Originally Posted by e92zero
Oh, interesting. Thanks for the heads up.
When I changed mine (the stock one), they were nice and tight but that was the first time I changed the plugs on this engine so I don't really know or have a reference point to how tight they should be. Do you mind teaching me a bit on how to identify that it was not tight enough or blow by? I did notice the threads are a bit damp compare to the honda engines that I have changed plugs on before. I just thought the engine mixture ratio were different between the 2. Thanks in advance for your help.
With plugs the correct tightness if doing it by hand is either 1/8 turn or 1/4 turn after hand tight that does depend on the configuration of the plugs.
This is not always the most effective way. I have in the past when working on Formula Mazda's witht eh rotary engine seen people go as far as turning the plugs hand tight then trying to align them a certain way for better flame path progression.
AS I said I did 28 N-m on mine and seem to remember reading somewhere that the tool for BMW was just an inital indicator to be used to tighten them and guarantee not going over with a torque wrench then set to 28N-m for the remainder.
I highly doubt knowing most techs even use a torque wrench however let alone a special tool.
A little oil on the threads is normal on these cars, however if there is any oil above the threads such as on the hex or on the ceramic/porcelain and if the plug didn't "untorque" then it may of been a little loose in the cylinder.
When I pulled one of mine out it came out prety easy and did exhibit a little bit of oil above where i would expect it to be. Its not really anythhing to worry about. The area of the plug is so small even at high compression cylinder pressures the chances of it stripping the threads are pretty slim...Also once the car is running and warm the expansion in the metal probably tightens around the plug preventing it from back out more. Although I did do my car right after driving home and again it was just looser than I would of liked. But yeah any oil above 3/4" of the thread from the bottom I would consider too high. This is also a method used when tuning my shifter kart. We can tell how rich or lean it is running by the height of the oil up the thread.
23N-m is probably fine...but 28N-m felt fine to me too, not like I was stripping threads or anything like that.