Hello everyone,

I just finished replacing the timing belt and water pump on a first-generation Kia Sportage. I replaced every rubber hose there is. I can see rust(?) corrosion inside the old hoses. I was looking at this cleaner from Prestone and I am wondering if it is safe to use, or are there any other methods that are better that a cleaner? It’s an old car but I want to make it last a bit longer.


I used a Prestone cooling system cleaner on my iron head/iron engine 50 year old Ford truck years ago. Didn’t harm anything, but never found that method an improvement over just thoroughly flushing the system with a garden hose, followed by a refill w/ fresh coolant. I didn’t dare use it even a single time on either of my vehicles with aluminum cylinder heads though. IMO unless there’s a clear reason to use it, don’t.

If you want a super-duper flush, remove the radiator and flush it w/a garden hose upside down. Then remove the hoses to the heater core and reverse flush it too.

A simple flush followed by replacing the coolant more often is probably the best use of your time and dollars. Every 2 years rather than every 3, etc.

1 Like

Hello George!

I have seen some people use the garden hose method. What do you do with the remaining water from the garden hose?

I have read that you are not supposed to use regular water in the cooling system, and I suppose some will remain inside somewhere.

I guess what I am trying to say is, what do you do as far as coolant mix is concerned? Do you use concentrated coolant + that regular water? Do you run the system with distilled water a couple of times and then do distilled + concentrated?

The way I do it, I first drain the radiator, dispose of correctly, then set the heater to high, then I disconnect the radiator top hose and rig up a way to catch the water from it into a big tub or garbage can. Next I start & idle the engine while I run the garden hose into the top of the radiator just enough to keep it filled. After a few minutes water will start to pour from the top hose into the tub. Watch carefully, as when this occurs you’ll have to add more water to keep the radiator full. After a while what comes out of the top hose will be clear, looks like water, stop the engine and let it cool off completely. Might take 4 or 5 hours. Then drain the radiator again, and refill with 100% coolant (the concentrated type), enough so you end up with a 50/50 mixture of the spec’d volume the car takes. I don’t use distilled water myself, hose water here is pretty good quality, not a lot of lime, but distilled water is probably better.

There is some risk of cracking the block what w/the cold water being added to a warm engine, but never had that happen on any of my vehicles. If that’s a concern you can fill the system with water, run the engine until it warms up, cool it down fully, drain, and repeat several times. Takes longer that way, but it seems like it is a little safer.


Thanks a lot George. I appreciate the time you took to explain this in great detail. I will try this method. =)

Oh, I just saw the last bit of your response. I will keep that in mind =)

I usually get really wet in the process. I do this job in the summer if possible.

1 Like

How to Flush a Radiator (with Pictures) - wikiHow

One caution w/the concentrated coolant method, the concentrated part can end up in one section of the cooling system and mostly plain water in the other. So be sure to use the car frequently with the heater on until the coolant has a chance to equilibrate throughout the entire system.

1 Like

Thank you, George. I did not know this. Appreciate the advice.

If you see rust in the cooling system, the only place that can come from is the cast iron engine block.

Doing a radiator flush won’t remove this rust.

Instead, a complete coolant system flush service is required to remove this rust.



Everytime I used a chemical flush, including Prestone products, I had to replace every hose and often the water pump within a few months of using it. This included one vehicle that had the hoses replaced a few months before I did the flush. I stopped trusting them a long time ago.

Maybe they are better now, but I’ve been burned enough times that I will not use them ever again.

I also do not flush a system anymore. I drain, then premix my coolant in old empty milk jugs and refill. This way, there is NEVER a chance for the cooling system to become contaminated. I do mix the coolant a little stronger than the 50/50 but never over 2:1. I do not worry about a little of the old coolant being retained in the heater core or block.

The key is to replace the coolant on time according to the maintenance schedule. If done on time, or reasonably close to on time, your cooling system will last for a long time. Hoses and the thermostat should be changed every other coolant change. After 15 years or 200k miles, then you will get the random failure no matter what you do. But they are rare.

1 Like

I noticed that too on my ancient truck. Don’t know if its a coincidence, but generally had some sort of water pump failure within 4 years when I did the chemical flush, but w/o the chemical flush the water pump seems to last longer, 7-10 years. The current water pump is 10 years old. Never had any hose problems as you describe though.