Help! Knocking/Rattling noise coming from engine bay...

[Matt 123]

Hi guys, I'm just new to the forum and i have a '97 318is coupe with 101000k's.

Today as I've been driving around i noticed a knocking noise coming from the engine. It seems to be coming from the front of the engine bay, somewhere near the alternator although im not totally sure about this. Its a constant tapping/knocking/rattling noise hapenning several times a second at idle. As i rev the engine a bit the tapping gets faster until the engine drowns it out towards 3000 revs (unless it's stopping at higher revs but i doubt it).

Oil level is fine and the oil is brand new (just had it flushed and changed a couple of weeks ago).

Any ideas on what it could be?? Anything would be appreciated.

Also, while i'm making a post, i think i need a new fuel level sender unit as the guage is being a little bit dicky, anyone got one for sale or know where i can get one? How much will i be looking at for one of them?

Cheers,

Matt

[steve R 0]

Hi guys, I'm just new to the forum and i have a '97 318is coupe with 101000k's.

Today as I've been driving around i noticed a knocking noise coming from the engine. It seems to be coming from the front of the engine bay, somewhere near the alternator although im not totally sure about this. Its a constant tapping/knocking/rattling noise hapenning several times a second at idle. As i rev the engine a bit the tapping gets faster until the engine drowns it out towards 3000 revs (unless it's stopping at higher revs but i doubt it).

Oil level is fine and the oil is brand new (just had it flushed and changed a couple of weeks ago).

Any ideas on what it could be?? Anything would be appreciated.

Also, while i'm making a post, i think i need a new fuel level sender unit as the guage is being a little bit dicky, anyone got one for sale or know where i can get one? How much will i be looking at for one of them?

Cheers,

Matt

edit..... should read more clearly

vanos?

Edited March 3, 2007 by 328imobbin

[Matt 123]

vanos?

Sorry if im being stupid but isn't the m44 non-vanos??

[TronSpec 0]

Hey Matt

Could be your belts pulleys bearings making this noise mate. I've seen this before on alot of different other cars aswell

[Matt 123]

Hey Matt

Could be your belts pulleys bearings making this noise mate. I've seen this before on alot of different other cars aswell

Hmmm... The car's just had a major service and all belts were replaced, plus a belt tensioner too i think. I think there might have been a pulley with a shot bearing that was replaced as well, but i'm not sure, i may just be thinking of the belt tensioner.

Does anyone have any recommendations for easy ways i can eliminate common causes of this as the actual problem??

[will 169]

Hmmm... The car's just had a major service and all belts were replaced, plus a belt tensioner too i think. I think there might have been a pulley with a shot bearing that was replaced as well, but i'm not sure, i may just be thinking of the belt tensioner.

Does anyone have any recommendations for easy ways i can eliminate common causes of this as the actual problem??

doesn't sound like a belt from what you describe, but to eliminate it, just put a hosepipe down there and spray the belts with water while it is running. The water will eliminate or soften the noise if it is the belts.

Use a stethescope or screwdriver or length of tube against your ear to more accurately pinpoint the source of the knock if it is coming from the engine. I would suggest it is a lifter problem.

Will

Edited March 2, 2007 by will

[TronSpec 0]

Use a stethescope or screwdriver or length of tube against your ear to more accurately pinpoint the source of the knock if it is coming from the engine.

Just about to say that. haha Will you are old and wise

[topless 13]

Just about to say that. haha Will you are old and wise

so why didn't you?? got too much sex on the brain???

[Matt 123]

Ok, just used a piece of dowel to listen into the engine (such a good idea by the way!!) and the noise defintely seems to be coming from alternator. Engine sounds quite as when the dowel is on it but as soon as i stuck it on the alternator the noise sounded real clear thropugh the dowel.

Does this mean bearing in alternator is shot?? Easy to fix??

[topless 13]

could be a bearing but also could be one of the cooling vanes is bent a bit and is hitting the alternator at a specific point.

I would remove the belt from the alternator and spin it by hand and feel for the knock. If it is catching something, you will get the hookup point, then bend the offending vane clear. If it is a bearing, you should be able to feel it in the pulley. Replacing the bearing is not too difficult but you will need a puller.

[Matt 123]

could be a bearing but also could be one of the cooling vanes is bent a bit and is hitting the alternator at a specific point.

I would remove the belt from the alternator and spin it by hand and feel for the knock. If it is catching something, you will get the hookup point, then bend the offending vane clear. If it is a bearing, you should be able to feel it in the pulley. Replacing the bearing is not too difficult but you will need a puller.

Bugger, my dad has taken his tool kit away with him for the weekend, so i dont even have so much as a spanner to loosen off the alternator. I'm assuming it'll be ok to drive around for the weekend unless the alternator actually stops charging. Fair assumption??

Thanks everyone for all the help, btw.

[topless 13]

Bugger, my dad has taken his tool kit away with him for the weekend, so i dont even have so much as a spanner to loosen off the alternator. I'm assuming it'll be ok to drive around for the weekend unless the alternator actually stops charging. Fair assumption??

Thanks everyone for all the help, btw.

should be ok, just keep an ear out for it getting worse.