Engine takes silicate-free coolant, repair shop has put in 3l of some coolant containing silicates. I have run it for some 300 km in two weeks:

  • first 100 km the way picked it up from the repair shop
  • next 200 km in the process of flushing the system (drain radiator, fill with distilled water, drive, drain radiator...etc)

i have read somewhere that those silicates are fast to bond to metal.

My question - should I do specialized chemical flushing or is it pointless for the time and mileage in question ?


My other question: Do any of the radiator flushing chemicals on the market clean the supposed protective glass surface formed by silicates ?

1 Answer 1


Here is some background:

Silicates are designed to chemically bond with the metal surfaces inside the engine. In this way they block corrosion from occurring on those metal surfaces; they are a class of chemicals called corrosion inhibitors.

Such a coolant also contains chemicals that prevent the silicates from reacting to form silica which settles out of solution as an abrasive dust. Pumping that abrasive around inside your engine will eventually grind away at the water pump impeller and the water pump will fail. This is why you need to replace the coolant at the right interval, or at least to test the coolant with a special paper test strip that changes color if the chemicals that keep the silicates from reacting have been used up.

In your case, there will be very little silicate remaining in your engine after a complete flush, so you do not need to worry about wrecking your water pump with silica.

  • Water pump, other gaskets, I don't know and don't want to find out :-) Do you think some 5% remaining of the old stuff mixed in with new, silicate-free, coolant will be fine for the next 5 years ? There is no easy way of flushing it all out of the block engine for this vehicle.
    – kellogs
    Commented Aug 16, 2023 at 8:39
  • I do not know, sorry. Commented Aug 16, 2023 at 16:55

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