my wifes car is a 97 buick lesabre and i keep getting a brown build up around the radiator cap. i have recently replaced the water pump and flushed the whole system with one of those prestone kits. i get it cleaned out and a few weeks later i take off the radiator cap and there is a brown sludge type build up all over it and i can see it down in the radiator. is the cap causing this or is this caused by an old radiator just falling apart and coroding? someone said change the radiator cap but i can't see how just the cap would fix the problem. last time i flushed the system i poured a whole jug of antifreeze in the radiator before i filled it up with water so i don't think it's not because i don't have enough coolant.

 

oil in the coolant. head gasket failure.

 

Does it look like a milkshake or is it just a rusty looking water mix? Your car just might be really nasty inside the cooling jackets in the motor and needs to be really flushed out well again.

 

No milkshake look. It does look like a rust color. And it is not really mixed together. It's like sludgy looking stuff. It's like it doesn't really combine with the water it's just there if that makes any sense.

 

you sure its not oil. have you checked the oil for a milkshake color?

 

Yes there is no water in the oil. If it's possible to get oil in the coolant without the other way around let me know. I will try and get a pic of it tomorrow.