I'd flush the system. It's a cheap easy way to give yourself some peace of mind.

Just keep an eye on your engine dipstick. Leaking head or front cover gasket maybe, or just old rust deposits that got absorbed by a longer trip. If it's crud loosened up that's a good thing. I'd flush the radiator and see if it reoccurs.

Frank/Rebop

Bristol, In ( by Elkhart) 

Its brown crud..... ? Dont think its anything to worry about, sounds like your motor has done a bit of work and moved some muck.. Im sure you've checked the oil and trans oil.. If its only on the cap..pfft dont worry, pretty sure mine has a bit of that..



"Came too close to dying to stop living now!"

This morning, before starting the final leg on a trip to Southern California, when I checked the water, there was a layer of dark brown material on the radiator cap seal. When I got home 180 miles later, the stuff had been deposited again. It hadn't been there before, but I seldom go that many miles between checking fluids. I just reinstalled the engine about a week ago after being out for about three weeks, but didn't do anything to the motor's cooling system while it was out. I'm using the same brand anti-freeze, Prestone, as before. The aluminum radiator has been in for a while. The only thing new to the cooling system is transmission cooling lines to take care of the C 4 in place of the FOM.

Anybody have any thoughts on what these deposits might be? I doubt it's the trans cooler as there would have been water in it when I uncapped it to install cooler lines.

Thanks,
Don