Got a clean running 7.3 out of a '90 F350 that sat for 15 years, but it fired up immediately with fresh batteries and diesel. The donor truck had a blown ring/pinion, and would only go in reverse, so the owner backed it up to his garage and then passed away. I found a engine rebuild sticker on the engine, and due to the lack of built up grime, assumed he had planned on getting the axle fixed after the fresh engine rebuild.
I put a rebuilt ATS 088, had the IP built to 110cc, and injectors built to 90cc.
Then put it in my '89 Centurion "Bronco".
Swapped the E4OD to a ZF542, then swapped to '04 SD axles and RS kits front and back, and went hydro boost.
Thought I was ready to blow coal but then started to see what I believe is coolant leaking down at the ZF dust cover.
Pulled it off and couldn't see any obvious pathway, so fired it up and took a couple pictures.

You can see it coming off the transmission and the crossover pipe
I collected some of it in a container.

I'm a little concerned about the color, but am fairly certain this is coolant only, and am assuming it's picked oil and grime on it's way between where ever it's leaking from to the place it's dripping on the floor.
I hope so anyway.
The only coolant path in the back of the engine I can think of would be the freeze plugs.
I only gave them a cursory look, and assumed they were good based on the general condition of the engine.
It never occurred to me that once they guy got his truck back that he may have topped off with tap water, which then could have sat there rusting away for the entire 15 years it sat.
I've already checked the obvious, it's not a heater hose, the heater core would leak onto the cab floor before finding it's way down.
The tub I used was my bolts container when I swapped the valley pan, and I didn't clean it out very well, so that could be contributing to the contamination in the fluid.

I'm learning everything as I go, I've had gassers, built a couple hot rods, rode and raced motorcycles, but this was the first diesel I've ever owned or worked on.
Which is why I'm putting all that out here, hoping there might be some seasoned folks out there who've already "been there and done that".
Any insights, observations, or suggestions are appreciated.
Thanks

 

Very likely the leak is coming from the oil cooler. Check that closer and do check your oil for any crossover leakage in the oil cooler. Check the radiator for signs of oil contamination as well.

 

I did replace the oil cooler, but took it to a well respected diesel repair shop to have the ends pressed on because I was worried about the seals.
I'll drop a bore scope down and look for a leak.
If I set the gaskets wrong I'm guessing there should be something showing?
Thanks

 

You're positive it's not fuel?

 

I poured some out and tried to light it.
Thinking about it I'll see if there's any separation in what's left, and try to light the top layer.
That said, it didn't smell like diesel.
As mentioned before, I just replaced the valley pan.
Used new return line, seals, and caps, and used my own aftermarket screw hose clamps instead of those spring steel ones.
There's no fluid collecting on the pan, and only a couple very minor cap leaks.
I had also deleted the mechanical fuel pump, put a Holley Red on the frame rail at the tank.
I then ran AN6 from the new pump to a Racor 500 clone I fabricated a mount bracket

Separator Bracket

Relays

Red Set

Fuel pump and Diesel heater relays
where the OEM tire jack was to mount it, due to the water separator is plastic, and I didn't want to chance a rock breaking it if I located it on the rail.
I used the back side of the bracket for the power strip and relays.


Fuel supply Front
I just realized I never touched or looked at the return line from engine to tank solenoid/valve.
I deleted that as they cut 1 1/2' off the frame to make a Bronco, and there's never going to be a 2nd tank.
(They pulled the tank switch out of the dash, tapped it to "rear" with cheap electrical tape, and stuffed it against the rear of the firewall).
I only found it because I had to swap the brake pedal assembly to a brake/clutch one for the ZF5.

 

The valley pan seal can't break it's seal and leak coolant, like the 6.9's can, due to the coolant passages being plugged up there. The 7.3ls can only leak oil from there, so you've got to suspect the source is either a freeze plug back there, or it's coming from the front of the engine and it's just running back towards the rear, making it look as if it's a rear leak. Check out the t-stat housing and look all around the waterpump.

 

Yeah, I figured that out, after tearing into it.
I've been amazed at the differences between gasser and diesel engine work.
Aside from the much more heavy duty quality of the parts, access is a lot more simplified.. sort of.
I should be able to trace a water path from the front to back somewhere on the exterior of the engine if it is the WP.
When swapping it out I had the engine on a stand and resealed it, including new timing cover and water pump gaskets, with new main seals front and back.
I'll give it a thorough exam later today.