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I rebuilt the oil cooler on my 7.3 over the weekend and am in the process of flushing the system. I had a little oil in the coolant but not too much. I opted to not try to remove the block drain plugs as they are rusted up quite a bit and didn't want to create more problems. My method is to fill the radiator, drive a few miles to get the engine up to temp, let it cool down to a safe temp, drain radiator and refill with water.
First flush after replacing cooler I added some auto dish washing detergent to the system with tap water to help remove the oil. I then flushed the system with running tap water with engine running a bit to get the detergent out. After this all 4.5 gal fills of the radiator were with distilled water. While the water coming out of the system is getting more clear, it is not clear like I thought it would be after a few flushes. IThe numbers on the bottles is the percent of tap water left the in the system for that flush cycle (so I don't forget). Should I expect the water to run as clear as the water from the creek they make Coors beer with or is that like looking for the leprechaun's pot of gold? Or maybe I just need to keep flushing the system. Any comments or questions are welcome.
If all coolant has been drained the proper flush would be to fill thru the inlet hose going to the heater core and plugging the water pump outlet where the heater hose goes into. Then let the distilled water over flow the Degas bottle till you see clean water overflowing, drain radiator do it one more time, drain again, fill the rest with coolant and your done. This is how I have done it and works great and you don't waste that much water.
The block holds quite a bit, including any sediment. At least do the one on the drivers side, it's pretty easy access. Do NOT get it mixed up with the OIL plug
I tried being "lazy" after rebuilding my oil cooler. Figured I had already flushed it well a few months prior, etc. It took FOREVER to get it all clear, so I ended up pulling plugs anyways.
I had a similar question with flushing the coolant my Ranger . I have come to terms with the coolant never leaving the system crystal clear.I literally had to flush the system about 8 times before the water was draining relatively clear. I ended up filling, driving for 5-10mins, and flushing up to 17 times until I was satisfied with the level of clarity in the water.
Having said all that, I'm willing to bet the water looks cleaner looking down the neck with the cap off. I was probably overkill, but I was happy with my work.. In my defense, a drain and refill my ranger was about 2 gallons only. Like other posters stated, there will be sediment inside. This could flare up any remote OCD trying to remove all debris.
This would be a good time to switch to an ELC CAT EC-1 rated coolant. I also have heard that there is a newer version of this type of coolant but don't know anything about it. The main thing is to get ALL of the old stuff out and completely flushed with distilled water first. That being said I would (did) replace all of your hoses while you are at it just as a CYA. The stuff is a bit pricey so best to be sure that you don't need to get into it again any time soon.
Thanks for the feedback guys. I ALMOST was going to report back that everything went great after I got down to the last flush and fill. We'll, I guess if you consider success putting coolant back into the system after the 7th flush and heading over to a friend's house and everything looking great UNTIL you smell coolant when you park the truck that is. Pop the hood and hey, look at that, the water pump is now leaking . It couldn't start doing that during any of the other flush cycles now could it?! Had to wait till the coolant went in. Sometimes I feel like this truck just wants to see how far it can push my patients. Now I'm off to Riffraff to order a water pump. Guess I'll give those drain plugs a try since I'll have a few days to contemplate life and why my truck hates me. I guess on the bright side I can say the oil cooler rebuild was a success!
JP
Thanks for the feedback guys. I ALMOST was going to report back that everything went great after I got down to the last flush and fill. We'll, I guess if you consider success putting coolant back into the system after the 7th flush and heading over to a friend's house and everything looking great UNTIL you smell coolant when you park the truck that is. Pop the hood and hey, look at that, the water pump is now leaking . It couldn't start doing that during any of the other flush cycles now could it?! Had to wait till the coolant went in. Sometimes I feel like this truck just wants to see how far it can push my patients. Now I'm off to Riffraff to order a water pump. Guess I'll give those drain plugs a try since I'll have a few days to contemplate life and why my truck hates me. I guess on the bright side I can say the oil cooler rebuild was a success!
JP
Are you SURE it isn't the thermostat housing. No-Tour-eous for that
My oil cooler went a few months after my flush. My coolant was contaminated by oil before I did the injectors.
I probably change my ELC more than most change their "regular" coolant
I am so glad you mentioned to check the thermostat housing. I replace the old one and the new one was leaking immediately. I tightened it down ( this was before I noticed the leak I thing is coming from the water pump) here's to resolve the leak. Perhaps after pressure system it started leaking again. I will check that tonight and report back my findings. Come to think of it, It is only leaking when pressure builds so your thoughts are very well founded.
When I changed my first water pump and went with the aluminum thermostat housing, it also leaked. After that I went with a very thin bead of high temp RTV when reinstalling. It has worked everytime.
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. In my defense, a drain and refill my ranger was about 2 gallons only. Like other posters stated, there will be sediment inside. This could flare up any remote OCD trying to remove all debris.
. It couldn't start doing that during any of the other flush cycles now could it?! Had to wait till the coolant went in. Sometimes I feel like this truck just wants to see how far it can push my patients. Now I'm off to Riffraff to order a water pump. Guess I'll give those drain plugs a try since I'll have a few days to contemplate life and why my truck hates me. I guess on the bright side I can say the oil cooler rebuild was a success! 
