Quote:
Originally Posted by deansbimmer
I’m sorry but this assumption is simply incorrect. The central bolt does not hold the spring in place. It may cover one end of the spring but it does not retain it. It holds the center of the vanos hub (rotors) against the cam. The spring tensions the outer ring (rotor housing) of the vanos hub to prevent rattles under operation. There are pins on the other end of the spring that the spring nests in and tensions against but the cap keeps the spring coil from walking off the front of the vanos unit.
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Hi deansbimmer,
The washer and central screw definitely cover a few mm of the spring end, and it appears that this would be enough to keep it in place. The cover is relatively weak, as you know, and it appears that it is not actually pressing on the spring at all. Maybe it helps a bit, but difficult to say imo.
I found a document with some good cutaway schematics and description of the vanos adjuster units, which help a lot (you've probably seen them, I will post when back at the PC). It says that the spring is used for "coordinating the adjustment time between the advance and retard adjustment." Sounds like it acts as a sort of dampener between the two opposite motions of the vanos (advance one way, retard the other).
Dealer tech mentioned that it sets a home or central or neutral position, but it seems there is a separate locking pin for that, that seems to engage when there is no oil pressure.
Seeing those schematics makes me think that the only way the covers/caps could have rotated might be due to some shock loading and inertia effects i.e. The rotor being activated and hitting hard against the housing, perhaps after the oil drains/leaks out of the units, and thus causing the covers to shift very slightly due to their inertia. This could be part of that cold start rattle issue that I've read so much about...?
I'll post those schematics soon, they are extremely helpful in understanding how these adjusters work, and I couldn't find much detail at all via Google or the dealer, so really glad I stumbled across them!