1999 Acura TL. I want to drain radiator and refill. I've heard flushing it with a hose is not recommended by Acura. Anyway, once drained completely shoul I pour new coolant (50/50 mix) straight in radiator? I also bought new cap because that helped my older Honda Civic. Advice?

Removing the drain plug and just letting old coolant drain out and then refilling doesn't really flush it out. It only drains what is in the radiator and it doesn't circulate and flush what is in the engine and heater core.
Take radiator cap off, then take top radiator hose off where it comnects to the radiator..only disconnect that side of the radiator hose aim end of hose downwards and leave it there. Take a wet rag and push it into the radiator where the hose was connected..you don't want to push it in so far you have trouble removing after flushing...the wet rag is just to limit the amount of water that will come out of radiator where hose is no longer attached..crank car and coolant will start to slowly come out the vend of radiator hose aimed downward...have a hose or 4 or 5gallons of water...right after you crank the car pour the water or befilling the radiator with the hose...you want to keep the water going in the radiator as to keep it fulI...replace what is coming out of radiator hose...continue to add water until what is coming out of the radiator hose is clear water.. this way the water is circulating through the entire cooling system and engine. When water is coming out clean...turn car off remove rag from radiator and reconnecupper radiator hose..the drainplug is at the bottom of the radiator on the side of radiator that is on the drivers side of the car....remove drain plug and drain water left in radiator..replace drain plug and crank vehicle and fill radiator with coolant recommended for your vehicle... Sounds more complicated than it really is..other option take to a repair shop and have them flush with machine..usually around 100 bucks at ashop..Iif you have any questions Iwill be glad to answer..

Follow these steps: http://www.wikihow.com/Flush-a-Radiator

Refill with proper coolant and regular hose water, following manufacturer or product recommendations.

IF there is plug there it will probably be flush with the bottom of the tank and have a large cross cut into it, It may be above the tin splash plate that covers under the radiator to sump. Otherwise undo the hose clamp at the bottom of the radiator and gently remove the hose. It will be messy so do it in an area you can clean up after.

1: Drain coolant system
2: Purchase coolant flush, making sure you have the proper amount for your size of coolant system
3: Pour coolant flush into your radiator, filling the rest with water
4: On the coolant flush bottle it will tell you how long to run your vehicle
5: Once done running, let cool enough to open radiator cap, and drain system COMPLETELY by first draining out of pep **** on radiator, then taking one side of the hoses off the radiator and draining those
6: Put hoses back on and fill system with coolant. When the fluid gets to the top of the fill port on radiator, start vehicle and let run, allowing air to escape the system, and fill as necessary

Once the engine has cooled, locate the radiator drain plug and place a large catch pan underneath it. To expedite the draining process, remove your radiator fill cap to allow air to enter the system. With the cooling system refilled with tap water, replace the radiator fill cap and run the engine allowing it to reach operating temperature.drain radiator,
At this point, if you have opted to purchase a radiator flush kit, you should refill the cooling system with tap water and add the caustic fluid as directed.
Run the engine for as long as the radiator flush kit calls for (usually less than 10 minutes). follow directions on bottle for flushing. if you feel you want to use a T connection just cut into return line, from heater core. then you can use a garden hose to flush system.

There are several methods for flushing the cooling system on ALL engine cooling systems. Time honored is drain the radiator (drain ****). Fill with fresh water and run engine to operating temperature until cooling fans turn on. Drain cooling system again. Refill with 50-50 coolant. Another method is purchasing a "T" vlave (coolant flush/service kit) from Autozone, PepBoys, NAPA, O'Reilys, CarQuest, etc.). This "T" valve is installed in one of the heater hoses & attached to a garden hose. Remove the radiator cap & turn on the water supply to the garden hose. Let water run until flush water is 'clear'. Remove garden hose from T valve & refill radiator with pure coolant until the T valve drainage turns green/orange. Install T valve cap... DONE!

If you don't see a cap, you don't have one. If you are flushing in hopes of correcting an overheating problem, be aware that if the radiator is partially obstructed, the flush chems sold today are too mild to actually do much. The better chems were all banned by the epa.
If you are just doing routine maintenance, easiest method of draining is to remove the lower hose at the radiator, let the system drain, put the hose back on, fill with water and any chems you want to use, run it as per instructions, drain again, fill with more water and repeat with water at least twice before draining and filling with new antifreeze.(do all flushing with heater on full heat) Keep the cap off while doing this so you don't build up pressure and be careful draining hot water. Even though they are mild for the job, chems can still irritate your skin so be careful. When filling for the final time, make sure the system is full and the thermostat has opened before closing it up. Always check everything over for leaks.Any other questions? Just ask!!

You'll need something to catch the old antifreeze in as its a federal law not to allow coolant to go into storm drains etc. Open the drain petcock or butterfly valve on the lower corner of your radiator (It's better to do this when vehicle is cool to avoid getting burned) and NEVER open a radiator cap when the vehicle is hot. After coolant is drained if it looks like it may have thick residue or rust in it I'd recomend adding a bottle of prestone cooling system flush (follow directions on the bottle) if not put your water hose in the radiator neck opening and turn the water on halfway. Your vehicle will need to heat up to operating temp for the thermostat to open so the water will then in turn go through and flush the rest of the system out. Allow vehicle to run with water on until all you see is clear water coming from drain spout. Turn off water, wait 1 minute and turn off vehicle as this will circulate extra water from system, allow to drain completely then close drain I'd recommend using a long life coolant like dexcool (the orange antifreeze) which is good for up to 5 years as opposed to the green etylene glycol which should be replaced between 1-2 years. For added protection you can add a bottle of water wetter additive if vehicle has had a history of running at a hotter temp than normal as well. You can get the dexcool in a premixed 50/50 mixture to take the guess work out of it. Remember as well when refilling once the vehicle has cooled you'll need to add a gallon and wait for thermostat to open back up so you can fill the rest of the system as well. drain and flush reservoir coolant tank as well. Check the following morning after you've filled it to ensure it's full. Rinse of any coolant you've spilled while refilling or it will smell like that for a month.

Welcome to Fixya

Thermostats almost always reside in a housing at the engine side end of the upper radiator hose. Drain coolant first, then loosen radiator hose to access thermostat housing. If you can't find the housing, consult your vehicle service manual for location. Loosen the bolts that hold down the thermostat housing. Remove the housing to reveal the thermostat. Use a scraper to remove old gasket material from all mounting surfaces. Place new gasket on housing. Use a small amount of grease or adhesive to hold it in place during reassembly. Reconnect all hoses. Close radiator petcock. Refill cooling system with recommended 50/50 blend of water and coolant. Run engine and heater to purge air from cooling system. Recheck the coolant level once engine is cool.

Please see this link. This came from one of our good expert here in fixya.

Thank you for using Fixya!

If you need further help, reach me via phone at https://www.6ya.com/expert/elixirjose_00375ea24bd8141b

you need to flush the radiator out.
With the engine cold, remove coolant bottle cap to release pressure.
Drain engine coolant from drain plug on radiator.
With the drain plug removed disconnect the highest hose connected to a radiator.
use an hosepipe and put it in place of the disconnected radiator pipe.
turn on the water to the hose pipe and let it flush out any sludge accumulated in the radiator. after a few minutes turn off water supply, reconnect radiator hose and drain plug and refil using recommended coolant mix for your galaxy (purchased at most autofactors and garages).
Also check your thermostat as if this is faulty it would stop the flow of coolant running around your engine.

hope this helps