What Typically Kills the 6.5?

[Detroit Dan]

I wish these posts had a "like" button like Facebook, so we could just click like on comments like Kennys ChrisK comment. Haha

 

[Crankme69]

I wish these posts had a "like" button like Facebook, so we could just click like on comments like Kennys ChrisK comment. Haha

Or DISLIKE haha

 

[ak diesel driver]

I thought about this thread quite a bit and I keep remembering a post by Schiker. He theorized that IIRC when things heat up that the fuel would be more apt to ignite sooner so in a way advancing the timing. Just wondering myself if the earlier ign could cause extra stress and be a contributing factor to cracks and such. I would imagine if it ignited soon enough that it would have a similar effect as preign on a gasser. I wonder if there is anyway to determine if this actually is happening? Would explain alot of failures.

 

[Big T]

:thumbsup:

so the 99 stayed home because of a ripped cv boot? I had a ripped boot, clean in two, drove it every day and plowed two seasons with it before it started hinting at making noises. I had spares at home (thanks Joey D!) so I just left it alone. Couldn't believe how long it lasted after the grease was washed out of there by salty water and mud. I always thought a ripped boot was the kiss of death, maybe for a front wheel drive 4 cyl, but mine held up fine. Earned a few grand plowing and got my moneys worth out of it. And actually, it never did get loud or fail. The opposite side went bad and started clacking, so I changed them both at once.

Yes, it stayed home. There was grease everywhere. The part was under warranty AND no reason to chance it when the son let me use my old '95. It was like driving my favorite blanket again.

 

[Veg_Out]

Mine died due to 2 factors. Out of balance (though they were fairly new) injectors, and a harmonic balancer that we bad, but made no sound, and looked great. Therefore I say, check your injectors at a reputable injector shop and, change that balancer whether or you need to or not.

I had also overheated the piss out of it the summer before.

 

[Matt Bachand]

Mine died due to 2 factors. Out of balance (though they were fairly new) injectors, and a harmonic balancer that we bad, but made no sound, and looked great. Therefore I say, check your injectors at a reputable injector shop and, change that balancer whether or you need to or not.

I had also overheated the piss out of it the summer before.

I wonder what effects that severe overheating can have on the injectors and/or the balancers.

 

[WarWagon]

but if you intend to keep it... would the synthetic not be a better investment than new engine?

Actually not. The 6.5 / 6.2 is good for about 200K before you need to pull the heads off. And IF it makes it that many miles who knows what kind of cracking it has. So you are better off saving for the replacement engine.

Now if you can justify a MPG gain with synthetics that equal or exceed their cost... But, that is hard to do with the short oil change intervals of 2500 miles extreme conditions.

 

[Turbine Doc]

Not to Jinx mine 212 miles and running strong, I think key is to have never overheated it, which to my knowledge has never happened to mine.

When I got it new to me @ 37K in 2000 the truck was "granny driven" & had never towed.

I run synthetic Amsoil in mine with bypass filtration, sample the oil about every 10K, if it comes back good I don't change it, 27K was my high interval on that oil, TBN was getting low due to bad injectors, still was in serviceable spec per the lab, but since I was going to be away from home another 3 mos at the time I change the oil @ same time I changed injectors, about 10K on that oil now, black but still in lab specs for the oil.

Good quality dino oil Rotella/Delo will serve you well also, I ran that for the 1st 70K just requires more frequent oil change than the synthetics, I can afford what I consider to be the best because of intervals I run with it, I don't try to save a few $$$ on oil I think I'm about break even with interval I run, even with the lab tests which I did even with the more frequent changes I did when running dino oil.

An old habit from my USN days to sample my oil, overkill probably but IMO a necessity to know if oil is serviceable vs guessing if it is or not.

 

[schiker]

I thought about this thread quite a bit and I keep remembering a post by Schiker. He theorized that IIRC when things heat up that the fuel would be more apt to ignite sooner so in a way advancing the timing. Just wondering myself if the earlier ign could cause extra stress and be a contributing factor to cracks and such. I would imagine if it ignited soon enough that it would have a similar effect as preign on a gasser. I wonder if there is anyway to determine if this actually is happening? Would explain alot of failures.

Yep, most everyone agrees that heat kills. But as we measure "heat" its typically EGT and ECT. Both of which are more indicators of head "heat" than lower block heat. I just don't see the correlation to metalurgy sp? issues with heat in the mains as heat affecting the metal strenght. But yeah I can see the heads and combustion areas getting significantly hotter than anticipated and causing earlier fuel combustion and thus more pressure/force across TDC and directly hammering the main bearing caps with non crankshaft torque producing pressure and force on the piston/rod. I think the biggest benefit to modern common rail diesels is the better cylinder pressure management with injection more variable not directly dependant on crank timing.

 

[WarWagon]

I think the biggest benefit to modern common rail diesels is the better cylinder pressure management with injection more variable not directly dependant on crank timing.

Better block design that is not prone to cracking has a lot to do with it.

As far as timing changes for different things like high intake charge temperature: Yes, But. You should hear a Duramax in high gear towing a mild (read not 10% grade) hill in high gear. It starts to sound like spark knock from a gas engine. From the CAC getting hot and the calculated timing not changing. Computer has the ability, but GM did not use it in 2008.

 

[schiker]

Agreed. I am suggesting that is how hi temp seems to do the killing of the 6.5. Over heat seems to be the common denominator to early death. But anything that leads to hammering of the main bearing is hard on a 6.5 and shortens lifespan ie a bad injector, unstable IP, harmonics from bad dampener etc. The block design and metalurgy is not doing it any favors for strenght/robust design.

My point was just the fact that they can break up the injection into pilot and quick metered bursts maybe semi independant of crank/IP time comparing common rail to the DS IP is huge. Even if they don't exactly correlate it to cylinder and or intake temps.

I am not sure how you would prove my hypothesis. The hi temp seems to be a significant stress increaser that leads to an accelerated fatigue failure. Its not a clear cut catastrophic failure mode (unless held at hi temps until failure like a gualled piston). Other contributors do chime in enough to not be able rule them out entirely. I think it would take a group of engines and experiment with high heat indicators and a control group kept cool then still would be a statistical analysis.

I have seen hydraulic pressure recorders measure pressure spikes and "hammer wave affects" when valves close. If one had the money maybe the glow plug hole could be used for a similar high speed pressure sensor and peak cylinder pressure vs crank time correlated for normal operation vs hi temp indicators. I have no idea if the hi temp and compressiblity of the gases could be measured and timed accordingly ????

I have seen hi speed photography of the flame of diesel spray ignition/combustion for different cylinder temperatures. Saw it on an internet site a good while back. It showed fairly clearly the hotter it is the faster it "explodes". And this faster explosion nearer to TDC in my mind has to be hell on twisting the block and hammering the main bearings/caps when the hi temp indicators are up there on the scale.

 

[schiker]

Another thought .... its all about the pressure spike at TDC in my mind. I think because its IDI the precup is getting so hot it might almost acts a little like an external combustion enigne too (in additon to the fuel exploding a little faster).

Use your imagination here I am not saying it could be done....
I would bet if the compression ratio was low but you got the head and precup really really hot (like it gets when under heavy load and ECT/EGT are really high) and started the engine rotating you could almost turn the fuel completely off and get enough thermal energy out of the head/precup to run the cycle for a little while and make just a few horse power (until air cooled the head and precup). Of course the turbo couldn't work but a naturally aspirated engine probably would. Again it kinda sorta almost would act like an external combustion engine (iirc a Sterling engine or cycle). External combustion engines are really ineffecient and big for just a few HP but do work.

 

[Matt Bachand]

I'm not a synthetic junky, but in my 6.5 it makes such an amazing fast/easy starting in the frigid weather, and engine is much quieter and smoother upon fire.

It also spools faster, and just feels overall better. I can tell the difference. I went back to Dino once and noticed instantly. I change it every 5-7k miles with no analysis. I burn about 2 quarts in that time frame. I buy 10 quarts, and once the 2 that I burn are used up I change it out again.

I recommend everyone at least try the synthetics on their 6.5 at least once.

I'll never use non again in this engine.