Eric Experience
Well-known member
I have a failed 315 motor in my workshop. I have started investigating the problem and will post the details when I find the cause. Any 315 owners in Melbourne are welcome to inspect the motor. Eric
Really does sound like you have done all the right things Steve . Keen to see what Eric finds in there .My Main bearings where replaced only about 10,000ks ago, this will not help.
Investigation so far has proven that it is bad to go into something like this with preconceived ideas. I found no metal in the sump other than pieces of the failed bearings. All the oil galleries were clean. The general condition of the motor is very good apart from the crank shaft and bearings. Looking at the damage I now think it must have had sudden loss of oil pressure. The sump was full of the correct oil, the filter is not dirty. there are no blown gaskets or O rings. The item I suspect is the oil pump pressure relief valve. The valve is very similar in design to the Toyota "H" motor, this consists of a piston working in a bore with ports in it, the piston is moved towards the ports by oil pressure and returned by a spring. In the 315 the piston is PLASTIC and the bore is aluminium. With this type of valve the piston works over a limited stroke just at the point of opening the port. The plastic and aly are both worn. The question of what to do to prevent failure is not as clear as I had hoped, The fact that MB have not been able to fix it is a clue that it is not easy. There is a plug in the end of the gallery that could be used to fit an oil pressure warning switch. This plug can be accessed by removing the alternator, the plug is 23mm diameter with a 1.5mm pitch thread. the switch would have to be small to clear the alternator. the plug can be removed with a 10mm hex key. to restore the pressure if it was low I think would require replacing the oil pump as the valve is not likely to be sold as a part. Some one with a reamer could clear the bore and make an oversize piston out of steel. Eric.
Can anyone answer whether the design of the NAS aka NAFTA newer 2.2L twin turbo engine is similar or the same? Edit: After a quick search I presume that "315" refers to the NCV3 model 315 Sprinter and not the older OM315 engine....To me the pump is just to small for the twin turbos. What we need to do is fit an oil light as a matter of urgency. With the price of the rebuilt motors now at $13k plus fitting we need to stop the damage. If the light comes on then we drop the sump ... The greatest flow is the cooling flow for the turbos. Eric.