Coolant Flush

[Eggman]

A few weeks ago I picked up forum member pawpaw's original heater core. Today I ran an experiment to see what might clean it out. Have a look:

It's an old bottle I had sitting around waiting to be used:


Notice the warning about aluminum:


First flush on the right, half Parsons' Sudsy Ammonia (wish it wasn't sudsy...) and half water on the left. The right hand jar was dumped after two hours of soaking in the half & half solution:


Left bottle is the second flush:


First flush sediment:


Second flush sediment:


Third bottle of clean solution prepared for another soak & flush:




Third flush using a bottle brush to remove more contamination (disregard the blue material found in the brush bristles):


Third flush sediment:


I'm currently soaking a fourth batch of half sudsy ammonia and water. Thanks foama for the suggestion.

[foama]

Question: About at what temperature was the solution?

That product is actually an alkaline-based chelating cleaner, so is Cummins/Fleetguard Restore. Chelating cleaner because it is sudsy, alkaline because ammonia gas dissolved in water ("ammonia solution") is a strong alkali.
NB: Heating ammonia-water is not a good idea, because ammonia gas becomes released with increasing temperature.


It is remarkable how much blue was flushed out! Blue is the colour of the OEM coolant, and that much blue tells me the OEM coolant must have been unsuitable for the car.

I flushed mine thoroughly and replaced it with Glysatin (BASF) coolant G30 after contacting the manufacturer for advice. They also sell their stuff to the states, then it gets confectioned and sold as some Zerex/Valvoline product. Wonder if anybody has asked Zerex what product better suits the Mirage than the unsuitable OEM brew?

[Eggman]

Question: About at what temperature was the solution?

It’s about 66℉.

It is remarkable how much blue was flushed out! Blue is the colour of the OEM coolant, and that much blue tells me the OEM coolant must have been unsuitable for the car.

Yeah I’m surprised at that too. More blue color and some sediment at first with less color and more sediment showing with subsequent soaks, especially after using that bottle brush. The fourth soak will be sitting for about 24 hours.

---

I chose against cutting it open in order to find a way to flush out the goo without dismantling an interior. So far this looks promising.

I can imagine using a vibratory pump to circulate a solvent through the heater core (unless a full system flush is the goal.) A centrifugal-type pump would circulate a solution okay but the pulsing ought to help loosen up goo. Use it with flexible tubing to direct the solvent at different parts of the core. Something flexible enough to snake through the inlet and outlet tubes all the way down to where the goo accumulates at the far end of the core.

Also my borescope camera is just a hair too big to fit in either tube fitting. Sure would be nice to get a close-up view of the goo before and after cleaning.

[Top_Fuel]

The blue color might be coming from the ammonia interacting with the aluminum...

[pawpaw]

For what it is worth the coolant used in my Mirage after attempts at flushing and cleaning the heater core was some mix of the below. I think both of these are silicate free formulations.

[7milesout]

What about thermocure? I don't think this has been mentioned in this thread. I used in my 1972 Plymouth Scamp. Worked good, maybe too good. Had a couple small leaks afterward where the sediment had blocked up tiny holes. This stuff cleaned that out. Had to pull the radiator and had it fixed after that. Not expensive to have those holes fixed, and the radiator is in good efficient shape now.

[Eggman]

What about thermocure? I don't think this has been mentioned in this thread. I used in my 1972 Plymouth Scamp. Worked good, maybe too good. Had a couple small leaks afterward where the sediment had blocked up tiny holes. This stuff cleaned that out. Had to pull the radiator and had it fixed after that. Not expensive to have those holes fixed, and the radiator is in good efficient shape now.

What exactly was it that was flushed from your Scamp? The goo found in the Mirage heater cores is presumed to be some type of silicate gel, which would explain why an alkaline substance such as ammonia would dissolve it. It seems not many coolant flush products out there are effective against silicates.

[7milesout]

I think what flushed out was everything but coolant. Mostly it looked like calcium buildup (just guessing). That stuff smells like rotten fish when its working.

[foama]

The blue color might be coming from the ammonia interacting with the aluminum...

I wanted to check and did this simple experiment:

I took an old aluminium cooking pot and poured the strongest ammonia solution available (25% ammonia!) into it, about 1/2cm (1/4inch) high. It was left in the garage at 5°C ambient temperature for the rest of the day and overnight, 20 hours in total.

The results:
After all that soaking, the aluminium was barely tarnished, practically no harm done at all. The 25% ammonia solution had become cloudy, just an ever so faint hint of blueish colour. The solution was completely ammonia-depleted, that is it did not even smell like ammonia any more. The leftover stuff looks like the jar "second flush" in Eggman's post #51

Just for comparison, household ammonia cleaners have between 1 to 2% ammonia, this stuff was 25%.

Conclusion:
Putting 25% ammonia (extreme strength) into an aluminium container and waiting until the ammonia has fully reacted will not harm the heater core.





Edit: FYI, the active ingredient in Thermocure is Diammonium Phosphate.

[Eggman]

What about thermocure?

Updated the chart in post #2: Included Thermocure and updated other entries.