2001 325i Engine Knocking Sound - E46Fanatics E46 BMW Social Directory E46 FAQ 3-Series Discussion Forums BMW Photo Gallery BMW 3-Series Technical Information E46 Fanatics - The Ultimate BMW Resource BMW Vendors General E46 Forum The Tire Rack's Tire Wheel Forum Forced Induction Forum The Off-Topic The E46 BMW Showroom For Sale, For Trade or Wanting to Buy

Welcome to the E46Fanatics forums. E46Fanatics is the premiere website for BMW 3 series owners around the world with interactive forums, a geographical enthusiast directory, photo galleries, and technical information for BMW enthusiasts.

You are currently viewing our boards as a guest which gives you limited access to view most discussions and access our other features. By joining our free community you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is fast, simple and absolutely free so please, join our community today!

If you have any problems with the registration process or your account login, please contact contact us.

Go Back   E46Fanatics > E46 BMW > General E46 Forum

General E46 Forum
This is the place to get answers, opinions and everything you need related to your E46 (sedan, coupe, convertible and wagon) BMW!

Thread Tools Search this Thread Rating: Thread Rating: 5 votes, 5.00 average. Display Modes
Old 08-20-2010, 01:58 PM   #1
Registered User
Join Date: Jul 2008
Location: Texas
Posts: 6
My Ride: 2001 325i
2001 325i Engine Knocking Sound

I'm trying to figure out what the noise is! My car was recently the victim of some overheating damage which left it stalled out on the side of the road for a little while. I let my GF drive it for a small trip she had to make, and the reservoir tank cracked on her, leaking out all of the coolant.

She told me it was making a clanking noise afterwords, and we had the reservoir tank replaced at a firestone center in the town she was staying at.

The car made it back to me just fine, but now instead of just idling a bit rough (3 out of 4 O2 sensors went out on me), it idles rough at times, stalls out, and occasionally makes a horrid loud clunking noise toward the rear end of the block.

I performed a spark plug swap and changed the oil. After all of that, the clunk is still present, all be it a little less loud after the oil change which makes me think that maybe through the heat damage, an oil bearing on the crankshaft has slipped a little bit.

Please help me figure out what this noise is, we've narrowed it down to a piston rod, but if anyone could speak from experience and let me know that it's just a sticking valve, I would love to have that peace of mind.


Last edited by Hazy31184; 08-20-2010 at 02:10 PM.
Hazy31184 is offline   Reply With Quote
Ads by Google

Guests, get your FREE E46Fanatics.com membership to remove this ad.
Old 08-20-2010, 02:03 PM   #2
Registered User
Redline's Avatar
Join Date: Dec 2009
Location: Florida
Posts: 2,267
My Ride: ///M3 Vert

Redline is offline   Reply With Quote
Old 08-20-2010, 02:05 PM   #3
Registered User
Join Date: Jun 2006
Location: Cherry Hill, NJ
Posts: 106
My Ride: e46
Why is it that people's cars only break when their girlfriend or close relative is behind the wheel?
nastyemu is offline   Reply With Quote
Old 08-20-2010, 02:07 PM   #4
Registered User
Join Date: Jul 2008
Location: Texas
Posts: 6
My Ride: 2001 325i

As much as I would like to blame her, I didn't check the fluids before the trip... at least that's HER copout... somehow that would've prevented the crack in the reservoir tank!

See dear... there's this thing called a THERMOSTAT!

Hazy31184 is offline   Reply With Quote
Old 08-20-2010, 02:15 PM   #5
Join Date: Apr 2010
Location: My buddies w/ 350hp
Posts: 510
My Ride: lackbof turbos
Sounds like possibly a dying cylinder. It's hard to say since it doesnt seem rpm dependant.

Need more info. Anything weird in the oil? Noise pick up speed when you give it gas? how long did she drive it after the tank busted?
usernamehere is offline   Reply With Quote
Old 08-20-2010, 03:25 PM   #6
Registered User
Join Date: Jul 2008
Location: Texas
Posts: 6
My Ride: 2001 325i
It's definitely RPM dependent. Forgot to mention that it doesn't happen at 1k RPM or higher. The throttle seems to take a few seconds longer to pick up too.

Nothing in the oil seemed too strange, no milky, gravy consistency to allude to water, etc.

She drove it until it overheated and shut itself off, almost getting her rear-ended on the highway.
Hazy31184 is offline   Reply With Quote
Old 09-03-2010, 05:17 AM   #7
Registered User
Join Date: May 2006
Location: Los Angeles
Posts: 125
My Ride: 2000 323i
When I was diagnosing a possible oil separator problem on my '00 323 (slightly rough idle and several codes related to fuel trim, fuel control, and O2 sensors, all for both banks), I removed my oil filler cap to test for the amount of vacuum, and during this test I got the same intermittent loud knocking sound that you have. For me it only happened when the oil cap was removed and around idle or low rev as I recall.

You might have some sort of related vacuum leak. For me, the final culprit was a broken lower oil separator hose (see the story and pictures here: http://forum.e46fanatics.com/showthread.php?t=773551 ). The oil separator has 4 associated hoses which fail over time, and the oil separator itself can go bad as well. All my codes and rough idle were cured by replacing this one broken hose.

Is your check engine light on? Do you have any diagnostic codes? Other sources of vacuum leaks can be the rubber intake boots between the air filter box and the engine (they get cracks in the accordian folds, especially the "Y" near the idle control valve), or a leak around the gasket for the DISA valve. I never removed the oil filter cap after I replaced the broken hose, so I don't know if the knocking sound would occur again after the hose fix.

Hope this steers you in the right direction. The noise you have is identical to my previous noise and may be related to crankcase pressure (for example, the oil separator hoses or valve, AKA Crankcase Ventilation Valve, PCV and other names). Good luck.
gsbmw is offline   Reply With Quote
Old 09-09-2010, 12:18 PM   #8
Registered User
Join Date: Sep 2009
Location: Charlotte NC
Posts: 40
My Ride: 2000 323ci
im having a similar noise and i hope its not a dying cylinder... will check hose in above reply have you solved the problem?
Sjobey is offline   Reply With Quote
Old 10-27-2010, 03:06 PM   #9
Registered User
Join Date: Jul 2008
Location: Texas
Posts: 6
My Ride: 2001 325i
Thanks for all of your input, fellas. I was the Oil Separator (and when you ask someone in Autozone for a price qoute, their heads explode).

It wasn't the separator itself though, the hose leading from the dipstick branchoff to the bottom of the separator was completely severed. I replaced the hose with fuel hose and it runs like a dream now.

Now on to the other issues...

Thanks again folks!
Hazy31184 is offline   Reply With Quote

clunking, engine, noise

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Censor is ON

All times are GMT -5. The time now is 04:39 AM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
(c) 1999 - VerticalScope Inc. All rights reserved.