Tech Forum : Strange noises

melloh	Posted Monday, Dec 8th 6:45am [Edit] [Quote] [IMS] [View car]
Member Post nr. 115 California, USA (San Jose) 1980 320is, 1991 318is	Well, I finally have my car back after one of my cylinders went out. Apparently it was a combo of things (bad wires, rotor, cap, clogged injectors, plugs, valves too tight....again, too lean). The car holds cold idle better now, but I hear this strange noise more consistently now (it was only very intermittent b4). If/when i rev it up and then let go of the gas (IE: for down shifting or even out of gear), there is this sound like a combo of bubbling or like something (a marble or nut) bobbling around in the engine. Is this what "knocking" is? Thanks for any help. PS: I would take it to the mechanic, but I feel guilty. He spent 3 days troubleshooting and only charged me for parts and a couple hours for the tune-up (total 300 and bonus 12 of guiness & becks). Probably saved me 200-500 in labor costs.

Max	Posted Monday, Dec 8th 7:17am [Edit] [Quote] [IMS] [View car]
Member Post nr. 8 OC, CA, USA 85 635CSi euro, 89 325iA	Check for loose muffler and/or metal heatshields or something like that. If it's from the tail pipe you might have mixture/timing set wrong and have the remaining fuel burning in the exhaust. It's hard to diagnose things like that w/o seeing and hearing, if I were you I'd ask the mechanic who worked on it what it is. Sorry, did not help much. good luck! Max

melloh	Posted Monday, Dec 8th 7:51am [Edit] [Quote] [IMS] [View car]
Member Post nr. 117 California, USA (San Jose) 1980 320is, 1991 318is	Perhaps by coincidence, but you're right. My muffler hangers disappeared (again). But, the noise seems to be comming from the engine bay. I'll try and 'pinpoint' the noise. I know I didn't give much useful details. Still learning...

Tricord	Posted Monday, Dec 8th 2:23pm [Edit] [Quote] [IMS] [View car]
Administrator Post nr. 350 Belgium, Europe 323i Baur	Could indicate worn conrod bearings.

RDAvena	Posted Monday, Dec 8th 5:06pm [Edit] [Quote] [IMS] [View car]
Staff Post nr. 288 SELECT * FROM users WHERE clue > 0 1981 323i, 1988 545is, 1997 528i	My thoughts exactly Tri. Sounds like a low knocking that keeps time with the engine? Might have starved one of your con rod bearings and caused it to wear prematurely. Catch in time with a new set of con rod bearings and fix it. The hardest part will be removing the oil pan.

melloh	Posted Tuesday, Dec 9th 5:08am [Edit] [Quote] [IMS] [View car]
Member Post nr. 118 California, USA (San Jose) 1980 320is, 1991 318is	Wow... i've never even heard of that part before. Thanks for replying. Also, just noticed today that it begins to be heard and around 3k rpm, and becomes louder & more frequent as it goes higher in rpms. So, what is a conrod? Purpose? Thank you and sorry, I'm trying to learn!

Blauundweiss	Posted Tuesday, Dec 9th 5:26am [Edit] [Quote] [IMS] [View car]
Member Post nr. 35 Phoenix AZ, U.S.A. 1983 320i	You've got you're crank -[_]-[^]-[_]-[^]- (crude I know) to which the pistons are attached, the con-rods stand for connecting rods ergo they attach the pistons to the crank and allow power from combustion to be transmitted to the crank and turned into useful energy such as twisting a transmission and wheels and such. very useful things that need well lubricated bearings in order to survive the force of gasoline burning in confined spaces. if they become starved for oil they wear and tolerances get sloppy. so you get a nice tock, tock, tock at increasing rate as the engine revs.sounds a little more severe, no scatch that a lot more severe than a sewwing machine. but they can and should be replaced before anything catasprophic (spell check?) happens like a rod being thrown off that rotating crankshaft at high velocity (much damage). anyway there's a crude crash course for ya, post any more ?'s you've got and everyone else make sure I haven't goofed up. -Chad

melloh	Posted Tuesday, Dec 9th 10:00am [Edit] [Quote] [IMS] [View car]
Member Post nr. 119 California, USA (San Jose) 1980 320is, 1991 318is	Thanks. Connecting rods sounds more familiar. obviously, ill need to do some serious studying if I want to understand/learn much more than what you told me. It's also pretty clear that I shouldn't try doing this on my own at this time.

Tricord	Posted Tuesday, Dec 9th 10:35am [Edit] [Quote] [IMS] [View car]
Administrator Post nr. 351 Belgium, Europe 323i Baur	Actually, it shouldn't be too hard for you to do it yourself. On the other hand, I suppose you don't want to pull the entire engine just to replace the connecting rods. If you can jack up the car high enough so you can work underneath, you can remove the oil pan and you will have direct access to the crank and the conrods. You just turn the crank until there's a piston at BDC (bottom dead center, lowest point) after which you can unbolt the rod from the crank. Push the piston a little upwards and remove the cap. You can now remove the two shell bearings, and replace them with new ones. Oil everything properly, pull the piston a little back down, seat the rod back on the crank and retighten the cap to specifications, move to next cylinder. Oh, and since you've an M10 engine, it's 1/3 less work for you than for us

M42powered	Posted Tuesday, Dec 9th 7:15pm [Edit] [Quote] [IMS] [View car]
Staff Post nr. 228 Arizona, USA 1981 BMW 320i	Sticky wrist pin perhaps? Does the noise go away over time (ie after the engine warms up)? or is it there all the time?

melloh	Posted Wednesday, Dec 10th 5:11am [Edit] [Quote] [IMS] [View car]
Member Post nr. 120 California, USA (San Jose) 1980 320is, 1991 318is	It's there all the time. Can't tell if it gets worse or I just notice it more over time (other noises going away), but definitely does not get better over time. Thanks Tri. Its tempting. I will just need to find a place to do the work, then! If i decide to do it, this will be revisited with inquiries for full instructions (so that a literate monkey could do it). First, I'll call the mechanic and see if he noticed it on test drives. Maybe he'll let me borrow/rent some garage space . I'll have to load em up w/ a ton of Guinness' !!

g323	Posted Wednesday, Jul 22nd 5:36pm [Edit] [Quote] [IMS] [View car]
Member Post nr. 337 California 323i 1982	Must I replace the conrod bolts when I change out the conrod bearings? Also, do i need any of the different sizes or should I buy standard?

Yety	Posted Tuesday, Aug 4th 2:38pm [Edit] [Quote] [IMS] [View car]
Member Post nr. 170 Europe, Romania 320i/6	I had the same type of increasing noise (knocking) a few hundred miles before the bearings from the 1st piston slipped one over the other stalling the engine. In my case, before that "disaster" (crankshaft fitted already with +0.25 bearings was ruined) the knocking was distinct (the "tock, tock, tock" Chad mentioned) especially at startup just until the oil lamp went out and also over 3k rpm, especially at WOT. IMHO that noise could be caused by the bearings from the piston that "went out" - they have been surely submitted to a high level of mechanical stress during the incident... so the sooner you change them, the higher are your chances to save your crankshaft (a micrometer would be very useful in order to mesaure the diameter of the crankshaft where the conrod bearings are fitted - specifications can be found in any E21 manual). Usually, the bearings wore out faster than the crankshaft, as they are made of a softer kind of metal than the crankshaft, meaning that if they are replaced as soon as they start knocking, the crankshaft can take the wear with another set - maybe even 100k miles if driven "softly".

g323	Posted Friday, Aug 7th 12:05am [Edit] [Quote] [IMS] [View car]
Member Post nr. 340 California 323i 1982	http://forums.bimmerforums.com/forum/showthread.php?t=1271063 and see this video: http://www.youtube.com/watch?v=5Gs9Lc2CIKk&feature=player_embedded All help will eb useful for diagnosis - Im lost!