Random knocking [Archive] - Bimmerfest - BMW Forums

: Random knocking

03-18-2005, 09:16 PM
528i knocking noise (not coming from the engine). Sounds like its coming from the pass side of engine compartment, close to the box behind pass side headlight. The noise is intermittant. Anyone know what this is?

03-21-2005, 05:19 AM
More than likely the bushings in the control arms are needing replacing.

It would help if you posted year/mileage and any suspension work previously done on the car? When does it happen, etc, etc?

03-22-2005, 11:18 PM
Its a 98 with only 58k on it. It happens while at idle and sometimes while driving. Not coming from the engine though. I currently have it at the shop because it runs hot at stoplights. This may have something to do with it.

03-25-2005, 11:23 AM
those thrust arm bushes typically last 60k miles, so if you want to check them do the following:

Stop the car and turn the steering wheel one full turn either direction to display the tyre thread.

Give the tyre on the thread section a good kick and if the wheel rocks back & forth more than 2-3mm, it's those bushes.

04-01-2005, 09:29 PM
Thanks for the info on the bushings. I'm pretty sure the noise I was hearing was from the radiator. The tech's said that there was some air in the radiator, so they burped it. I haven't heard the noise yet.

04-03-2005, 03:16 PM
The vehicle is now making a low vibration right at start up. This noise stops after the vehicle warms up. I'm hoping a flush and fill of the coolant will take care of this problem. Any one know any other ideas, or experienced the same problem???

04-04-2005, 08:35 PM
Doesn't sound good man.

If the engine was overheating you could have caused some damage, especially if it's vibrating now.

I'd really have it checked out, I'd hate to take stabs at what the problem is and have you burn your engine up.

If it was overheating it could have caused some excess wear on your internal engine parts, like your pistons or rods. Usually the first thing to go is the rod bearings though. Being that your coolant really doesn't do much for the first few minutes it sounds like a mechanical problem.

It sounds to me like once the engine warms up (which causes metal to expand) whatever it is has worked itself out. So if there was some excess wear caused by overheating, after the engine warms up it has expanded to stop the vibration.

On the lighter side, your water pump could be shot. That could also make sense because if it was overheating the water pump may have just been corroded. In that case when your car first starts it could be hesistating to turn the blades on the water pump. (Kind of like a really old fan that starts to stick when you turn it on and you need to give the blades a whap).

Waterpumps get mis-diagnosed a lot. Usually the mechanic says it just needs a flush or the radiator is clogged.

If you want to check it yourself, disconnect the large hose coming off your water pump from your radiator. Have it aimed at a large bucket while somebody starts your car for a few seconds and shuts it down. It should have a pretty strong flow of coolant into the bucket, if it doesn't then your waterpump is bad. Get it fixed immediately.

I won't even talk about piston wear or rod bearings (usually when these have problems there is a tapping noise) because that required a complete engine rebuild IF the engine can be saved.

One thing you could try, but I don't think it works on BMW's is turning on your heat. If you don't feel heat then your coolant isn't circulating. I think BMW's have a separate system for heating though, which makes this method ineffective. However, if you notice your engine temp getting high you should turn on your heat full blast to help cool your engine.

The best thing to do is just pull over. If the temperature is REALLY high let your car idle for 5 minutes before shutting it off. When you shut an engine off there is "heat swell", which means the engine temperature continues to rise. By letting it idle the strain on the engine is gone which doesn't create as much heat, so as long as some coolant is moving it will help cool your engine before you shut it off, and DO shut it off unless you want to cough up $6k for a rebuild.

This is good advice for anybody who finds themselves in an overheating position.

As far as checking your tires, good tip there. One thing I see 99% of drivers do is turning their wheels while the car isn't moving. You should be moving forward or backwards when turning your steering wheel, otherwise your putting a lot of stress on your tierods and power steering unit which leads to early problems. By letting your car roll forward even 1 foot while turning your tire, you're increasing the life of your steering components.

It's just never a good idea to turn your tires if your car is at a complete stop. The more and more advanced our cars get and the more and more dependable they become, the more and more people will take things for granted. I'd put money on it that most of the people reading this never knew you weren't supposed to turn your steering wheel while your car isn't moving. It won't kill it, but it does put additional stress on the components (components are a lot better today).

Toledo, OH

04-06-2005, 04:14 PM
I just bought the car a few weeks ago, so I added the extended warranty to the car. I paid a little over 2000 for it, but it will probably be worth it. It covers a good portion of the mechanical and electronic equipment for 3yrs or 36k miles!!! I just have to keep the receipts for the routine maintenance.