Back in September 2021 I started rebuilding a 91.5 12 valve out of a D350 to put into a 2000 crew cab F350. I did a full rebuild on the engine and replaced just about everything. I will try to make a full list below. Just started driving it around earlier this month and its around 100 degrees down here in Texas. Whole ac system is new as well, running down the road with ac on seems to run around 180. This is using an autometer gauge with probe at rear of head. Once traffic slows down (normal rush hour traffic coming home from work) the gauge slowly starts rising getting up to 210 or more before speed picks up and slowly the temp starts to fall. I have swapped from a napa t stat to cummins 180 with no change at all- neither have temp swings like so many seem to have. Cummins t stat is installed with jiggle pins at 12 and 6 o clock. It gets up to 180 and stays there until it can't cool anymore and starts climbing. When it starts to get hot the upper and lower radiator hoses will be only have a delta T of 10-15 degrees (upper hose around 205 with lower around 189). I have tried 2 different fan clutches and am getting lockup now- verified by sound and feel of airflow being pulled through intercooler/rad. 7.3 fan shroud is installed trimmed down. I also have 2-12" pusher fans in the front bumper aimed at lower half of condenser (mounted before finding out first fan clutch wasn't locking up at idle). I installed another autometer temp sender at the front of head and hooked it to gauge to see if maybe the sender was off and it seems to read a little bit hotter as its right by the thermostat so I think the gauge is ok. Engine runs great otherwise but this has me stumped. The cooling stack is identical to the one in my 7.3 which will idle in 100+ weather with the A/C on indefinitely and never move the needle past 180 and that is with a 345K mile ac condenser that looks like hell vs all the new parts in this truck. The 7.3 is a stick so hard to compare idle egt vs the auto behind the cummins but the 7.3 will be around 300 egt at idle with the ac on where as the cummins will run 350 or so with ac off. Then once you put it in drive it will jump to 550 then add ac on and its over 600 and in drive at idle there is some visible black smoke out of the exhaust. Even in park it started creeping up to 210 the other day as I was hooking up my trailer though. I am running out of ideas, cooling systems are pretty simple lol and many people I have read about with the same or similar setups as well as the cummins in the dodges claim that they never budge over 180 either unless getting worked hard. The only thing left I can see is maybe the egts are too high? and the black smoke at idle in drive? overloading the cooling system at slow speeds? If anyone has any ideas or sees anything I might be missing I would really appreciate it. I am ready for a vacation from working on this thing for the last 9 months and would like to drive it to the beach as soon as I get this cooling problem fixed!
Things of note-
EGT at idle seem a lot higher than my 7.3.
In drive with ac on egts on the cummins are between 550-660
in drive at idle I have a bit of black smoke out the exhaust
fan seems to be pushing air OUT the sides of the shroud - I have already trimmed more shroud to let more air out the back (towards engine) but it still throws air out the small gap between shroud and radiator
Engine---91.5 12 Valve out of D350
VE pump rebuilt Farrell Injection
Duckys 5x12 injectors new bosch bodies
Hamilton 178/208 cam
Rebuilt HE351 with 12 volt on electronic wastegate making 30+ psi
cummins high volume low pressure lift pump
bored .020, New pistons, bearings, oil pump, valve job, 60lb springs
New cummins head bolts with slightly thicker Mahle head gasket accounting for piston protrusion
Many other things I am surely forgetting...
New 7.3 radiator
(New A/C condenser and trans cooler in front and cleaned intercooler while it was out - no airflow blockage to radiator)
New 12 valve fan clutch, fan, and hub assembly
New gates water pump
New napa thermostat changed out to cummins 180 thermostat (currently running cummins)
Fresh rebuild 4r100 from Dieselsite
billet triple disc converter, billet input, etc
trans cooler lines run to radiator first and then into huge 6.0 trans cooler in between condenser and intercooler