Take the core out and clean it whole in a heated ultrasonic tank. Release any oil first, then take off the dirt, rust and scale with a chemistry that suits the core's metal. Flush it, rinse it and bring it back to neutral. Then flow or pressure test it against a baseline. Cavitation works wherever the liquid reaches, so it cleans between the fins and inside every tube at once, without bending a fin or scoring a tube.
Is flushing a radiator enough?
A flush through the cooling system moves loose sediment and old coolant. It works only where the flow goes, so dead spots and hard deposits stay.
A fouled core on heavy plant has three deposits, and a flush reaches only part of one:
- Fin-side fouling. Dust, oil mist and debris matted between the fins. A pressure washer cleans the face and bends the fins it reaches. It misses the depth of the core.
- Tube-side oil sludge. Oxidised oil and carbon lining the tubes of an air-to-oil cooler. It insulates the tube, so the cooler stops cooling.
- Waterside scale. Carbonate and silica on the water side of plant and marine coolers.
When the engine still runs hot after a flush, the core has to come out.
The steps
- Identify the metal and the deposit. Read the nameplate or flange stamp. Copper and brass cores need a shorter, tested time in the descale bath. Aluminium cores do not.
- Release the oil. Oil coolers and oil-fouled cores are de-oiled first. An oil film holds the descale stage off the metal, so the chemistry does nothing until it is gone. The weir on the tank skims the released oil off.
- Take off the dirt, rust and scale. Immerse the whole core in CoreKleen HX at 20% v/v with CoreKleen Plus at 1 to 2% v/v, heated to 50 to 60 °C, with the ultrasonics on. A cooler core typically takes 60 to 90 minutes. CoreKleen HX works at pH 6.0 to 6.5 and is safe on aluminium and zinc.
- Flush and neutralise. Flush the core through and bring it back to neutral pH.
- Rinse and dry. Rinse with RO or DI water. CoreKleen HX passivates as it cleans, so it leaves short-term corrosion protection on the metal.
- Test it. Flow or pressure test against the baseline and record it against the core's serial.
Radiator cleaning methods compared
| Method | What it reaches | Watch for |
|---|---|---|
| Coolant flush | Loose sediment, where the flow goes | Bonded scale and fin-side dirt stay |
| Pressure washing | The face of the fins | Bends the fins it reaches; misses the core depth |
| Acid boil-out | Scale inside the tubes | Shortens the core's life |
| Ultrasonic immersion | Fins, tubes and headers together | The core has to come out and fit the tank; the chemistry must suit the metal |
Rodding is not on this list on purpose. It is a shell-and-tube method: you cannot rod a finned radiator core without scoring the tube walls. On exchanger bundles it is a real option, and the radiator and heat exchanger case study covers it there.
Copper and brass cores
Many heavy-plant coolers are copper tube. CoreKleen HX lifts the oxide instead of dissolving the base metal, but it chelates copper and brass on prolonged contact, so on these cores the time in the bath is limited and tested on that core first. Aluminium cores and zinc parts have no such limit.
Seals matter too. Use EPDM or Viton seals in CoreKleen HX. Never put magnesium in CoreKleen HX.
The machines and chemistry that do it
- Large industrial ultrasonic cleaners: tanks sized to the core, for truck and mining radiators.
- EvoSonic floor tanks: heated, with an optional platform lift so a heavy core is lowered, not dropped.
- UltraMax HX: long tanks for exchanger bundles.
- CoreKleen HX: the descale stage above, with SDS and TDS.
Questions we are asked
Is flushing a radiator enough?
A coolant flush moves loose sediment and old coolant. It works only where the flow goes, so scale bonded inside the tubes and dirt packed between the fins stay. When a flush no longer brings the temperature back, the core comes out and is cleaned by immersion.
Can you clean a copper and brass radiator this way?
Yes, with care. CoreKleen HX is safe on aluminium and zinc, but it chelates copper and brass on prolonged contact, so the time in the bath is limited and tested on that core first. The material is checked before any chemistry is chosen.
How long does it take?
A cooler core in CoreKleen HX typically runs 60 to 90 minutes at 50 to 60 °C. An oil-fouled core takes a de-oil stage first, and hard scale takes longer across the stages. A trial on your core sets the figures.
Will ultrasonic cleaning damage the fins?
No. Nothing touches the core in the tank, so the fins are not bent and the tubes are not scored. That is the difference from pressure washing.
How do you know the core is clean?
By a flow or pressure test against a baseline, recorded against the core's serial. Looking at the face of the core does not tell you what is inside the tubes.
Are oil coolers cleaned the same way?
Yes, with one more stage at the start. Heavy oil is released first in a de-oil stage, and then the core goes through the same descale, flush and test as a radiator.
Related: Radiator and heat exchanger case study · Heat exchanger cleaning · Mining equipment cleaning · Marine
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