Clunk from rear over bumps - Ideas?
02-11-2022, 01:05 AM
#47
Old topic I know, but I have had this issue for a few years - not bad enough to put much effort into it though, but it does bother me.
It's a "clunk" sound that happens only on a specific type bump - has to kick the rear up sharply at a relatively low speed or it doesn't happen and it is hard to find a place that will reliably repro the sound. Most speed bumps won't do it.
It sounds almost like I'm carrying a loose piece of 2x4 in the trunk - but there is no trunk back there! Or it makes me think maybe something is loose in the subwoofer chamber. I don't get any rattle or metallic sounds - just a clunk.
Just wondering if any wisdom has grown around this issue since...
It's a "clunk" sound that happens only on a specific type bump - has to kick the rear up sharply at a relatively low speed or it doesn't happen and it is hard to find a place that will reliably repro the sound. Most speed bumps won't do it.
It sounds almost like I'm carrying a loose piece of 2x4 in the trunk - but there is no trunk back there! Or it makes me think maybe something is loose in the subwoofer chamber. I don't get any rattle or metallic sounds - just a clunk.
Just wondering if any wisdom has grown around this issue since...
I am having this issue with my 991.2 carrera 4S too!! But my car doesn’t have a sunroof.
it’s bugging me a lot. I would love to know the cauae too
02-11-2022, 01:06 AM
#48
02-11-2022, 10:02 AM
#49
I don’t think I provided an update. My issue was that I didn’t replace my rear strut mounts when I put my new suspension in. Ordered new mounts (it was just the spacers that were bad) and boom it’s fine 😬
02-11-2022, 11:48 AM
#50
02-11-2022, 02:00 PM
#51
02-11-2022, 10:22 PM
#53
i changed that too on my c4s but the rear clunking noise still persists. I checked others things : bushes , sway bars they looks in great condition no play
02-12-2022, 09:37 AM
#54
Hmmm... All the mounts and strut nuts are properly spec'd too? There was another post that the owner mentioned the source of the clunk was actually the roof upholstery right behind the sunroof opening? Some weird echo... Also I don't know if you upgraded your suspension? I have bilstein's and they're just noisier in general..
02-12-2022, 09:43 AM
#55
Hmmm... All the mounts and strut nuts are properly spec'd too? There was another post that the owner mentioned the source of the clunk was actually the roof upholstery right behind the sunroof opening? Some weird echo... Also I don't know if you upgraded your suspension? I have bilstein's and they're just noisier in general..
02-12-2022, 10:33 AM
#56
RL Community Team
Rennlist Member
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Thread Starter
2009 C2S 178K miles
How many miles on your car?
At around 154K miles, I had a clunking in the rear... using chassis ears, I isolated it to a press-in bushing on the wheel carrier. This can only be remedied by replacing the carrier which is a really big job. I did this work myself and, "while I was in there" - dang I hate that approach - I replaced that foam mount. I cured the clunk but honestly, I could not say exactly which part fixed the problem because, obviously, I changed two things at one time. The foam rings on mine looked perfect.... after really examining the system, I could not figure out how those foam rings could have caused the clunking. Anywho.... mine is .2 so this all may not be relevant to you.
Another cause of clunking is the lower control arm, the one with three attachment points. This is a very common source of clunking. The Porsche katalog calls this arm a "whishbone" but it doesn't look like one.
The only way you are going to find the clunk is to use chassis ears (that I know of). The old way was to put a crowbar in there and find where the play was... but these cars are so dang tight, you won't find it that way. The suspension has to be fully loaded to get a clunk. We all have our own stories of chasing clunks down and you are not going to get a definitive answer here. If you do start to replace parts, buckle up, it could get expensive... or you could get lucky. Read here about chassis ears. Note that I discovered I could recreate the clunk by just rocking the car in place... and glad I could because it is massively time consuming and frustrating setting the car up with the ears and then heading out and driving. These ears are fabulous but incredibly noisy... this is not an easy task. Oh, and I put an ear up top of the strut and did not get a clunk so I can assume with high assurance it was not the foam ring.... but you are never really sure.
https://rennlist.com/forums/997-foru...ed-advice.html
Peace
Bruce in Philly (now Atlanta)
How many miles on your car?
At around 154K miles, I had a clunking in the rear... using chassis ears, I isolated it to a press-in bushing on the wheel carrier. This can only be remedied by replacing the carrier which is a really big job. I did this work myself and, "while I was in there" - dang I hate that approach - I replaced that foam mount. I cured the clunk but honestly, I could not say exactly which part fixed the problem because, obviously, I changed two things at one time. The foam rings on mine looked perfect.... after really examining the system, I could not figure out how those foam rings could have caused the clunking. Anywho.... mine is .2 so this all may not be relevant to you.
Another cause of clunking is the lower control arm, the one with three attachment points. This is a very common source of clunking. The Porsche katalog calls this arm a "whishbone" but it doesn't look like one.
The only way you are going to find the clunk is to use chassis ears (that I know of). The old way was to put a crowbar in there and find where the play was... but these cars are so dang tight, you won't find it that way. The suspension has to be fully loaded to get a clunk. We all have our own stories of chasing clunks down and you are not going to get a definitive answer here. If you do start to replace parts, buckle up, it could get expensive... or you could get lucky. Read here about chassis ears. Note that I discovered I could recreate the clunk by just rocking the car in place... and glad I could because it is massively time consuming and frustrating setting the car up with the ears and then heading out and driving. These ears are fabulous but incredibly noisy... this is not an easy task. Oh, and I put an ear up top of the strut and did not get a clunk so I can assume with high assurance it was not the foam ring.... but you are never really sure.
https://rennlist.com/forums/997-foru...ed-advice.html
Peace
Bruce in Philly (now Atlanta)
Last edited by Bruce In Philly; 02-12-2022 at 10:37 AM.
02-12-2022, 12:35 PM
#57
2009 C2S 178K miles
How many miles on your car?
At around 154K miles, I had a clunking in the rear... using chassis ears, I isolated it to a press-in bushing on the wheel carrier. This can only be remedied by replacing the carrier which is a really big job. I did this work myself and, "while I was in there" - dang I hate that approach - I replaced that foam mount. I cured the clunk but honestly, I could not say exactly which part fixed the problem because, obviously, I changed two things at one time. The foam rings on mine looked perfect.... after really examining the system, I could not figure out how those foam rings could have caused the clunking. Anywho.... mine is .2 so this all may not be relevant to you.
Another cause of clunking is the lower control arm, the one with three attachment points. This is a very common source of clunking. The Porsche katalog calls this arm a "whishbone" but it doesn't look like one.
The only way you are going to find the clunk is to use chassis ears (that I know of). The old way was to put a crowbar in there and find where the play was... but these cars are so dang tight, you won't find it that way. The suspension has to be fully loaded to get a clunk. We all have our own stories of chasing clunks down and you are not going to get a definitive answer here. If you do start to replace parts, buckle up, it could get expensive... or you could get lucky. Read here about chassis ears. Note that I discovered I could recreate the clunk by just rocking the car in place... and glad I could because it is massively time consuming and frustrating setting the car up with the ears and then heading out and driving. These ears are fabulous but incredibly noisy... this is not an easy task. Oh, and I put an ear up top of the strut and did not get a clunk so I can assume with high assurance it was not the foam ring.... but you are never really sure.
https://rennlist.com/forums/997-foru...ed-advice.html
Peace
Bruce in Philly (now Atlanta)
How many miles on your car?
At around 154K miles, I had a clunking in the rear... using chassis ears, I isolated it to a press-in bushing on the wheel carrier. This can only be remedied by replacing the carrier which is a really big job. I did this work myself and, "while I was in there" - dang I hate that approach - I replaced that foam mount. I cured the clunk but honestly, I could not say exactly which part fixed the problem because, obviously, I changed two things at one time. The foam rings on mine looked perfect.... after really examining the system, I could not figure out how those foam rings could have caused the clunking. Anywho.... mine is .2 so this all may not be relevant to you.
Another cause of clunking is the lower control arm, the one with three attachment points. This is a very common source of clunking. The Porsche katalog calls this arm a "whishbone" but it doesn't look like one.
The only way you are going to find the clunk is to use chassis ears (that I know of). The old way was to put a crowbar in there and find where the play was... but these cars are so dang tight, you won't find it that way. The suspension has to be fully loaded to get a clunk. We all have our own stories of chasing clunks down and you are not going to get a definitive answer here. If you do start to replace parts, buckle up, it could get expensive... or you could get lucky. Read here about chassis ears. Note that I discovered I could recreate the clunk by just rocking the car in place... and glad I could because it is massively time consuming and frustrating setting the car up with the ears and then heading out and driving. These ears are fabulous but incredibly noisy... this is not an easy task. Oh, and I put an ear up top of the strut and did not get a clunk so I can assume with high assurance it was not the foam ring.... but you are never really sure.
https://rennlist.com/forums/997-foru...ed-advice.html
Peace
Bruce in Philly (now Atlanta)
I changed the foam both sides of the rear struts. This is the before picture
2. Rebushed the bushes on both sides of the rear (the one contacted with the wishbone, yellow circled) Other bushes he said they all are in good condition. So he didn’t do anything to them.
After all, the clunking noise still persists. My next move will be rebushed all the rear bushes I can.
The old way was to put a crowbar in there and find where the play was... but these cars are so dang tight, you won't find it that way.
I found one video from the other guy posted online. He has the same noise as my car. (Even on an uneven road, you will hear a subtle clonking , clunking noises) But he hasn’t got any reply since 2016! I also forgot the original thread. Here is a link where he posted a soundclip. The obvious noise is from 2:00 onwards.
P.S. my car has pdcc+pasm sport
The yellow circle.
Thanks
Last edited by Birkinjay; 02-12-2022 at 12:46 PM.
02-12-2022, 02:21 PM
#58
RL Community Team
Rennlist Member
Rennlist Member
Thread Starter
That looks like the same one that went on mine. See my link in my last post. That bushing is in the wheel carrier (aka, knuckle, hub). There was no known maker that had a replacement bushing. I even contacted a maker in the UK... they told me they tried to make one but "wasn't worth it" or something like that.
Anywho, you would have to remove the carrier to press in the bushing anyway so you may as well just buy another carrier. This is a big job... I did it myself with the exception of having the spindle pressed out of the old and then pressed into the new carrier... just drove it all over to a speed shop. You need a hydraulic press for that. I did not re-use the old bearings since there were so many miles on them and pressing them out tends to destroy them, so I purchased new bearings and I pressed those into the new carrier myself (very proud!!).
Good luck, that has to be the worst bushing to go bad on this car. Re-read my link above and you will see I circled the same bushing... again, I found this by using my chassis ears. Oh, and to make that bushing clank, I could rock the car in place... although I pressed up against the roof line so you probably would have to open the door and you and a friend lift on the rocker to shake the car.
Peace
Bruce in Philly (now Atlanta)
Anywho, you would have to remove the carrier to press in the bushing anyway so you may as well just buy another carrier. This is a big job... I did it myself with the exception of having the spindle pressed out of the old and then pressed into the new carrier... just drove it all over to a speed shop. You need a hydraulic press for that. I did not re-use the old bearings since there were so many miles on them and pressing them out tends to destroy them, so I purchased new bearings and I pressed those into the new carrier myself (very proud!!).
Good luck, that has to be the worst bushing to go bad on this car. Re-read my link above and you will see I circled the same bushing... again, I found this by using my chassis ears. Oh, and to make that bushing clank, I could rock the car in place... although I pressed up against the roof line so you probably would have to open the door and you and a friend lift on the rocker to shake the car.
Peace
Bruce in Philly (now Atlanta)
Last edited by Bruce In Philly; 02-12-2022 at 02:23 PM.
02-12-2022, 11:24 PM
#59
That looks like the same one that went on mine. See my link in my last post. That bushing is in the wheel carrier (aka, knuckle, hub). There was no known maker that had a replacement bushing. I even contacted a maker in the UK... they told me they tried to make one but "wasn't worth it" or something like that.
Anywho, you would have to remove the carrier to press in the bushing anyway so you may as well just buy another carrier. This is a big job... I did it myself with the exception of having the spindle pressed out of the old and then pressed into the new carrier... just drove it all over to a speed shop. You need a hydraulic press for that. I did not re-use the old bearings since there were so many miles on them and pressing them out tends to destroy them, so I purchased new bearings and I pressed those into the new carrier myself (very proud!!).
Good luck, that has to be the worst bushing to go bad on this car. Re-read my link above and you will see I circled the same bushing... again, I found this by using my chassis ears. Oh, and to make that bushing clank, I could rock the car in place... although I pressed up against the roof line so you probably would have to open the door and you and a friend lift on the rocker to shake the car.
Peace
Bruce in Philly (now Atlanta)
Anywho, you would have to remove the carrier to press in the bushing anyway so you may as well just buy another carrier. This is a big job... I did it myself with the exception of having the spindle pressed out of the old and then pressed into the new carrier... just drove it all over to a speed shop. You need a hydraulic press for that. I did not re-use the old bearings since there were so many miles on them and pressing them out tends to destroy them, so I purchased new bearings and I pressed those into the new carrier myself (very proud!!).
Good luck, that has to be the worst bushing to go bad on this car. Re-read my link above and you will see I circled the same bushing... again, I found this by using my chassis ears. Oh, and to make that bushing clank, I could rock the car in place... although I pressed up against the roof line so you probably would have to open the door and you and a friend lift on the rocker to shake the car.
Peace
Bruce in Philly (now Atlanta)
I read your previous thread. Did you mean the bush I circled in red ( the one I still haven’t changed it?)
This red arrow right? Credit: elephant racing.
02-13-2022, 09:12 AM
#60
RL Community Team
Rennlist Member
Rennlist Member
Thread Starter
The lowest one, not the one with the red arrow. But it is really irrelevant which one as both have press-in bushings and there are (or were) no press-in options. At least I think that other one has a press in but my memory ain't so good anymore. Only replacement of the whole carrier will stop the rattle/clunk where there is a press-in bush.
Again, this can be confirmed with chassis ears and you don't have to drive with them, but rock the car in place (most likely you can rock and rattle it).
Most indys should have a set of chassis ears, they are a pretty common tool. My friend at Ford who worked his way through engineering college as Jaguar dealership tech said chassis ears are really the only way to find crazy rattles and clunks.
Peace
Bruce in Philly (now Atlanta)
Again, this can be confirmed with chassis ears and you don't have to drive with them, but rock the car in place (most likely you can rock and rattle it).
Most indys should have a set of chassis ears, they are a pretty common tool. My friend at Ford who worked his way through engineering college as Jaguar dealership tech said chassis ears are really the only way to find crazy rattles and clunks.
Peace
Bruce in Philly (now Atlanta)
Last edited by Bruce In Philly; 02-13-2022 at 09:19 AM.