under light breaking before a complete stop. All hardware was tightened properly.. The caliper however felt very loose.. What I did was got some caliper lube (synthetic kind, I think it was by permatex), took the caliper off, cleaned the caliper pins and put a good amount of lube on them and the bolts. Torqued everything to spec again, and that god rid of the noise.. Planning to do something similar to my other wheels.
Stas.
Stas.
Thread Starter
Melting Slicks
Joined: Apr 2009
Posts: 3,333
Likes: 0
From: DFW TX
Alright guys, I think I may have figured it out. When I started it up today, I blipped the throttle to put it in 1st, lo and behold, THE NOISE!!! It sounded exactly like I was going over a bump or applying light brake pressure. Immediately following this the engine RPM's dropped to around 400 and the exhaust sounded muffled (excessive and abnormally quiet). I'm thinking it is something with the exhaust. Are the baffles known to cause problems in the Ti's?? Anybody ever had problems with your own?
Outer splines... as in where the half shafts connect to the hub? That hadn't even crossed my mind. Good suggestion.
Outer splines... as in where the half shafts connect to the hub? That hadn't even crossed my mind. Good suggestion.
