Truck refuses to come up to temp?

Red Sleeper said:
To provide additional cooling to cylinder #6 was my reasoning. With the propensity of ring cracking on a stock 325 CR engine, I felt it was a wise decision.
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Ring failures are due to higher piston temperatures from the piston/injector cone angle design, a coolant bypass won't prevent it.
 
Smokem said:
Ring failures are due to higher piston temperatures from the piston/injector cone angle design, a coolant bypass won't prevent it.
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Is it true that the 325 engines especially 06-07 had tighter top ring gap contributing this problem? Any guidance on EGT limit to help mitigate?

I have never really understood the thermostat coolant bypass to control pressure...what happens if you zing it up to 4000 rpm when it’s in between opening cycles? I’d think pressure would get dangerously high.
 
It's been my experience that the 06 early 07 5.9 ran higher exhaust temps than previous common rail engines. I believe that Cummins needed to do this to reduce the Nox emissions to meet EPA requirements those years while the 6.7 with EGR and DPF were in the works.

As for mitigation, compounding turbos works.
 
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straight 6 roar said:
Is it true that the 325 engines especially 06-07 had tighter top ring gap contributing this problem? Any guidance on EGT limit to help mitigate?
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I would be surprised if that was the case. Mahle's "solution" for the later production ring package was to ceramic chrome coat the top ring to help tolerate the higher temperatures.

Snedge said:
It's been my experience that the 06 early 07 5.9 ran higher exhaust temps than previous common rail engines. I believe that Cummins needed to do this to reduce the Nox emissions to meet EPA requirements those years while the 6.7 with EGR and DPF were in the works.
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Based on my interactions with Mahle discussing this topic I would say that assumption is on course.

Red Sleeper said:
Increased cylinder temps also contributed from camshaft profile to provide in-cylinder EGR if I’m not mistaken.
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Decreasing the lobe separation angle on the CR camshaft did alter the exhaust valve timing events, remaining closed 24.5° longer on the combustion stroke and closing 9.5° later on the exhaust stroke. This was used in conjunction with the non re-entrant injection concept to reduce NOx emissions as well as an attempt to keep the soot on the leading edge of the flame front.

Liquid fuel impingement on the dome surface can be an advantage, but in an instance of injector failure can lead to catastrophic failure quite rapidly. This is also one reason that Bosch switched from a DLC coated guide needle on the P1309 nozzle to a fully DLC coated needle on the P1659 nozzle in later 325hp engines.
 
Smokem said:
Ring failures are due to higher piston temperatures from the piston/injector cone angle design, a coolant bypass won't prevent it.
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Then why is is spread to other engine platforms that don't share common iron?

Sent from my motorola one 5G using Tapatalk
 
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biggy238 said:
Then why is is spread to other engine platforms that don't share common iron?
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I was referring to this particular instance, there are several scenarios that may produce the same result. Ring material, ring land placement, and fuel impingement are all factors to these types of failures, which are most commonly caused by excessive heat in an attempt to meet emission standards. And Cummins is not the only nor the first manufacturer to implement non re-entrant injection.
 
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