Strange rattling sound in the engine...
 

Hiya all,

My Blob 2005 STi has just started making a very strange rattling noise at idle. The engine doesn't seem to have lost any power, and the temperature guage is what its normally on. When I opened the bonnet to film the noise it did seem a bit hot but I don't know if its always like that or not.

I've filmed it in the hope that someone will know what the sound is indicating is wrong!?

Thanks for any and all advice in advance!

Cheers!

Video is here -: http://www.youtube.com/watch?v=E58W8...ature=youtu.be

does it increase if you rev it?
sounds a bit belt/pulley related

get a long screwdriver and put the pointy end near a pulley and your ear on the handle and go round by the moving parts

Does the rattle go away when you push the clutch in?

Brilliant thanks for the advice Fudgey - it seems to disappear when you rev it a bit, and you can't hear it when you are driving.

6Volt - I'm not sure, I'll go and check and report back in a moment.

Didn't notice the video earlier, as fudgey says, sounds like a belt/pulley, try just pushing on the belts with your finger (engine off obviously) and see if you have much slack in them? It sounds a bit like your alternator belt is slipping a bit. Mine needs tightening every so often. If not it chirps a bit ike yours

JUst gone out and driven the car for twenty minutes - and as luck wouldn't have it, the car didn't make the noise! Annoying as I would have been able to get straight to the garage and have them look at it!

Because it isn't making the noise, I can't test if the clutch being pressed makes any difference.

I felt the air-con belt and the alternator belt, and to be honest they didn't feel slack at all.

I replaced the air con tensioner pulley about 6 months ago, as the previous one failed - I'm wondering if the new one could be on its way out, and thus making the noise? I've squirted a bit of WD40 on it, but again, because it wasn't making the noise to begin with today I don't know if I've fixed it or not.

My big concern is that it could be the cam belt about to go tits up? I did have that (and all tensioners, pulleys, water pump etc) replaced 5000 miles ago, so it should be unlikely, but is it possible?

What I guess I'm wondering is does this noise sound expensive, or just something that needs to be fixed but can be done relatively cheaply? I don't fancy a £3000 rebuild!

Thanks for all responses, appreciated!

Just seen this video on YouTube - I'd say its the exact same noise. The chap there reckons its his air con compressor. I think theres a good chance it could be the same on mine, I've used the air con loads over the last 3 days as its been so hot, and I've never used it before...

My video is here -: www.youtube.com/watch?v=E58W8zw6qo4

His video is here -:

I doubt very much it would be your cam belt, if you rev it it by pulling on the cable at the throttle body and it goes away when you rev it I would guess that it is something to do with your tension / pulley system. Ie. When revved the slack is taken up a bit thus stopping the slip of the belts. It takes a few minutes to take the auxiliary belts off , do that and give your tensioners/pulleys a spin to see if they make any noise when moving.

Just to add on that last vid.. It sounds a lot more aggressive than yours, almost like a shot bearing on one of the pulleys

Sounds like the best thing to do then is get those auxillary belts off (air con and alternator belt are two separate belts yeah?), and see if the bearings make any noise.

I think thats the first port of call, and then see what happens once thats been done.

However, I'll ask my girlfriends brother to do it, as he's a mechanic - I don't fancy the job myself if I'm honest.

Thanks loads for the replies so far though, really appreciated mate!

Yup, just 2 belts, easy enough to do.
Good luck getting it sorted

if you replaced an aux belt a little while ago, how tight did you do it?

as it could be too tight. that will result in bearing wear eventually. once the belt is fitted you should be able to twist it on its longest run (2 pulleys furthest apart from each other) about 45 using your thumb and forefinger. if wont twist that much without too much effort its too tight. if you can twist it say 90 degress its too loose.

if you can take the belts off, hold the pully by the top and bottom and see if it will rock on its axis. if it does then its worn bearings.

has it only made the noise since you changed the belt?

When the aux belt was replaced, it was done by a mechanic not me, so I don't know how tight it was done. I've gone out and checked the belts, and it does seem that they go about 45 degrees or thereabouts, so I think thats ok.

I'm pretty sure the noise was coming from the air conditioning compressor, as its only happened in the last few days since I've been using the air con - which I've never used before! And since I've turned off the air con, the following days the noise hasn't happened...!

Just been down to the garage to book a set of Bridgestone S001 tyres and some new brake pads though, so all good for now!

Thanks again for all the reponse/advice, cheers!