Artikkler/Råd: Skjørtebank/diagnosering av ulyder i motor

[Mr2Even]

Tenkte vi kunne samle litt stoff, artikkler og sider fra internett angående ulyder i motor i denne tråden. Her er to bra hjelpesider:

http://remanufactured.com/Engine_Noise_ ... is_101.htm

Skjørtebank:

When your engine is cold, the aluminum piston is small in comparison to it's surrounding iron cylinder. Why? Because with heat aluminum expands rougly 5 times as much as iron. Therefore the rather hollow piston slapping noise will be loudest first thing in the morning. After the engine warms up, the aluminum piston expands more than it's iron cylinder, reducing the excessive clearance between the piston and cylinder wall.

So, the test is this:

First thing in the morning, start the engine up and run it for 15 seconds while you listen carefully and memorize the sound and it's intensity. Shut it down quickly, pull the spark plugs and put two squirts of motor oil into each cylinder. Reinstall the plugs, fire the engine up again and listen.

If you have piston slap the noise will have been greatly reduced or even eliminated…..for 15 or 20 seconds that is, and then your nightmare noise will come back like a Marine Corps marching band coming toward you in the parade.

http://www.canadiandriver.com/articles/jk/020320.htm

So is piston slap a problem? Not for most engines built in the last decade and if the noise is there only for a few seconds during cold start. If the knock is in an engine of older design, the knock continues, or it is there during acceleration, then engine work is in the future. The worst part about piston slap is trying to explain that a cold start knock on newer vehicles can be normal, especially when you try to sell your vehicle!