what causes knocking?
 

I can hear over my blinkers! not good.

any tips? why? causes? solutions?

(please keep the witty sarcasm to a min. :) )

It should not be knocking because modern engines have knock sensors that will retard ignition timing if it detects the possibility. However, if you haven't been doing so, switch to premium fuel, and/or another brand.

Is it Knocking all the time? How many miles? What type of gasoline are you using? Do you do in between oil changes? Does it just knock upon start up? Lets start with these questions, and narrow it down. It might be your camshaft going bad. But do a search about this. There was an bulletin about these engines for the 540i years ago. It stated about customers complaining about there engines knocking. BMW told them that it is normal and will not cause any internal damage, and that it can be driven for many miles more. Don't know the details but, search it out. Good luck.

The traditional description is "pre-ignition" that is the gas-air mixture is ignited before top dead center causing the position to knock. Diesels count on this to function, hence the noise. Usually, a hot spot caused by carbon deposits is the cause of the knock. A mechanical knock can be caused by a failing connecting rod as well. Have you changed your plugs?

thanks for the note. yeah, knocking all the time. ok, maybe a little exaggerated with the amplitude, but it is definitely noticeable. Chevron premium, even thought it's about 3.25 here in San Fran.

i bought that gas treatment, but that might be more damage that good. plus, it's prolly going to be a surface fix... then going for an oil flush come my next inspection.

any other advice/comments?

My 3.0l idles really loudly if it is low on oil or needs an oil change. It's the valve gear I am pretty sure though. How is your oil?

My personal opinion, drop some oil flush in the engine, let it run for about 15 min or so. Even better, drive it around the block a few times, drop the oils, let it drain till there is no more drips. Then add some BMW HP 5-40 oil and I'll bet you it will be a lot more quiet then now. Also, Tomaz had a good question. Did you change the spark plugs yet?

1. can u recommend a flush brand.
2. nope, havent changed the sparkies yet. good idea. :thumbup:

this is bad advice. how is this going to going to alleviate anything?


to the OP. does the 'knocking' only happen when you're accelerating or going uphill?

either you got a really bad tank of gas or there's oil in your intake. ingesting oil will promote dentonation. check the oil seperator.

the knocking is pretty much all time. it's a chugging type of knocking. even when sitting idle. i can hear it. cluck cluck cluck cluck.

2001 4.4 x5 with only 51k miles on it. mostly city.

i got the stp gas treatment, going to use that on my next fill up. i suspect bad gas, who knows. then i had a sludge post too...

http://www.xoutpost.com/x5-e53-forum/...e-remover.html

I just posted in that thread.

injector cleaner would not hurt either - if injectors clogged or gummed up also cause hot spots - fuel mixture also acts like a coolant - once a week on the interstate, drop down a gear, and run high revs could also help - used to have to take my Mom's '69 280SL out on (the then incomplete) I-78 to blow out all the carbon buildup as all she did was local stop'n'go driving.

haha, i red line my car all the time. i race anything on the street. yeah, that's right. no wonder i only get 4 miles to the gallon. :rofl:

Yeah, but that doesn't get engine temps up long enough to do any good, especially when you have to come off the gas right away - these engines love med-high revs(2500-4000) for long "autobahn" runs - Knew a guy who drove a Ferrari in NYC, every other week it was in the shop because of fouled plugs - he never gave it a healthy "gallop"

good point. will be sure to site this entry when cop pulls me over. ;)

like I said, drop down a gear - but I admit that's no fun - out west here, I can run 100+ for long periods of time :nanana: :rofl:

That right there says it all.

Detonation occurs when excessive heat and pressure in the combustion chamber cause the air/fuel mixture to autoignite. This produces multiple flame fronts within the combustion chamber instead of a single flame kernel. When these multiple flames collide, they do so with explosive force that produces a sudden rise in cylinder pressure accompanied by a sharp metallic pinging or knocking noise. The hammer-like shock waves created by detonation subject the head gasket, piston, rings, spark plug and rod bearings to severe overloading.

Mild or occasional detonation can occur in almost any engine and usually causes no harm. But prolonged or heavy detonation can be very damaging. So if you hear knocking or pinging when accelerating or lugging your engine, you probably have a detonation problem.

Another condition that is sometimes confused with detonation is pre-ignition. This occurs when a point within the combustion chamber becomes so hot that it becomes a source of ignition and causes the fuel to ignite before the spark plug fires. This, in turn, may contribute to or cause a detonation problem. Instead of the fuel igniting at the right instant to give the crankshaft a smooth kick in the right direction, the fuel ignites prematurely causing a momentarily backlash as the piston tries to turn the crank in the wrong direction. This can be very damaging because of the stresses it creates. It can also localize heat to such an extent that it can partially melt or burn a hole through the top of a piston.

My advice is to change your driving habits.

Everyone has a valid point here. But I've heard the knocking of other X's and I truly understand what this man is talking about. Look, try the flush, at the same time, drop some fuel cleaner in there also, it will not hurt. If non of these things help, then do the spark plug change. If that doesn't help, then you will need to find a good indy and get to the bottom of this problem. I don't want to scar you, but you might have a camshaft problem. Lets hope that maybe the flush or the spark plugs can help.

Good flush is the Gold Eagle brand... Any parts store has it. Like I said before. I had a little knock in my engine when I first bought it. I did the flush and dropped some BG44k cleaner and the engine quited down not right away but after maybe 2 oil changes later. Now she runs the way she's supposed to. Good Luck my friend. Let me know if I can help with anything else. Wish you lived closer to me, I've got a great indy, that can tell you within 10 mins to what is going on.

Everyone has a valid point here. But I've heard the knocking of other X's and I truly understand what this man is talking about. Look, try the flush, at the same time, drop some fuel cleaner in there also, it will not hurt. If non of these things help, then do the spark plug change. If that doesn't help, then you will need to find a good indy and get to the bottom of this problem. I don't want to scar you, but you might have a camshaft problem. Lets hope that maybe the flush or the spark plugs can help.

Good flush is the Gold Eagle brand... Any parts store has it. Like I said before. I had a little knock in my engine when I first bought it. I did the flush and dropped some BG44k cleaner and the engine quited down not right away but after maybe 2 oil changes later. Now she runs the way she's supposed to. Good Luck my friend. Let me know if I can help with anything else. Wish you lived closer to me, I've got a great indy, that can tell you within 10 mins to what is going on.