Draining the Radiator

I have the closed system on my 90 MJ and am planning to flush it out this week.
Is there a drainage plug underneath the radiator somewhere (I haven't looked yet)?
Is there a special procedure for draining and flushing the closed system?
How much radiator fluid (to water ratio) can I put in the system and can I use the low tox fluid?

TIA
PRL

On my 1990 with 4.0 engine, I installed a Prestone flushing T in the line to the heater. A garden hose attaches here through a pressure reducer. Turning on the water flushes the whole system- not like just draining the radiator. Follow the instructions for getting the antifreeze back in (it's heavier and sinks, so it can be added to the water-filled system and it flows down and displaces water. The displaced water has a very low percentage antifreeze in it, although it looks green). This avoids the hassels of emptying the closed system then getting air trapped in the cooling system, and having to pull the temp sensor in the rear left corner of the engine to release the air. If you want to get serious about it, I also transfer deionized water in to replace the chemical-laden tap water, then add the antifreeze. I have had great luck with Mopar (Autopar) antifreeze from the dealer- 12 years on my factory two-core rad, then it split a seam...never did plug up. Using Prestone, I never got more than 6 years from a radiator (same schedule, replaced at 50:50 mix every second year). 4xBob

On my 94 XJ the drain valve is on the passanger side, to get to it I had to remove the grill.

JOe

Remove the grill. I think it is 10 phillips screws. You will find the drain petcock at the bottom of the tank on the passenger's side of the radiator. I have no tips for flushing it. Mine was so bad, I had to replace the rad and about everything else. Make sure you use distilled water when you mix the antifreeze.

On my 98 I would drain as much as I could thru the side drain or use a hand pump and a long hose thru the filler but on the closed system thats not an option. Once I got the mix out I would refill with tap water and add the prestone 7 hour flush and go for a long drive, turning the heat on every now and then to get it thru there. Then I would drain and back flush with the prestone kit [heater on]. At that point I would dump full gallon of Mopar coolant in followed by a gallond of distilled water. At that point I would dump a half gallon of distilled water in the freshly emptied Mopar gallon and then add a half gallon of pure coolant the fill that half empty gallon jug. That gives you two 50/50 mix jugs to work with.
Now I take to my buds shop, use the snap-on machine to pull a vacum and suck the old stuff out, refill with water and cleaner and do the drive then take it back and suck the dirty cleaner/water out and then use the machine to pump in my mopar mix that I make up ahead of time. He thought I was a little nuts the first time till he found out I had over 190,000mi on the original pump and rad. Personally I think the mopar coolant and distilled water is what makes the difference...
I'm actually looking for one of those machines for the house or a more simple one [read $cheaper$] when I see garages closing up or at auctions but no joy so far... it will also give me an excuse to buy a compressor

If I open my closed system at any point- will coolant spray out and require a coolant flush? I am in the process of putting my valve cover back on (fixing blowby) and I am worried that I might have to disconnect the hoses running to the front of the engine right near the front of the valve cover. Any thoughts on getting the cover back on?

I just did the same on my '89 last weekend. It's a tight fit, but you can get the valve cover back on without removing the two hoses. If you decide to remove them, the only radiator fluid you will lose will be from the pressure bottle, since it sits higher than the hoses. I decided removing them would be more of a hassle than maneuvering the valve cover around them. I think it depends on how much you can get the hoses to move while you're wrestling the valve cover back in place.