rear-end knocking

[omniruss]

Dave, while at s2kdays I touched on this briefly... I realize how eager everyone is to get your advice, so I left it alone for the time being. But I am becoming more concerned about a knock which I think is coming from the driver side rear end. You already elliminated the possibility of needing to re-torque the hub nut due to how often the noise occurs. The knock is becoming more frequent.

I first started to take note of it about a month ago. Any time I would hit a bump just right, I would get a single knock. Though that's still true, it has worsened. It is most prominent while "things" are still cold. When I first start up and drive down the road, simply getting on the gas results in a series of aperiodic pops and knocks. Noises subside shortly thereafter, maybe after a minute or so. But again, if I hit a bump just right even after things are warm, it still might make a single knock.

In mid-summer I had removed my diff and shipped it to puddymod for some tuning. Prior to driving to s2kdays, which was about a 3-hour drive for me, I jacked up the car and checked over all of the nuts and bolts to make sure everything was tight. I didn't find anything loose, I and visually inpsected everything. Nothing obvious.

Do you have any ideas?

Thanks.
Russ

[repiv]

When you accelerate moderate to hard, do you get a vibration or hear anything? This would point towards the inner CV joint going bad, as is noted in many cases where the car has been lowered for a while. However, even when not lowered, the same symptoms can appear when the CV joint is going bad.
As for the single knock when you go over a bump or something, this points towards something loose in that corner of the car. Check all you wheel weights to make they are all stuck one real good. Are your lugnuts on tight? Check your suspension bump stops to make sure they aren't the problem.
Too bad we couldn't have gone for a drive and have you show me these noises at the time.

[omniruss]

There's no vibration when I accelerate. I just had new rear tires put on the Thursday before s2kdays... the knock was happening before that. And I assume they put new wheel weights on. But I did notice that while on the freeway coming back I was getting some vibration around 70 mph+. But that's not even consistent as I don't always notice it on my drive to/from work which I drive 70 mph+. Is there such a thing as breaking in new tires and getting some vibration? I also checked all my lug nuts, they were ok.

Something else I just remembered, maybe not an issue... at the beginning of summer my engine light came on. I can't remember the code but I looked it up to be "evap canister." I cleared the code and it never came back. Isn't the evap near the driver side rear?

I will check my bump stops when I get home this evening.

[repiv]

New tires sometimes need breaking in and can exhibit some odd vibrations but there shouldn't be a noise like knocking. Occasionally, you can get a tire that has a defective cord construction and create all sorts of problems that can't be solved, but this is not likely your situation as you say the issue was there before the new tires.
You could still have wheel bearing issues.

As for the EVAP cannister, it's that thing near the left rear wheel that has the honeycomb pattern on the end. Maybe there's something loose with it. It's attached in a couple of places,one of which is the cross bar. Go under and give everything a wiggle and see if anything is loose.

[omniruss]

I just took a picture and was going to post it.... ah, looks like website tech problems that I've heard about. Anyway I currently have both back wheels off. The only thing I found was a disconnected hose near my evap canister. Two hoses drop down from the frame there - the one toward the rear was off, so I reconnected it. I can believe that might have been the reason my engine light came on a while ago, but I really have to stretch my imagination to think that's a piece of my knocking mystery. Which, by the way, did not happen on my drive back home.

I gave everything around the wheel wells a confident tug/twist/pull and found nothing alarming. How do I assess bump stops?

[repiv]

How do I assess bump stops?
That's easier said than done. Look at the following picture:

http://www.slhondaparts.com/browse.asp?Model=S2000&Year=2004&TrimLevel=2DR+S2000+&TransLevel=6MTKA&Section=F&Category=B++30++%7CREAR+SHOCK+ABSORBER&Doors=2&Emissions=KA&PartCatalogId=14S2A0&ViewParts=true

The bump stop is on the damper (part #15) and is the first of many components that comprises the rear damper/spring assembly. It's what limits the total amount of compression movement in the rear shock. You might want to also check the big nut at the top (part #19) to make sure that whole assembly is bolted down tight. You'll need to gain access to that from behind the trunk liner. All that stuff on the interior of the coil spring can become loose and rattle around whenever you hit a bump.
I'm not sure that a backyard mechanic can safety tackle this job. Be careful.

[omniruss]

Unless we have a real good idea that it could be bump stop or assembly bolt, I don't really want to touch this assembly. I realize the safetay factors, and I don't have the tools - though that's normally my excuse to go out and buy new gadgets.

I've been taking very close note of the noise. To be honest, when I first heard it a month or so ago, I thought it was coming from the front. As time went on, I thought for sure it was the rear. Now I'm unsure again.

One thing that I am positive about - it's very dependent on ambient temperature. Yesterday was in the 30's when I left for work, and when I first left the house, it was very noisy, but only when I was on the throttle (like a normal human) on a smooth road. The effect eventually faded. I've noticed this behavior for a while now, but that was probably the chilliest that I've driven it this Fall. Then it sat all day in the parking lot at work, sunny around 60, and when I left to go home, it never made a peep. This morning was in the 50's... when I left for work, it made a little bit of noise, but it was clearly less severe than yesterday morning. This doesn't seem like bump-stomp or loose shock assembly behavior, does it?

I think I might have to remove front wheels and have a look around. I'm not sure how to isolate the location of the knock.

[repiv]

If it's temp related, it could be to do with shock valving.

[S2KPUDDYDAD]

Maybe a diff mount.....Did you have any of these knocks and pops before you had the diff worked on by me? One of the aluminum mounting bars may have a crack in it, this would cause the sounds you are having and be temp sensitive. If you find you need one of the mounting bars, mounts, or anything diff related please let me know and I will send it out free of charge. Mounts can be expensive and are not part of my service but, I will take care of anything that maybe diff related to this issue you have. I will be gone on holiday from the 11th to the 17th
If you know something by the 10th I can get what you need sent out if not let me know when I get back.

Good luck:)

[omniruss]

Ben, I didn't notice anything even after I got the diff back from you, then again, those were pretty warm days too. Would you particularly suspect one of the two mounting bars on the front of the diff would be making such noise, or are any diff mounts equally questionable? How visually obvious is a crack, or what do I look for?

[S2KPUDDYDAD]

Ben, I didn't notice anything even after I got the diff back from you, then again, those were pretty warm days too. Would you particularly suspect one of the two mounting bars on the front of the diff would be making such noise, or are any diff mounts equally questionable? How visually obvious is a crack, or what do I look for?

You may have to remove each one to have a real good look. Do one at a time starting with the front then if you find nothing go for the large rear aluminum bar mount. I am not sure if this is the issue but, to me your description sounds like a fractured metal part of some kind. Check all around the rear frame section for stressed or fractures around bolt holes, welds, and alike.
Keep us posted. If you had no issue before the diff removal and install it is more probable to be something around the diff area.

[omniruss]

Looks like typical 3rd party is photobucket. Here's the evap canister hose that I reconnected:
http://s468.photobucket.com/albums/rr41/omniruss/diff%20mounts/?action=view&current=DSC05010.jpg

I removed each front diff mount yesterday. I didn't see any cracks or abnormalities. It's suppose to be a beautiful weekend for which I cannot live without my S, so I refrained from taking anything else apart and getting in too deep. So here's pics for the record:
http://s468.photobucket.com/albums/rr41/omniruss/diff%20mounts/

I crawled around on my back with my mini mag light and took a good look under the car. Nothing.

It's been around 50 degrees when I have been leaving in the morning, and I haven't been hearing any knock noises. I hate to let it go until something breaks. :yikes:

[omniruss]

I have a new/updated assessment... the noise seems to be coming from underneath the car, toward the direction of the engine. Last night dipped down to about 30 or 32 degrees. When I drove this morning the noise did not subside like it normally does after making my way past a couple stop signs.
Do you suppose an engine mount or anything of that sort could speak out until temperature is up?

[repiv]

I'm sure this is getting quite aggravating. A noise that is hard to locate is especially hard to diagnose. If it were coming from the rear of the car, that would be one set of possibilities. A noise that comes from another part of the car creates a whole new set of parameters.
Since it seems to have migrated forward, you can look at a few things. First of all, try to establish that it isn't the base of the shifter. These have been known to make a clunk or two when the car is jostled. A bit of lubrication to the based of the stick will resolve this.
Certainly, inspecting the engine mounts and the rear rubber tranny mount is worth while. Has the tranny ever been pulled? Check to make sure the tranny to engine bolts are intact.
Have you ever lost an oil fill cap mysteriously, thinking that it dropped down and fell onto the road while driving? A few people have reported this only to discover that the cap fell down onto the top curved section of the tranny and when they hit a bump the thing would rattle around. As things get hot and expand, the space the cap is wedge in, closes up and no more noise.
While you're under the car, check out the propshaft to make everything is bolted down tight. And have a look at all the frame strengtheners to see if any bolts are loose or missing.

[omniruss]

First of all, try to establish that it isn't the base of the shifter. These have been known to make a clunk or two when the car is jostled. A bit of lubrication to the based of the stick will resolve this.


Well I got the S out for a couple days and I had forgotten how aggravated I was. I looked underneath the car again this evening but forgot to check the base of the shifter. What exactly needs lubricated?

With these cold days the noise is very prominent. It sounds like a creaking ship for the duration that I accelerate in first gear, even second. After whatever it is warms up, only a 'finely-tuned' bump in the road can jostle any noise out of it.

Certainly, inspecting the engine mounts and the rear rubber tranny mount is worth while. Has the tranny ever been pulled? Check to make sure the tranny to engine bolts are intact.
Have you ever lost an oil fill cap mysteriously, thinking that it dropped down and fell onto the road while driving? A few people have reported this only to discover that the cap fell down onto the top curved section of the tranny and when they hit a bump the thing would rattle around. As things get hot and expand, the space the cap is wedge in, closes up and no more noise.
While you're under the car, check out the propshaft to make everything is bolted down tight. And have a look at all the frame strengtheners to see if any bolts are loose or missing.


Engine mounts & tranny mount look fine and are secure. Tranny has never been pulled. Tranny-engine bolts are ok. The only thing I really noticed here was oil residue. Not sure if this is normal, but seems reasonable considering it's the bottom of the engine:
http://i468.photobucket.com/albums/rr41/omniruss/S2000/P1010040.jpg

Never lost an oil cap. Prop shaft bolts are all secure.

As far as frame strengtheners, are you referring to the 'sub-frame'?

The only other small thing that I notice is a fine crack on the heat shield that connects to the header down pipe (down is forward in this pic):
http://i468.photobucket.com/albums/rr41/omniruss/S2000/P1010037.jpg

This is starting to worry me, let alone tee me off. I'd hate for something to give out while I'm doing any significant speed. MIght have to throw in the towel on this one and take it to the shop.

[repiv]

Well I got the S out for a couple days and I had forgotten how aggravated I was. I looked underneath the car again this evening but forgot to check the base of the shifter. What exactly needs lubricated?

The only thing I really noticed here was oil residue. Not sure if this is normal, but seems reasonable considering it's the bottom of the engine:

As far as frame strengtheners, are you referring to the 'sub-frame'?

The only other small thing that I notice is a fine crack on the heat shield that connects to the header down pipe (down is forward in this pic):


The part of the shifter base that is lubed is the ball at the bottom, however, this is more of a "ringing" sound. I doubt this is your noise. But just the same, try to hold the shifter when you would normally make the noise with the bump. You might be able to feel it if it's related to the shifter.

The oil residue under the tranny is fairly normal. It can be just engine oil seapage making its way down to the lowest point. It can also be a bit of seapage through the rear main engine seal and this flushes some of the clutch disc dust with it.

I wouldn't worry too much about that heat shield crack.
Next time you're under the car, start hitting stuff with the palm of your hand to see if it duplicates the noise. Maybe the exhaust system is hitting something when you go over certain bumps. Are any of the shocks leaking?

[omniruss]

The part of the shifter base that is lubed is the ball at the bottom, however, this is more of a "ringing" sound. I doubt this is your noise. But just the same, try to hold the shifter when you would normally make the noise with the bump. You might be able to feel it if it's related to the shifter.

Ok, I will try this next time I go somewhere. Something else I thought I might try is putting it in neutral when I know a noteworthy bump is coming up. If I remember correctly, releasing throttle and pressing in the clutch doesn't help, except of course when engine power induces the noise before everything has warmed up.

Next time you're under the car, start hitting stuff with the palm of your hand to see if it duplicates the noise. Maybe the exhaust system is hitting something when you go over certain bumps. Are any of the shocks leaking?

Yes, I've been hitting things in just such a manner, when car has been both cold and warm. Nope, no leaky shocks.

[My_yella_s2k]

Russ - just give up and give me the car...
BUT paint it first :D then ship it down, ill take the noise problem off your hands

[omniruss]

Russ - just give up and give me the car...
BUT paint it first :D then ship it down, ill take the noise problem off your hands

Hmm, can't remember, do you have ap1? Could be a tempting trade!

[s2kobsessed]

I'm curious to find out what the clunking noise on your car is Russ! I once had this noise but it was an exhaust hitting rear lower tie bar mount on the passenger side.

I'm puzzled though... please keep us updated.

[wtmohr]

Russ - just give up and give me the car...
BUT paint it first :D then ship it down, ill take the noise problem off your hands


But Mike, it's already the perfect color! You'd have to pay Russ to take the :shortbus: !!!

[omniruss]

Finally through in the towel on this. Took the S to the garage yesterday, their initial hunch was sway bar/bushings. Waiting to hear back from them any minute now...

[bimdub]

keep me informed, I have been trying to resolve a very similar noise for a while now (2 years) and have had no luck.

[omniruss]

Stopped by on my way back from work... they were ready to give my car back to me because they couldn't hear anything. Granted it was in the balmy 50's today, much warmer than my recent cold start problems. The S had not been run for a few hours, so I got one of the mechanics to hop in the passenger's seat and I drove around the block. I was able to point out the noise, but it was indeed very faint. But at least they know what I'm talking about now. I will post again when I have more info.

[omniruss]

The shop ordered front sway bar links and bushings. They let me have my car back until the parts are delivered. I'll be really happy if that's the fix, but I don't understand why these pieces would need to be replaced with only 25,000 miles on the car? We indeed have some rough roads around here, but it's not like I drive it like a pickup truck.

[repiv]

The shop ordered front sway bar links and bushings. They let me have my car back until the parts are delivered. I'll be really happy if that's the fix, but I don't understand why these pieces would need to be replaced with only 25,000 miles on the car? We indeed have some rough roads around here, but it's not like I drive it like a pickup truck.

I hope that's what it will take to fix it, however, I have my reservations. I drive my S2000 all year round and sometimes, I do drive mine like a pickup truck, as do a couple of other S2000s here in town. We all have odd creaks and rattles and knocks and ticks, but none are considered to be of importance. Perhaps yours is such a sound. Too bad we never got a chance to go for a spin when I was there.
I wish you the best of luck.

[omniruss]

I hope that's what it will take to fix it, however, I have my reservations. I drive my S2000 all year round and sometimes, I do drive mine like a pickup truck, as do a couple of other S2000s here in town. We all have odd creaks and rattles and knocks and ticks, but none are considered to be of importance. Perhaps yours is such a sound. Too bad we never got a chance to go for a spin when I was there.
I wish you the best of luck.

Yep, you're right.... sway bar bushings and links replaced and I still got the noise. I heard a couple/few thumps after I drove away from the repair garage last week - initially I thought it might have been quieter, but I drove the S to work on this 30F morning and I really can't say it's any better. I just talked to the shop, guess I'll bring 'er in again this evening so they can have another look tomorrow morning, suppose to be another chilly one.

[omniruss]

I think this is a eureka. When I started up yesterday, the noise was prevalent, so I opened the hood and started poking around again. I found that pushing down on the front of the engine resulted in a vibration - my "creak" as I came to call it. Long story short, my s/c blower is bumping against the frame where Comptech says to fold it over with a crescent wrench. I remember being very liberal with this step. The blower should have plenty of room. So here's what I found:
http://i468.photobucket.com/albums/rr41/omniruss/DSC05404.jpg

The fasteners are burrowing into the mounting bracket. The top 2 fasteners are burrowing into the front of the bracket as in the picture, and the bottom fastener is burrowing into the back side of the bracket. There's enough sag in the whole assembly to result in small collisions between the blower and car frame. After the engine gets hot, things sufficiently expand to lift the blower up a bit, after that, only a good bump in the road just might jar the engine enough to cause another collision.

So, #1, why? The fasteners have built-in spacers that apparently aren't quite long enough to do their job.
http://i468.photobucket.com/albums/rr41/omniruss/DSC05405.jpg

I must have over-torqued the bolts and now I have this problem. Not sure of the best solution. The first thing that comes to mind is to drill a couple of holes in a metal strip and devise a spacer for the front face of the mounting bracket, and do the same for the bottom fastener. By the way, the mount underneath the after cooler looks fine:

http://i468.photobucket.com/albums/rr41/omniruss/DSC05412.jpg

I'm also very concerned for the bottom of the blower. I plan to remove the whole assembly today (ughh) to do a full inspection. Unfortunately, I've developed yet another noise around 4-5000 rpms that sounds like a vibrating heat shield.... I'm keeping my fingers crossed that I didn't puncture a hole in the bottom of my blower.

If anyone has any suggestion for remedy I'd be glad to hear them. Otherwise I'll keep you posted on my progress.

[repiv]

You could always get new bolts if the old ones may have been over torqued. On the other hand, once you have the blower off, you can then do the proper cross member bending to make sure clearance will no longer be a problem. Then you can re-use the old bolts. If the bottom of the blower is beginning to wear, if it's not getting too dangerously thin, you can put a patch of some kind of metal epoxy.
The other possible factor that may contribute to the blower being yanked down too hard is over tightening the belt. When you get it all back together, ensure this is not an issue.
Funny we've all been looking to the rear of the car for the source of this noise. :p

[omniruss]

Funny we've all been looking to the rear of the car for the source of this noise. :p
Yeah I ruled out the rear end quite early, I'm almost ashamed of the thread title.

Here's the cross-member, seems like plenty of a bend, but I'll push it over more before I re-assemble everything. You can see bare metal where it's been wearing.
http://i468.photobucket.com/albums/rr41/omniruss/DSC05417.jpg

Here's the blower. I don't think I have anything to worry about. The wear is on the edge, should be plenty of girth there.
http://i468.photobucket.com/albums/rr41/omniruss/DSC05420.jpg

Every single mount has quite a bit of wear. This is somewhat alarming to me. I can't remember from the day that I installed the kit if the mounting bracket had recessed mount points. I don't think so, regardless these are bad signs of wear.
http://i468.photobucket.com/albums/rr41/omniruss/DSC05422.jpg

This is the bottom mount point on the back side of the bracket. It's the worst of them all, reasonably so since it takes the brunt of the weight.
http://i468.photobucket.com/albums/rr41/omniruss/DSC05423.jpg


You could always get new bolts if the old ones may have been over torqued.
I don't understand what this would help (?)

On the other hand, once you have the blower off, you can then do the proper cross member bending to make sure clearance will no longer be a problem. Then you can re-use the old bolts. If the bottom of the blower is beginning to wear, if it's not getting too dangerously thin, you can put a patch of some kind of metal epoxy.
Yes, I will put a little more bend into the cross member. I don't think it's necessary to patch anything. I plan to re-use my bolts. I think I will pick up some nylon washers from the hardware store and use them to provide some kind of buffer on the mounts, this would also provide a means to fill in the worn out metal. Would you advise against this? My concern might be that I need high-temp parts?

The other possible factor that may contribute to the blower being yanked down too hard is over tightening the belt. When you get it all back together, ensure this is not an issue.
Ok, will do.

[repiv]

Getting new bolts is only if you think the over torquing may have stretched the threads too much and caused some degradation in the bolt itself. It won't help your immediate situation at all.
Are these the upgraded mounts that Comptech came out with after the initial introductory run? They had terrible problems with the old mounts cracking from vibration and went to mounts with rubber to absorb the vibrations. This does allow some tiny movement and it's this movement that may be causing the wear.
Unless you can find the exact thickness of washer to take up the wear, I wouldn't bother with it. It might create another problem that wasn't there to begin with.
Like you say, that wear is on an edge. Nothing to worry about. If it were me, I'd bend that beam further out of the way, put it all back and be done with it.

[omniruss]

Getting new bolts is only if you think the over torquing may have stretched the threads too much and caused some degradation in the bolt itself. It won't help your immediate situation at all.
Are these the upgraded mounts that Comptech came out with after the initial introductory run? They had terrible problems with the old mounts cracking from vibration and went to mounts with rubber to absorb the vibrations. This does allow some tiny movement and it's this movement that may be causing the wear.
Unless you can find the exact thickness of washer to take up the wear, I wouldn't bother with it. It might create another problem that wasn't there to begin with.
Like you say, that wear is on an edge. Nothing to worry about. If it were me, I'd bend that beam further out of the way, put it all back and be done with it.

Yes I have the new mounts. The only metal-on-metal is right where my problem is.

I just got back from the hardware store and couldn't find any nylon washers, or any other washers for that matter, that would properly fit as you say. So I'll just plop in the old ones and hope for the best. I'll take your advice and just put everything back. I'm still concerned that the mounts will simply keep eating into the mounting bracket and everything will keep getting sloppier. But I'll take careful provisions to bend over the cross member a bit more, to not over-torque the mounting bolts, and not over-tighten the belt.

[omniruss]

Hmm, I retract... the lower mount has close to 1/8" of back-and-forth slop. I'll have to come up with something.

[omniruss]

Found some fiber washers at home depot. It wasn't quite the right size, so I sanded it down to fit.
http://i468.photobucket.com/albums/rr41/omniruss/DSC05433.jpg

It's just the right thickness, and it avoids metal-on-metal. Only the bottom mount really needed something.
http://i468.photobucket.com/albums/rr41/omniruss/DSC05434.jpg

Just got back from a test run. No noise, perfect! I'm so relieved. This went on for way too long.

[repiv]

I guess persistence pays off. :thumbup: