Gunk in/on overflow tank cap
 

I'm the owner of a 94 fd, about 70k miles on her, I did a coolant flush about 3-4k miles ago, oil change 2k ago
I was checking fluids today, oil is about 75% on dipstick, coolant about 85%
Strange thing was this sludge I have never noticed on my AST cap and on the inside edge... Picture below
What do you guys think this could be? What should I do/check to try and get this fixed?



Attachment 497359



Attachment 497360



Attachment 497361



Attachment 497362


Thanks for any input guys,

Steven

If you replaced the coolant and did a flush,Maybe you didn't quite get all the crap out of the system.

gross, get that cleaned

did you use a machine to flush it? or poor mans "drain and fill"?

Poor man method lol

I drained both plugs radiator and the one one the block, and flushed both with distilled water till water came out clear...
I might have to re-flush the system and maybe pressure test the system to see what's up..
Any other parts I should look out for to clean when I get around to doing this?