I have a 2003 F-350 6.0 diesel and there is the smell of antifreeze when the engine is warmed and been driven. I changed out the coolant tank, cap and checked the heater coil but it is not leaking nor is the smell present,and now again the smell starts to over take you when driving. I also have a lot of black exhaust at all times

The most likely reason is that there is air in the system from when you drained down the system. Raise the front up a bit to get air to come out from the heater core. Heater must be on full heat when burping the air out. Continue to add coolant until the radiator fan starts.

Details in the link.

https://www.google.com/search?q=burping+coolant+system

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Open the container of antifreeze. Using a separate EMPTY gallon-size container, pour out HALF of the contents into the empty container, making sure not to spill any. Now, FILL the newly filled container with tap water. Fill the rest of the antifreeze with water, also. Now, you are ready to add antifreeze to your vehicle! Simply locate the radiator cap, (Don't touch it if it's hot!!) and unscrew it. Pour the desired amount of your mixed antifreeze into the radiator. Remember not to do this without proper knowledge!

Souinds like beginning of blown head gasket. could be due to corrosion on either head or block. "Diesel knock" could be due to excess compression from water in cylinder (will explain steam, antifreeze smell).

• One is the radiator and the other is an overflow tank. Sometimes anti freeze will back pressure a bit and need somewhere to go and other times the antifreeze gets low in the radiator. That is the purpose of the radiator.
• Put the antifreeze in the radiator fist and then add to the reservoir. Pay attention to the cold/hot level fill on the overfill tank.
• You need to find out where all that antifreeze went to if the radiator was empth. Pull the dipstick and look for a chocolate milk look on the oil. This would be a head gasket or a cracked head.
• Otherwise keep an eye out for a leak and repair it soon.
• Hope this helps and thank you for using FixYa.

Regards, Tony

You have an air bubble in the coolant system. When the engine is cold, loosen the radiator cap to the first notch. Start the engine and warm to operating temperature. Turn the engine off and top off the radiator and overflow tank. Tighten the radiator cap and allow to completely cool down. After the engine is cold again, top off the overflow tank. The heater should work properly.
Good luck.

If the thermostat was recently replaced, it could be trapped air in the cooling system. First, you need to establish that the thermostat is working. Remove the radiator cap and start the engine. Let it warm up to normal operating temperature on the temp guage. Make sure the heater is set to the hottest setting. Observe the coolant in the radiator. If the coolant is flowing when the engine is cold, then the thermostat is stuck open and the heater won't get warm. If the coolant is not flowing, continue to watch the coolant. When the thermostat opens, the coolant level will drop in the radiator tank, add antifreeze to bring it back to full. Each time the coolant level drops, add more antifreeze. should the thermostat close while doing this, antifreeze may spill over from the radiator tank. No to worry. As son as the thermostat opens up again, add antifreeze to fill the tank. Continue to do this until the coolant level no longer drops. Sometimes it is necessary to raise the front of the vehicle so the radiator is high than the engine in order for the air to escape. Put the radiator cap back on. If the problem was air in the system, then the heater should be warm now. In the old days we would just drill two 1/8 inch holes in the new thermostat before installing it. That allowed the trapped air to escape slowly. Might still be an option.Let me know if this helps.

check heater core lines seems like they are dripping and hitting the exhaust,but check all hoses ,no mixing orange antifreeze and green is not going to hurt your engine but the orange is longer lasting then the green mixing them changes that by a little.

There should be a petcock along the bottom of the rad. Most newer rads don't have a cap the antifreeze is added through the overflow tank.

with the engine cold,remove radiator cap.fill w/antifreeze so you can see it.start engine.as engine warm up look for movement or flow of coolant.at normal temp,no flow--water pump bad. if you see bubbles it's a head gasket,quite likely if it was driven while overheated.

The antifreeze tank is held on by I believe two bolts on the side. It's pretty easy to remove,

Just unbolt, remove hose and do the reverse with your new one.

As far as a replacement, I'd junkyard or ebay one. Lot cheaper, quicker, and easier than trying to get an aftermarket one and modifying to fit.