Hey guys,

Happy Friday ;)

Please speak from EXPERIENCE if possible because I've heard enough theory on this issue.

I'm confused about the truth about a radiator coolant flush.

As you know, some people recommend after draining the fluid to run distilled water (Note: NOT Tap water) through the engine for 15 minutes with the Heater running to get sediment and gunk out which coolant left behind (As well as old coolant itself) and afterwards re-fill with 50/50.

It's a minority opinion in my experience, but I have run across a few people who I consider pretty technical engine-wise saying that you can't truly flush the system that way (Running the distilled through the engine) -- not only because the chemical properties of the distilled can't get the coolant out (Water vs Anti-Freeze), but also because the engine itself doesn't produce enough pressure. (These people to flush their systems take it to a shop that has a kit with a high-pressure hose etc or they have a kit themselves etc).

Can anyone give me some peace of mind here? I would LIKE to just drain, run distilled through the engine, drain again, and refill with 50/50.

i didnt even use distilled water when i did mine,

just got the motor warm, drained, filled with water, ran motor to open up thermostat, drained, filled again and ran motor, then drained and filled to my mixture i wanted.

also just opening the petcock and sticking the garden hose in works sometimes, just letting the water flow.

I have had no problems with a flush don't thi way but I drain/fill with distilled about 3 times before I add new or change colors. It is about as close as you can get without doing a high pressure flush.

thanks for the reply gentlemen.

personally i think a high-pressure is taking it too far -- it is definitely ideal, no doubt about that -- if it was a cheaper job then maybe i'd consider it... but for $150 or more... i'm not sure i believe in it.

i agree, sometimes you dont want to do a flush, being an older vehicle with corrosion inside the motor, a flush can dislodge come rust and clog up heater cores and radiators.

I bought a kit that hooks the garden hose up to the cooling system and just turned the hose on and ran it for like 10 minutes. It seemed to work fine.

I know some people who don't even change radiator fluid; let alone flush.

"If my temperature gauge isn't showing that the car is overheating... the radiator+fluid is doing its job!!!"

I guess if you take that literally, it does make sense - the if it aint broke dont fix it mindset.

I did mine a few weeks ago, and yes I suffer from a little OCD.

If the system has been fairly well maintained you could probably just drain and fill but if it has been neglected or you don't know the history I would be thorough doing it the first time.

Drained radiator
Opened heater valve
Disconnected heater hose from heater valve on passenger side of truck
Flushed heater core with water hose
Flushed engine block with water hose thru heater hose ( water will come out the top of the radiator)
Used compressed air to blow out all water
Put heater hose back on
Put 1 gallon of Toyota red in radiator
Put 1 gallon of distilled water in radiator
Removed and cleaned overflow bottle
Filled overflow bottle about half way with coolant
Closed it all up drove it and let it cool
Check overflow bottle and top off as needed

well kind of, thats where some peoples thinking is off. by not doing maintenance, it could lead to larger problems.

example of not changing your oil, you need to change your oil.

coolant also serves an anti-freeze purpose, which over time loses it's ability to resist freezing. So if your coolant is old, and freezes in the block during the winter, it'll put a nice fault line down the center of your block.

Coolant/Anti-freeze doesn't so much fail at circulating and cooling the engine but modern coolant is filled with widely varied additive packages. These additives prevent corrosion and pitting to the passages and components. Also the PH level of the coolant changes as these break down. Sure it will work to cool and may even resist freezing still but I've seen OE water pump impellers pitted and dissolved to the point they no longer circulate the coolant and passages that look extremely chewed up. Not to mention plenty of gasket failures as a result.

Not trying to sell you something lol but many people don't understand that there is more to it than "looks clean".

And you can change it yourself with any of the methods mentioned above.... then if you want to get really nerdy about it pick up some test strips (basically litmus strips specifically for testing coolant PH/Acidity). Also remember to check your freezing resistance/mix with a hydrometer. When you don't get all the coolant out to start with it can make 50/50 a big guessing game.

My rule of thumb has been to drain the radiator ever five years or 30,000 miles, whichever comes first, since the date the car/truck/SUV rolled off the assembly line. A flush on a well kept car can sure add life to its coolant system.

Looking at older autos can be tricky since who knows what is in the cooling system, including the possibility of pepper and x amount of Bars. I have always used a Prestone hydrometer when looking at used cars as well as testing my coolant once a year. I need one day to pick up some test strips.

As long as you control the percentage of ethylene glycol, I fail to see how the freezing (or boiling) temperature could change. It's a physical characteristic; it's not going to change if you leave it there for a thousand years. Time will deplete the anti-corrosion characteristics, but not the freeze and boil protection (if you top up with the same mix you have in there.)

I do the hose flush, but I have water with zero metals and low calcium (~70ppm). In many parts of the country, I wouldn't risk it. You never get it all out, and hard water can kill your anti-corrosion effectiveness. I still use distilled for the fill. I run Toyota Red for 50k. If I were changing at 30k, I'd stick to the cheap stuff, as long as it used phosphates and had no borates or silicates.

along with the above, with iron/aluminum engines electrolysis becomes a problem.

the coolant should be flushed every couple years. even just a drain, flush with water, and refill is fine.

I've had a 1974 Ford F100 for 16 years. The heater core is not in the best of shape, but I keep it going the best I can. Three times since I have had the truck (It may not seem very often, but I've only put 50k on it in that time) I have flushed the radiator in the fall before I've needed the heater. After draining the coolant I disconnect both heater hoses from the block. I put an inexpensive 5/8" female garden hose connector on one of the heater hoses. Hook a garden hose to the connector and the other end to a water spigot. Point the other hose toward a container to catch the first gallon of so. Turn on the water and let it run until it runs clear out of the opposite heater hose. Once it runs clear for a bit, reverse the procedure and put the connector on the other heater hose and turn on the hose. Repeat back and forth until you are satisfied that it is clear of gunk that may have settled in your heater core over the warmer months. This will prevent it from getting into your engine block. Don't forget to reconnect heater hoses to block before adding coolant!