My 2012 VSK YD25 let go completely at 360,000km.
No definite cause but it has no compression on any cylinder.
Suspicion is that camchain wear allowed the pistons to lightly touch the valves, although it also looks as if the pistons have got very hot on the exhaust side.
I'm not sure if that's normal or not for a relatively high-mileage engine.
There are really light marks on the valve reliefs in the pistons, such that you can only see them with a bright light at the right angle, but it does look like they made enough contact to scuff the carbon on the pistons. No bright metal is showing on the pistons or valves.
It went quietly, without overheating or any other sign of impending doom. One day it went into limp mode, cleared that and it made another 300m before going into limp again. After that it went into limp mode on every start and after a few of starts, nothing- it was totally dead.
Mechanic initially suspected a fuel issue, replaced the fuel suction valve with no result.
After the final start it cranked slowly, as if it had done a bearing, but as I said, no overheating and also no metal in the oil.
Engine removed by my mechanic who confirmed no compression but due to labour cost hasn't done more than remove the head to look for damage.
I'll get to it in time and work out exactly what went wrong, unless I exchange it for a rebuild, but for now I have two questions:
1. There was no camchain noise, ever, so is it really likely that the chain was stretched or slack enough to cause contact? As I understand it, the 140kW YD25 has the weak camchain issues solved. The tensioner can always fail, or course, but everything was checked and the timing was OK before the head was removed.
2. A wrecker suggested that the gudgeon bushes wear and allow the pistons enough vertical movement to contact the valves. This sounds unlikely to me, especially as there was no knock (even if there was unnoticeable, very light contact with the valves, surely I would have heard the little ends knocking???), and I have searched the forum and found no previous mention of a similar issue.
Is this a known problem?
Update: I've spoken to my mechanic again, he thinks the injectors are the cause of the failure and the pistons are worse than they look. We turned it over and one of them is definitely very tight. I say one, because it has a tight spot when #2 is near the bottom of the bore. There's no damage visible in the bores and no tight spots when the other pistons are at the bottom.
TIA for your input.
Rich
No definite cause but it has no compression on any cylinder.
Suspicion is that camchain wear allowed the pistons to lightly touch the valves, although it also looks as if the pistons have got very hot on the exhaust side.
I'm not sure if that's normal or not for a relatively high-mileage engine.
There are really light marks on the valve reliefs in the pistons, such that you can only see them with a bright light at the right angle, but it does look like they made enough contact to scuff the carbon on the pistons. No bright metal is showing on the pistons or valves.
It went quietly, without overheating or any other sign of impending doom. One day it went into limp mode, cleared that and it made another 300m before going into limp again. After that it went into limp mode on every start and after a few of starts, nothing- it was totally dead.
Mechanic initially suspected a fuel issue, replaced the fuel suction valve with no result.
After the final start it cranked slowly, as if it had done a bearing, but as I said, no overheating and also no metal in the oil.
Engine removed by my mechanic who confirmed no compression but due to labour cost hasn't done more than remove the head to look for damage.
I'll get to it in time and work out exactly what went wrong, unless I exchange it for a rebuild, but for now I have two questions:
1. There was no camchain noise, ever, so is it really likely that the chain was stretched or slack enough to cause contact? As I understand it, the 140kW YD25 has the weak camchain issues solved. The tensioner can always fail, or course, but everything was checked and the timing was OK before the head was removed.
2. A wrecker suggested that the gudgeon bushes wear and allow the pistons enough vertical movement to contact the valves. This sounds unlikely to me, especially as there was no knock (even if there was unnoticeable, very light contact with the valves, surely I would have heard the little ends knocking???), and I have searched the forum and found no previous mention of a similar issue.
Is this a known problem?
Update: I've spoken to my mechanic again, he thinks the injectors are the cause of the failure and the pistons are worse than they look. We turned it over and one of them is definitely very tight. I say one, because it has a tight spot when #2 is near the bottom of the bore. There's no damage visible in the bores and no tight spots when the other pistons are at the bottom.
TIA for your input.
Rich
Last edited:
3 litre diesel.
