HELP - what is this steady knocking noise?

[XKxRome0ox]

UPDATE - the noise is almost certainly coming from the ac compressor

did i break my car?
can anyone identify the noise?


so I swapped out the TA's last Saturday
everything was fine driving it back home over 70 miles from my friend's house
but when I ran diagnostic at home I saw an error code for coolant temperature sensor

drove it on Monday and Tuesday without any issue
tonight, I heard a change in the noise in engine bay
noticed that my fan wasn't running most of the time
I drove it home since it's cool and moving air should be fine
engine wasn't overheating

the noise was not like this at first ...
now there is a consistent knocking noise that sounds like ... it's plastic hitting something

doesn't appear to be the fan
the noise was there whether or not the fan was running
the knocking increased in speed when i stepped on the throttle

my totally noob wild guess ... could it be the little plastic arms that connect to the throttle actuator?
when putting in the new TA, I did think it is crazy how little the plastic arms were

gonna open up the car tonight night after work to check all the connections and see if i can identify the problem

[ryguy0492]

could it be the idler pulley? Also I would have just started crying

[XKxRome0ox]

Originally Posted by ryguy0492

could it be the idler pulley? Also I would have just started crying

I'm still crying

I rushed to get my TA swapped because I have a track day on may 11
if I can't get this taken care of, I just threw away money on the track day registration fee and the expedited shipping on the parts

I really really hope it is just something like I did not reconnect all the sensors and hoses properly

[SAMM3Y]

Does the noise stay consistent with the revs when you rev it? Check to make sure you haven't shredded a belt and it's slapping something as it goes around.

[XKxRome0ox]

Originally Posted by SAMM3Y

Does the noise stay consistent with the revs when you rev it?

the noise changes as the RPM goes up
i think it got faster as the RPM went up

[SAMM3Y]

Originally Posted by XKxRome0ox

the noise changes as the RPM goes up
i think it got faster as the RPM went up

I'd check the belts, if you can get the car in the air and remove the bottom shroud you can pull the belt off the idler and start turning accessories by hand see which ones noisy, or if the belts shredded and slapping something as it goes around. I know you just did actuators the closest belt run accessory to that is the water pump I believe make sure nothings fouling against the pump pulley.

[XKxRome0ox]

Originally Posted by SAMM3Y

I'd check the belts, if you can get the car in the air and remove the bottom shroud you can pull the belt off the idler and start turning accessories by hand see which ones noisy, or if the belts shredded and slapping something as it goes around. I know you just did actuators the closest belt run accessory to that is the water pump I believe make sure nothings fouling against the pump pulley.

thanks


I don't mind getting a little dirty and working on the car
just wish I had a little more time buffer

[cae93]

Ok, I'll be the jerk for today......

Did you leave a key and some candy inside?

[Siajoon]

Might as well be bearings

[Dpc2u]

Originally Posted by cae93

Ok, I'll be the jerk for today......

Did you leave a key and some candy inside?

[sibhusz06]

sounds like something off of the serpentine belt,,ie tensioner, idler pulley or bad bearing in accessory.

[SAMM3Y]

Originally Posted by XKxRome0ox

thanks


I don't mind getting a little dirty and working on the car
just wish I had a little more time buffer

You got this! Red Bull's and adderall!! Get er' done!!

[mapster37]

remove belt and start engine. is noise still present?

[XKxRome0ox]

took off plenum and rechecked every connection
it wasn't anything in there

there is actually no fault code at all when I scanned today
not even the coolant temp sensor which showed up earlier in the week

narrowed down the source of the noise
seems to be coming from the pulleys
fan turns on when engine is at operating temperature
no issue other than the noise


how foolish is it to just take my car to the track on Saturday and deal with this afterwards?

[SAMM3Y]

Very foolish..

This belt diagram might not be Correct but the accessories are labeled.. figure out which ones making the noise.

Added a pic of the block and the thread I got the pics from https://www.m3post.com/forums/showthread.php?t=1162212

[Bemo]

OP - instead of performing "Internet forum diagnostics," why don't you rush the car to your preferred Indy or local dealer?
Hopefully they'll patch you up in time for the track event.

[Scharbag]

Do NOT track the car with bad belts. If you lose the water pump belt at a track, you will likely cook your engine. Been there with an M42 and boy it breaks things fast.

Get the problem solved first.

[XKxRome0ox]

took it to a local indy BMW shop
belts and pulleys are fine
almost certain that it is the ac compressor
when I turn on the ac the noise goes away

not a catastrophic item, right?
so I'll go ahead with the track day and then address the ac compressor afterwards

[///M Power-Belgium]

Originally Posted by XKxRome0ox

took it to a local indy BMW shop
belts and pulleys are fine
almost certain that it is the ac compressor
when I turn on the ac the noise goes away

not a catastrophic item, right?
so I'll go ahead with the track day and then address the ac compressor afterwards

Track is not worth the risk . Keep in mind , our S65 is not cheap my friend .

[kimiraikkonen]

Originally Posted by XKxRome0ox

took it to a local indy BMW shop
belts and pulleys are fine
almost certain that it is the ac compressor
when I turn on the ac the noise goes away

not a catastrophic item, right?
so I'll go ahead with the track day and then address the ac compressor afterwards

That's good to hear. You are probably low on refrigerant. I would say, give it a recharge and see if the noise disappears.

[SAMM3Y]

How was the track day? Did the car make it?

[XKxRome0ox]

Originally Posted by SAMM3Y

How was the track day? Did the car make it?

nope
the ac compressor totally crapped out
the pulley cracked and fell off
so the car is sitting at a shop now
waiting for the compressor to be shipped this week

thankfully it happened during tech check the night before and not while i was driving
because losing power steering mid turn would have been real bad