After ages hunting down various ideas on what exactly causes this, it turns out its 1 thing that happens to involve to issues! Depending on the state of your runners and the black tabs that slide along the rail, it involves NO assembly!!
As you may guess this has become something of a pain, with various threads shedding no real light, and the issue.... The tabs being loose in the guide rail that the sunroof sits in!
Step 1;
Open the Sunroof fully, best thing to do so you can see what to look at is to place card key in the ignition, and keep your eyes over the top of the front of the sunroof as it opens.
Step 2;
Observe the front outer edge of the runner where the sunroof slides along the rail, you should see I supporting tab that is held in with a Torx screw, this is one of the possible faults.... Here's where the beginning of the fault lies (possibly but bare with me)
Step 3;
If like me you have a scenic MK 2, you will need to remove the long metal trim that runs from the boot to the window with the roof rack tabs on it, prise them of gently from the sunroof side out, the front and back clips are tough or otherwise they will snap (like I did) ***128535;
Step 4;
Remove the Torx screw that holds the sunroof up, don't worry it should just flop off or shatter, providing you support the underneath and gently release the tab, which now should be able to slide freely without the sunroof on it. Then slide it halfway along the roof, and there should be a nice wide point to pull this link out.
Once out you should see a piece of metal with a hole at one end, and two pins with two plastic/rubber runner tabs attached.
Step 5;
Depending on the degree of weathering these black tabs May sustained, they may need to be replaced, they may be scuffed and scratched, but anything more, even if it's cracked or the black shell has worn, change them! Scout about on the ole eBay, they may be £15 or so for the 4 you need but Renault charge nearly £90-£100 for the kit with these in! They should simply slide off the pins that hold them in place on the metal link, but if it's been on there a while, a set of pliers and a gentle twist should do it!
Once you have the new ones (or if they are in okay condition) refit, and apply some grease, just to stop the friction as they do twist and move on the pins under pressure so will be worth it.
Step 6;
Refit the metal link back into the sunroof guide rail, in the reverse of taking it out, line up the tabs with the rail and twist in and should slide back into the gap.
Apply some grease to help lessen the friction of the sunroof. Now do the same on the other side if needed, then refit the Torx screw to the sunroof by holding up the sunroof, sliding the metal link to the position, line up the holes, and screw in.
Step 7 (the bit people DON'T know);
After doing this, I closed the sunroof, and all was good, no whistling..... For about a week!!
Then after tampering I des covered something....
With the sunroof open, if you look along the rail towards the front, the rail goes in a step down sort of shape or a laying down 'S' shape.
This is the problem, this bit is where when the sunroof is about to close, it sinks into the roof, you will know if this is the issue as you should feel play if you have the sunroof is closed and you push upwards against it from the inside, (in mine, the passenger side was the culprit with the noise and had play or a loose feel when pushing against it.
This is down to the 'S' bend bit, widening over time, with the force of the sunroof manoeuvring through it when opening and closing! You may not see it but it's definitely the issue I found on mine!
To solve this,
Simply grab a hammer, and a blunt object, say a large Allen key!
Place the Allen key or blunt object against the upper part of the bend, and tap VERY GENTLY (the metal is ver thin, thus will and can split / crack if hit violently!), but keep tapping from the top to the bottom in a .5 of a cm gaps one tap every 0.5 cm, this should close the gap between the top and bottom of the runner, now I'd advise only do one pass at a time, eg: tap 0.5cms along from top of the bend to where the sunroof stops and check the tightness by closing the sunroof!
Once closed, push up from the inside of the car and you will see the play has gone!
If so this should solve the whistling!
In brief, over time the opening and closing of the sunroof widens that section of the rail causing it not to seat flush into the closed section and this wind wisp up into the gap!!
Try it, take it for a test drive!
Take it from me, before I did this, I only had to drive 55 mph and it would whistle, I took it to 70 on a blustery day after doing this (today) and nothing! No wind noise, no play!
Simply reclip in the metal roof strip, and hopefully hay presto, it's done! No need to grease or remove seals, it's just a wearing issue! The rails seemed to be made out of a thin alloy that flexes easily hence why I reckon the gap widened!!
All that remains is to try it, and let me know how you get on!
I will attach pictures soon as using my iPhone to do this lol.
Sorry if this was posted into wrong section, didn't know where to post this lol
