My thinking or the ticking issue and the reason the new HVA's are not fully rectifying the problem is that the HVAs pull in air on start up. The issue I think is not that the compressed adjuster at shutdown is bleeding down but what happens when the engine is started-up with an adjuster that has bled down. I think it is impossible to believe that the HVAs won't bleed down over a period of time.
The HVA is under load at shutdown it bleeds down slightly. The oil leaks into the head and drains from the head to the crankcase. Remember the HVA is not cycling so no air is being introduced in, just some oil has leaked out. However upon startup the HVA begins to cycle and needs to be refilled since it has lost some oil. However oil pressure has not reached the head and the HVA pulls in air probably almost immediately. If the engine is run long enough, the air will be exchanged with oil and all is well. However with short trips the air is not all fully evacuated from the HVA when the engine is shut down again. The vicious cycle continues with these short runs, maybe or maybe not all on the same HVA. The valve in the revised head I believe retains oil in the head for the HVAs to pull back in after they bleed down versus air. I don't believe the valve holds oil pressure or does it keep the HVAs from bleeding down.
However; the one thing that is confusing is that is it always is just one HVA in the rear that makes the noise. This is common with almost all situations.
Also we don't hear multiple HVAs ticking.
- Maybe it is due to resonance and that makes it sound like the ticking is coming from the rear of the engine.
- Or the engine shuts down roughly at the same crank position, which is doubtful but could be tested.
- Or the rear HVAs are closer to a oil drain passage in the head so they are mostly affected.
- Or the rear HVA is the furthest from the oil supply thus last to get fresh oil on start-up. The others would tick however they get oil to them fast enough that they don't pull in much air. I bet this is the case.
Just my thoughts.
Last edited by kkowalsk; 02-18-2010 at 03:35 PM.