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
315 exploding motors.
- Thread starter Eric Experience
- Start date
This is a real problem for all owners or potential owners of these vehicles and i do not wish this on anyone.
This motor is from my 315 which i bought from Mainheim auctions, i needed a commercial vehicle for a new business so i thought i would look around for a Mercedes sprinter because i liked the loo of them, size and more importantly stupidly thought that these vehicles being Mercedes benz diesel motor would last a long time.
Boy wasi mistaken, after a lot of research i found out that these motors have some sort of design flaw where they where seizing the main bearing at between 220,000 klms and 250,000klms. So i took every precondition which was suggested to prevent this from happening because i would not afford to buy a new $13,000 motor but it still happened.
One tip that i can give you guys is If see a oil level light turn on even briefly check out your oil pump or make sure you investigate why because the evening before this happened to my motor the oil light came on for a short period, i stopped and checked my oil level and found it was fine then the next morning my engine started making noises.
I think it is a total disgrace on Mercedes because they clearly know this is happening and have done nothing to help people.
This motor is from my 315 which i bought from Mainheim auctions, i needed a commercial vehicle for a new business so i thought i would look around for a Mercedes sprinter because i liked the loo of them, size and more importantly stupidly thought that these vehicles being Mercedes benz diesel motor would last a long time.
Boy wasi mistaken, after a lot of research i found out that these motors have some sort of design flaw where they where seizing the main bearing at between 220,000 klms and 250,000klms. So i took every precondition which was suggested to prevent this from happening because i would not afford to buy a new $13,000 motor but it still happened.
One tip that i can give you guys is If see a oil level light turn on even briefly check out your oil pump or make sure you investigate why because the evening before this happened to my motor the oil light came on for a short period, i stopped and checked my oil level and found it was fine then the next morning my engine started making noises.
I think it is a total disgrace on Mercedes because they clearly know this is happening and have done nothing to help people.
Sorry to hear that Steve. I certainly agree that this is disgraceful from a company like MB. I spoke recently about this issue with a friend who is a BMW Master Tech and an MB specialist. He suggested that I should bite the bullet every 150K kilometres replace the main bearings and accept this as part of Sprinter ownership. Such a shame as the Sprinter is perfectly sized for my needs, has a beautiful ride quality compared to other vans of this genre and is well appointed. He also felt it was imperative that these vans be taken out for a good long drive at highway speeds regularly to allow heat to clear the DPF.
I bought mine ex Sydney where it had been a prestige shuttle. I subsequently found that a few of the oil changes had been done without the Low ash oils. I have just replaced all fluids. I am using the Fuchs GT1 PRO FLEX SAE 5W-30 which has the MB 229.51 rating. I was also advised to change oil&filter at 15,000klms interval at the most.
Hopefully the damage is repairable. Will follow this thread with great interest.
I bought mine ex Sydney where it had been a prestige shuttle. I subsequently found that a few of the oil changes had been done without the Low ash oils. I have just replaced all fluids. I am using the Fuchs GT1 PRO FLEX SAE 5W-30 which has the MB 229.51 rating. I was also advised to change oil&filter at 15,000klms interval at the most.
Hopefully the damage is repairable. Will follow this thread with great interest.
Really does sound like you have done all the right things Steve
. Keen to see what Eric finds in there 
.MB must know what they issue is but lousily won't own up to anything. Was your vehicle an ex-ambo?
Everything now points to oil pressure to the main bearing failing for some reason, it's obvious replacing main bearings will not provide the solution to the problem.
If I was an owner of one of these engines I'd be installing an aftermarket oil pressure gauge ASAP & keeping a close eye on it.
If I was an owner of one of these engines I'd be installing an aftermarket oil pressure gauge ASAP & keeping a close eye on it.
Eric Experience
Well-known member
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.
Eric,
Does the plastic piston have seals/rings or is it relying on being a tight fit in it's bore to provide a seal for the oil pressure to act against.
Is the Oil pump/relief valve that is used in this engine the same part number as that used in current engines. If MB have changed this part for the later series it would be a strong indicator that they know exactly what the problem is but don't want anyone else to know.
" main focus of the economy-driven configuration of the OM 651 was the design of the oil system, (NO GUESSING WHY ! ) The controlled variable for the delivery volume of the pump is the oil pressure in the main oil duct of the crankcase. This arrangement offers the benefit of a requirement-driven control system that is independent of the load condition of the oil filter and works perfectly together with the switchable piston cooling. For this purpose, a separate oil duct that supplies the oil injection nozzles is located in the crankcase. The oil supply to this oil duct is controlled by an electric valve. In addition to the consumption potential due to the lower oil delivery volume, the resulting capability to switch the piston cooling on or off based on the performance map features a HC emissions module due to the higher piston temperatures during the warm-up phase. The oil pump in the Mercedes-Benz OM 651 is a closed-loop vane cell pump that provides for automatic and adaptive control of the delivery volume."
extract from Scribd article
" main focus of the economy-driven configuration of the OM 651 was the design of the oil system, (NO GUESSING WHY ! ) The controlled variable for the delivery volume of the pump is the oil pressure in the main oil duct of the crankcase. This arrangement offers the benefit of a requirement-driven control system that is independent of the load condition of the oil filter and works perfectly together with the switchable piston cooling. For this purpose, a separate oil duct that supplies the oil injection nozzles is located in the crankcase. The oil supply to this oil duct is controlled by an electric valve. In addition to the consumption potential due to the lower oil delivery volume, the resulting capability to switch the piston cooling on or off based on the performance map features a HC emissions module due to the higher piston temperatures during the warm-up phase. The oil pump in the Mercedes-Benz OM 651 is a closed-loop vane cell pump that provides for automatic and adaptive control of the delivery volume."
extract from Scribd article
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owner
Oz '03 316CDI LWB ex-Ambo Patient Transport
So Eric, were all the bearings damaged, not just number 4 main? I guess that's the one under the most stress either way.
I had an old mini in which the similar design oil pressure relief valve would bind open in its bore. You had to blip the throttle to cause enough vibration/pressure to break bit free. The solution there was to use a stronger spring. There wasn't much else you could do, it was an alloy plunger in an iron bore. As long as it still opened at around 60-70psi it was fine.
Also, I'm assuming the pump is the same as in the lower output om646's, which don't seem to have this issue that we know of? I guess if the valve is stuck open, then there is still some oil pressure getting to the mains, but maybe it just too low a pressure to protect them from the forces in the high output version. Maybe it needs a smaller exit port?
I had an old mini in which the similar design oil pressure relief valve would bind open in its bore. You had to blip the throttle to cause enough vibration/pressure to break bit free. The solution there was to use a stronger spring. There wasn't much else you could do, it was an alloy plunger in an iron bore. As long as it still opened at around 60-70psi it was fine.
Also, I'm assuming the pump is the same as in the lower output om646's, which don't seem to have this issue that we know of? I guess if the valve is stuck open, then there is still some oil pressure getting to the mains, but maybe it just too low a pressure to protect them from the forces in the high output version. Maybe it needs a smaller exit port?
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Eric, Just a thought, as this is happening to the same main, at about the same kilometers, with the rest of the bearings in fair condition and abruptly with no audible indication of main bearing rumble could it be a fracture to the crankshaft due to design or metal fatigue allowing the shaft to flex and destroy the bearing?
does the oil light that steve saw flicker the night before the big bang have a sensor that can detect oil contamination? murray
does the oil light that steve saw flicker the night before the big bang have a sensor that can detect oil contamination? murray
Eric Experience
Well-known member
Further investigations today. I though i would look at other oil pumps on different models. the 2.7 316 also uses the same plastic valve, the 2.2 313 also has the same plastic valve. The thing that is different is the size off the pump. the 315 pump is smaller than the others but is run at a higher speed. 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 and fit a pump from a 2.7. the pump is bigger and if we change the sprocket to the 315 one it will be running faster with even more oil. The slight problem is the design of the sump. the 315 sump is about 100mm deeper than the others so the pick up tube would have to be extended. The sump on the ML270 is deeper than the 316 so a pump from it would function ok with the pick up about 50mm from the bottom of the sump. The pickup from the 315 will not bolt onto the 2.7 pump because it is the smaller size. The question of why is the pump ok for the first 180k then no good is a not clear yet but I have done some internal leakage test on the 280k motor and and there are small leaks all over it things like the 16 tappet adjusters with a few drips per minute from each one, ads up. The greatest flow is the cooling flow for the turbos. Eric.
Eric Experience
Well-known member
Murray.
The main damage is on no 4 main but no 3 and to a lesser extent no 2 show signs of damage. I have not looked for cracks in the shaft. The report that the oil light flashed confuses me because the light only shows oil level. I did notice when i took delivery of the van and started it to listen to the noise that the brake pad light was flashing. Eric
The main damage is on no 4 main but no 3 and to a lesser extent no 2 show signs of damage. I have not looked for cracks in the shaft. The report that the oil light flashed confuses me because the light only shows oil level. I did notice when i took delivery of the van and started it to listen to the noise that the brake pad light was flashing. Eric
I don't want to take this off topic, but I have a quick question.
Adding an oil pressure gauge and switch sure seems important. I would think that a small length of tubing can be used to extend out past the congested area of the engine tap to a Tee and allow both the warning light switch and a tap for a gauge.
Interesting discussion. Good luck.
vic
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.
Adding an oil pressure gauge and switch sure seems important. I would think that a small length of tubing can be used to extend out past the congested area of the engine tap to a Tee and allow both the warning light switch and a tap for a gauge.
Interesting discussion. Good luck.
vic
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owner
Oz '03 316CDI LWB ex-Ambo Patient Transport
Yes I can confirm it is the OM646 as found in the ROW NCV 4cyl van range with 4 different output ratings - 150HP being the highest. This engine shares the same bottom end as the older OM611 found in ROW 4cyl t1n sprinters.
The newer OM651 has larger main bearing journals, which could be saying something about this problem.
I like the idea of a fractured crank. It fits the symptoms perfectly, and also explains why its only the 150Hp version that suffers from this problem, and explains why MB cannot fix it.
The newer OM651 has larger main bearing journals, which could be saying something about this problem.
I like the idea of a fractured crank. It fits the symptoms perfectly, and also explains why its only the 150Hp version that suffers from this problem, and explains why MB cannot fix it.
Eric Experience
Well-known member
Roger and Vic.
This 646 motor was not sold in USA so you can sleep easy, Eric
This 646 motor was not sold in USA so you can sleep easy, Eric