Weird noise at 2900rpm!!

The Oily Bits S1 Specific Topics
1

Hi guys,
has anybody had a noise coming from the rear of the car whenever the engine is at approx. 2900rpm? Sounds like its coming from the exhaust.

Rooney

2

What kind of noise? A rattly tizzy noise (could be baffles / something loose on the exhaust) or resonant?

Or grinding screatching metal on metal noise (not good ) ?

3

I would also suggest baffles - my original ones blew out in a couple of thousand miles, and sounded like I had just got married and was towing Heinz’s entire 57 along behind me…

4

Yeh it is a rattly tizzy noise, but only at 2900rpm! I suppose the only way to know is to put on a ss exhaust. Want one anyway.

Rooney

5

It could just as easily be the undertray or diffuser. Get under the back of the car and try tapping in various places. The bolts could be loose, or you might need a bit of foam tape sticking along the edge where the two panels meet.
On my car, one of the bolts securing the rear edge of the diffuser panel was long enough to just touch the silencer. I cut the end off the bolt, and problem solved.
I’ve also had a rattle from the boot tray panel when one of the securing bolts came loose. It might be worth checking that as well.
Come to think of it, I found another rattle in the boot; Somebody had left a large washer lying under the foam boot liner.

6

It could just as easily be the undertray or diffuser. Get under the back of the car and try tapping in various places.

Very true, I find that the two large central allen key bolts will always come loose if you do not threadlock them in. The other bolts go into c clips and so are exposed on the inside - dirt tends to get into the threads and make sure they don’t move easily.

7

…if you do not threadlock them in.

Bloody good, that Bob Marley bloke isn’t he?

8

…if you do not threadlock them in.

Bloody good, that Bob Marley bloke isn’t he?


LOL

9

Hi Rooney,

I seem to be the only one who has solved this problem in this way…I had a similar noise . I was convinced it was the undertray but when i got underneath a cold engine it seemed fine . It was ages before I realised that when the thing got hot, the exhaust expanded just enough to start vibrating against the edge of the cut out in the undertray . A bit of judicious re-shaping solved the problem . Result = no ‘zizz’

Regards

10

Thanks 83, was the zizz noise happening at all revs or just a specific amount?

11

Thanks 83, was the zizz noise happening at all revs or just a specific amount?

Rooney
Are you thinkin that if it was the undertray rubbing youd get it at every engine speed ?

12

I would have thought so. Its like it only happens when the exhaust vibrates at a certain frequency.

13

it’ll have a resonant frequency and depending on some other stuff you might not get it at other speeds or it might not be vibrate enough to cause the ‘tizz’

14

tiz a mystery, then…

15

i’m in a tizz … having just come home from a Burns supper…

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i’m in a tizz … having just come home from a Burns supper…

Yeh, Mike - my wife cooks like that, too

17

Yeh, Mike - my wife cooks like that, too

LOL

18

Thanks 83, was the zizz noise happening at all revs or just a specific amount?

Mostly at low revs, although variable with load, attitude etc - all to do with the engine and ehaust moving about on their mounts I suspect.

Regards