Im working on a 7.3L IDI. During hill climbing and periods of hard fueling, the engine will overheat. A mechanical aftermarket gauge was intstalled and verified that the temp is climbing while loading up. It will go as high as you want it too, but it has never been let to get too hot. This has always been an issue. I rebuilt the engine due to guy using either as a starting aid. Cracked number one cylinder wall. Sleeved the cylinder and installed new bearings and rings. Reassembled ran great but pesky overheat under load is still there. Heres whats been done. Thermostat, radiator rodded out, waterpump removal and inspection, fan clutch replacement. Im thinking its a timing issue. This truck has always been louder than all the other IDIs ive ever heard. Pump gear dot is meshed with cam dot. Timing marks are lined up on the housing. Cold start timing advance switch is de-energizing. This engine does not black smoke at all. This is unusual for a naturally aspirated engine at full throttle right? Truck is completely stock. Its a retired U-haul. The radiator hoses are firm during operating temp. No bubbles through radiator. When you pull it over after an overheat situation, The fan is removing a heck of a lot of heat from the radiator. The hood is so hot you cant touch it. The engine is just creating too much heat for the cooling system to handle. Outside temp plays a big factor in the severity of the overheat. The hotter it is the faster the temp climbs. One thing that probably doesnt help is the non overdrive c6 and having to do 3,500 rpms to keep from getting runt over on the freeway. I guess next step would be to intstall pyrometer. Can high egts cause overheating? This problem only happens when throwing the fuel to her. I know this engine is capable of handling anything I can dish out because ive personally been inside it and seen its condition. Pistons were perfect. So were bearings. No signs of fatigue. Just a big crack in the cylinder. Keep in mind truck had exact overheat situation from day he bought it used from uhaul. He has been babying it. Rebuild was done to fix crack not overheating. Piston cooling nozzles were removed and could they possibly misaligned? I have never ever been able to figure this out and he is getting fed up with the truck and me too I guess. Nothing has been done to the pump except removal and replace.

 

Mix too lean. If you never see smoke it is too lean.

 

I will richen her up a little and see if that helps.

 

Do NOT touch that fuel screw!!! Don't go anywhere near it before you fix your overhating issue!!!

Diesels are not like gassers, a gasoline engine will indeed run very hot if it's air/fuel mixture is too lean, but a diesel is just the opposite - the more fuel you add the hotter it runs. The smoke you see is unburned fuel, the darker/thicker the smoke the more fuel is getting wasted and the higher the combustion temperatures are - ideally you want to see no smoke, with just a slight haze coming out the pipe under heavy load, this means all the fuel delivered to the cylinders is getting burned completely and the temperatures are not climbing too high.

You mentioned water pump were checked, radiator cleaned, and thermostat and fan clutch replaced - fan clutch seems to work, and radiator is probably good, but maybe the water pump simply isn't moving as much coolant as it should be? Also the thermostat, what kind did you put in the truck? You should only use a Ford or International thermostat, there is only one aftermarket thermostat that works decent but getting it seems to be a hit or miss thing.

Also, do you have an external transmission cooler? You need it, big time - install the largest one you can find in front of the factory radiator (or A/C condenser if you have it), and you may also wanna bypass the factory transmission cooler in the bottom of the radiator because at this point the transmission is only adding more heat to your already strained cooling system.

 

The C6 puts out tremendous heat ford spec is 250 degrees. That is what my is doing when I pull a hill. Normal it runs at 190. I have my gauge in the cooler line at the radiator.

Picking a cooler is hard some rated at GVWR and others are in BTU
I have one of these and I think it is too small?
http://www.transmissioncoolers.us/Me...roduct_Count=2
But it still is not overheating the coolant, according to the stock gauge.

Were is you coolant temp sender mounted? what is normal operating temp for these engines? What shape are the injectors in? What type of fuel millage is it getting? I get a bit over 13 MPG @ 2600 RPM and I wonder if it could be leaking injectors. Would that give too much fuel making it run hoter?

 

Sup guys. I think I figured out whats wrong with it today. I put two bolts through an old fan clutch we found laying around and now its direct drive. First I used some peices of under house pipe holding up strap stuff and hooked it to the water pump bolts and the fan bolts, it worked good till I shut the truck off and the fan kept turning while the engine stopped and it ripped em off. The belts squeek a little when you shut it off now like a semi, bit they are holding. Also at idle the turbine or stator or whatever it is in the clutch that now has a 3/8 bolt in it is bouncing back and forth on the bolts causing a little bit of clatter, but goes away immediately when you accelerate. We climbed monteagle mountain which is a 4 mile 6% grade with 60 50 lb bags of taters in the back and the hottest it got was 200. ***** to the wall. A/c on. Flat out on the interstate at about 65 the temp runs at 170, but it sounds like a tornado under the hood and definitely turns some heads in town. I kept waiting for it to fly apart and go through the radiator but it didnt. Will a motorcraft or IH fan clutch come on when It needs to to get the engine cooled. I know that hayden junk will not. Fuel mileage has decreased to approx 12. Was getting 15 or better. I know its cause its not at operating temp half the time and the fan is robbing hp, but I just dont trust those thermal fan clutches. Moderate gray haze leaving tail pipe under extreme load. Theres two trans coolers one in front and one on the bottom of radiator. Also a spin on filter under the truck for the trans. Its retired u=haul and they kept it up pretty good. Stealership wants 350 for new clutch. Havent checked IH yet but im sure they want some cheese for it too. Have to sell some taters first.

 

Haha, seems like you followed in my footsteps with that locked fan - I first used aluminum straps between the water pump and clutch bolts and it broke them immediately, then I put steel ones and it broke them in few months, and now I have upgraded to some thick braces running from the water pump bolts to the fan blades Watch out for that bolted clutch though, now every time the engine shuts off the fan will try to unscrew itself off the water pump, if that ever happens you'll need a new radiator and likely hoses.

 

Dude I know I didnt tighten it when i put it back on and he shut it off and i was looking at it and it spun about half way off. I put the air chisel on it. I thought about putting lock tite on it but then I though what if we do get the money some day for a new clutch and have to take it off again.

 

Don't take chances man, pull the clutch off and put locktite on it - you should always locktite on it anyways, blue is recommended for regular use, but given the circumstances I'd go with the high-strength red stuff. Later on if you ever wanna take it off you'll just need to heat it up good - MAPP gas torch works good for that, no need for an oxy-acetylene beast, so no worries there. Don't forget to use the air chisel to tighten it again after the loctite.

 

How long have you had yours locked up and whats the highest rpms you had it at. Do you think this fan will hold up. Its a ford blade. What about the water pump bearing will it hold up? I know the 3 gates belts are good to go, they are tight and I can spin the crank with the fan lol. Were supposed to go to scottsville ky in the morning and I will do that locktite before we go definitely.

 

You say the temp is climbing, but how high is it getting?

237 at the upper tank of the radiator is not uncommon on a hard working engine.

 

It's been locked for right about an year now. The highest rpm? Well, right against the governor actually, which in my case happens to be about 3800-3900, and that for several 200-mile trips So far it's held up just fine... And yeah, the fan blade will hold up.

 

Well, I decided to put off the locktite and chisel tighten the clutch till after we got back today because it was 5 am when we left and there was not enough light. Stopped at hardees and shut it off and heard a clunk. Fan unscrewed and fell down but did not damage radiator. Put it back on and didnt cut it off for the rest of the day. Truck ran awesome never ran over 180 over hills idling whatever, it worked great. Got home and shut it off and it didnt fall off but it unscrewed half way off. I put locktite on it and chiseled it tight. Then I put a strap in the opposite direction under tension to keep it from making noise and unscrewing too. I tested it several times and it held. Just lets out a little squeek from the belts everytime you cut it off. Phew close call. Thats what you get for cutting corners. I wonder how hard it would be to drill a precise 1/8 hole through the threads in the water pump and fan both and put in a cotter pin too? Maybe overkill, but I thought locktite was overkill too but obviously not. Fuel mileage is sucking big time. 12 mpg thats with idling for two hours cause we didnt want to shut it off again.

 

I used to get 12-13 city (stop and go all the time) no matter if the fan was locked or freewheeling, my freeway fuel economy though is consistent 20-21 mpg, that's with the fan locked. I drive 55-60 mph at 1900-2000 rpms.

 

Yeah you got the e4od and lock up tc. This trucks got the C6 and at 60 the engine is turning 3,000 rpm. And its got a big box on the back. Maybe ill talk the guy into putting a gear vendors od unit on there.