Originally Posted by markjenn
Thanks for clarification. I was reading the shop manual process for valve clearance checks and noticed that they said only to line up the marks and then check #1 without the normal check one makes to see if the valves are both closed so you have the right TDC. I thought that meant that those index marks only line up when 1 is TDC between compression and power. Very clever.
While we have the experts in this thread, what are we seeing with respect to cam chain wear and clearances at that first 18K check?
Normally, I like doing valve clearance checks myself, but there are a couple of special fixtures and this is the first motor I've worked on which has a check for valve timing. So I'm thinking of just leaving it to the dealer. (I tend to be mistrustful of whether dealers actually do the work given that a "clearances are fine" clean bill of health is essentially unverifiable.)
When you are checking the valve clearance, you need the little BMW special toolkit. It consists of the following:
- A small threaded pin which is used to fix the engine in TDC (cyl 1)
- A calibre with two sides. Side A is used to check the camshaft timing at the 18K service. When side A doesn't slide on de camshafts, side B is used to re-align the camshafts to fixed angles (i believe 1.6 degrees for the intake camshaft and 1.7 degrees for the exhaust camshaft).
- A substitute cam chain tensioner which needs to be fitted before
you adjust the camshaft timing .
- A small round tool with a standard issue ratchet socket on the other side, which is used to rotate the camshafts along the sprocket.
- And finally, not included in the BMW kit, a torque wrench (or more like a torque screwdriver) with a range of 0-5 Nm. The substitute cam chain tensioner used during the adjustment of the camshaft timing needs to be torqued to exactly 1.2 Nm.
If you are performing the 18K service yourself, remember that besides checking the valve clearance, you also have to check the camshaft timing. If the camshaft timing is within spec, all you need is the threaded pin to block the crank in the prescribed position, and the calibre to check the timing. If the timing is out of spec, you need the whole set of tools.
Replacement of the timing chain (and the timing chain sprockets of course) is only necessary when the camshaft timing is out of spec, and also out of the adjustment range of the sprockets.
This job is doable, but don't spare money on the tools, you really need them to perform this job accurately. We are talking about .1 degrees here. Also, double check every step you make, and read every step in the manual twice before you proceed to the next step. The tech in this engine is about as precise as it gets. F*ck ups are easily made, and also easily avoidable.