SL55 strange noise/issue - possibly S/C

[Lenny63]

Replacement plastic pulley:

https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.com/ulk/itm/323775727789

Replacement bearing idle metal OEM pulley
Bearing 6203 ZZC3 6203zzc3 6203ZC3 6203zc3 dimension 17x40x12 KOYO JAPAN | eBay

 

[Dickster]

I got the belt off - as you say, very easy (with a 17mm socket).

so I’ll try driving the car Saturday morning and see if it sheds any light.

all the bearings seem good, nice and smooth. But there’s slight play in all of the pulleys, is that normal? The dual pulley has the most play but even the SC pulley has some play.

 

[Lenny63]

My dual idler pulley has slightly play as well...check our the links above as you can replace the plastic (complete) and the bearing in the metal

 

[Dickster]

Tried driving with no SC and the noise is still there. Actually drives ok!

Anyway, the SC still spins with the belt removed, so is the test conclusive?

It does appear to be speed related as the noise starts at around 30. I do need a new throttle pedal ( came up when codes were read) which I’ve ordered, but could that cause the issue?

 

[Alps]

it wont be your supercharger, might be worth popping to an indi to take a quick look

 

[Dickster]

Yeah, I've ordered a code reader, and I want to try that and the throttle pedal before taking it anywhere.

The (water cooling) pump for the SC appears to be a weak spot, and so I wanted to isolate it by removing the fuse. However, looking at the diagrams the fuse should be behind the drivers seat, and the fuse (really difficult to get to with fingers!) is only rated at 7.5A - should be 40A? I haven't yet removed it for fear of not being able to get it back in!

 

[Dickster]

I believe that the 7.5A fuse was the correct one (after a search online), so I removed it and went for a drive - no difference.

It definitely sounds like air escaping rather than liquid (there's no sign of any liquid leaks). Starts at around 30mph, but is not continuous. It does occur at regular intervals, almost in time with the wheels turning, and increases with speed.

What areas/parts would be under more pressure with more speed, rather than engine revs? And was definitely set off by a high speed run.

Hopefully, the code reader will throw up the answer, if not, I'll try the smoke test in the intake.

 

[Dickster]

Code reader pulled up a load of codes but none relevant.

I stopped the SC turning with a wedge and tried again - still no joy.

Noise does not appear until more than 30mph.

I tried driving in manual, to increase the revs. No difference. So the issue definitely appears to be speed related rather than engine rpm or boost.

Tyre pressure monitoring? Could that cause a noise? Loose body panels? I did hear something that sounded like physical "slapping" when it initially happened.

I'm at a loss.

 

[Dickster]

This is driving me nuts. I am determined to solve it without taking it to a specialist!

I'll try removing the wheel, inspecting the tyre, and inspect all the arch liner panels.....

 

[Dickster]

Some further thoughts. Perhaps, it is sucking air (rather than air escaping), from the intake. Bypass valve perhaps?

Is the air going through the filters under much pressure as speed increases?

I am going to start removing items on Wednesday until I find it!!

 

[Dickster]

Finally found the culprit. The plastic under tray that runs the length of the car each side. The drivers side tray had come away at the front, dragged on the road, and gotten damaged. Now there is just a flap at the front of the car that hits the road as soon as you reach around 35mph.

Trimmed the plastic and noise is gone. Now I need a new under tray.......

 

[E55BOF]

Glad you found the solution, and that it wasn't serious.

 

[Dickster]

Cheers, it’s a massive relief, it was driving me nuts!