: How long can an M50 "tap"

10-01-2009, 08:04 PM
My 92 525i has had a "tap" since it hit 204k. It just passed 242k. It's a 5 speed so I am able to keep the revs up when it feels a little sluggish. In the long, long hot summers here in Houston I use 40w about 8 months out of the year and 20-50 when it cools off. When the a/c is on full blast on a hot south Texas day the tap is pretty loud . The car still runs good and I drive it everyday. How long can it last?????

10-01-2009, 08:05 PM
I have heard 300-350k for them. Getting your money out of it!

10-02-2009, 08:03 AM
i think i have the same problem when the engine is hot and my current oil fill is over about 3,500 miles old. I think it is fuel dilution. It stops when i change the oil. Go figure. :)

10-05-2009, 05:01 AM
You are using too heavy an oil. Heavy oils don't flow well to the valvetrain and this could be your "tap". Use what the book recommends.

10-05-2009, 05:45 AM
You are using too heavy an oil. Heavy oils don't flow well to the valvetrain and this could be your "tap". Use what the book recommends.

If you are refering to me. I have used 0w40, 5w30, 5w40 to 15w50 on this engine. All synthetic. Heavy oils give me a cold engine "rattle" that goes away when lifters pump up. 0w40 would not rattle on cold start, but engine would sound like a thrashing machine. Best weight I have found for "this" car is 5w50 castrol syntec No rattles cold or warm for about 3,500 miles. Then a warm idle "tapping" creeps in an get more prominant as mileage increases. Believe it is fuel dilution. Other engines may behave differently. Just my to date experience.

10-05-2009, 03:52 PM
It could be a number of things going on in the head, but there are 3 that it is most likely, of which can be a fairly easy and inexpensive fix.

1) Sticky lifter: You can try adding 12oz of gasoline to the oil. It acts as a strong detergent but also thins out the oil, allowing oil to fill up the lifter. The gas will eventually evap through the vent hose back into the engine so the oil thickens back up. Believe it or not, this is a very common, and inexpensive trick to fix a sticky lifter that has not completely failed.

2) Vanos: Now being a 92', I am not 100% sure if you have it or not, but it will look like a lump on the front of the engine. Fortunately this can be repaired for ~$300 and is the most expensive fix. Now a failing Vanos will result in a loss of power in certain RPMs, and starts tapping when it has failed (or about to). You can find everything at http://www.drvanos.com/ just be sure to also rent the tools if you don't already have access because they make the process a WHOLE lot easier. They also include the instructions and everything.

3) Loose Cam bearing nut: Probably the most unlikely, but still I have seen it happen, usually after someone removes/installs the cams. This will result in a loud tapping as if a lifter has completely failed.