Microlighters

Did pre-flight, water in radiator was typical antifreeze green and good level.

After landing check water and its Grey and frothy

Drained radiator and put some water in jar, after a few hours a very fine black powder settled about 3mm thick in base of jar.

Fetch magnet and draw sediment up side of jar, ...its magnetic.

I have stripped the water-pump and removed ceramic seal (broke when I removed it ) no sign of any damage anywere.

Was short-block 100 hrs ago, but second hand Solo-wings radiator fitted at some point in history.

General consensus at club, its radiator sludge. Any comments or suggestions are welcome please.

Could also be some sort of "stop leak" additive that was in the rad before. Had this with one of my vehicles.

Make sense. Ta

Arnt rads made of brass, what about the rotary shaft.

Ive checked the seal between Rotary Valve and water pump and it seams fine, meaning, even if there was wear happening on rotary valve, the filings would have no way of getting into the water.

So back to closed system and the only mechanical moving part is the water-pump impeller and shaft, which are fine.

Depending on which type of radiator you have, they can be made off brass or aluminum.

Problem found

I stripped the Thermostat housing, when realising that the thermostat is another item that may give off magnetic filings (not sure how though)

Bobs your auntie, there is the problem.

At the furthest end of the thermostat, i.e. the bit that sticks the deepest into the engine, is a circular plate that seals flow when fully extended. The aluminium seat that it pushes up again and the thermostat are both worn. Whilst the thermostat itself is seated square, the plate on the end sits at an angle and as such causes wear when it supposed to be sealing off.

The thermostat is not nearly as worn as the aluminium seat as it is a much harder substance, and I did confirm that it is magnetic, all be it a type of stainless.

I am pleased to have found the problem, now I need to find a solution.

The picture does not really show the wear very nicely, next time I go to the hanger I will try to remember to take the camera to show the state of the seat.

Oh

Just tested thermostat in hot water and when in the fully extended position, the whole thing extends skew, so the thermostat was the item that has caused the problem.