Originally posted at http://www.koalamotorsport.com/tech/misc/v8shortblock.htm

What's wrong with the V8 ?

09/19/04.  The original "What's wrong with the V8" article was written in 1997.  It's time for an update.  The original, unedited, article is below.

First, let me make it clear that any and all warranties on this engine are long over.  The 6yr 100K mile warranty ran out some time around 2001.  Don't expect BMW to come to your aid if you have a problem, it's not their fault that previous owners of your car didn't act on the chance to have the problem corrected.

An important point in the Nikasil issue that has become quite clear over the last couple of years is that it's really not an issue any more.  BMW, for the second time in history, succeeded in forcing a change in US fuel production.  Some time around 1997/1998, the US fuel companies cleaned up their fuel, removing the large amounts of sulphur that had been commonplace before then.  

If you are considering the purchase of an M60 equipped vehicle, you should have it checked to see if it has a Nikasil or Alusil engine.  If it has a Nikasil engine, you should have a leak down test performed.  If that leakdown test shows results below 15% on all cylinders, you should not consider the engine to be a problem.  If the engine has not failed, it probably will not fail due to the new fuels.

We personally have seen Nikasil engines with 30+K miles on them with 4% or less leak down, because the engines were installed at or about the time that the fuel changes took place.

Read the original article below, determine the engine, have the leak down test performed if necessary, and make your own decision.


Original article.

BMW released the M60B30 and M60B40 V8's with the 93 model year 5,7 and 8 series. These engines ran until the 95 model year. From the 96 model year, they were replaced by the M62B44. The 3.0L was dropped in the US, but the rest of the world got the M62B35, a 3.5 litre V8.

There are many rumours about the fate of the M60 engine, but only one is true. The engines have been known to suffer damage to the cylinder bores from the excessive amounts of sulphur in the US fuels.
The blocks are made of  Nikasil, which is Aluminum impregnated with Nickel and Silicone. Apparently , sulphur reacts adversely with the Nickel , causing very slight blemishes in the top few millimetres of the cylinder bore. The cylinder bores are crosshatched, which is the name given to a pattern scratched into the surface of the cylinder wall. These scratches help seat and seal the piston rings, allowing good compression.

When the cylinder walls become damaged, the piston rings can no longer seal properly. As a result, the engine suffers from "leak down". This is the term given for the amount of air that can escape past the piston as it attempts to compress the air into the combustion chamber.  A near new engine , in good condition, should have a leak down rating of approximately 5-8%. BMW's maximum allowable leak down , on any engine, is 15%. Anything beyond that requires repair to the engine.

Leak down can also be caused by poorly seated valves.

The problem in the V8's manifests itself as an EXCESSIVELY rough idle. These engines, due to their performance oriented cam shafts, have a noticeable "rock" at idle, this is completely normal. However, excessively rough idle will cause the entire car to shake, usually unevenly.  The problem can also cause the engine to lose so much compression  that it will no longer start.

While BMW was investigating the cause of the problem, several different methods of repair were tried.

First, they decided to raise the operating temperature of the engine, in an attempt to get a better burn of the gas, and therefore lessen the damage.  The benefits of this campaign , which included replacement of the engine EPROM and thermostat, were negligible, if existent. However, they were an attempt to fix a problem that was not yet fully understood.

Once it was decided the engines needed to be opened and repairs made, the first try was installation of new pistons and rings, this was only tried on a few engines and was immediately dismissed as not viable.

Next step was to replace the short block assembly. This is what is still being done now, however, until the problem was 100 percent diagnosed by BMW, the replacement short blocks were of the same material as the original engines. This was not so much an oversight, but the only possible way of keeping cars on the road until a permanent solution could be found.

As a measure of good faith, BMW initiated an engine warranty, covering all internally lubricated parts, which includes the short block, for 100,000 miles, or 6 years. Until this, the engines were only covered under the standard 4 year 50,000 mile warranty. 

Now, as the short blocks were being replaced with the same exact part, future problems could be expected without a doubt. The result of this situation is that some cars have had 2 and even 3 short block replacements.

As of early 1997, all replacement short blocks were of the new material, called Alusil. This material has been used in the V12 engines since their inception. No reason was given for the change to Nikasil, but I'd like to bet that guy no longer has a job.   Anyway, Alusil does not suffer the same problem as Nikasil and if the Alusil short block has been installed, you no longer need to worry about the situation.

How do you tell which material is in your short block ?

That part is fairly easy. But it requires getting under the right front of the car. All M60 and M62 blocks have casting numbers on the right side, directly alongside the 3rd cylinder, slightly above the coolant drain bolt.

These are the casting numbers to look for :

Nikasil M60B30    1 725 970 or  1 741 212
Nikasil M60B40    1 725 963 or 1 742 998
Alusil M60B30      1 745 871
Alusil M60B40      1 745 872
Alusil M62B44      1 745 873    NOTE, all US market M62 engines are Alusil.

This is the only way to determine which M60 you have, short of removing a cylinder head.

In performing engine repairs or rebuild procedures in the future, it is imperative that you correctly identify the cylinder block, as the pistons and rings used in each style are different and not interchangeable.

What do I do if my engine idles rough ?

If you feel your M60 is idling roughly, make an appointment with your dealer for an idle quality check. This check is free, under the conditions of the 100,000 mile engine warranty. During this test, the technician hooks the car up to the BMW diagnostic computer system, which monitors the condition of the engine. If, during this test, the computer finds that there is a potential problem, it will order the technician to perform a manual leak down test.  If the tech finds any ONE cylinder to have more than 15% leak down, you will be advised of the need for a new short block. You will then be requested to either leave the vehicle, or make an appointment to bring the vehicle back. The dealer will require the car for approximately 5 days, during which , they are to make a rental or loaner car available to you. If you have the test performed, but the results do not show the need for a new engine, do not go running to the next dealer for a new test.  The dealer gets paid by BMW for his time, however, repetitive testing will not be covered, so the second dealer will not get paid for his time. This is unfair to the dealer.  If your car passes, but you feel it should fail, take it in for another test in a few months, not straight away.


Return to E38.org