| The
BMW M60 V-8 and BMW M52 6-cylinder engines (the M52 Nikasil
engine never came to the USA) with Nikasil cylinder bore linings
are particularly vulnerable to fuel (gasoline or petrol) with
a high sulfur content.
The sulfur
in the fuel breaks up the Nikasil
lining in the cylinders, causing a loss of compression. Once
the lining is damaged, excessive bore wear of the soft, underlying
alloy occurs very quickly. Some Nikasil engines have failed
in as little as 30,000 miles. And the effect
is cumulative, so if the engine has ever been run on high
sulfur fuel, the damage may already have been done and premature
bore wear may result.
Some symptoms
of the Nikasil problem are rough running at idle and difficult
cold starting, both due to loss of compression. In severe
cases, the loss of compression is so bad that the engine loses
power. Oil consumption increases dramatically as oil is sucked
up the side of the leaky pistons. In extreme cases, the compression
decrease is so severe the car will not start in cold weather,
especially M52 6-cylinder engines.
Over the
years, BMW has provided replacements with steel, cast-iron
or Alusil lined engines, at considerable cost to the manufacturer.
Often, disgruntled owners have borne the brunt of these replacement
costs, and prospective buyers are at risk, too.
The Nikasil
coating process was developed by the German firm Mahle, originally
for use in the Mercedes Wankel rotary. Audi, BMW, Ferrari
and Jaguar have all used Nikasil engines in their production
cars. Porsche used Nikasil in their turbocharged 917 - 935
series of race cars. In racing two strokes, both Morbidelli
and Rotax have had great success with Nikasil.
^More
at the top right^
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Nikasil
has been used in thousands of professional grade chainsaws,
motorcycle and marine engines, and even many NASCAR Winston
Cup and Formula One engines. Nikasil has been used in high
performance engines because it allows the total elimination
of poor-cooling cast-iron, and it is harder and more oleophilic
(oil-liking) than cast-iron.
The
Nikasil cylinder coating is a nickel and silicon carbide matrix
coating about 0.07mm (.0025-.003") thick. The Nikasil
treatment coats a layer of nickel-silicon carbide, usually
by electrolytic deposition, to the inner surface of aluminum
cylinders. The nickel matrix is very hard, yet it is relatively
ductile. Dispersed through the nickel are particles of silicon
carbide less than 4 microns in size. These extremely hard
particles make up 4% of the coating and form a multitude of
adhesion spots where oil can collect. Beside providing a long
wearing surface for the piston and rings, the silicon carbide
particles contribute to longer engine life by ensuring good
cylinder lubrication.
So why
is there a problem? BMW reportedly did not discover the problem
with Nikasil in their original testing because they used only
high-quality fuel. Sulfur should be extracted from fuel before
it is used, but since it is a costly process, oil companies
may not remove as much as they should.
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 Once
BMW was aware of the Nikasil crisis, BMW replaced the cylinder
blocks and also tried to ameliorate the problem by re-programming
the DME to ensure higher combustion temperatures.
Check
your engine. Only the M60 and the European M52 engines are
affected.
The M60
was fitted to all the E34 530i and 540i V8 cars. It was not
fitted to the earlier E28 5 Series or the later E39 5 Series.
Also, the early E34 3.0 cars (pre-1991) were M30 powered 6-cylinder
cars and were not affected.
The M52
was fitted to the European E36 3 Series, E34 and E39 5 Series.
The early models had the M50 (no VANOS) engine, and the later
ones had the M54 (double VANOS) engine. It is only the European
single VANOS M52 units that were affected, and even then,
not all of these engines were affected.
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