The property class of a metric (carbon) steel bolt is indicated in two numbers separated by a dot. The first number before the point indicates the maximum tensile strength expressed in hecto-Newton per square millimeters. The second figure behind the dot indicates the ratio between the minimum yield stress and the minimum tensile strength, times ten. With other words, the commonly used 8.8 property-class has a minimum tensile strength of an 8.8 bolt is 800 N/mm2 and a minimum yield strength of 640N/mm2.
In the European automotive industry, property-class 8.8 is commonly used and where necessary (e.g. high stress), 10.9 or even 12.9 is applied, but 8.8 is the minimum. This rules out the general bolts that you can find in your local hardware store; these are generally no better then 4.6 or 4.8. These are OK for general non-critical applications, but generally not suited in cars.
This also is the reason why stainless steel bolts are not used in cars. Stainless steel has a much better resistance to corrosion then surface treated carbon steel, but does not have the high tensile strength from a steel bolt. However, for non-critical applications, stainless steel bolts may be used to rule out the concerns of corrosion. One such place is the crank-sensor. It is fitted with a single M5x12 bolt that can be fastened with 6.4Nm max. But 5Nm will also suffice and this allows the use of a stainless steel bolt of A2 property class. Do not use the commonly used A1-class as these allow less then 40% of the tensile strength of an A2 class bolt. The allowed 2.4Nm simply is too low, even for a simple sensor.
I also made a start with the overhaul of the engine wiring-loom by cutting the damaged section. The plan is to make an entirely new branch to length and solder it onto the engine-wiring loom. The branch that has been cut will be kept for future reference. It is needed for properly installing the connectors for the three temperature sensors.
From each wire, I cut a section of roughly 1cm in length to determine the exact color-coding. If possible, I will source new wiring with the same color-code.
To determine the condition of the copper stands, I stripped the insulation of one wire. Apart from the expected oxidation, the conductor is pretty much OK. This is good news as there is no need to strip the wiring-loom any further in this branch.
More worrying is the insulation of the main-supply lead for the starter-relay. The insulation is ******* due to aging and conductive losses, or simply heat. Even though that the operating voltage just is 12V+20% and the required creepage distance is less then the depth of the cracks, that is no more then a layman’s approach.
In reality, the load is inductive and during switch-off, the voltage will rise according to V = L*dI/dt. Depending on inductance of the load and change of current during the switching time (dI/dt), a voltage transient rising far above the battery voltage will be induced. This transient voltage can be in excess of several hundred volts and with the insulation damage, a break down to another conductor may occur. This can eventually lead to damage of electronic parts.
In fact, these cracks were the reason for me to prefer a new engine-wiring loom, but since these are no longer available, I need to replace the conductor. This requires the entire disassembly of the middle branch, which is much more difficult then replacing the branch for the temperature senders.
My plan is to create a list of the required parts and create a schematic of the circuit before further disassembly.
Last but not least the alternator; it has been replaced in the past as it lacks the BMW part numbers. It is however a genuine Bosch part. From a technical point of view, there is no need to replace it, but I do not like the corrosion on the pulley and the blades. A new alternator is 320 Euro from BMW and 240 from a Bosch specialist (rebates excluded).
The brushes still have enough life left in them, but they differ in length as can be seen on the following picture.
After removing of the pulley and the cooling-blade, the alternator looks pretty much OK and just needs some mild cleaning.
If the cooling bade and the pulley are available as separate parts, I will simply replace them together with the brushes and the interference suppression capacitor (22uF/100V).
SOLD 
Linear Mode
