Fan noise or rattling under acceleration

[Wilbert]

Hi!

I was hoping my inaugural post to the forum would not be in this section (will post a separate post soon on the new acquisition!), but wanted to use the knowledge of you good folks in order to diagnose a noise from the engine bay.

I've recently bought myself a 2003 3.0i 6MT roadster with 206 000km (approx. 128 000 miles) on the odo and it has been fantastic! However there's a noise that occurs at approx. 2.5-3.5k RPM and usually on 2nd or 3rd gear. It sounds like a metal fan or rattling, not really loud but enough for me to notice it. There's also some jerkiness on cold starts shifting from 1st to 2nd. I've recently changed the DISA valve and am suspecting the VANOS, which will be taken care of in the near future, but could this be something else? It does not seem to matter whether the engine is cold or warm. No warning lights or any other symptoms, idle is smooth and stable. I've also decided to replace the air intake rubber boot, as I hear it can cause some nuisance as well.

Possibly paranoid, but I guess it's better to be proactive

Thanks in advance!

 

[bigwinn]

Morning

It would be difficult to do so but try to film/record it? Does it do it when going through the revs when the car is stationary?

Initial thoughts with the mileage would be vanos rattle…

Added to the jerkiness and cold performance

Stuart

 

[Wilbert]

Thanks for the input! I will try to record it towards the end of the week when I have time. Have not noticed it when stationary but again, will see when recording. Also noticed that once the roof is up it is inaudible inside - maybe I'm just on a wild goose chase :roll:

 

[Wilbert]

Apologies for the long delay. I have been unable to get a video of the issue whilst driving, but tried to recreate it revving at idle. Not sure if there is something there or not.

https://youtu.be/o1APWM0BjKg (embedding the video does not seem to work)

Almost dropped the phone at the end of the video, too!

After trying to read more about the issue here and elsewhere, I've decided to try a fuel additive which might cure carbon buildup to some extent. We'll see how it goes.

 

[bigwinn]

I'd check my DISA first bud- search on here how to get it off and check thats not loose- if it is its a big issue!

 

[enuff_zed]

I'd check my DISA first bud- search on here how to get it off and check thats not loose- if it is its a big issue!

Think he's done that already according to the first post?

 

[bigwinn]

I'd check my DISA first bud- search on here how to get it off and check thats not loose- if it is its a big issue!

Think he's done that already according to the first post?

Ah- good spot

Will listen again

 

[enuff_zed]

Sounds like a vibration? Sort of thing you'd hear if a bolt was a bit loose and the washer could move around?

 

[patriot66]

Was your new DISA valve a decent quality one or a cheap Chinese affair ? If it is the latter then bin it ! Ask me how I know
If the DISA is good then I'd bet it's the infamous VANOS rattle. Mine rattled before I rebuilt it last year. Do yourself a massive favour and rebuild it (or get someone to do it for you). It's the one job I wish I'd done immediately having bought the car and not 5 years later :roll:

 

[enuff_zed]

Was your new DISA valve a decent quality one or a cheap Chinese affair ? If it is the latter then bin it !

That does sound a good shout, but I read it that the DISA valve was done to try to cure the rattle that was already there?
Always good to get warnings about these cheap parts though.

 

[Wilbert]

Thanks for the input everyone, really appreciate it! The DISA is to my understanding of OEM quality, although made by Vaico (sure enough cost as much). I will have to try to unplug it next time just to be sure.

It seems like the view here leans on issues with VANOS - might have to bite the bullet and order a fully rebuilt one from Dr. Vanos. What I will try next: use the fuel additive to "cure" carbon buildup, unplug DISA and listen for sounds and replace the VANOS. Will report back once these have been taken care of and what the result is.

Cheers everyone!

Edit: initially replacing the DISA valve was done just due to age (never replaced before) as there were no apparent sounds. The old one was nigh falling to pieces so it was high time too!

 

[enuff_zed]

Thanks for the input everyone, really appreciate it! The DISA is to my understanding of OEM quality, although made by Vaico (sure enough cost as much). I will have to try to unplug it next time just to be sure.

It seems like the view here leans on issues with VANOS - might have to bite the bullet and order a fully rebuilt one from Dr. Vanos. What I will try next: use the fuel additive to "cure" carbon buildup, unplug DISA and listen for sounds and replace the VANOS. Will report back once these have been taken care of and what the result is.

Cheers everyone!

Edit: initially replacing the DISA valve was done just due to age (never replaced before) as there were no apparent sounds. The old one was nigh falling to pieces so it was high time too!

Ah, so there was no noise, you replaced the DISA and a noise appeared?
Unplugging it will possibly make no difference though, as the flap can still rattle, if indeed that is the problem?
Have you tried the old trick of placing a screwdriver against components and your ear on the other end? Sometimes that helps work out where the noise is coming from.

 

[Wilbert]

Have not tried that and for some reason have not put together 1+1 that the sound could be indeed resulting from the DISA change, thicky as I am. Seems that I have a bag of tricks to use now, fingers crossed!