Trunk Boom: I solved it by tightening the rear rubber studs

Many have been suffering from trunk clunk, but I have been suffering from trunk boom. On bad roads, the trunk will give a booming sound and the cabin will suffer from pressure variances pressing against the eardrum giving a sensation of BOOM. After reading the alternate solution for trunk clunk - tightening the trunk clamp - I turned the studs clockwise until they could turn no more. This shortened the studs. Voila! No more trunk boom. This is against expectations - it should be worse, because now the trunk is not so tight anymore. But to start with, the studs on my car were on maximum length, so I guess now it gives the anti-resonance mechanism a chance to work better.

You may have the right idea here. Thinking on it....this would make the rubber bumpers on the sides of the hatch tighter. Worth a try any way.

Ok, so with that a couple of questions first. When you do this is the hatch is easier to close now? Also when it is closed can it move up and down a bit? I have to use a reasonable amount of force to close mine if the windows are up and a firm press down when the windows are down some. I never got the clunk problem fortunately.

1) The hatch has never been easy to close by pressing. However, if I keep one door open, I can close it by just slamming it down. 2) Before and after, you cannot make it move up and down by using your hand. The forces on it during actual car movement are far greater and the size of the hatch makes even a few milimeters movement induce pressure waves. My take is that the anti-resonance mechanism has to have a chance to work. If the latch is too tight, it increases the frequency of the trunk movement, thus negating the efficacy of the anti-resonance mech. Once I shortened the studs, the trunk had more latitude of movement (maybe 3mm worth less tension) and thus, came within the parameters of the anti-resonance mechanism's effective range. It is utterly perfect now, to my surprise.

I just went out and looked at my hatch. The studs were about 3/4 of the way out. In this position when I push on the hatch there is no movement. I screwed them in all the way and now when I push on the hatch there is quite a bit of movement. I'll give it a shot but it doesn't look like it will work on my car.

it made the boom worse in mine! bummer

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Works! Engineer here! Electronics, Communications, Mechanical. Automotive is not my discipline however. Ok so I did the adjustment. caySman you deserve the credit for this one because it pretty well fixes it with an 80% improvement!! Well done!! :banana::beer::cheers: So I checked the result at the hatch. The middle is firm and movement change is not really noticeable. The left and right corners can more a bit more up and down but not much. The force to close it is about the same. Its difficuilt to figure out the exact mechanism of the boom, but I have a new theory. If the lid is held firm, it flexes when you go over bump creating the pressure wave. However if the step function (jolt) is lessened by assorbing the jolt energy transfer (via the rubber seal) then the flex does not occur as much. With all that in mind, it seems the situation is governed by the set-up of the bumpers, latch position, holding force and everything else must be set just right to prevent the problem. An extremely difficuilt task IMO to get just right however it does indicate that its possible to fix all Caymans by way of adjustment. In effect with this, the bumpers are removed from the equation. Bearing in mind if the hatch did not flex in the first place then we would not have this problem. Anyway thats my current new theory now based upon caySman's findings. MANY THANKS

I need to try this in the morning and hope that this works. 80% improvement is better than 0%! Thanks for the tip!

I can't take credit for this. I stood on the shoulders of giants. First was the article on padding the resonance mechanism, which stated a 2-3hz counterweight-based resonance absorbtion. Then was the recent article on solving trunk clunk and boom by tightening the latch. The intuitive leap was adjustment of the rubber studs to allow a suitable tension in order to allow the 2-3hz counterweight to work.

can someone post a quick picture of the rear rubber studs

this is the one, picture courtesy of the excellent alternate clunk solution article.

Woah, now I got some clunk noise now which I never got before. I adjusted them back a few mm's and will see how this goes now.

Tightening the latch helped my clunk. Excellent suggestion.

Dudes: Screwed in (shortened) the two rubber knobs at the corner of the rear hatch about 1/4 turn. Trunk boom/clunk gone! Awesome! I am eternally in debt to whoever figured this out. Ole Joe

If this solution really helps, then it's a validation of the principle of Occam's razor: "All things being equal, the simplest solution tends to be the right one."

No such luck on that theory. Im sure winding them in now changes it from the boom to the cluck. I will do some experiments on this.

Theoretically, continued adjustments via 1/4 turns might solve your issue. Either side.

i tried tightening them all the way up, and got more of a clunk, then loosened them all the way down and got more of a boom, which is better than a clunk i think. Is there a happy medium, where we get neither?

Do they back out all the way (removable)? Then I could lay down a thin silicone gasket... ==RedEye

yes they come out all the way, just like screws.

Im fooling around with a soft peice of rubber in the bump recess.

I found the same thing. Tightening all the way would eliminate the boom, but if one of the rear wheels hit a bump, it produced a bad "clunk" on that side. If both wheels passed over the bump at the same time (like a speed bump) all was well. I have been making small adjustments outwards to see where the best compromise is between "clunk" and "boom".

well let us know if you find the right place for the screws, i too will experiment on this.

what do you mean by recess?

The circular recess the bumpers drop into on the car near the spoiler.

My clunk was not to bad but did happen on certain bumps but the boom or pressure rumble bothered me. I turned the mounting post in 1/4 turn (shortened) and boom/rumble is almost totally gone and the clunk is more of a thud now and much improved. I can push on the hatch lid and there is very slight play in the latch maybe 1/16 of an inch, before the adjustment there was no latch movement at all. Thank you!!!

I went longer then shorter and everything in between. Finally removed the back panel and did the foam weather stripping wrapped around the weight and silence was mine. Worked great. Step by step instructions posted here was perfect. Also the pillow stuffing of the Bose subwoofer also worked wonders. Stuff to taste, I tried various amounts, finally stuffed full and now love my Bose .:banana:

ok, i did one short and one long, and it seems to be much better, still have the clunk but not nearly as much. Try it out, see what you think.

Im not having much luck to stop the clunk without the boom. The cluck is really really annoying , and now I get passengers that ask whats that clunk? So now Im going back to boom. argh....:crazy:

Apologies for digging out an old thread, but has this problem been sorted out on the Gen 2 Cayman ? I felt a bit odd when driving all the loan car Caymans I have had whilst my Boxster has been serviced. I am currently trying to thrash out a deal on a new Gen 2 Cayman , but am a little concerned.....

I know it goes without saying... But I still find it AMAZING that we all have to have this thread in the first place. I'm actually in a fairly zen-like state about it so that mostly I find it comical. Mostly... Then again, I drive fairly rarely these days due to walking to work, so maybe that's the deal... :crazy: