Rattle at idle - 1.9TDI PD

[sasquartch]

Recently my 2005 TDI 115 has developed an intermittent rattle at idle that seems to disappear once the revs get past say 1500.

It seems worse when hot but sometimes almost goes away then comes back again.

The car drives fine and the engine power seems normal.

I beleive the 115 PD does not have DMF and as said drives fine.

I've had a listen to it and of course the noise isn't there so much at the moment but there is definitely a hard rattle present on the drive belt side of the engine.

The aux belt seems to run true.

Any ideas ?

I'll wait until it comes back and have another look but any pointers would be welcome

[insanitybeard]

I'm pretty sure you'll have a DMF- most of the Mk2 TDI's will have one I would think. Is the noise a metallic rattle?

Might be worth pulling the top plastic timing belt cover off and checking the cambelt condition/ tension, is this due anytime soon? If you've got a dodgy bearing in the idler, tensioner or water pump it could also make a noise but that'd be more of a squeal than a rattle I'd expect, unless it was sloppy enough to be knocking.

Could also be something other than the belt in the auxiliary belt system like the belt tensioner, air con compressor, alternator clutch pulley etc.

Next time it happens see if you can make the noise change by pressing the clutch pedal in or by switching on the air con, heated front screen or turning the steering lock to lock etc.

[mrhiviz]

Hi.

Mine is a wee bit rattly at times. I'm sure it's alternator related as I think it generally happens when the alternator gets an electrical load. At other times it's almost sewing machine smooth. ( and I don't mean when it's switched off!) Don't know if this helps...

[sasquartch]

I've ordered a new aux belt tensioner - the rattle seems to be in this area although cant be sure.

At 99k miles its probably well past its best so wont do any harm to change it

Will let you know the result.

[insanitybeard]

I renewed my tensioner earlier in the year, it wasn't noisy really but on a few occasions the auxiliary belt started to slip with the steering on lock (extra load on the power steering pump) and the heated front screen on (large load on the alternator), so in my case it was more that the tensioner spring had weakened with age and use rather than the unit being noisy.

[SirDavidAlhambra]

Water pump on its way out? I had a terrible rattle once on my Saab and it turned out to be the water pump. Couldnââ,¬â,,¢t hear it at high revs but was very loud at idle