Mud in Coolant Overflow Tank

[bordin34]

Is it normal for there to be mud in the coolant overflow tank. Today I removed mine to clean it and there was enough mud caked on the bottom and sides to make a tennis ball sized glob. I assume that it has never been cleaned before. I got out all I could and now the tank is soaking in bleach. The coolant that poured out of it was a greyish nasty green. Also, any recommendations for getting anything the bleach doesn't get out. Right now I am thinking almost straight simple green and letting it soak.

[RD]

its not mud, but rather a rust that has bonded to other materials.  flush your system.  any (decent) local mechanics shop has a machine that will flush and clean your system for a reasonable charge.  well worth it.  i used to flush coolant systems at a shop i worked at.  30 min and its done,... nice and clean.

[hutch]

its not mud, but rather a rust that has bonded to other materials.  flush your system.  any (decent) local mechanics shop has a machine that will flush and clean your system for a reasonable charge.  well worth it.  i used to flush coolant systems at a shop i worked at.  30 min and its done,... nice and clean.

It will do that too if you use a "heavy water" from a well or some souce in your system.  The same thing is in the bottom of most hot water heaters as well.

[bordin34]

Is there an easy way to remove it from the inside of my overflow tank, bleach did nothing except make the plastic whiter, which is what I wanted it to do.

[hutch]

Is there an easy way to remove it from the inside of my overflow tank, bleach did nothing except make the plastic whiter, which is what I wanted it to do.

You could swtich to a stainless steel overflow.  I think this is just going to keep happening but should not be any big deal if you get your system flushed every so often.