Nightmare rattle/ knocking - LotusTalk - The Lotus Cars Community
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post #1 of 21 (permalink) Old 09-25-2018, 06:58 PM Thread Starter
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Nightmare rattle/ knocking

I have a crazy rattle at 65mph and up. I have taken the entire dash apart . Fender liners . Everything . And from my research this doesn’t seem
Like a common one but it is almost undrivable on the highway . Attached a video. Andy help/ ideas would be awesome
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post #2 of 21 (permalink) Old 09-25-2018, 06:59 PM Thread Starter
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post #3 of 21 (permalink) Old 09-25-2018, 07:28 PM
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@LFMWaffles - If it is speed related, then it could be caused by aerodynamic forces or by an out of balance wheel and tire. My first guess would be to look at the underbody panels (forward and middle undertrays and the rear diffuser). Ensure these panels are secure with all fasteners in place and tightened.

Two large bolts secure the leading edge of the diffuser and are covered by the middle undertray. I once installed these two bolts loose, then installed all the other fasteners. I forgot to tighten the two bolts and installed the middle undertray. While underway, the bolts backed out and rattled against the undertray . . . a heck of racket.

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post #4 of 21 (permalink) Old 09-25-2018, 07:57 PM Thread Starter
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I guess to add more clarification . The sound comes from RF . In front of passenger . And sounds like a small flag pole hitting the aluminum or something. It’s speed related but seemingly only because of the amount of air hitting whatever is rattling . It’s more random than something rotational . And yea checked every panel underneath
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post #5 of 21 (permalink) Old 09-25-2018, 09:17 PM
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Did someone drop a coin or something down defroster?

(Happened to me....)

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post #6 of 21 (permalink) Old 09-25-2018, 09:19 PM Thread Starter
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A coin ?! Why would they do that ... lol I might have to pull the dash and vent part again
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post #7 of 21 (permalink) Old 09-26-2018, 04:28 AM
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Quote:
Originally Posted by LFMWaffles View Post
. . . The sound comes from RF . . .
More guesses. Do you have an oil cooler? The oil cooler lines are secured with a tywrap through a plastic block held to the crash structure with double-sticky tape. The tape gives up over time and could allow the line to move around.

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post #8 of 21 (permalink) Old 09-26-2018, 04:38 AM
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To me, I am going with the suspension related or aero related. Think of the frequency of sound a 67 pickup with a broken shock makes, even on smoothish pavement, that kinda rat a tat rat a tat. The speed variation due to either the normal wheel imbalance that is no longer restrained properly or the windforce getting high enough to start moving a panel in and out of the air flow.

If it really sounds like it is coming from the passenger footwell, perhaps it is telegraphing in that right rack mount.

Maybe take that passenger sill panel off and the foam underneath out, have a passenger reach in and grab the hoses etc to see if the vibration can be felt.
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post #9 of 21 (permalink) Old 09-26-2018, 05:21 AM
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It almost sounds like debris flapping around behind the passenger footwell vent leading to the blower fan. That might explain why you hear this more at speed from the increased cabin air flow. Does the rattling change at all if you turn the HVAC fan on?
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post #10 of 21 (permalink) Old 09-26-2018, 06:15 AM
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Quote:
Originally Posted by LFMWaffles View Post
And yea checked every panel underneath
How did you check, and what panels did you check? Also, do you have any aftermarket pieces like side skirts or a splitter?

"Lots Of Trouble; Usually Serious"
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post #11 of 21 (permalink) Old 09-26-2018, 06:31 AM
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@LFMWaffles - Another thing to check is the anti-rollbar mounts. They are on the other side of the forward bulkhead.

Quote:
Originally Posted by cyow5 View Post
How did you check, and what panels did you check? . . .
It’s a pain, but thoroughly investigating each suspect is the fastest way to find the culprit. The forward undertray has lots of little fasteners near the lower trailing edge of the clam - I don’t remember any empty holes, so if you see any, they would bear investigation.

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post #12 of 21 (permalink) Old 09-26-2018, 06:44 AM Thread Starter
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Thanks for the help everyone. I found it . After about 6 hours of fun. I’ll post a picture after work
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post #13 of 21 (permalink) Old 09-26-2018, 07:29 AM
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Wow. I've read what seems like hundreds of these threads over the years and it is rare that someone solves it!
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post #14 of 21 (permalink) Old 09-26-2018, 07:32 AM Thread Starter
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This was the culprit .... taped it down and all gone . What a loud noise from a tiny piece of plastic . Never made noise till recently . So strange
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post #15 of 21 (permalink) Old 09-26-2018, 07:50 AM
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I think that is the water drip from the A/C? No one will believe me now but I was about to suggest that.

Before I knew what that was for on my car, I added a plastic zip tie to mine since it looked loose.

Last edited by David Craig; 09-26-2018 at 08:02 AM. Reason: grammar
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post #16 of 21 (permalink) Old 09-26-2018, 08:01 AM
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Here's the hose on my car for comparison. I tied it and also tried to raise it a bit so the profile of the car from underneath would look better.
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post #17 of 21 (permalink) Old 09-26-2018, 08:03 AM Thread Starter
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Haha! Crazy. Glad it was simple. Sad I spent so much time for a tiny stupid hose . Oh well. Hope it helps someone else someday
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post #18 of 21 (permalink) Old 09-26-2018, 11:05 AM
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Oh now that is funny


Supposed to be a little ty wrap mount holding it down I think
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post #19 of 21 (permalink) Old 11-26-2018, 06:32 AM
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I'm glad I had been reminded of the A/C hose recently in this thread.

My car started to make a rattling sound that sounded like a loose plastic fitting. It sounded like it was something near the passenger seat, possibly a loose fitting in the door.

Anyways it turned out to be the A/C hose. I had put a plastic tie there a few years ago but it seems to have come loose. I put another tie on there for now.

As I was posting this picture I noticed that there is a hole in the aluminum frame nearby. I might redo the plastic tie so it goes through that hole. In fact, that's what I had done originally.
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2009 Saffron Elise
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Last edited by David Craig; 11-26-2018 at 06:35 AM. Reason: more detail
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post #20 of 21 (permalink) Old 11-26-2018, 06:38 AM
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I should mention too that the noise was very annoying. It made the car sound like a cheap plastic toy.

I'm really happy that this noise only appeared now. I had just returned from an 11 day road trip to the US and had the car being making this noise I would not have enjoyed that trip at all.

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