White crusty stuff on coolant tank

[RossTA]

Good afternoon, 

Can anyone tell me what this white stuff is on the top of the coolant tank is please? It isn’t ad blue as my Rav 4 is pre ad blue. It’s the 2WW engine by the way. Do I need to be concerned? 
 

I checked the coolant cap and it seems fine to me. The coolant level was a little lower than normal so I topped up (About 2mm from the Max line)

Many thanks if anyone can help. 
 

Ross. 

 

[TonyHSD]

Hi, 

this is same stuff as inside home kettle, the lime scale ( organic matter) that forms from the hard water evaporation. The same white thing is even present on the cap of a brand new Toyota original pink ready mix container. Most likely in the very hot weather the expansion tank cap or dedicated pressure relief valve has opened and released some hot coolant or coolant vapour that cooled of there and stick to the tank. You can clean with wet towel and monitor if more is forming. If continues then it might be a sign of higher than usual pressure into the cooling system. Until then if anything happens at all there is nothing to worry about it. If the cap looks good too. 
Regards 

[RossTA]

Hi TonyHSD,

Thank you for sharing this. I will clean it up and monitor it and if it goes away then it was a one off. If not I’ll take it into the garage to be sorted. 
 

Cheers.