morning, I havn't seen CJ post recently but he is very knowledgeable guy and it does explain a lot.
The previous all alloy twin cam engines had camshafts chains and tensioners lubricated by engine oil, and a considerably less sophisticated method than this engine. And I got 150,000 before I changed a chain. My Q4 has done 100,000, before the chains and tensioners were changed. Many more thousands that don't appear on this site will have similar reliability, I am sure. because the Variable Camshaft Timing System is continually working; never stops being involved with the ECU in determining the right advance/retard, the drain is spewing oil over upper chains continuously, cooling them as you say (oil enters the block after oil cooler) and treating the chains, sprockets, guides and tensioners to a veritable "Niagara Falls", cascading out of the camshaft drains.
The bottom chain tensioner is treated exactly the same as the cam shaft bearings, the crankshaft bearings, the hydraulic tappets and the con rod bearings. Oil starvation, may well be the issue that results in low tensioner pressure, but the afore mentioned are not given the same attention as the tensioner, particularly the lower one. The higher grade oil 5/40 may well have been specified originally because as has been said, "You would not use engine oil in your gearbox", perhaps it provides a little extra protection for the sprockets and chains.
However, as spray of oil continually coming out of the orifice of the lower tensioner; the pressure translated only by the diameter of the galleries and the orifice, but non the less being determined by an oil pump running at 3 - 6 bar, is not in my opinion; if the integrity of the system is soundly maintained, the problem Taking IAMBRERA's figure of potentially 20,000 unit failures out of a production run of 1,000,000 is 2%, if I have interpreted IAMBRERA'S correctly. This is not a major design problem. Production problem? Yes! Quality control problem, most certainly.
For this Engine, cast in Mexico, shipped to Australia, assembled, then shipped to Italy: torn apart and modified/rebuilt, it seems remarkable it should come anywhere close to that figure. If we are going to question the issue of engine against gearbox oil, one cannot neglect the quality of the steel and then Nitriding; previously mooted, comes into the equation. And if one wants to argue the case for an oil more suited to gears, then a valid observation was made in an earlier post about an "Oil Pre-heater".
The bulk of these cars are not new and therefore the quality of the maintenance work done on them is questionable? That they may have been maintained by Alfa dealers, sadly leads one to be more suspicious!
Coming into an enthusiasts ownership, it is implicit one understands this. And, if unlucky as was originator of this thread, it is unfortunate. That is why, if we are serious about Alfas, one needs to understand their DNA. If one doesn't then, given the cost of parts and labour, someone is going to empty ones bank account on the pretext of fanciful reasons for their unreliability. There is nothing wrong in complex systems that do not work, to pick the wrong reason to analyze why. That's the way research and de-bugging prototype systems works. And I know this, having spent many years abroad working to make systems, that left the development lab not working, let alone production, work!
Oil pressure is a fundamental issue for engine's wellbeing, not just the tensioners. Wear will reduce the longevity of the engine, but it will start to make unhealthy sounds.
A code failure can should be an early warning, not a terminal illness diagnosis. I still don't recognize the difference in the length of those two chains as an indication of stretch, certainly not length at least.
IAMBRERA, posted a brilliant link which could give a clue to that code error, but I have been reluctant to introduce it. However, here it is.
All cables have capacity - fact (and inductance but we will ignore that)
Timing for this engine is derived from two crankshaft probes and, I believe one camshaft probe.
The probes are primitive, in so much as they give a pulse on the Leading edge and the lagging edge of a slot.
These can be seen as a series of spikes, having a sharp leading edge and a sloping exponential lagging edge (curve)
The curve is indicative of the capacitance of the cable. Zero capacitance and it would simply be a spike.
The size of the capacitive element on the cable, determines how short or long the exponential curve is.
These pulses enable the ECU to determine the correct engine and camshaft advance timing.
Dirt on the crankshaft disk can cause errors with these pulses.
Dirt on the cable connectors; substantially oil fowling, "can and does increase the Effective Capacity of any cable".
Increase the capacity of these probe cables by fouling and a) the amplitude of the pulse will be reduced, or b) if the increase in capacity is so great, the pulse is lost: "Its energy is expended in charging up the capacitance of the cable"
It is easy to check this as many modern D.V.M's have a capacitance test position.
And if anyone has a mate who works for Alfa, the value can be checked on a new one from the stores.
So, nothing is ever that simple as designing in oil starvation to meet emission standards.
My priorities are:-
1. Low oil pressure as a consequence of wear. At 100,000 miles one should expect some deterioration.
2. Failure to maintain oil in tensioners due to seal/gasket failure.
3. Wear of tensioner and guide faces, which should be the principal reason. "The chain is not going to stretch by more than the nylon tensioner and guide faces are going to wear. I'm not saying they don't stretch, but the distance the chain revolves around the sprockets, guides and tensioners is going to decrease faster with worn nylon faces; faster than a chain is going to stretch.
4. Poor seal of gaskets on tensioners from new, vis a vis mine 100,000, thread started, 48,000.