tompollock Posted January 31, 2023 Share Posted January 31, 2023 I've been trying to find the cause of a rattle coming from the passenger side on lumpy blacktop. Its not coming from the front or rear suspension and sounds like its coming more from the middle of the chassis, but where?The exhaust mounting is sound with a new bobbin fitted, and the windscreen frame screws are all tight, as is the heater box assembly and the dry sump tank. Not much else to rattle.Then came across the Mystery Bolt (11/16 AF with a short head) on the inside of the "door" card adjacent to the lower edge of the dash. Could this be the culprit? This was a little loose and took nearly a full turn to tighten up. What does this retain? There isn't a corresponding bolt on the driver's side.Thanks in advance,Tom. Link to comment Share on other sites More sharing options...
Area Representative paul richards Posted January 31, 2023 Area Representative Share Posted January 31, 2023 Sounds like a bolt used to blank the hole where the petty strut goes. Doubt that's your rattle. Link to comment Share on other sites More sharing options...
TomB Posted January 31, 2023 Share Posted January 31, 2023 It took me a while to find it, but my LH sidecrotch belt adjuster rattled on the floor. I put a thin piece of tool drawer foam under the tiller seat and it stopped the noise. Link to comment Share on other sites More sharing options...
SM25T Posted January 31, 2023 Share Posted January 31, 2023 Sounds travel around a 7 chassis. It could be somewhere different ! Link to comment Share on other sites More sharing options...
Wrightpayne Posted January 31, 2023 Share Posted January 31, 2023 Thin headed bolts are only used in two places - rear brake disc to hub and rear FIA bar or cage bolts that fit over the top of the shocks. The FIA bar bolts are 5/16 UNF (shiny top one) and the cage bolts are 1/2 UNF (powdercoat covered bottom one - used to hang the cage from when coating!)are they like one of these... Link to comment Share on other sites More sharing options...
tompollock Posted February 1, 2023 Author Share Posted February 1, 2023 Yes, its bright cadmium plated and shiny. Haven't taken it out to measure diameter but similar to the bolts that used to retain an old fashioned seat belt swivel bracket, the one mounted on a saloon B post. The rattle occurs with a passenger strapped in so don't expect it to come from the seat belt or fittings. Link to comment Share on other sites More sharing options...
Leadership Team SLR No.77 Posted February 1, 2023 Leadership Team Share Posted February 1, 2023 Have you checked the great big jubilee clips on the exhaust heat shield? Link to comment Share on other sites More sharing options...
tompollock Posted February 1, 2023 Author Share Posted February 1, 2023 Mine doesn't have a heat shield. Link to comment Share on other sites More sharing options...
Area Representative Geoff Brown Posted February 2, 2023 Area Representative Share Posted February 2, 2023 I had a similar annoying mid chassis noise in the nearside area that I could not locate by checking all the usual suspects.Try checking the pax seat to rail attachments for tightness. Once tightened no more annoying 'buzz'. Link to comment Share on other sites More sharing options...
tompollock Posted February 2, 2023 Author Share Posted February 2, 2023 Thanks Geoff. I'll try the seat fixings anyway but its a definite rattle, not a buzz or a sizzle, and is dependent on the depressions in the road surface and not on engine revs/hf vibrations. Link to comment Share on other sites More sharing options...
Gridgway Posted February 3, 2023 Share Posted February 3, 2023 I'd be looking at suspension if it's road surface dependent. Drop links on rear arb perhaps?I've discovered such problems before using a shaker plate (probably wrong name) that mot places have. Link to comment Share on other sites More sharing options...
Ivaan Posted February 3, 2023 Share Posted February 3, 2023 Loose baffles inside the exhaust can? Link to comment Share on other sites More sharing options...
Bumble Bee Posted February 3, 2023 Share Posted February 3, 2023 My Sigma Roadsport had an annoying rattle from passenger side which took me ages to diagnose. Eventually tracked it down to loose rivets fixing the screen wash bottle bracket to the bulkhead. The noise reverberated like a drum! I drilled out the rivets and replaced with bolts & nyloc nuts. No more rattle (except the usual 7 noises).It may not be your rattle, but worth checking. Link to comment Share on other sites More sharing options...
tompollock Posted February 4, 2023 Author Share Posted February 4, 2023 Thanks for all the suggestions. I'll rule out the silencer for now because I've just had it off to get the front tube re-welded where it had parted company with the box itself - absolutely sound as a pound inside there with nothing loose, surprising after so many years. It's also just been through the MOT and I know what a stickler the tester is, he lets nothing through. I'll check the screen wash bottle though and anything else fastened with rivets. It's not going to get the better of me! Link to comment Share on other sites More sharing options...
AndyOH1697456946 Posted February 4, 2023 Share Posted February 4, 2023 Mine made a tapping noise on uneven surfaces from the rear I just couldn't identify. To cut a long story short after Tim Ward from sevens and classics drove the car he identified the noise a the float on the fuel level sender hitting the side of the tank. Link to comment Share on other sites More sharing options...
SM25T Posted February 4, 2023 Share Posted February 4, 2023 #14 ..... are you using the centre support ? If not it is common for the continual sag and bounce to fracture the front end of the silencer. Happened to me too. Now got another bracket welded to silencer to pick up centre support bush in the chassis. If you don't have the hole exposed, it is between 803-805mm from the rear one. Link to comment Share on other sites More sharing options...
mjdm Posted February 5, 2023 Share Posted February 5, 2023 Loose honeycomb in the side chassis? I think they are only held on by double sided tape. I have a constant 'knock' on uneven roads that I've never managed to trace and am assuming it's inside the side panels. Mike Link to comment Share on other sites More sharing options...
tompollock Posted February 11, 2023 Author Share Posted February 11, 2023 Hi Everyone,Thanks for all the suggestions . My C7 is a 1990 1700 Supersprint (no honeycomb in those days!) with competition manifold. There is no centre exhaust support bracket on this model but that's just down to poor engineering in the first place.The system really needs extra support.As I said I've just had the silencer front pipe re-welded to the main box after the weld failed. I'm amazed the manifold itself hasn't failed somewhere considering all the loads placed upon it. A little job for me to rectify in the future. I think I'll revisit the underside next and look around the gearbox mounting area for the source of the rattle.Meanwhile here's the MYSTERY BOLT. Lhs door card. Not one on the other side. Still no ideas anyone? Link to comment Share on other sites More sharing options...
John Vine Posted February 11, 2023 Share Posted February 11, 2023 #18: Meanwhile here's the MYSTERY BOLT. Lhs door card. Not one on the other side. Still no ideas anyone? Didn't #2 have the answer?JV Link to comment Share on other sites More sharing options...
Area Representative paul richards Posted February 11, 2023 Area Representative Share Posted February 11, 2023 Yes. That's blanking the hole where the petty strut goes. Link to comment Share on other sites More sharing options...
tompollock Posted February 12, 2023 Author Share Posted February 12, 2023 Thanks Paul. I saw your original answer but didn't realise the petty strut went that far forward. Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now