Cracked head

[Benjamin9669]

125,000 miles on rebuild, shop says cracked on top by number 4 injector bore? They don’t have any ideas what could cause it. Trying to see if anybody else has had an issue like that.

[hookliftpete]

Deleted engine?

[Benjamin9669]

(07-15-2025 )hookliftpete Wrote:  Deleted engine?

Yes sir. Being 125,000 miles and I’ve never had it over 215 water temp. The one time I had it at 215 was because of a coolant line blew and I had no choice but to let it get to 215, usually I always run 175-190 coolant and 225ish oil temp. Depends on the pull. I sent the shop haggai number and asked for them to have them check it because it is missy between 1150 and 1400. Never boosted over 31-32 unless I was running 1350-1450rpm. I sent them his number more as a precautionary now that it is getting rebuilt again, I got the blame for lugging it or over revving when i always run it 1450-1700.

[hookliftpete]

Likely a bad program, but you are also keeping it too low in rpms, cummins engines generally are best 1500 rpm or up to lessen wear on the liners, if you can, have the program reviewed by Rawze. Original turbo or something else?

[mikkhh]

What was done during rebuild? The head was replaced?

[Rawze]

(07-15-2025 )Benjamin9669 Wrote:  125,000 miles on rebuild, shop says cracked on top by number 4 injector bore? They don’t have any ideas what could cause it. Trying to see if anybody else has had an issue like that.

Its unfortunate, but you got exactly what you paid for... I try like h#ell to warn people against using after-garbage components.. but most people do not listen ...
reference: https://rawze.com/forums/showthread.php?...4#pid80864

and yes ... copy the program from the ecm and e-mail it to me for a proper review of what someone did in there.
info: https://rawze.com/forums/showthread.php?...5#pid72945

[Rawze]

(07-15-2025 )Benjamin9669 Wrote:  

(07-15-2025 )hookliftpete Wrote:  Deleted engine?

Yes sir. Being 125,000 miles and I’ve never had it over 215 water temp. The one time I had it at 215 was because of a coolant line blew and I had no choice but to let it get to 215, usually I always run 175-190 coolant and 225ish oil temp. Depends on the pull. I sent the shop haggai number and asked for them to have them check it because it is missy between 1150 and 1400. Never boosted over 31-32 unless I was running 1350-1450rpm. I sent them his number more as a precautionary now that it is getting rebuilt again, I got the blame for lugging it or over revving when i always run it 1450-1700.

cracked cylinder head aside ...
It also sounds to me like you have been lugging to death too. That is no way to drive an ISX!. They have light-weight pistons and shortened connecting rods... they like higher rpm far better than lower rpm. It should be in the 1500 - 1900+ range in a pull, .. and 1650 - 1750 is the center-point for that engine. Someone is lugging it if they run it at high fuel pedal positions much below 1500 .. where it beats up on the liners due to lugging it. It has been talked about countless times on this forum before.

example: I can get in my truck and drive it for the next 5 years at 1900 RPM, a gear down, .. heck, even 2100 and the engine will not miss a beat!. ISX's LIKE THE HIGHER RPM BANDS>>> THEY WERE DESIGNED AROUND MAX LONGEVITY AT THE 1650- 1750 AS A CENTER POINT!!!. - THE RED LINE IS ADVERTISED AT 2400 rpm (and the non-advertised mechanical red line is actually 2700 rpm).

Matter of fact... when I rebuilt mine.. I drove it around for about a month or so in the highest RPM bands that I could while breaking it in. I was bobtail, and loaded alike, running it at 1800 - 2100, against the rev limiter for days on end with it ... and never let it go below about 1500 or so .. not even when bobtail for that first month or so. - I wound it out every change I got till the rings finally wore in good, and she finally didn't smoke and smell like oil any more whenever I cranked it.


(Lugging it aside) ...
==============

Even so .. lugging it would not cause a cracked cylinder head, not unless it wes severte and it was in a heavy-haul application, someone torturing the engine at 100% operating loads at real low rpm's for hours on end. So ... If someone is blaming RPM range on the cylinder head failure .. then they are an idiot, looking for excuses!.

Likely causes of a cracked cylinder head after rebuild ... Lets see .. take your pick ...

== Garbage-can delete programming. (copy program out of ecm and e-mail it to me for inspection).

== After-Garbage cylinder head and/or other major internal components were used during the rebuild.

== NO ONE BOTHERED TO do a second over-head valve adjustment at the 50k mile mark (after an inframe) after the valves all seated and finally settled.,... and then they were now riding the cam, allowing for combustion gasses to seep past them, overheating the exhaust valves, etc.

== Slipped cam, and now the injection timing is off, causing internal detonation, etc... .. this is as bad as a bad delete program. .. and NO,.. a driver cannot feel or hear this issue until its too late, and damage occurs.

== Improperly mounted cylinder head, and its under stress. Fails/cracks after several heat cycles. - caused by not torquing it to proper specs,... and/or not torquing it down via the recommended torque pattern to ensure it is not stressed.

== External devices being used like those 'power-boxes', etc. - This is just as harmful/bad as a typical bad delete program.

Take your pick.

Like I mentioned above, my bet would be that after-garbage cylinder head, and after-garbage overhaul kit. Next to that ... likely bad delete.

Just about All the other things that I mentioned can be tested for, to see what went wrong.

[Benjamin9669]

I shift it at 1450 to 1750. That’s not lugging it. I never let it drop below 1400.

[Benjamin9669]

I’m 70 mph at 1600-1700. If I let it come down that 1450-1500 on a hill that is not lugging. That is letting it pull. Also lugging aside I spoke to said shop and they agreed over speed and lugging would not cause the cracked head which I did neither of.