6nz c15 weird on going high EGT issue, unloaded

Sorry in advance for this being long. I really need to figure this out and don’t have to money to just drop it off at a shop and wait.

I have an 02 W900 with a 6nz(6nz57967) C15. I’ve had it a few months and have been having a high EGT issue that I cant seem to figure out. Taken it to 2 shops no luck. Motor had a full documented Cat rebuild, new head, cam, turbo etc. at a large dealer in Kansas 200,000 miles ago.


What it does. Pulling an empty belly dump it will run 600-700 deg level ground no wind. Any hill(Oklahoma) will push it to 900 to maintain 65mph. Loaded is even worse cant hardly keep it below 900 deg. I have to back out of the throttle and start downshifting. Truck will also make over 35 psi(highest guage marking) at 60-70% throttle. I makes boost right off idle easily. Pulling the hill I’ll have to back off to 20-30% 25 psi boost to get the temps down to 800-900. Water and oil temps stay at 180.

Truck does not black smoke(on any tune) Runs good minus the high egts. I’m not sure how good or bad it would pull as I always back out. I have noticed on the cold days(below freezing) it does a lot better.

Things I have checked swapped or replaced

New EGT probe, wire, gauge. Also swapped out a known good probe and gauge from my other truck. Pulled turbo checked waist gate, clean and free moving. Turbo in great shape. Put a regulator on my shop air tested waist gate actuator, good. Checked for boost leaks. Intercooler is 2 years old fins are straight and clean. At idle with fan on will hold a shop rag up. Scoped inlet and outlet, clean. Had over head run, good. Injector tests, good. Changed tunes, 475, 550, 600(custom 7cz tune that works great in another c15), no change. Bigger tune made boost easier but still same egts on lower tune. Found a bare wire on crank sensor, fixed and replaced sensor, no change, new air filters, new fuel filters, new straight pipe exhaust turbo to tips. Pulled peanut cover, checked cam gear timing marks, good. No fault codes in where found by either shop. I did find the bad crank sensor wire after it been to the shops. Is there a way to get the codes at home?

I recently found this thread my truck starts exactly like this video. Tomorrow I’m going to try and unplug each sensor.

Cam and crank sensor issue on cat motor




?

 

Leak in the charge air system?

 

checked no boost leaks.

 

Restricted exhaust?

 

Did you upgrade the turbo? More fuel requests more air . Preferably a non wasted gated Borg Wagner. Others might chime in for the specifics.

 

I forgot to mention new exhaust from turbo to tips, no muffler

 

Its a cat reman(has a cat sticker with part number that matched up) factory waste gate turbo. I want to go to a larger non waste gate turbo in the future, but first I want to fix the current issue

 

First of all your not going to hurt anything at 900 degrees. That's not extensively hot. Cats bridge engine (mbn) would run 1300 all day long from the factory pulling hard.

Now then , even if yours topped out at 1000 or 1100 that is acceptable. Is it a little high compared to most 6nz engines? Yes a bit. But not crazy. It could be how the cam was timed when assembled or double check both sides of that turbo charger , make sure the divider in the middle that exhaust manifold is not burnt out either...

And if you get tired of watching that egt gauge the 0000 borg warner will drop it 200 degrees.

 

Thank you for the reply. I had read somewhere that cat says 1200 is ok. Are there any physical differences in the MBN to help it handle the heat? The other guy I know with a single turbo C15 that had the custom tune in it. That I now have in mine pulls past me on the hills running way lower temps.I just didn't want to melt the motor

 

Today I unhooked the arm that goes from the waste gate actuator. I put wire around the waist gate arm to hold it open. Below 1500 rpm egts where higher. However in 9th(17th) i could put it to the floor at 1500 rpm and hit 32psi and 900 deg. Hooked everything back up same pull pushed the needle past 35psi until it hit the gauge housing and 1100 deg. The piece coming from the actuator looks likes you can adjust the length