Im US Forum wird mal wieder heiss diskutiert ueber dieses (eventuelle) Problem beim M70 Motor, wo es genau so sein soll wie beim R6, dass sich die Schrauben loesen und durch fehlende Oelversorgung groessere Schaeden entstehen, wie eingelaufene Nockenwellen etc.
Der V12 hat ja acht Schrauben insgesamt dafuer, die abgesichert werden sollen.
Beim R6 ist das ja nun schnell gemacht, aber beim V12 ist das ja nun mit erheblichem Zeit- und Kostenaufwand verbunden. Allein die Dichtungen fuer die Ansaugspinnen kosten ja schon so um die 500 EURO, wenn sie dabei drauf gehen sollten. Und die muessen wohl runter, oder sonst kommt man nicht an die Deckel ran, denke ich.
Wer hatte denn nun schon einmal beim M70 wirklich solche lockeren Schrauben festgestellt? Bei KM-Stand??
Waren vorher thermische Probleme wie Thermostat defekt oder aenhliches, die da auch schon zu beigetragen haben koennen?
Gab es abgerissenen Kofschrauben? Soll ja bei den vor-facelift- Motoren auch ein Problem gewesen sein.
Mein Motor laeuft im Moment os sauber und ist super dicht, kein Oelverlust, kein Wasserverlust, da will ich nicht soviel Geld fuer evtl. nichts ausgeben, ganz abgesehen von dem Zeitaufwand.
So nach dem Motto:
Remember if it Aint Broke don't fix it
Hier mal eine Kopie von einem Beitrag aus roadfly:
Donzo is right on the money with the info on the banjo bolts- this is all correct. Without the tightness in these, the cams are not being lubricated, and the surfaces eat away at eachother. This is what happened in my M70. On some rockers, the surfaces were severely eaten away on the edges- NOT good. The way you can tell this is happening is near impossible without disassembling the engine to inspect it. By the time you can hear the valvetrain noise, like in my car, it is too late, and you have a major PITA on your hands. I see your car only has 86k miles on it, so chances are your engine is still good at this stage. However, I would recommend you open it up and do the much-documented procedure of locking in the banjo bolts, as 'insurance,' especially if you plan on owning the car for the future. It isn't THAT bad to get to, once you get past the dreaded intake manifolds, which, handled the right way, aren't too bad to get off either. You first must remove the thin acoustic insulation strips between the rocker cover and the manifold, then you have straight access to the bolts holding the manifold to the head, without needing the use of swivel joints- just extensions required.
Again, this is HIGHLY RECOMMENDED, i would recommend it to any 750 owner.
The head bolts. Again, Donzo is correct by saying that the only causes of head bolt failure are overheating, or a prev owner not replacing them. I had roughly 140k miles on my car when I began my M70 rebuild (just about to start putting back together next week hopefully =)) and all my head bolts looked brand new, despite almost EVERY other part on the engine being on its deathbed. It is therefore VERY unlikely that your car, with 86k miles, would have any problem whatsoever. In the unlikely event that a head bolt does break, it is unlikely to have a massive effect, as there are lots of them, 14 on each head if I remember correctly. Assuming that many of them broke, for argument's sake, the things you would notice would be the same for a head gasket failure: massive consumption of coolant (leaking from water jackets into cylinders), loss of power, exhaust changes, etc. Again, this is unlikely on your car, and even on the worst cars it seems to be fairly rare.
I hope I've answered your questions,
Best regards from Australia,
John