i recently removed my coolant overflow tank to put in a new one. when i removed it there was, what looked to be, mud and dirt. it wasnt really black though, as i comonly hear from the exhaust gases leaking in to the the coolant system. what does this mean? thanks a million

 

exhaust in the coolant system means your coolant seals are going bad, which means rebuild.

Everything I've seen, "mud" looking substance is usually oil mixing with the coolant. That kind of looks like a chocolate milkshake.

 

yeah its a brown muddy substance caked on the bottom and a little bit on the sides of the overflow tank, does this mean rebuild????

 

I've had gunk in my overflow tank for about a year now. There are no other symptoms of coolant seal failure since I've found out about it, so to my knowledge, as long as you aren't seeing excessive white smoke out the exhaust or low coolant levels, you should be okay.

randy

 

it also might have been from the previous rebuild. i just thought of that.

 

It's fairly common. Theory which has been thrown around is that dirt and grim from the road makes it way into the tank through the vent hole.

 

Over the years, some sediment will eventually work its way into the cooling system. The overflow tank provides a place for it to settle. Once it settles there, it can't really go anywhere. When the cooling system gets flushed, the overflow tank rarely gets cleaned out. It's normal to find some sludge in there..

 

It is not dirt! It is caused mainly by using tap water (contains many mineral contaminants) along with the mixture being old and thus worn out.

You will never see it when using distilled water and changing the fluid as leaste every 3 years. I have never had it in any cars that I have owned since 1966.