Another crank failure theory .... oil temperature
Ok I was talking to my cousin who mechanics a lot over the holidays. He works for a municiple garage and sees a lot of engines. Recently 5 broke 6.5 cranks over a couple of weeks/months. He said oil temp may be an issue and the bearing and journals are getting too hot. I asked him what he thought about the harmonic balancer failures and he did not comment on the appearance of HB on these particular failures but he mentioned Fluidamper and importance of a good HB. He mentioned oil passage size at the front cam bearing changed but I missed the specifics, as I pointed out the oil spray coolers and increased oil flow for 97+ engines.
It has always struck me that the 6.5 has so little oil capacity compared to the other pickup diesels. But have read many times cylinders have very little wear with many miles on the engine so I let it go and figure oil is probably adequate.
I use to think oil should get to 212F then a few threads a long time ago and several hours of reading changed my mind. A new thread started me thinking again and I wonder just how hot does oil and bearing surfaces get in the engine? I have read too much to find it all again but thought I saw a blurb about cam journal bearing getting really hot (can't find it again but 300-400F I think). And of course the piston face is seeing really hot temps up to 3000F combustion temps and EGT of up to 900-1000F are measured towing. Blowby will be related to EGT and I never really thought about just how hot the upper ring and oil is getting. But apparently it lives ok.
Back to the crank and main bearings. After reading I am now curious just how hot do you think the crank and journals are getting locally? I've never heard anyone say the crank was blued or changed color due to heat but after failure its hard to determine the last few moments and chain of events. I also haven't read of many spun bearings but maybe its not getting hot enough to gual but still hot enough to encourage failure???? I have read the turbo will choke or oil will coke if shut down hot. I am guessing mains and cam bearings are not that hot and/or can dissipate the heat better. I imagine the continuous flow keeps the oil from cooking but I am starting to think it momentarily gets really hot at some points in the engine.
Just food for thought.
Harmonics Issue, not thinking oil issue here
Oil capacity can be increased by addition oil bypass system and larger filters if one desires.
Not being an engineer, I can only guess that smaller engines I've seen mounted w/rubber bushings on things like the AC compressor, alt, p/s pump, etc are there to reduce harmonics on crank resulting in a smoother/longer operating power plant.
We see GM's attempt to smooth thing out w/balancer and lower pulley assemblies being isolated by rubber, or?, on the 6.5.
Right now we have the option for the Fluid Damper to make things even smoother on the 6.5.
I remember someone herein the forums mentioning the forces upon the crank which could lead to crank failure when there is a miss, or stumble like so many 6.5's w/DS4 IP live with; This I think is the issue!
Crank getting too hot not the oil
I am a little embarrassed I miss communicated this theory and took it off on a tangent. However it is a little related.
I don't think it is a definative route to failure but just pondering things "the crankshaft getting too hot" may have SOME merit.
Just thinking this possible scenerio. GM did not make a good call on the block material so in my mind the crank material could be suspect too. The OE GM crank was some ductile cast iron that is forged to shape then machined. This cold working forge process makes it "stronger" (on edit "stronger" not tougher really its just increases its yield strenght due to the "prestraining" of forging. I can't remember the curve I think ultimate yield strength remains realitively the same) than it would be in annealled state. Now you heat it up and vibrate it which could destress and negate some of the cold working benefits. After some time you are left with a weaker crank that just adds to the problems of harmonics and not as rigid block as desired, and other bad combustion timing issues.....etc.
How hot does it take WITH Vibration to "anneal" the material I don't know and how hot does the crank get I don't know. Just thinking turbo diesel and really hot piston and hotter bottom half of engine vs a gasser just maybe it was a learing curve for GM. Again they added the oil sprayers, bigger oil lines, and bigger oil pump. Was it some attempt to help engine durability and or help with a cooling problem. I think so.
Reading the article in Maxx Torque about oil temperature in the Duramax reaffirmed some of my concerns of oil temperature in the 6.5. No its not the same but I still see some relation.
I do believe the oil gets really hot. Maybe momentarily that it can tolerate but still it gets hot.
Just thought I would post something different and converse about it.