Whistle and rattle = unhappy Captain

[jasper5]

Whatever your interpretation of "adverse use", I always believe in changing belts sooner than the recommended time.

Don't forget, that there is also a time limit, eg, 5 years or 96,000 miles, whichever comes first.

[Captain Jack]

Next time I post with a problem, just ignore me 'cos I am wasting everyone's time. (I am just saying that, really...)

Basically, the rattling/whistling has sod all to do with the bottom pulley - or anything in the engine for that matter. I was driving back home on the motorway, doing 60mph, listening carefully to the engine for signs of bottom pulley disintegration. The radio was set to 0 volume. As is usual, traffic announcement came on at full volume, scaring the bejesus out of me. In annoyance, I promptly switched it off using the "off" button and resumed listening to the engine... only not to be able to hear any more whistling or rattling See where this is going yet?

Yep, the "rattle" was coming from the speakers. Or to be precise, from the new amp that I replaced the factory JBL one with. As the radio with the volume down still turns the amp on, I was listening to the speakers humming thinking it was the engine. DOH!

Anyway, this is obviously an alternator whine problem finding its way into the amp. It's power fed directly from the battery, with the ground point somewhere under the rear seat. I have temporarily gotten rid of the whine by turning the input sensitivity down, but I guess I'll have to fix it properly (finding a better earth point or some noise suppresion jobby).

Topic closed (but if anyone knows of a simple way to get rid of alternator whine, I am all ears)

[HimBigChief]

You can get inline supressors for alternator whine. Not sure if ground loop isolators are just a fancy name for the supressors, but you can get them aswell. Assuming you're using RCA cables to connect the headunit to the amp, here's an eBay linky.

[jasper5]

Put an extra earth wire to the alternator from the body (a thick one, at least 8mm).

Put an extra earth wire to and from the amp, again, about 8mm.

[Welly]

You Doughnut Cap'n

Actually my standard jbl setup used to make a faint whine/whistle from the speakers

[steve_earwig]

Hi there, just passing through (v. v. v. busy ) I just thought I'd agree with Jasper et al re belt life, anyway how do you know the miles are correct and how it's been driven? I think I'd be changing the belt regardless...

[Captain Jack]

Put an extra earth wire to the alternator from the body (a thick one, at least 8mm).

Put an extra earth wire to and from the amp, again, about 8mm.

Where does the wire connect to on the alternator?

The positive and ground wires to the amp is already around 8mm - I do have another one I can use though.

[mjb]

In annoyance, I promptly switched it off using the "off" button and resumed listening to the engine... only not to be able to hear any more whistling or rattling

Excellent!

[Captain Jack]

The funny thing is, if I did remove the aux belt, the rattle/whine would disappear, further misleading me to the problematic crankshaft pulley!

I ordered some ground loop isolators, so hopefully they'll do the job. I also temporarily tried connecting the ground point of the amp to the chassis of the factory head unit and the whine was reduced by quite a bit. So, tomorrow I'll run a cable to it properly, hopefully cancelling out the inteference.

[406silverhdi]

get the belt done sooner rather than later, you probably wont own the car when its due its next cam belt, so get it done

[HimBigChief]

Thinking about it, how good an earth point does the amp have? If it's not a very good earth then it can cause similar problems. I remember having a similar issue years ago when I had huge stereos in my car. Cleaned up the earthing point and it made the issue a lot better.

[jasper5]

Put an extra earth wire to the alternator from the body (a thick one, at least 8mm).

Put an extra earth wire to and from the amp, again, about 8mm.

Where does the wire connect to on the alternator?

Use one of the alternator mounting bolts, fit an earth lead that would normally be used as a battery earth, ie, a thick cable with a mounting hole at each end.

[Captain Jack]

Thanks Jasper. A job for the weekend.

I'll wait for the belt till my next service (7000 miles to go). I do around 700 miles a week so that'll be about 2.5 months

[bangernom1cs]

Whoah there!

I said that and lost the tensioner last week at 63,000.Belt slipped a few teeth and sounded horrendously loud.
As a P.S. the mechanics (and the AA man) were telling me that on HDi engines the rocker arms are designed to collapse
with total belt failure thereby saving the valves and pistons.
Is this true?

T

[steve_earwig]

Yep. Although I'd guess how effective this is would be inversely proportionate to engine speed...