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