I discovered some fuel in the water (with maybe a little oil), about a cupful. I asked and was told a cracked injector cup could cause this. I just finished pulling all the injectors and cups. There was no visible problem with any cup. A couple of the injectors had what appeared to be bad o-rings - partially worn away.
I am getting ready to put new cups in and put it back together. I am confused though as to how fuel or oil could get into the water without a bad cup. There is no sign of water in the crankcase or any other contamination. Is there anything else to check?

 

Tell us what made you think what you thought. Was the antifreeze contaminiated with diesel and or oil? If so, possibly could be a head gasket.. Let us know what exactly you found

 

If the O-rings are bad on some of the injectors, it'll cause the cross-contamination.

 

I to have this issue.I changed anti freeze about 3 months ago checked today and brown.My truck is 1999 7.3 crew cad drw 120,000 miles bought 2 years ago.When i bought it they sad they replaced a injector may the o-ring be bad? how big of a job is it the check o-ring and cups? I also have a shake at 40mph goes away little before and after.When it shakes turned off over-drive rpm goes up shake goes away?Any ideas?

 

Yep -- an injector can do that. You have to pull the VC, then it's just a matter of removing the injectors and inspecting. BUT, you should be have new O-rings to go in when you pull them out. Putting them back in with old O-rings will probably just cause more problems.

Of course, oil, fuel, & coolant will end up in the cylinders -- you can use a hand pump to suck them out, then pull the GPs and crank the engine with the CPS unplugged. Whatever's left in there will shoot out...

 

I looked in the degas bottle one day and there was about a half an inch of fuel floating on the water, with traces of black (oil). I skimmed it off with a mightyvac and never had that much again, although there is a film streaked with black (I also haven't driven that much).
When I pulled the injectors, except for two cylinders where the o-rings appeared mashed, all looked fine. When I pulled the cups, all looked fine (no sign of cracks I had heard about). But there was no sign on any cup of sealant (locktite) on the upper end, and only the faintest sign of any sealant on the lower end.
The cups fit over the water jacket at the bottom of the head, with the fuel and hp oil rails above that. I just couldn't see how fuel could get into the water without a bad cup. I assume there is no fuel passage going into the block so the head gasket would not seal against that. I wonder if some assembyman just didn't put sealant on these cups at the factory? (truck is '01 F350).

 

Head gasket would be coolant in the oil issues, not fuel in the de-gas bottle for sure. I think you're onto it now...

 

It is not a terrible job to r&r injectors and cups, but you need some special tools. I have heard of people pulling the injectors and pressurizing the cooling system to look for leaks in the cups. You may or may not see a leak this way, and since you already have the injectors out, why not r&r the cups? You have to buy new o-ring sets for all the injectors anyway, and the cups are about $10 ea, so why not do them all while it's apart.
The shake could be a weak cylinder showing up at a certain rpm. If you have a scanner that will do a cylinder contribution test that may pinpoint the problem.

 

I finished the job - new injector cups, new o-rings, new glow plugs. There did not appear to be anything wrong with the old cups (no visible cracks). A few of the old injector o-rings appeared eroded/bad. After cleaning up for a few miles, runs fine, seems less noisy. I filled with water, used cooling system flush, ran for 15 miles pulling heavy trailer, drained water (smelled of fuel, cream-colored). Flushed, refilled, ran again 15 miles, drained water (smelled of fuel, cream colored). I know the entire cooling system was contaminated with the fuel before, but I don't know if I got it or not. I'm using concentrated detergent additive to get any fuel or oil out of the system.
It runs fine, no other symptom or contamined oil, etc. I don't want to think after all that work it could be a cracked head.