THE BMW V8 NIKASIL MYTH
There are many dire warnings on the Internet about the 'Nikasil Problem' that affected the M60-engined E31's, E32's (730i V8 and 740i V8) and early versions of the E38 V8's that used the same engine from 1995 - 1996. All of these reports are completely out of date, it is time to revisit these claims in 2012!
Nikasil is a manufacturing process that was used by BMW to turn the relatively soft aluminium cylinder bores into a bearing surface. This process involved impregnating the bores with a Nickel-Silicone compound which chemically bonds with the Aluminium bore surface. The resultant bore has exceptional wear-resistance, much superior to the standard Iron liner.
Unfortunately, the high Sulphur content of some fuels (not necessarily the cheapest) broke-down the chemical bond resulting in a bore that was essentially machined aluminium. Where this problem occurred the piston rings would rapidly wear away the cylinder bore to a point where compression was lost. Once compression was lost the engine would fail to tick-over smoothly and power-output would reduce. Most noticeably, the car would become very difficult to start as the lack of compression at cranking speeds would not produce combustion. The cure (as is so often quoted) is to replace the short block, there is no chance of reconditioning the bores. The usual advice was to look out for V8's that rocked at tick-over or that smoked when started.
The above is all pretty standard stuff, and all pretty out-of-date. In 2015 the Nikasil issue is over 23 years old. The Nikasil problem has really been and gone. The fuel available in the UK is low in Sulphur and any V8 that was affected (and there were very few genuine cases) are either sporting replacement engines or being recycled. Once the Nikasil-impregnated bores were compromised they very rapidly deteriorated to a point where they were un-driveable and un-saleable.
One interesting point is the test for bore-wear is the
'leak-down test' which measures the amount of air that leaks past the
piston-rings at a given air-volume. The equipment consists of a reservoir of
compressed air at a pre-defined pressure that is passed through an aperture of a
given cross-section, this gives a metered amount of air. This air supply is
connected to one cylinder at a time who's piston is set to the bottom of the
power-stroke. The measured pressure at the cylinder is compared to the primary
air-pressure before that aperture and expressed as a percentage with greater
than 14% difference being a fail. What is important about this is that a
flooded M60 will fail the test whether has bore wear or not! Anyone
who has tried to start a flooded M60 will notice just how fast they turn-over,
this is because the oil that is normally between the piston-rings and the bore
has been washed away by the over-rich fuel. I wonder how many M60's have been
scrapped just because they were flooded.
However, the 'Nikasil problem' is brilliant news to buyers of V8's as it makes them less desirable and hence, cheaper. I have never heard of a genuine case of bore-wear on the M60 due to Nikasil and I've been driving 7-Series cars for a long time, including an E32 V8 730i! The lumpy V8's have all turned out to be caused by the usual 'oil down the sparkplug holes' or PCV valve failure, both of which are easy to repair (we have full instructions here). My own '93 V8 730i was sold as a 'Nikasil' case and demanded a low buying price, just like every other V8 E32 I have known, the fault was a punctured PCV valve!
There are some E32's with
worn-bores, but that is true for any car with 15-year-old bores, you are just as
likely to see worn bores on an M30 or M70 as you are on an M60. In 2015 the 'Nikasil Problem' is
over and done!
Go and bag yourself a bargain V8