Coolant Recovery Mud

[911/Q45]

I just cleaned the coolant recovery bottle and it had what appeared to be yellowish mud in it. The cooling system itself has been well maintained and there was no evidence of this in any coolant passages or hoses, all of which were just replaced. This was probably the first time anyone was anal enough in 13 years to clean the recovery bottle. What's the mud?

[Q45tech]

Since the ethylene glycohol is non reactive, it must be the additives and water and the oyxgen in the air plus of course the aluminum alloys and rubber inside the hoses!

Since the compounds dissolve in hot coolant they come out of solution in the cooler bottle where there is no flow.

[PalmerWMD]

Also unless the previous owner used only distilled/deionized water you will see a lot of mineral precipitation.

Many minerals are soluble by themselves, but when they recombine with something else, the resulting product is often insoluble.

Those insolubles will make up the bulk of your "mud" in additon to the things mentioned by Q45tech.

Fred...