TDCi DW10 Engines: Cam Chain Oil Supply

[AlCan]

Originally Posted by kevino

Wouldn’t worry about it.

Thanks! Would love to be able to take that advice!

However, I have a 2011, done 259,000km, one prior owner, fully maintained, no noticeable cam chain noise.

In contrast, the 2013, 133,000km but already 4 or 5 prior owners, (was cheap, but) probably badly maintained, already has this problem. I was hoping the 2013 would replace the '11 as that one has clutch/gearbox issues...

You know what they say - the best laid plans... But I was hoping the '13 would keep us on the road. I'm hoping that if I can get the tensioner sorted, it might be ok.

Oh, and, I've watched too many Alan Howat videos...! It looks to me like lack of clean oil causes these issues, and it seems, once it starts, it's one way.

[AlCan]

Originally Posted by AlCan

Oh, and, I've watched too many Alan Howatt videos...!

Like these:

https://www.youtube.com/watch?v=UBs1FLVyxdk

https://www.youtube.com/watch?v=aVFa8H1RpSY

https://www.youtube.com/watch?v=-jLzRoDQdyo

https://www.youtube.com/watch?v=08VYLAQ5xr0

It looks like the MD has many more cam chain issues than its predecessors.

The cam chain is a redesign, which on the face of it, looks like it should be good. It saves space by turning the tensioner the other way up, allowing an oil filler / handy cam chain inspection hole to be placed in the rocker cover, but this may be also be why it seems to fail so often.

In the earlier models, the cam chain tensioner presses down on the upper pass of the chain. This causes the chain to wrap further around the sprockets as it wears. However, the new design pushes UP on the upper pass of the chain, which has the opposite effect. I can't see that that's a big deal because either way, it's on the slack pass of the chain, and because the presser foot is facing upward, you'd imagine, if it's still pushing oil out through a hole in the foot, that this would lead to improved oiling of the chain, but they seem to snap more often. Maybe they reduced the oil supply at the same time, making it more prone to blockage?

However, when you look at the way the chain sits when the tensioner is not tensioning, such as at 7:48 in the https://www.youtube.com/watch?v=aVFa8H1RpSY video, you start to get an idea of what might be happening.

With the tensioner pressing on top, it's working in the same way as gravity. The chain will naturally hang down even if there's no tensioner, and the tensioner plunger itself will come to rest after a stop, hanging down on the chain after the oil has drained away. The spring inside it will ensure that too.

However, in the case of the tensioner pushing upwards, once the internal spring breaks, the tensioner will drop over time causing the chain to take on an M shape as per 7:48. It's easy to imagine that when the engine starts from cold with no oil pressure, the slack chain coming off the driving sprocket (LHS, [rear] exhaust cam) is going to crash into the side of the tensioner foot, and if it's a bit worn and stretched, it's likely to jam and be dragged between the tips of the sprocket teeth and the side of the tensioner. It can only break...

I would almost guarantee that's what's causing these chains to snap. I haven't surveyed it, but I'm willing to wager that snapped MD chains always have broken tensioner springs (first). And that they always break on startup, after a longer period of not running.

Howzat, Alan Howatt?

[AlCan]

Originally Posted by AlCan

I would almost guarantee that's what's causing these chains to snap. I haven't surveyed it, but I'm willing to wager that snapped MD chains always have broken tensioner springs (first). And that they always break on startup, after a longer period of not running.

EEeeee! Well, I got that wrong... Watched some of the video of the split cam sprocket hub again.

Having an intact tensioner spring is no guarantee that your MD chain won't break. So I guess the overriding thing is chain wear, which comes down to chain lubrication.

Franco - Thanks for your adventurous account! What a machine! Yes, I believe these engines are very durable and can take a thorough hiding, so long as the oil is maintained. Howatt's taxis have been getting much higher k's - equal numbers of MILES! Like I say, my 2011 engine has even more k's on it than yours, and is still going strong. Maybe 90% of its ponies still home. It even still has its original EGR valve still connected and working correctly (touch wood), so it hasn't had a lazy life. (Haven't tried disabling that one [no need anyway] as it has an ECU return signal so would probably throw the Mother-In-Law light...)

I've towed a fully loaded, covered 8x4 trailer to the South Island multiple times - it gets around 8l/100km on those trips but can still get 5.6l/100km on a trip through snow and ice in Tiptronic mode (without trailer of course). And the cam chain is still quiet...