How do I know if I need a valve adjustment?

[JJJames]

I know these are required periodically - are there warning signs or is it just a number of kms/years thing?

[chriscotech]

In BMW terms this is an inspection I item, meaning it should be checked every 4th inspection. That doesn't necessarily mean an adjustment is needed. My car was bought with a full service record at 17 years old and I doubt it could ever have been adjusted. When I enquired about it both the main dealer and another big one closer to me in Sydney Australia they couldn't do the work as they didn't have the shim removal tool. Apparently the most senior mechanic, who had been there for over 20 years, had never done one. I don't know if that is really true but they told me to go elsewhere. I was always going to do it myself if possible anyway, I was trying to source the shim removal tool.

My car had about 8 valves out of tolerance from memory. all but one had slightly larger gaps but that can be the other way. Tighter gaps is not good as you run the risk of the valve never quite closing. Apart from the obvious loss of compression, exhaust valves can burn. This is an extreme case scenario. You should be able to hear a tapping if you have loose tolerances. If your vanos is noisy the sounds might be confusing. If in doubt, pull it apart and measure them. The full job is a bit time consuming and quite expensive at a dealer (If they have the shim removal tool). You can get away with using a screwdriver to replace the shims but the right tool makes it much easier. Finding someone who will sell you a tool these days is another issue. I managed to get one on special order from Schmiedmann in Denmark. If you are not doing the work yourself, you may need to shop around to find somebody with the capabilities and, ideally a decent selection of replacement shims so you don't have to wait for them to arrive while your engine is apart. I measured my gaps, put it back together and pulled it apart again when the order came in. I also did a full vanos rebuild and replaced the camshaft sprocket diaphragm springs. My engine is very quiet now.