7 replies to this topic

[Cooper Mac]

Hi all!

I’ve just finished 2 week since the Mini had been back on the road, and have now covered just over 400 miles of shake down.

Yesterday I noticed a noise like a vibration when driving, but couldn’t locate it. I had greased all of the suspension before the noise started, and today, I’ve checked all of the front suspension, changed the knuckle joints and looked for anything loose.

I took it for a drive this evening, but the vibration is still there! It is only noticeable when the engine is running between 1700 and 2000 rpm. I can make the vibration appear by holding the revs in this range, and make them disappear by knocking the car into neutral and coasting. The noise come in on increasing or decreasing revs. Because of this I’m 99% sure it’s just a resonance.

I was thinking it could be either the brake or Petrol pipe vibrating against the floor, but then wonders if it could be the exhaust? The noise may have only appeared since I refitted the exhaust last week, due to a slight leak. When I fitted the exhaust I checked that wasn’t touching anything…..

The exhaust is a maniflow LCB, stainless linkpipe and stainless single back box RC40. The back box is on rubbers and is free to move.

If it is the exhaust, how to I stop it vibrating, other than clamping some weights to it to change it’s natural resonance?

Below is a clip of the test drive this evening….

https://youtu.be/d7hIPu6Uzuc

Cheers!

[DeadSquare]

" I took it for a drive this evening, but the vibration is still there! It is only noticeable when the engine is running between 1700 and 2000 rpm. I can make the vibration appear by holding the revs in this range, and make them disappear by knocking the car into neutral and coasting. The noise come in on increasing or decreasing revs. Because of this I’m 99% sure it’s just a resonance."

 

When you knock it into neutral, do you keep the revs between 1700 and 2000 ?

 

Does it happen in more than one gear ?

 

Does it happen when stationary if you use the "slow running / idling" screw on the carb, to bring the engine speed up to the critical rev range ?

 

[slidehammer]

If the noise seems to appeared after you refitted your exhaust I would start double checking that isn't the cause. See if you can put your hand on the transmission tunnel and feel any knocking. I had a similar problem and the silencer was knocking on the seat belt mounting point on one side and you could feel it through the floor.

[Cooper Mac]

" I took it for a drive this evening, but the vibration is still there! It is only noticeable when the engine is running between 1700 and 2000 rpm. I can make the vibration appear by holding the revs in this range, and make them disappear by knocking the car into neutral and coasting. The noise come in on increasing or decreasing revs. Because of this I’m 99% sure it’s just a resonance."
 
When you knock it into neutral, do you keep the revs between 1700 and 2000 ?
 
Does it happen in more than one gear ?
 
Does it happen when stationary if you use the "slow running / idling" screw on the carb, to bring the engine speed up to the critical rev range ?

Thanks Deadsquare, it happens in any gear and in idol in that rev range. I haven’t tried it while stationary I must admit!

Maybe I’ll give that a go tomorrow!

[Cooper Mac]

If the noise seems to appeared after you refitted your exhaust I would start double checking that isn't the cause. See if you can put your hand on the transmission tunnel and feel any knocking. I had a similar problem and the silencer was knocking on the seat belt mounting point on one side and you could feel it through the floor.

Hi Slidehammer, I have tried feeling the transmission tunnel, but I can’t feel anything through it, but then there is a lot of dodomat, heat matting and the original carpet underlay, so this might mask it!

I’ll have another look underneath and probably just remove the exhaust and refit again and see what happens this time…….

[slidehammer]

 

If the noise seems to appeared after you refitted your exhaust I would start double checking that isn't the cause. See if you can put your hand on the transmission tunnel and feel any knocking. I had a similar problem and the silencer was knocking on the seat belt mounting point on one side and you could feel it through the floor.

Hi Slidehammer, I have tried feeling the transmission tunnel, but I can’t feel anything through it, but then there is a lot of dodomat, heat matting and the original carpet underlay, so this might mask it!

I’ll have another look underneath and probably just remove the exhaust and refit again and see what happens this time…….

 

That sounds like a plan, just try and get it as centred as possible in the tunnel. Also check it is nowhere near the gear change. Good luck, these can be very frustrating jobs to resolve.

[roughneckin]

If the noise seems to appeared after you refitted your exhaust I would start double checking that isn't the cause. See if you can put your hand on the transmission tunnel and feel any knocking. I had a similar problem and the silencer was knocking on the seat belt mounting point on one side and you could feel it through the floor.

Hi Slidehammer, I have tried feeling the transmission tunnel, but I can’t feel anything through it, but then there is a lot of dodomat, heat matting and the original carpet underlay, so this might mask it!

I’ll have another look underneath and probably just remove the exhaust and refit again and see what happens this time…….

I just went through the tunnel and exhaust rubbing issue and the biggest thing I found was I could feel the vibration through the gear shifter a lot. Ended up being that I’d lost a bolt on the tunnel at the gear shifter end and it had shifted over and touched the exhaust. Maybe not your issue at all but figured it may help someone else too.

[Cooper Mac]

UPDATE!

I got time today to have a look at the exhaust. I couldn’t see if it was touching anything at the front, but when I waggled the tail pipe, I could hear the front of the exhaust hitting a fixing on the heat shield!

I removed the rear box and pipe from the LCB, cleaned them and then refitted them, and couldn’t make it hit the heat shield again. A 90 mile drive then confirmed that the problem was solved!

Thanks all!