I noticed a judder sound from the engine compartment on idle, intermittent but constant, if you know what I mean, on and off Only noticed it when I started the car to go home from work today, only on idle, when I revved it went.

Got home and listened with the bonet open and it was from the left side, looked around and saw a part attached to the engine was shudering quite violently when the sound occured, I have no idea what the part is or whether it should be doing that.

Have attached image and circled the part that is shuddering.

Really I want to know if it's driveable as I'll need to get the train otherwise.

Edited 23 October, 201312 yr by Antimus

That looks like the aux belt tensioner.

 

If it is juddering then either the tensioner is failing or the alternator pulley has failed.

Ok, assuming one of those 2 things is true my question then, is it safe to drive for a day or 2 until I can get it to a garage or should I be taking this STRAIGHT to the garage?

You need to take care. In theory you can drive it, but if one of these components fails completely and the aux belt comes off there is a very small chance that the loose aux belt could get tangled in the cam belt and cause the cam belt to fail too....causing many £££ of damage.

 

It's unlikely but is possible.  

Who knows?  It could be fine...  It could frag at next start up...

More usefully, if it fails, it could throw the drive belt, which will leave you without any current to your battery.  Depends on the state of your battery how far you get.  Will you be far from home? Will you be in the middle of nowhere?  Will it make you miss an important appointment?  Will worrying about it distract you so you make a silly mistake?

A booke23 says, the impending failure could result in mechanical mayhem which could destroy your engine. 

Weighing the odds about the consequences of failure is what keeps you awake at night.

Thanks for the help guys

I initially thought mine was making a noise on idle from the same place, turned out to be the DMF!

However, if you can see your tensioner moving and it coincides with the noise, then I doubt it's that same as mine.