sludge in coolant overflow
 

I just found some oily deposit (sludge) looking stuff in my coolant overflow. Does anybody know what this can point to? Seems like bad water seals in the engine, is this a serious problem or should I just keep my coolant clean and drive till my engine blows? It is a FD is that makes any difference.

I have the same thing! I just got the car, 93' R1, so I don't know if the coolant/radiator has ever been flushed or maintained. I'll be watching this thread.

i got sludge in my overflow for my fc
the system's never been flushed i don't think, cuz i looked and it's like silt flowing inside there
but the sludge is also greasy, so i'm afraid to flush it because it might worsen a possible oil leak

Well, its nice to know that I'm not alone. But is this a major problem, or is it common for rotaries? I also can smell a hint of antifreeze in the exhaust when the engine's cold, so all signs point to worn water seals. I guess I'm gonna flush this weekend and see what my coolant looks like.

The coolant should be changed every two years, and it should be inspected (for color) periodically.. coolant that is cloudy or dark needs to be changed, as it is permitting rust and corrosion to occur.

It's normal to have some "settled" sludge... when changing the coolant, you could run the engine for a few minutes to stir it up so it drains with the coolant.. but if you're flushing the system I guess it's a wash. :)

My coolant gets a greasy sheen as it ages, but it hasn't been a problem so far -- check your coolant and oil levels regularly.. the coolant level should stay the same.. oil consumption should be within specs for your engine.

Lenny, before you do the coolant flush, try draining your overflow tank with a siphon--preferably clear tubing so you don't slurp coolant (blech! happened to me). Run the tube to the bottom of the tank. You can tell when it "bumps" the bottom. This should clear much of the sludge and settlement. If the sludge persists, your seals are definitely on their way to oblivion.

I've heard that it's perfectly normal to see some black sludge in your coolant dipstick (for a FD). I see it from time to time too. I don't think it's anything to worry about. Just flush the coolant every 2 yrs or so and you'll be just fine.