How long should a coolant flush take on semi truck?

Takes what it takes. If the system is full of oil or fuel it can take several flushes to get it clean.

 

For maintenance I would agree with 2hrs plus .5 if it has a filter.

Contamination with oil or fuel is totally different story as stated above and sometimes it takes 10 hrs or more to get it done right.

 

And how are you flushing it? In Florida you would need to be in a facility with a recycle waste water loop.
I do not have that problem but try to be nice to the earth. Normally do the regular Cascade, Dawn, Simple Green, Greased Lighting type thing. Run them and drain it out. That can easily be two hours.
Started doing that and hooking a hot water pressure washer up to the block. After the engine has ran a half hour or better open the drain on the radiator and take the radiator cap off. Fire up the pressure washer and run it until the soap suds stop. Then a bit longer and drain it all out.
When transmission coolers fail I have never found anything that really gets all the stuff out. 6 hours on one.
Two hours is reasonable in my opinion.

 

You would have to define flush, if you mean drain it and run a hose in it until it runs clear 2 hrs may be high, but if you mean drain it, and run cleaner through it, than it's about right, depending on what you run into.

 

Ok, so here's my question:
These new cooling systems are extended life coolant (OAT) or (NOAT) mixed with clean, distilled water. Regular coolant testing/analysis is the only true way to keep up on the maintenance of such a fluid.
Then, the system is flushed with tap water plus some other magical cleaner....adding contaminants throughout the system. Drained and refilled with (hopefully) the correct coolant.

How does that NOT leave contaminants in the system? It's like draining the engine oil, filling it up with water to "clean" it, draining the water and refilling with oil

 

I think ot depends on the system. I flushed a system 7 times once. That coolant looked like mud to start with. Last two times was without Dawn.

 

I have a Cummins that is muddy after oil cooler went out. How much dawn should i use compared to water

 

When mine went out, I flushed 12 hours a day for three days straight. I bought a bottle of Cascade about the size of a gallon oil jug. I'd say it was about half a gallon. I flushed with a third of it three times in a row to use the whole jug. Then I flushed four or five times with Dawn. Basically I just gave it a good strong squirt each time. Then I flushed with hose water. Still oily. So I flushed a couple more times with Dawn. Good healthy squirt each time. Basically a stream of Dawn for about three seconds. Then I flushed with hose water again, and it was a lot better. After that, I bought two bottles of actual Superflush, and flushed twice in a row with that. Then I flushed with hose water again. After that, I flushed out the hose water with twelve gallons of distilled water. I drained the distilled, and filled with six gallons distilled water, and six gallons of concentrated antifreeze.

Anyways, don't be scared to put too much soap into it. It's going to take a lot. And each time I flushed, I ran the engine at 1,200rpm for two hours. It took forever.

 

It takes longer to flush one out with oil/fuel in it than it takes to do the job to fix the problem usually. Way longer. But you really are not "working" on it for that time. Fill, run, drain. repeat. So 2-3 hours of actual work is probably about the right amount to charge unless it is really really bad.