Scania 2004 580 v8 . Seems this truck has over heated badly. It burst a water pipe, the large pipe .
The low water warning light was not working, driver drove it until it stopped, engine oil light came on. Truck had new pipe fitted and was refilled but now there seems to be a knock on start up when cold. It stops after a few seconds.
Oil pressure is around 4 on gauge but moves up and down slightly , just under 4 to 4, very small movement. So question is, what is damage, what is knocking.
Should I drop oil to inspect it for debris .
Oil pressure goes to 8 when revved up .
One can only guess at what has happened, probably a piston/liner seizure due to lack of coolant maybe followed by a bottom end bearing partially disintegrating because the oil got too hot. The damage is done, time to pull it apart; or not considering the age of the vehicle and its probable value. Best option is possibly to retire it to yard shunting. Occasionally engines will run on for some time after an overheating seizure, but they will eventually expire - when that will be is in the lap of the gods. What isn’t clear is whether the oil light came on because the engine had stopped or while it was still running. What you can say is that the engine will not live long with a bottom end knock, whereas some makes can survive for a while with scuffed pistons and a knock.
Ouch, that doesn’t sound good, I’d be getting that on the next boat to Walvis Bay. 
Grabbed a piston.If a main had grabbed your oil pressure would be way under 4 bar and lack of coolant wont make a main or big end pick up.
Truck has run fine since. Still has a knock, what I see is unburnt fuel on one outlet of exhaust manifold. So over fueling on one injector, I suspect that is also the knock. Injector knock due to too much fuel, you can really heard it when pulling a load, a fast tapping sound under the normal engine noise .
This could be unrelated or an injector nozzle could of got damaged when truck over heated ■■? Can an injector nozzle melt, I think I read that somewhere?
Is removing this injector easy, what is down time to do a repair? Injector is working, probably needs nozzle and carbon build up removed.?
Because the piston has grabbed you have no compression to burn the bloody diesel.
Maybe you were right. So engine got worse, knocking bad and could not be driven.
It ended up with two damaged pistons, these have been replaced. The truck does not sound right though, very rough idle.
How do I smooth out this idle. Injectors and valves /tappets have not been adjusted, do they need to be to enable smooth running.
Engine sounds poor. Could all this unburnt fuel have coated exhaust valves with carbon?
What should oil pressure be on tick over ? Goes to 7 when revved up.
argosy2006:
Maybe you were right. So engine got worse, knocking bad and could not be driven.
It ended up with two damaged pistons, these have been replaced. The truck does not sound right though, very rough idle.
How do I smooth out this idle. Injectors and valves /tappets have not been adjusted, do they need to be to enable smooth running.
Engine sounds poor. Could all this unburnt fuel have coated exhaust valves with carbon?
Did you change the liners? If not you have wasted your time and money.
argosy2006:
What should oil pressure be on tick over ? Goes to 7 when revved up.
When the engine is warm oil pressure at tickover should be between one and a half to two bar.
I was always lead to believe anything !!! with Scania written on it was the greatest thing since sliced bread and just never !!! went wrong ?.
argosy2006:
Maybe you were right. So engine got worse, knocking bad and could not be driven.
It ended up with two damaged pistons, these have been replaced. The truck does not sound right though, very rough idle.
How do I smooth out this idle. Injectors and valves /tappets have not been adjusted, do they need to be to enable smooth running.
Engine sounds poor. Could all this unburnt fuel have coated exhaust valves with carbon?
WOW , you didnt set valve clearance and unit injector force AFTER changing a piston why FFS…
whats the chassis number then i can tell u if the scania diagnosis can check compression and injection via the lap top…have you got a pic of the pistons u took out■■?
get the valves set
shugg:
I was always lead to believe anything !!! with Scania written on it was the greatest thing since sliced bread and just never !!! went wrong ?.
I was always taught that a nice wife ,a couple of kids and a pretty little house would make me a happy man.
What a load of bollox,still you live and learn dont you.
Valves and injector were not set after pistons were fitted.
argosy2006:
Valves and injector were not set after pistons were fitted.
who on earth would pull the heads of any engine let alone a holy V and not set valve clearance ,did they put the pistons in with a hammer n chisel as well, please name and shame , still waiting to see them old pistons !!!
I expect that working out the firing order of a Vee engine was beyond them. 
Why would the valve clearances have changed so much because you pulled a cylinder head?
Did the push rods get longer or the head gasket get shorter?
We are hardly talking some bloody racing engine here are we.
These bloody things run with half a mill clearance hardly state of the art are they.
They are a donkey and thats why they can run for a million cliks.
But once you cook them they need a full repair.
500 horse out of a 16 litre engine is hardly mega power is it.
I would have loved to see old pistons too. I did not see them. One was in bits in sump, of course people do exaggerate, one was badly scored . Got injectors and valves so on set . Truck sounds much better.
This garage that set them said 6 solenoids on injectors were broke? So needed 6 fitted, cost another 1600.
Truck pulled great , would these solenoids effect pulling power? I guess not considering 6 were no working, pulls same now.
Exhaust seal rings in manifold are gone, this is causing a lot of noise under load. It’s almost a tapping sound as the exhaust leak is so small around these rings, it’s like a tommy gun under load.
Also a knocking sound in engine, but when I listen to scania v8 pulling loads in vids on youtube I can hear this sound in all of them, it’s under the engine sound. Must be v8 sound.