Issues flushing dirty coolant

[SurplusFan98]

Seems like vinegar is a pretty common approach, but I'd be cautious about it.
The low pH induced by putting vinegar in the water causes metals to become soluble in water. Metal erosion rates increase dramatically when dropping into this regime. Not a big deal for a thick steel block or head, but can be a problem for an aluminum radiator or heater core if the pH is below 4. You could purchase some pH strips and see

I'd be more inclined to use Thermocure perhaps altering with the Prestone product. Thermocure attacks rust without lowering pH while the Prestone product works more on scale.

Anyhow, if you are using the Prestone, I'm not sure you should be expecting the coolant to ever be clear or nearly clear at the end of an exposure cycle. It may take hundreds of hours of exposures and flushed before the water is clear at the end of a cycle.

Yep, you're probably correct. I'm still flushing this thing. Its improved to the point that the water doesn't go brown while I'm still filling it, but when I fill it and cycle it through for 10 minutes, its still basically southern sweet tea after the fact. Can't even tell you how many jugs of distilled water I've run through it at this point. Going to have to switch tactics. Will try some of what's suggested here.

 

[RCP Phx]

You dont need distilled water for flushing the system!

 

[Ralph77]

There is this product I use for rust removal of small parts called Evapo-Rust.
Stuff is awesome, can be reused to a certain extent, and says right on the container that it is safe for your eyes.
Which I find funny for a product that works so well.
Well they make this stuff called Thermocure for cleaning out cooling systems.
Never used it but since I like there Evapo-Rust so much if I needed to clean a cooling system would give it a try.

 

[maxbraketorque]

There is this product I use for rust removal of small parts called Evapo-Rust.
Stuff is awesome, can be reused to a certain extent, and says right on the container that it is safe for your eyes.
Which I find funny for a product that works so well.
Well they make this stuff called Thermocure for cleaning out cooling systems.
Never used it but since I like there Evapo-Rust so much if I needed to clean a cooling system would give it a try.

Yeah, same company. Probably the same product with a different name. I've used Evapo-rust at work. Its impressive.

 

[fenns7]

Another vote for Thermocure here :thumbup: Helped clean out the cooling system of the abandoned '96 I rescued a few years back. That cooling system was disgusting with a significant rust build up in the engine block and radiator.
Ran a dose of Thermocure for a few hundred miles (during which there was no over heating which was interesting) and then drained what looked like black water - v. impressive. Couple of flushes later and the replacement coolant did eventally turn slightly grey/black - still doing it's job I presume - but with no deterioration in cooling efficiency.
I've just completed another radiator/ water pump/ theormostat swap (after two years) with a further flush and the new batch of coolant currently remains a nice shade of blue (we dont have the dayglo orange/red/green coolants you guys have in the ex-colony:us: )
I'd previously fitted one of those Champion coolant filters in the upper radiator hose to monitor the coolant and to trap any pieces of rust coming loose from within the block and elsewhere in the system. After a couple of years it still catches a few small pieces which suggests flaking within the iron block is a continuous thing - the rad and water pump are new so I know its not from there.
After the latest work I noticed a piece of gasket was trapped in the filter mesh which shows that no matter how careful/OCD you are small pieces can go adrift and workk their way thru' the system
If I remember I'll find a link to my brief YouTube vid of the filter in action.

 

[fenns7]

here's a link to a vid of the coolant filter in action - 2nd flush with plain water.



https://youtube.com/shorts/vIsouBqWrPI?feature=share

 

[maxbraketorque]

The amount of debris is interesting.

 

[fenns7]

The amount of debris is interesting.

I had also cut open the plastic end tanks of the rad I replaced (just to see how the trans cooler was plumbed) and each contained a surprising amount of black sludge in the bottom. Bear in mind this system had been thoroughly Thermocured and then flushed (x6 times?) prior to fitting that rad back in 2021 so it was surprising to see just how much rubbish is generated over two years within the cooling system on an old engine which had been thoroughly cleaned & flushed - one of the reasons I wanted to try out the Champion coolant filter was to see what moves around.
My guess is that it's an ongoing process - pieces continue to break off from the engine coolant jacket; pieces from the heater core and perhaps some from the rad (but since that was new and predominantly aluminium the amount would be minimal).
The other thing I noticed this time round was the heavy corrossion on the end of the metal tube exiting the water pump to the heater core (which I therefore replaced) small pieces of which would have been carried into the sytem as it corroded further.
I also replaced the original (28 yrs old) thermostat housing as there was evidence this too had started to break down internally and therefore introducing bits of aluminium into the system.


Again, if I can I will add pics of these items so you can see what I found. It'll be interesting to see what the filter picks up over the next few months after fitting a new radiator (better quality than the last cheapo ebay special), new w/pump, new heater return pipe and thermostat housing.

 

[fenns7]

Here's a link to a video of the old rad showing the sludge in the end tanks after just two years - bit of a surprise. This was running nice and cool. No over heating issues.


https://www.youtube.com/shorts/zww6BEH0W1E

 

[fenns7]

.... and here are pics of the corroded pipe from w/pump to heater core and the inside of the thermostat housing where you can see part of the housing has broken away (but it was 28 years old!)

All these rusted pieces had entered the cooling system over the years and had now been caught by the filter:wave1:
*click on the thumbnails and you should be able to enlarge.