[Sejin26]

My sons 100 came back from the workshop 2 days ago after having a new engine put in. The problem is there is a noise between 1500K and 2500K it sounds like something is rubbing. Now I know it's not the engine as the noise was there with the old engine. But the back breaks have been checked and adjusted by myself this afternoon so it's not them. The noise does sound like it comes from the back of the car. I will try and get a clip of the sound but all I can descried it is like a groan sort of noise.

Any help would be great as I am stumped.

 

[MattL]

but it only happens at specific rpm? Does it happen when the car is stationary?

 

[DEViANCE]

could one of the exhaust clamps be loose? and it only rattles/groans at a certain back pressure...

 

[Sejin26]

Could be but the hole exhaust is brand new except the cat. I will check the tomorrow.

 

[randomdave]

Hi, Could be a rear wheel bearing or an unbalanced rear tyre. An unbalanced tyre can give all kinds of symptoms like vibration and sound resenance through the car. Also check the exhaust isnt touching anything metal under the car like the bodywork or the suspension try sitting someone in the car to see if the suspension touches too.

 

[Sejin26]

Well I took it out on the motorway for a good half an hour and the noise gets unbearable. It only does it when the car is warm and it happens between the revs that I said but you just have to tap the throttle pedal and the noise is there. To be honest I don't think the noise is from the rear of the car but just sounds like it is. It does not seem to do it an more or less if you go round corners but it does do it more if say you get to 30MPH and put it into 5th and make the engine work more the noise is louder and worse.

 

[Vincero]

Check that the airbox and general air intake system is secured properly. Get junior to rev the engine whilst you have a look and listen as to what it may be.

 

[Sejin26]

Filter is new as is most of the air box pipe work. When you rev it on the drive it's fine. Luckily enough for me I live on a little private estate and I did it when I got home and the noise is not there at all.


Keep the suggestions coming.

 

[Sejin26]

When driving the car today I decided to have the window open and you cant hear the noise outside the car. So what could it be?

 

[Dr Dave]

Loose spanners in the boot?

 

[Vincero]

I just had a crazy idea involving 4 axle stands.........

 

[Sejin26]

No spanners in the boot. The only thing in the boot is a spear wheel.

 

[MattL]

see if you can still hear it when the clutch is dipped while the noise is happening, first of all see if you can hear it when the revs drop to idle but moving at the same speed then see if it will do it when raising the revs to where the noise was before but with the clutch dipped.

Basically im trying to decide wether its speed related or engine speed related. Powertrain noise or non powertrain noise (such as bearings)

 

[Sejin26]

Ok thanks MattL I will try it later tonight.

 

[Sejin26]

Tried what you said. The noise is there when the clutch is down but it is a lot more faint and only starts at 2500K instead of 1500K. When the clutch is full up it starts at 1500K and stops at 2500K.

Hope that makes sense.

 

[Sejin26]

Decided to take the spear out and see what happened. It was not better or worse. Has anybody get any ideas. The noise was there with the previous engine and is there now on the brand new one so it cant be that.

 

[randomdave]

Gerbox bearings? The input shaft turns a bit in neutral with the clutch in thanks to drag but not as much as with the clutch engaged giving a reason why the noise is there but less evident with the clutch dis-engaged and more promenant with the clutch engaged. Im thinking input shaft bearings in gearbox. While driving these bearings will give a rough rubbing noise almost crunchy sounding and will appear moreso under load at low revs because thats where your engines peak torque is.