Hello!

I'm currently in the middle of a cooling system flush on my 1998 5vze 5-speed rig. I have drained out the dirty, gunky Prestone green coolant and flushed distilled water through the system. Due to the amount of rust and crud in the system, I suspect the genius who owned this before me used hose water to dillute the prestone instead of distilled water. I have also replaced the thermostat.

My process has been add about 7 qts of water, run for 10-15 minutes, drain, repeat. So far, I have flushed 14 gallons of distilled water through the system. I can't get this to clean up at all, and each batch looks like unfiltered apple cider. Any thoughts on why I can't get this flushed clean?

Thanks in advance!

I recently went through this on a 98' I bought at auction. I ended up using some prestone radiator flush and let the car idle for about 20 minutes which seemed to clean the system pretty good. It wasn't perfect but it got most of the rust cleaned out, the bottle recommends running it for 300-400 miles depending on how badly rusted the system is and I'd imagine you could use a couple bottles if need be without harming the cooling system.

Heres a link to it on amazon, but I'd imagine pretty much any part store would carry it (I got mine from an Oreilly's)
Amazon.com: Prestone AS105 Radiator Flush and Cleaner - 22 oz.: Automotive

Have you though about/tried using one of those attachments that lets you hook a hose right to the radiator and constantly flush water through? At this point it might be your friend though I have a feeling something's up with the rad. When was it replaced last? I've heard your ground water has to be decently hard for it to screw up your cooling system that bad, but as someone that lives with extremely soft water I can't confirm or deny it, just something I thought might be worth mentioning.
Before replacing the rad altogether I would try the snake oil mentioned above and see how it goes. Who knows, maybe it'll work and save you a couple bucks.

Pull the rad hoses off, pull out the thermostat. Then use a garden hose. Let it flush the rad til it runs clean. Run it through the engine (engine off) until it runs clean.

Then you reassemble and do one final distilled water flush.

I do this once when I first buy a vehicle, then just timely drain and fills from now on.

Don’t fight it, buy the OTC power flush gun. After doing all that you could then do a Prestone chemical flush and then fight finished up with the distilled if you want.

I say this as a guy that used to be a professional mechanic, I wish I had this gun 25 years ago. Pull the thermostat out, flush the system bottom up, top down isolate out the heater core, and the rear here to core if you have one flush forwards and backwards also. Both of my heaters were plugged solid.

Here’s the Amazon ASIN: B000F5ECRW

It’s a design flaw in the cooling system, the heater core flow valve is up to high and is prone to being exposed, and then corrosion does this thing. I’ve seen two with the top of the valve corroded out. Also if your radiator is in bad shape, don’t fight it and just replace it also. They’re like 120 bucks from a dealer. Probably the easiest radiator I’ve ever installed in my life.

I've flushed my cooling systems for many years with a garden hose, bottom plug pulled, running engine, etc. Never overheated anything, gets the systems nice and clean.

The rust has nothing to do with a garden hose, but rather from coolant that is either used for far too long or mixes that have too much water vs glycol.

I disagree with that. Hose water contains a lot of heavy metals which will cause more corrosion/rust in the cooling system compared to distilled water and coolant or pre mixed coolant.

so I have done flushes with thermo out, garden hose style from a hose bib on house....then followed with distilled water flush, then correct coolant and distilled water. I thought if I flushed out the system with distilled after a garden hose flush I would be good.
you think I still have some heavy metals in there after a distilled flush ?
I drink the same water that goes to the hose bib...thus into the cooling flush..but I chase out the heavy metals with beer

Take a look at my thread on this. It's been about 3 years and my cooling system still looks good.

Flushing with distilled water after flushing with a garden hose will get the majority of the garden hose water out of the system, and it's much better than not flushing with distilled water after the hose flush. When I flushed my cooling system I used only distilled water. By comparing the cooling system capacity 2.5 gallons (10 quarts) with how much fluid I recovered from the cooling system when I drained it between flushes including pulling the thermostat housing (9 quarts) I determined that every flush diluted what was in the system by a factor of 10.

Short answer: Flushing 1 time with distilled water after draining the cooling system by removing the thermostat housing reduced the amount of hose water in the system when you filled it with coolant/distilled water to 1-2 oz of the total cooling system.

Link please

well I got to swap a radiator and thermostat in about 2 weeks, so maybe Ill just use distilled water for all the flushes....not like its tons of money.

me too want to see

It hasn't been mentioned but it's best not to put green coolant back in. Our cooling systems and radiator are aluminum and the green coolant doesn't have the additives to prevent corrosion. The pink and red coolants (Toyota LL and Toyota) do and will resist rusting for much longer. Green isn't a death sentence, it will just break down faster than the others.

The issue with dealing with major rust problems in the cooling system is that rust did not magically appear and it has likely done some sort of internal damage. If it is continuing to come out that rusty after 4-5 chemical flushes (though 15 minutes isn't enough for the chemicals to do what they are supposed to) the radiator, heater core, or coolant passages have gotten clogged up with rust. Although I have never seen it with the Toyota engines I have worked on, many American manufactures also have water pumps that rust until the fins stop existing.

Using a pressurized flushing gun as several others have suggested is a great place to start. Using distilled water on something coming out that dirty is nothing shy of a complete waste. As far as chemicals go, I have had much better luck with solving rust issues using BlueDevil radiator flush where I have better results getting rid of calcium deposits with the Preston flush. Putting the proper heat/pressure with these chemicals over a longer period of time would net you better results than most of your other flushes combined.

Hope you get it solved without any major repairs!

It is funny how the added corrosion/damage and more frequent flushes from the cheaper green end up being even more expensive than (not even mentioning the tons of extra work needed) just running the red/pink from the start.

The smart and quick way to do it when getting ready to put the good stuff in.