Debugging engine knock on 325e - BMW Forum -
BMW Forum BMW Forum

Auto Insurance

» Featured Product
Wheel & Tire Center

Go Back   BMW Forum - > BMW Model Specific Forums > 3-Series (E21, E30)
Register Home Forum Active Topics Gallery / Showroom Auto Loans Garage Search Today's Posts Mark Forums Read Auto EscrowInsurance

3-Series (E21, E30) Chat relating to the BMW 3-Series from 1975-1983 and 1984-1991 line. Specific models: BMW 315, BMW 316, BMW 318, BMW 318i, BMW 320/4, BMW 320i, BMW 320/6, BMW 323i, BMW 320i. E30 Family models include: BMW 325e, BMW 325i, BMW 325is, BMW 325ix. is the premier BMW Forum on the internet. Registered Users do not see the above ads.
LinkBack Thread Tools Display Modes
Old 05-30-2006, 11:43 AM   #1 (permalink)
Join Date: May 2006
Posts: 1
vw_michael is on a distinguished road
Debugging engine knock on 325e


I'm trying to figure out the 'new' old car engine noise. I was hoping someone here can shed some light. My current educated guess is that it's piston slap. The noise is only present for ten minutes after cold morning start. The noise is most apparent under load below 2500rpm, and when blipping the throttle.

I made a recording available at:

The recording was made with a pro microphone in the engine bay by the firewall, connected to a laptop. I drove at around 10-20km/h, at 1000rpm in 2nd gear with the breaks lightly on (this seems to make the noise louder).

I analyzed the recording with spectrum analyzer software, and it seems that the frequency of the noise is the same as the rpm (i.e. at 1000rpm, i get 17 'knocks' per second) with a very regular interval, which points at one of the cylinders.

Pic at:

The car is an 1985 325e, 2.7l, 75k miles. Other than the d**n noise it's running very well, so I'm determined to figure this out. I'm currently looking at a new piston, rings, and possibly a rod. I'm going to find out which cylinder it is by taking out the respective sparkplugs and listening for the noise while driving.

Any help/comments appreciated!

Attached Thumbnails
Debugging engine knock on 325e-bmw_noise.jpg  
vw_michael is offline   Reply With Quote
Sponsored Links
Old 05-31-2006, 08:06 PM   #2 (permalink)
5th Gear Member
Join Date: May 2004
Location: NC
Car: Opening soon:
Posts: 1,118
Starmavin is a jewel in the roughStarmavin is a jewel in the roughStarmavin is a jewel in the roughStarmavin is a jewel in the rough
Hmm, I tried the link but it didn't work for me, however from what you are saying it could also be a wrist pin.
Starmavin is offline   Reply With Quote
Sponsored Links

  BMW Forum - > BMW Model Specific Forums > 3-Series (E21, E30)

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools
Display Modes

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 Off
Trackbacks are On
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
can a e46 m3 engine and trans fit a 85 325e italianant02 3-Series (E21, E30) 4 03-18-2006 09:35 PM
86 325e engine swap to 91i idle problem lemonhead 3-Series (E21, E30) 10 02-21-2006 06:05 PM
'01 530i engine knock lotsacars 5-Series (E12,E28, E34, E39, E60) 12 11-17-2005 06:15 AM
BMW P83 Engine triggrhaapi Bimmer Talk/Motorsports Talk 0 07-21-2003 02:03 PM

Powered by vBadvanced CMPS v3.2.2

All times are GMT -5. The time now is 06:08 AM.

Powered by vBulletin® Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Content Relevant URLs by vBSEO 3.3.2
Garage Plus vBulletin Plugins by Drive Thru Online, Inc.