mikilu88

I was checking the water and oil on my father 95 4runner (3vze) and i found out that it had some white residue on the radiator cap. My 89 4runner had it on its oil cap and i know that means bad headgasket... (changed it twice). Is there any reason for it to appear on the radiator cap.? Because it hasn't overheated in a while and the radiator isn't that old(no more than 2 years old). And the 95 runner rarely goes offroading... its too heavy and it just loves gasoline.

ovrrdrive

Do you use distilled water in it?

mikilu88

it has antifreeze an regular tap water

Godzilla

Ya, you shouldnt use tap water. Tap water contains impurities and minerals/salts that will build up in your system. This may be your source of the residue.

Matt16

You can use tap water as long as you don't have hard water. One the West Coast, it seems fine.

ovrrdrive

I'd guess the white residue is just minerals and calcium then. If it was in the oil I'd worry more, but deposits like that on the rad cap are probably ok.

I don't suppose you could post a pic of it could you?

thook

How old is the radiator cap? It doesn't sound like it's sealing well.

bcope

yeah usually that is a leaking cap. Not holding its 15psi.
But that means it can be your rubber seal on the cap, the cap spring or the
radiator is corroded/chunky where the cap meets and seal. (Down in the neck)

mt_goat

X2, plus the salts (ions) speed up the electrolysis process, which causes pitting on all the aluminum parts in contact with the coolant. Which BTW can undermine the head gasket surface along with other gasket mating surfaces.

thook

^^^^ Yep....what I was thinking^^^^

mikilu88.....you might do some reading about coolant electrolysis. Bad news, it is.

mikilu88

wow... thanks for the input... i never thought i would be so scientific lol! thanks again.. ill flush that B*&^h and change the cap. Hope that fix it... have no money for the new hg!!!