BMW 5 Series cool car has a lot of noise when it starts fire, which has been encountered by many car owners. The possibility of BMW 5 Series cold start sound is: the sound is very small after starting for about 1 minute, which is a normal phenomenon. It is recommended to warm up the car for 1-2 minutes first; After starting for a while, the idle noise is still very loud. If there is a loud noise from the engine, please repair it in time. BMW 5 Series cold start noise, not necessarily a fault.

寶馬5系打火噪音大原因分析：

Analysis on the causes of loud sparking noise of BMW 5 Series

1、如果冷啟動，發(fā)動機聲音偏響，一分鐘后趨于安靜，熱啟動時聲音就很小，這種屬于正常現象。因為停車后，發(fā)動機內的機油會自動流回油底殼。第二天冷啟動的時候，機油會慢慢從油底殼回到汽缸蓋附近。如果是熱啟動，發(fā)動機內的機油都已經到位，潤滑和密封良好，聲音自然會小。所以，冷啟動聲音會比較大，但是持續(xù)時間不會很長，多2分鐘。

1. If the engine sounds slightly during cold start, it tends to be quiet after one minute, and the sound is very small during hot start, which is a normal phenomenon. Because after parking, the engine oil will automatically flow back to the oil pan. During cold start the next day, the oil will slowly return from the oil pan to near the cylinder head. If it is a hot start, the oil in the engine is in place, the lubrication and sealing are good, and the sound is naturally small. Therefore, the cold start sound will be relatively loud, but the duration will not be very long, 2 minutes more.

2、如果在冷啟動時發(fā)動機聲音大，而且還發(fā)出咯吱咯吱的響聲，那么就檢查一下機油的使用情況，如果使用的是質量較差的汽油，也會導致發(fā)動機動力下降，造成發(fā)動機內部積碳增多，發(fā)動機噪音也會增大。

2. If the engine makes a loud noise and creaks during the cold start, check the use of the engine oil. If you use poor quality gasoline, it will also lead to the decrease of engine power, the increase of carbon deposition inside the engine and the increase of engine noise.

3、如果發(fā)動機有共振的現象，也會造成發(fā)動機的噪音大。對于咯吱咯吱的響聲應該是水泵皮帶或發(fā)動機皮帶老化后出現打滑而導致的異響，或者是水泵葉輪、水泵軸承或發(fā)電機軸承等部位缺少潤滑后已經出現磨損。還有可能是發(fā)動機抖動幅度較大時，發(fā)動機機爪與支架發(fā)生摩擦所產生的，逐項檢查這些，就可以找到原因。

3. If the engine has resonance phenomenon, it will also cause the engine noise. The creaking noise should be the abnormal noise caused by the sliding of the water pump belt or engine belt after aging, or the abrasion of the water pump impeller, water pump bearing or generator bearing after lack of lubrication. It may also be caused by the friction between the engine claw and the bracket when the engine jitters greatly. Check these items one by one to find out the cause.