I got the 166 (3.0 V6 Sportronic) back today from a cam belt service at 180 000(ish) km - plugs, oil and filter, air filter, cams, idlers, tensioner, (plastic) water pump, power steering flush. I should really have done the rotors, but I couldn't afford it (I'll be hunting down local replacements). All-in it came to the equivalent of 600 pounds UK using their parts and labour (I was in a hurry and I get a year's warantee on the engine if the cam belt goes). They've got an interesting labour breakdown, with a fixed labour component for a set job. Thus, even if they take three days to actually do the job, the system prevents booking three days of labour against it.
Million to one things happen nine times out of ten
. I'm a very lucky guy for once: on the old (OEM) cam belt (fitted at 90 000ish km), ******there is a 10mm hole in the middle of the belt!!!!****** Lots of abstract impressions of the hole shape are along the outside of the belt and it has higher than normal scaling. Idlers are blemish free. The hole looks to have been there for some time, as the colour of the edges matches the worn colour of the rest of the belt.
I'm patting myself on the back now for insisting that no-one drove the car until the cam-belt was done. There was no obvious indication of impending failure, other than a barely audible tick-tick-tick (now gone) that you may expect from a variety of sources (worn valves etc). There was no "tooth hum" or "belt bounce" noise that would be an indication of poor tensioning. (from what I've read, it seems a large number of 166 cambelt failures are due to dodgy tensioners, with a slip and possible rip of the belt once the tensioner gives up).
In this case, it looks like it may be a screw or a bolt was dropped into a running engine. Comments? Freak event? Observation of other belt failures?
The water pump impeller was also starting to crack. I'm beginning to think that these cracks are latent defects. From the moment the plastic impeller is forced onto the shaft, a crack is formed on a very sharp edge, and the crack lengthens over time. Poor design, with no stress relieving features.
The car now runs smoother, smoother idle, more power, but still lags a bit (hardly sporting). Not great acceleration from pulloff, gets better after 2000rpm, but very consistant from there until redline, which is not what you might expect (is this just the way they are?). My manual (stock) 2.5l BMW seriously outpaces it. It's a bit of an unfair comparison, but I'll be hunting down possible problems one at a time, starting with the MAF and moving on to lambda (?) sensors. I'm guessing an engine specialist is probably better equipped for this testing compared to the agents. Maybe when I have some money....
Currently it runs 13.5 litres to 100km, mixed circuit (city/highway commute).
I'll see what I can do about retrofitting a metal impeller to the water pump and new SKF bearings to the idlers, then flogging them second-hand on e-Bay. The tensioner will be tossed.