I'm getting some strange noises whenever I run my car.

I posted awhile ago saying I just bought it, anyway all the fuses in my car went kaboom so I replaced them all, and i've since gone about checking the coolant system, which is 100%. The engine dosen't smoke, and everything works like it's supposed to with the exception of one motor mount needs to be changed.

When I start the car there is a very, very loud "scraping" noise coming from the engine bay, I have no idea what is causing it but it sounds like it's either coming from the engine, or underneath it, I can't really tell because it's so loud it could be coming from anywhere.

After the engine warms up a little bit and I rev it to 5k or so, the noise becomes much quieter. Also, when I go all the way to redline, i'm treated with some nice exhaust pops and a funny smell, is that normal?

 

well the pops and funny smell is normal, that the smell of exces combusted gas and oil, however the scraping isnt normal, unless you mean it sounds like a pulley is going, they you need clutch work, pulley bearing going bad noise= bad throwout bearing, scraping = something very very bad will happen soon.....

check to see if you are constantly losing coolant with no leaks, and finaly check the compression, it should be 3 strong puffs between 80 to 120 ish psi

 

well it's an automatic... so clutch work is kind of out of the deal.

 

ok well what about the other stuff? compression? do you no were the noise is exactly coming from?

 

it sounds a lot like a fan hitting something, it's not from the engine becuase my car has a ghetto cutoff switch that kills everything but the engine, and the engine sounds GREAT when nothing else is going, so could it be a rusted pulley or maybe even the clutch fan has a rusted screw or something.

 

old belts will start making noises, also the smog pump could be going out

 

old belts may be the cause, but would they get quieter at higher rpms?

and i'm pretty sure there is nothing as far as cats go, it's a florida car, and it looks to have an aftermarket exhaust, when i looked underneath i didn't see anything resembling a cat.

 

well they could get quieter only because you cant hear them as much because of all the engine noise

 

alright, i'm gonna go into this as much as possible.

when i turn on my vehicle it cranks up nicely, then when everything gets going there is a nice scraping noise.

i have no idea what it is, but it is very loud. when the engine heats up enough for me to start revving it a bit when it goes back to idle it gets much quieter then before.

the only way i can describe the noise is a metal on metal sound, like something clanking about inside of something else.

i know it isn't the engine becuase my car has a cutoff switch that when pressed, kills everything except the engine, and the engine sounds great and smooth with everything off.

 

perhaps its something rattling inside another part of the bay

 

do you still have the smog air pump?

 

if its turbo. i'd check the turbo.

 

It could be the alternator too.

Possibly the starter sticking in?

The kill switch puzzles me, but if you push it, the noise stops, but the engine continues to run?

 

so, on further inspection, WITH THE SWITCH OFF, everything continues to run, the car drives great, and there are no wierd noises!

could it have something to do with the starter? it could be a fuel cutoff...

when i turn the key into the ignition slot all the way with the switch off it shows a fuel light on the idiot box on the dash. however, when the key is in the straight up and down and i flip the switch, it's the only way to start the car...

how strong are the starters in the s4?

 

Do I understand you to say that you turn the key to RUN and flip the switch to on to start the car?

If you turn the key to START (all the way forward) it doesn't do anything but light a light on the dash?

If that is the case then the switch operates your starter (equivalent to turning the key to START in a normal car.) Flip the switch ON only long enough to start the engine and then turn it OFF. If I read the above post correctly, that switch leaves your starter engaged to the engine (revving the engine to 5,000 rpm is a really bad idea in this case.)

(Please disregard this diagnosis if I am wrong in reading your post above.)

 

i have since learned that yes, the switch probably does leave the starter going...... thus me revving to 5k was probably a really bad idea.

i'm pretty sure that was it though, but thanks to you all saying things i have gone about checking everything in the engine bay and it's all in great shape. i guess i really did get a good deal for $600, all it really needs is a motor mount now.

 

Great, I'm glad you got it figured out. I would try to figure out how to fix the ignition switch so that you don't need that other switch.

Yeah, you got a pretty good deal.

Happy rotoring.