cooling system quick flush...

[pipes1]

i will be doing a quick flush of my coolant soon and was just checking to make sure I've got the procedure on point... all i have to do is drain out the coolant from the rad plug, fill it up with distilled water, run it through, and then do the same procedure , but refill with coolant afterwords, am i right?
(remember, just a quick flush not a total flush.

[sly]

you need a "rinse" run (drain and fill with water) after the flush run and then fill with coolant. You can typically get by without the rinse cycle though, but it does help.

[IPreferDIY]

The big consideration for me would be how much coolant is left in the block when you only use the rad drain. (I've never tried draining out more than two gallons from the rad drain, so I have no idea how much you can actually get out.) If you assume a four gallon capacity and only get three out, you have one gallon of a 50/50 mix that will be diluted. That would translate into a half gallon of undiluted coolant left in the system. When you drain the water (another three gallons), you'd still have 1/8 gallon of undiluted coolant in the system. If you do a second round of water, you'd end up with 1/4 of 1/8. I'm too tired to do the math at this point, but that's the process you'd have to go through to make sure you're close enough to the 50/50 range.

[sly]

I think it's just one more gallon in the block. jack up the back end and you'll get more out.

[mitymerc]

I am refreshing the coolant in the Megamerc (the dilution ratio is goofed up since the multiple S.F. overheats ). I drained the Rad & jacked the back way up w/the lower rad hose disconnected. It seems like I only got about 5 Qts out of it. It has been refilled w/Distilled water & Prestone Flush. I will drive it 2 miles to work & back tomorrow, let it run for a while w/the heater on & drain again. How do you get all of the old coolant out? Refill w/water & drain again? I don't have a fitting installed on the heater line but that would fill it w/tap water anyway. What do you guys do?

Thanks

[IPreferDIY]

I like pulling off the upper rad hose from the rad and attaching something to it to drain into buckets. Then cover the upper inlet on the rad and run the car until the thermostat starts cycling. Whatever's in the system will expand before then, so keep that in mind. Once it's cycling, keep filling the rad with distilled water through whatever opening is normally used. When you figure there's only distilled water left in the system (I'd guess after around eight gallons or so), figure out how to drain half the volume of the cooling system and add that same amount of straight coolant to give you 50/50. If you add the coolant while the engine's running, there's a risk that some coolant will take a shortcut and come right back out, so it would help if you could drain and add half the volume of the system while the engine is off.

[gadget73]

Loosen one of the heater hoses. A bunch more comes out. Can't get 100% of it out though unless you're feeling brave enough to try and get one of the block drains that live somewhere around the motor mount loose.

I usually do something similar to DIY's method though. Get the whole thing full of water, drain what you can get, refill with 100% green juice. It comes out pretty darn close to 50/50.

[jaywish]

Caution Radiator fluid can be HOT HOT HOT. It can burn you badly. Best to start with a cold engine.

This procedure may be a bit more than a quick flush but it won't take much more time overall and will almost certainly give better results for a small additional effort.

If you buy a prestone flush kt for $6.50 I think it works out well.

Open the rad cap and the radiator drain. Install prestone "T" in heater hose, in lieu of the thermostatic control if you have one.

AT this time you can detach the hose from the rad bottle to the rad neck at the neck. Let it drain into bucket and flush out bottle repeatedly as best you can with hose.

When rad is mostly dry I suggest removing the lower rad hose to drain out a nice big splash of old anti freeze. Then remove top hose at rad. You can shoot your garden hose into the rad cap fill and the rad upper hose opening. this will get a lot more sediment out.

Reattach the top rad hose. Attach prestone fill adapter to "t" Attach garden hose to "T" adapter. Turn on the garden hose it will push out a lot more antifreeze from the lower hose. You can pulse the water supply to move around some sludge. When that is running clear shut off water supply and reattach the lower hose.

At this point the rad cap is still off and drain open but all hoses main are attached. Start garden hose water supply again. Run motor until the thermostat opens and you are happy with the clean water exiting the top of the radiator. Then shut off motor and water supply. When the water is cool enough for you to work remove lower hose at rad. At this point you should be getting only water out so no need to capture or contain what is draining out.

Reattach rad bottle to rad neck. Shut off and remove garden hose and prestone adapter. Install Cap on prestone "T" or reinstall your thermostatic control.

If you are changing the radiator or other system component this is where I would do it now that most crap is out of the cooling system.

Now you have a choice. If you want to have mostly distilled water and antifreeze in the system start at
A: if you just want regular water and antifreeze start at B:

A: When Rad is empty, reattach lower hose and close drain. Keep rad cap off. Fill rad with distilled water. start engine, turn heat on. Keep the system full with distilled water as level will probably drop as air pockets flush out and T stat opens. Did I mention fluid can be boiling HOT? When t stat opens just run for a minute longer to mix the water. Turn off engine, stuff can be hot so be careful and open rad drain. Remove lower hose again when it is cool enough. Now proceed to B: I guess if you are really nuts about this you can repeat A: again before going to B: to get a bit more regular water out and distilled water in.

B: When rad is empty, reattach lower hose and close drain. Add straight antifreeze. The amount will be equal to 1/2 of your total system capacity. Even if you can't quite fit enough in radiator you can also fill the now empty overflow bottle to the cold fill line with the remaining straight antifreeze required to get you to 50% of total system capacity. As gadget said it will be pretty close even if you don't measure it. Start engine with cap off and heat on. The fluid level will likely drop. Add distilled water or any remaining antifreeze required to reach the 50% fill requirement. Keep an eye on things. Fluid may drop again when t stat opens or sometimes it surprises you and overflows, be prepared. Put on radiator cap. You will need to run the engine briefly at speed to bleed out the bubbles, I go around the block in second or use whatever bleed procedure is appropriate for your setup. Note if you have the prestone "T" still installed and it is at a high point you can loosen the cap to perhaps get out a few bubbles, (Caution HOT) don't forget to re-tighten.

Keep an eye on the gauge if you have bubbles the engine will get hot. If you blow out the bubbles the temp should drop quickly to normal range. When the engine has cooled to cold you will most likely have to add more distilled water to either the radiator, the bottle or both. It should be pretty good at this point but I think you should check the levels again after it is cold one more time. Carry a jug of distilled water with you for a couple of heat cool cycles. Note, if you remove the radiator cap during the a cooling cycle you may break the vacuum and it may not suck down the bottle properly that time, no problem at all just remember to check the bottle again after a full hot to cold cycle.

What I do is use a label maker to say "coolant change due ..." Clean the top of the radiator and stick it right there where you can see it when you are checking you engine. This is why I use at least the 5 year coolant. Time flies and I can no longer remember for certain if I don't right things down.

Every engine is a bit different. If there is a recommended bleed procedure, find it out and use it.

It is very important to make sure you have the correct antifreeze particularly with some of those foreign cars some folks have started buying. Even the new American cars are using different stuff

I generally don't use engine flush additives, particularly if the system is relatively clean to start with (i.e maintained) but you may choose differently. If the system is crapped up, I still hesitate but sometimes go ahead with a chemical flush anyway.

Ever see anybody burned by radiator fluid? They can be pretty bad, Don't screw yourself or anyone else here, Caution is king.

[IPreferDIY]

The biggest safety concern is that the system is under pressure when closed and hot. The coolant expands as it gets hot, and the rad cap allows the pressure to build up to a certain point before allowing it to drain off. Trying to take the rad cap off when it's hot would be like opening a can of pop after shaking it, but with much more serious consequences.

When you start with an open system and allow it to get hot, the pressure doesn't build up, but you're still dealing with coolant that's around the temperature of your thermostat, usually somewhere around 195F. If you feel comfortable proceeding, definitely proceed with caution.

[jaywish]

YUP what he said.

And the the pressure in combination with the antfreeze/antiboil allows the coolant temp to exceed the boiling point of water (212F) so it can be superheated. So opening a hot radiator can allow pressurized superheated oil and water to spew out in all directions.