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Discussion Starter · #1 ·
Hello,

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...

Cooling system-
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)

Trans-
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
 

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Discussion Starter · #6 ·
Thanks for the responses.

9297oldram- the 2- 12" cooling fans are in addition to the stock dodge fan clutch which is all new. They were only added to keep the ac cool at idle because the first mechanical fan clutch was not locking up at idle. The new fan clutch is pulling air through the radiator at idle along with the 2 pushers. As for air in the cooling system, When filling the degas bottle I left the plug out on the front of the head right next to the thermostat to let air out while filling, and have ran the engine with the cap removed. I have over 600 miles on it so I think if there was any air left it would have worked out by now?

Antonm- The mechanical fan is definitely pulling air the correct way through the radiator (I don't think the fan can be mounted backwards on the clutch if I am remembering correctly as the fan is offset to mounting surface). If I put my hand or a piece of paper in front of the intercooler I can feel it sucking and it is blowing a bunch of air towards the engine. It almost seems like the air blowing out the side of the shroud is due to the air leaving the edge of the blades and hitting the inside of the shroud and being routed out the side instead of out the back. This is only felt significantly on the drivers side. Like I said I can feel a ton of air being blown toward the motor as well as being pulled through the lower radiator. It almost seems like the is to far into the shroud. I know how important shrouds are which is why I am running one, but I have thought about removing it and driving to see if it is somehow causing turbulence, and maybe trimming it some more. Something of note. Even with a fan plugged into the wall and hanging on the front bumper in addition to the 2 electric pushers and mechanical fan the temp creeps up at idle. Yes brand new 7.3 mounted and plumbed exactly as stock. Also when filling the truck was parked uphill with degas for sure at highest point. I also teed into the line from degas bottle to the radiator yesterday and put 13 psi on which held for a few minutes so rad cap seems ok.

When I get a chance here in the next few days I am going to beat on the 7.3 when its hot out and then let it idle and check upper and lower radiator hose temps to get a baseline.

Any ideas on the black smoke out the pipe in drive at idle or if 550-650 egt is too high for being in drive at idle with A/C on?
 

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Discussion Starter · #8 ·
I backed the smoke screw off 5 turns from how it was sent after rebuild to get egts manageable. I will pull the top off and see if it is flush. IP was locked when I received, installed with #1 at TDC and cam and IP gears lined up to "E". I went to advance the timing an 1/8" about a week and a half ago as I thought maybe it was slightly retarded causing high egts but I was not even able to get an 1/8" bump before it bottomed out on the slotted holes. Maybe got 1/16" which seemed kind of odd as I have see where people can push it all the way to the head. As far as injectors I am not sure but I would assume so as they are brand new injectors with new bosch bodies.

You think it would be worth jacking up and leaving overnight with the degas cap loose? I pulled the plug at the front of the head yesterday to install the new temp sender in that spot and and amazing amount of coolant came gushing out before I could get the sender seated because it is so much lower than the degas/radiator. I
 

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Discussion Starter · #10 ·
I will give that a try. Do you know what your EGTs are in drive with ac on in your blazer? I wish I had a way to load up that 7.3 at idle to get the EGTs up to 500-600 so I could see if the cummins is indeed running too hot overloading the cooling system or if it is actually a cooling system issue. That would be a really long burnout though lol.
 
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Discussion Starter · #12 ·
I have not tried with the A/C off yet. Currently adjusting the A/C charge each day trying to get the temps as low as possible, once I get that done I will drive around with it off and see if that makes any difference. This thing will hit 1300 + no problem once the converter locks and that is with the smoke screw backed off 5 turns and the fuel pin turned back to the almost stock position, smoke under acceleration is minimal to none now once the turbo spools. I also tried backing the full power? screw on the back of the pump off some but I got long cranks where I had to give it throttle to start so I moved it back to where it was set and it starts immediately again so I am guessing that is already at the least aggressive position. Also I made a boost leak tester and had pretty good leak at the intake horn that was fixed with a new gasket and some sealant on the intake bolt threads. I should probably boost leak test again but I cant imagine that could cause an overheat at idle.
 

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Discussion Starter · #14 ·
I will leave the A/C off on the way home today and see if it behaves any different in traffic.
 

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Discussion Starter · #18 ·
The fan I have is new and the part number shows it fits 91(intercooled)-2002. It is a 22" 7 blade.

Antonm, It looks like you are still in the process of your swap and your other trucks are sticks? I was curious if you had any input on EGTs at idle in drive as they seem really high to me 550-660? from what I can find on the forums it seems like 450 or so should be normal. LOL I actually don't mind the heat, only trying to get the A/C nice and cold so the girlfriend will be able to ride in/drive this truck.
 

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Discussion Starter · #20 ·
Thats about what my 7.3 runs at with ac on idling. I wonder what seems to be causing the higher idle egts on this 12 valve. Anyway I drove it home with the A/C off yesterday and it ran 190-195 until I got home and let it idle to see if it would creep at a stop and sure enough it slowly kept climbing- rad inlet around 206 and outlet around 180 which would be 190 plus with A/C on. I dont see how the fan could possibly be on wrong and the cup to the blades is facing the right way. I can feel it sucking air through the center of the radiator but blowing air forward at the corners. I was thinking maybe the fan was too far into the shroud and the air was being pushed into the shroud and back forward so I removed the shroud (and accidentally broke it in half in the process...) and the fan feels the exact same. Like it is sucking air through the center and blowing forward at the corners. Made no difference with or without shroud driving around and idling still have temp keep climbing. I looked at the fan on my 7.3 and it sits about halfway in and out of the shroud as opposed to this fan sitting completely inside the shroud (possibly causing it to not create a vacuum effect?) after all of that I noticed what looks like fuel or oil around the #5 injector hold down, it was either bubbling from the hold down or the heat from the head. Probably wont get back to the truck until the weekend now since I am not driving it until I figure out the injector issue. I am going drive the 7.3 to work towing the boat with A/C on shows it should be 103 out and then shoot the upper and lower radiator hoses after driving in traffic and after idling for an extended amount of time to get a baseline of what the inlet and outlets should be.
 

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Discussion Starter · #22 ·
The trans controller has a temp readout off of the factory temp sensor in the trans- the sensor is part of the solenoid pack so I would imagine the cooler line temp is hotter but it will keep climbing with trans temp at 170. Highest trans temp I have seen is 203 or so. I will make note to shoot the trans cooler lines next time the temps are hot and see what it is putting into the radiator.
 

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Discussion Starter · #25 ·
1. EGT's are way too high at idle. I think you have a timing or injector issue to be honest. This is evident by the black smoke at idle, high EGT's, and high jacket water temps. That is what I was wondering but have not been able to find much info searching. Is there an easy way to check VE pump timing while on the truck? I am guessing the injectors would just have to be removed and sent off to be tested to rule injectors out? Just noticed what looks like #5 injector leaking around hold down last night after 700 or so miles so I will have to pull the lines off anyway.
2. Fan should be a pull type. It is somewhat normal for a fan blade to throw air radially away from the fan blade. This is how centrifugal pumps work. I am thinking maybe I need to figure out a shroud that is closer to the radiator or somehow get the fan back further so it is creating more of a suction through the shroud rather than throwing the air around inside.
3. Are your electric fans mounted in front actually causing a significant restriction on the air flow? Are they moving air the same way as the mechanical? They are mounted inside the front bumper blowing the air into the condensers lower half (toward engine) where there is currently no airflow probably due to the poor shrouding. I guess I need to go back to the drawing board on the shroud and try to see what other people doing these swaps are using though I have seen a lot use the stock shroud like I have.



I've had a similar issue before and the coolant temps dropped way down when the timing was corrected. Sounds like that is what I will focus on now. Thanks!
 

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Discussion Starter · #27 ·
I will see if tightening the nut stops the leak for now so I can move the truck around. Interesting, the only fuel injection shop I can find in town said they don't charge to pop test mechanical injectors/check for leaking. Is that all that is required to rule out the injectors? Seems hard to believe anything is free lol.
 

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Discussion Starter · #31 ·
Also it only seems to smoke at idle in drive when there is a load on the motor. If I am sitting at a light and the wind is blowing toward the front of the truck I can see smoke coming by lol. Once it is in park/neutral its gone as far as I can tell.
 

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Discussion Starter · #33 ·
That is awesome to see that you have the exact same fan/shroud setup and have no issues. I am starting to think the excessive EGTs are the main problem but I cant help but think that for whatever reason my fan with or without shroud is only pulling air through the middle of the radiator and that I can feel and see it (with paper held up) blowing air back the wrong way through the radiator only at the corners that I have something weird going on. On the 7.3 I can feel it sucking air through the radiator the correct way at any point on the radiator. Since I broke the shroud the other day I cant take any current pics of it on but I have a couple from a few months ago during the build. I will have to grab another shroud and play with it. I am using the 1st gen water neck with no bleed hose, and I have my heater hose coming off of the fitting where your bleed hose goes to in the head. Can you feel any air being blown out the the front of your shroud? where the shroud meets the radiator?

Drove the 7.3 to work today to get comparisons to radiator inlet and outlet temps. I will update after the drive home in 100 degree temps.

F350 12V 3.73, 33.5" tall tires towing 19' ski boat, 38 miles

Ambient 79F - Radiator inlet 187F Radiator outlet 155F
Ambient 99F - Radiator inlet 204F Radiator outlet 189F

F250 7.3 3.73, 36" tall tires towing 19' ski boat , 38 miles

Ambient 75F - Radiator inlet 168F Radiator outlet 125F
 

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Discussion Starter · #35 ·
Are we talking enough adjustment in the slotted holes to make timing far off enough to cause something like this? It is a major pain to get to that back pump bolt but I will gladly retard/advance the pump with the adjustment slots if it could be off that much. Pump was locked when I got it back from being rebuilt, lined up to "E" on cam gear. I did have to pull the pump after cam break in to fix tappet cover leak but I did not remove the front cover, just locked the pump, removed, and slid back into gear/keyway.
 

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Discussion Starter · #38 ·
Ok. Cool. One other thing I was wondering. If by some chance the injectors were much larger than what I ordered (5x12) it seem like that might also cause similar problems. The flow specs for my pump are below. When I first got everything together the smoke/egts were nuts. I had to back off the smoke screw 5 full turns and rotate the fuel pin from where they had it when it was built (most aggressive setting) to almost the least aggressive setting. I talked to the pump builder and he said it should not have smoked crazy with only 5X12 with the way he set it up. I gave him all the build info before he rebuilt the pump. Injection shop in town said they could pop test injectors and test for leakage, but he said he would try to retard the pump and see what effect it has.


stock fuel pin and screw, 366 gov spring

1000 rpm/ 0 psi boost- 70cc
1500 rpm/ 0 psi boost- 100cc

1500 rpm/ 20 psi boost- 160cc
2000 rpm/ 20 psi boost- 160cc
2500 rpm/ 20 psi boost- 160cc
3000 rpm/ 20 psi boost- 150cc
3200+ rpm defuel
 

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Discussion Starter · #41 ·
I originally had a Napa stat in, have it sitting here it just says motorad 180F. I read about a lot of people having issues with aftermarket t stats so I called cummins, gave them the engine serial and they gave me the part number below which I ordered from Geno’s. The cummins t stat has a piece on the back that fits into the block (bypass?), the Napa did not have that though there was zero change in cooling. Also the cummins one has 2 jiggle pins that I placed at 12 & 6.

5292738
 

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Discussion Starter · #44 ·
So just to update everyone, my plan for now is to pull the injectors and have them tested (hopefully sometime this week or next) and then if those check out, buy a pump timing adapter to verify timing. I also have the old injectors that I pulled off the engine before rebuilding, I saw the engine run with those injectors but they are pretty damn dirty looking. I was contemplating cleaning them up and throwing them in just to see if there was any change.

Destroked 450- Is there anyway you could confirm whether you have any air being blown back forward through the radiator towards the bottom corners? I know it sounds weird, but feeling my 7.3 uniformly sucking air through the rad with a constant 30 degree delta t and the cummins truck sucking and blowing air all around with a constant 10 degree delta I feel that is part of my problem along with the high EGT’s being the major contributor.
 

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Discussion Starter · #47 ·
Awesome thanks! Sounds like I am running about 100-150 degrees hotter EGTs at idle in neutral and drive compared to most 12 valves.
 

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Discussion Starter · #48 ·
So after breaking my stock trimmed 7.3 fan shroud while removing it I ended up driving the truck for a couple weeks with no shroud. There was no difference in cooling compared to the 7.3 shroud. I took some measurements of where my 7.3 f250 fan sits (1/2 in/out) of the shroud and decided to make a fiberglass shroud for the cummins. It needed to be about 2.5 inches deep vs the 5 inch deep 7.3 shroud. I could stick a piece of paper on the front of the radiator with the 7.3 shroud on or even without the shroud and I would get air being sucked through in the middle of the radiator, but blown back toward the front of the truck at the bottom and sides of the radiator. With the fiberglass fan shroud allowing the Cummins fan to sit about 1/3-1/2 way out of the shroud I am getting suction (paper stuck to rad) through the radiator everywhere. In traffic/normal driving conditions it stays right at 180 now. I have seen it get up to 190 after purposely leaving it in drive for 3-5 min parked where before it would have been up to 200+ in that amount of time. It definitely runs cool enough to where I could let my girlfriend drive it to work now and not worry about it running hot. We are going to take it on its first trip at the end of the month, a 500 mile round trip to padre island national seashore so I feel much better now that I don’t have to worry about the temp creeping. I still think the EGT’s are about 100 degrees too high at idle I neutral and drive but that is something I think I will have to try to track down after we get back. Truck runs great otherwise. Couple pics of the truck and shroud mock up. Thanks for everyone’s help!


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