Sprinter-Forum    
 

Go Back   Sprinter-Forum > Regional Discussions > Australia, New Zealand, and Asia Pacific


 
Thread Tools Display Modes
Old 01-21-2017, 10:12 PM   #21
Midwestdrifter
 
Join Date: Sep 2013
Location: Charlotte NC
Posts: 9,432
Thanks: 1,867
Thanked 6,271 Times in 3,947 Posts
Default Re: Update on 315 exploding engines.

Quote:
Originally Posted by talkinghorse43 View Post
I'm thinking that maybe the oil is being called upon to do too much cooling (back side of the pistons), especially since the specific power (HP/volume) of the 315 is even greater than my OM612, and, under some circumstance, gets too hot, resulting in bearing damage and then enters a vicious cycle (more and more damage at lower and lower oil temperatures) leading to eventual failure.
If this is the case, monitoring coolant and oil temperature may be telling. I discussed monitoring oil temperatures with Eric, a thermocouple in the oil dipstick tube should provide a good bulk temperature reading.

Most oil coolers can cool the oil to within 5-10F of the bulk coolant temperature. So one would expect bulk oil temps to be around 90-105C?
__________________
2004 T1N | Overland Conversion in Process Completed...For now... | 101,000 118,XXX 137,078 165,000 miles | 140" | High Roof | My Build Thread
Another Random Blog | http://VagariesAbound.blogspot.com
Midwestdrifter is online now   Reply With Quote
Old 01-22-2017, 03:39 AM   #22
talkinghorse43
 
Join Date: Dec 2006
Location: near Pittsburgh, PA
Posts: 3,183
Thanks: 425
Thanked 955 Times in 693 Posts
Default Re: Update on 315 exploding engines.

I know I can monitor oil temperature by reading the temperature sensor (with Autoenginuity OBD tool) in the oil quality monitor (ASSYST), but maybe the 315 doesn't have that monitor?
__________________
'02 316 2500 SHC FTL 140 passenger, NAG1, 3.73 diff, 16" wheels, OM612 w/EGR (>415k mi.), '04 Golf PD-TDI (>160k mi.), both bought new
talkinghorse43 is offline   Reply With Quote
Old 01-22-2017, 06:36 AM   #23
Midwestdrifter
 
Join Date: Sep 2013
Location: Charlotte NC
Posts: 9,432
Thanks: 1,867
Thanked 6,271 Times in 3,947 Posts
Default Re: Update on 315 exploding engines.

So I looked up the bearing design handbook. I have a few suggestions.

First, most journal (hydrodynamic rotary) bearing wear occurs during the transition phase, this is during startup and shutdown when the RPM is too low to create the oil "wedge" which suspends the crank. This effect is worse when the oil viscosity is low due to high temperature.

Engines with higher stop/start cycles will see more main bearing wear.


The minimum kinematic viscosity of the oil at the bearings should be greater than 10 centistokes to prevent film breakdown. Unfortunately many 15W-40 oils will drop below 10 Cst when heated above 130C.


Oil temperature within the bearing will usually be 10C above the inlet temperature. This means that if oil inlet temp (after the cooler) is greater than 120C, there is a risk of film breakdown, and thus metal to metal contact. The higher output of this engine only exacerbates the load on the bearings and their temperature.

Operating at high RPM increases the heating of the bearing and oil.

At this point my approach would be to determine the cause of the low oil pressure, either bearing wear, or delivery issues. I would then identify the cause of bearing wear if present. It is likely caused by excessive start/stop cycles, or excessive oil temperatures (possibly related to high coolant temperatures.
__________________
2004 T1N | Overland Conversion in Process Completed...For now... | 101,000 118,XXX 137,078 165,000 miles | 140" | High Roof | My Build Thread
Another Random Blog | http://VagariesAbound.blogspot.com

Last edited by Midwestdrifter; 01-22-2017 at 07:02 AM.
Midwestdrifter is online now   Reply With Quote
Old 01-22-2017, 10:52 AM   #24
NORTON
 
Join Date: Jan 2011
Location: adelaide south australia
Posts: 510
Thanks: 86
Thanked 243 Times in 180 Posts
Default Re: Update on 315 exploding engines.

Until the crankshaft journals are accurately measured with a micrometer it's a waste of time.
Low oil pressure is predominantly caused by excessive wear of the crank journals and the bearings.
In almost all of the engines I have rebuilt suffering from low oil pressure the most wear was in the big end/ con rod bearings and depending on how far it was driven the mating journals probably due to the combined effect of compression and combustion combined with the extra forces created by the throw of the crank.
There seems to be a preoccupation with the main bearings but being central and subjected to the compression & combustion forces over a 720 degree cycle get a smoother pulse
Unless the oil pump has been subjected to foreign matter it's highly unlikely to not perform as designed.
From my understanding the engine is out so with an understanding of valve timing and firing order the big end / con rod journals could be measured with judicious care.
As I said before this is a good opportunity to find the problem.
NORTON is offline   Reply With Quote
Old 01-22-2017, 10:57 PM   #25
owner
 
owner's Avatar
 
Join Date: Sep 2011
Location: VIC AU
Posts: 2,022
Thanks: 704
Thanked 974 Times in 690 Posts
Default Re: Update on 315 exploding engines.

I too think its oil temp related. A DPF regen adds 10C to the coolant temp. I would assume the extra hot exhaust gasses would heat the oil flowing through the turbos a lot too. I'd really love to see the actual oil temp and pressure readings on a hot day, at idle just after a long high-loaded freeway run, AC on, and with active DPF regen, 200k on oil pump and bearings. Also note that 5w30 is an approved weight in these. All of these things together could conspire to cause the bearing interface to fail as MWD described above.
owner is offline   Reply With Quote
Old 01-24-2017, 10:04 AM   #26
Eric Experience
 
Eric Experience's Avatar
 
Join Date: Aug 2008
Location: Victoria Australia
Posts: 2,892
Thanks: 113
Thanked 1,570 Times in 1,038 Posts
Default Re: Update on 315 exploding engines.

In my previous rants I have said that the bearings looked OK in the 315 of Steves that I replaced the mains in and it still exploded. Just to clarify that I got the crank and shells from the exploded engine and remeasured them today. The big ends no1 47.97 x 47.92 no2 47.92 x 47.93 no3 47.78 x 47.93 no4 47.93 x 47.94.
Mains no1 57.93 x 57.91 no2 57.87 x 57.94 no3 57.94 x 57.81 no4 57.93 x 57.99 Damaged surface. no5 57.93 x 57.91
The big end shells on the undamaged cylinders were 1.74 at the thinnest part 1.75 unworn part. Eric.
Eric Experience is offline   Reply With Quote
Old 01-25-2017, 08:13 AM   #27
Iggy66
 
Join Date: Mar 2007
Location: Central Coast NSW
Posts: 232
Thanks: 42
Thanked 88 Times in 72 Posts
Default Re: Update on 315 exploding engines.

Wow Eric,
From those measurements there's no point replacing bearing shells when the crank has worn oval so much, it appears certain journals have ovalized causing a loss of oil pressure when hot and then #5 main bearing ( the one under the most load) has failed due to no oil.
Iggy66 is offline   Reply With Quote
Old 01-25-2017, 08:49 PM   #28
NORTON
 
Join Date: Jan 2011
Location: adelaide south australia
Posts: 510
Thanks: 86
Thanked 243 Times in 180 Posts
Default Re: Update on 315 exploding engines.

Correct Iggy, I don't know the nominal shaft size for this engine but with those measurements it compares to the 611 / 612 4 and 5 cylinder engines which are 47.950-47.965 mm big end and 57.950-57.965 mm for main journals
With 0.17 wear on big end 3 and 0.14 on main 3 being significant
This is only the wear on the crank journals , the bearing wear should be determined by re assembling the bearing caps with their specific shells and torqued to the correct number and the bore measured , no wonder it had no oil pressure.
This looks like the classical case of the Beancounters extracting more horsepower from an engine till it could endure no more, if it is based on the 611 engine it went from 80 to 130 and then 150 horsepower
Good work Eric as measuring the crank correctly is an arduous task and not not to be taken lightly.
Murray
NORTON is offline   Reply With Quote
Old 01-25-2017, 10:40 PM   #29
owner
 
owner's Avatar
 
Join Date: Sep 2011
Location: VIC AU
Posts: 2,022
Thanks: 704
Thanked 974 Times in 690 Posts
Default Re: Update on 315 exploding engines.

Yes the 150HP twin turbo OM646evo shares exactly the same bottom end as the old om611. Compared physically to the 611, as well as the extra HP, it also adds DPF (with its diluted and anemic oil requirements), and 2 oil paths through the turbos. So I agree its just too much for the old design to handle.

But the question is, what can we do about it?
I think the proper options are one or more of....
1. Detune it to 130HP or less via an ECU flash, especially the low rpm torque.
2. Delete the DPF and run it on full-fat 228.5/229.5 or maybe a fully synth 10w50.
3. Turn it into a 313 or 311 using a donor vehicle/parts - would need ECU set and single turbo and plumbing.

Any of the above should fix the problem, since the lower output om646 engines don't seem to have this issue. Also, these solutions weren't available to MB.

The other more experimental options like higher capacity oil pump, better oil cooler, seem to me like things that MB could have done fairly easily themselves during warranty/production. So its not looking like those are viable options, or they would have done it already.
owner is offline   Reply With Quote
Old 01-26-2017, 03:08 AM   #30
NORTON
 
Join Date: Jan 2011
Location: adelaide south australia
Posts: 510
Thanks: 86
Thanked 243 Times in 180 Posts
Default Re: Update on 315 exploding engines.

I agree, reduce the horsepower, possibly using Star to lower turbo output
Get rid of the DPF and I personally would use Penrite HPR 5 5w 40 which has plenty of zinc in it
Fit a scangauge or similar to monitor the load on the engine to keep it spinning freely and not lugging by using the gearbox appropriately
NORTON is offline   Reply With Quote

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump



All times are GMT. The time now is 01:43 AM.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2019, vBulletin Solutions, Inc.