Oil in the radiator overflow reservoir

probably either the intake manifold gasket, or a head gasket has failed allowing cylinder compression to escape into the cooling system and boiling the coolant. also look for milky oil(water in the crankcase), or for oil in the coolant system(rainbow sheen on top of coolant in the radiator, or overflow reservoir).

YOU GOT IT. I'm sure the oil pressure went low when the car was on ramps causing a CE light. The louder noise poss wrong belt or exhaust leak!?

When engine completely cools remove coolant from overflow reservoir to the cold mark on the reservoir which is the lowest mark on reservoir. If you continue to loose coolant you may have busted block.

there is a relief valve to dump the oil back into reservoir maybe thats what your hearing ,bad for the system to keep wheels fully locked would check powersteering level

It could be both your thermostat and water pump, it could also be an air lock in your cooling system. One way or another, I think pressure is building up in part of the system because its not circulating properly.

When its cool, take the top off your reservoir, give the bottom hose to your radiator a good few squeezes, see if the water goes down a little, if it does, you moved something on and probably cured it.

If not, run the engine up, to get it warm and bleed off any air in the system. (Assuming there are bleed taps in the system)

If that also does nothing, I reckon its your water pump. And if your changing that, I'd suggest changing the thermostat at the same time.

One thing to check is for coolant getting into the oil, which would indicate head gasket failure. Check oil dipstick and/or underneath of oil cap for a frothy brown/tan look to it. If so, do not drive the car.

Also check coolant reservoir for a leak. Evaporation is suspect, but maybe not to the point you are describing. Check coolant reservoir cap, as well as radiator cap.

yes, not having an overflow reservoir for your radiator will cause you to lose water. As your engine warms up the water expands and creates pressure in the cooling system. When the pressure reaches a certain point(usually about 15 psi.) the radiator releives the pressure by releasing water into the overflow tank. When the engine cools back down the water shrinks pulling water back into the radiator from the overflow. If there is no overflow, the everytime the engine warms up on a drive water will be lost and not recovered on cooldown.

if the radiator cools properly and engine does not overheat, I would probably change the antifreeze solution but not the radiator, does it leak? test its cooling capability by running the engine until the cooling fans operate. changing the fluids is a good idea, also lube driveline and suspension

I also recently bought a 2002. According to the owner's manual the blue light does not indicate a problem unless it stays on after the car warms up. If you have an automatic it will not shift into fourth gear until the coolant warms up at which time the light should go off. Have only had the car for a week and notice the blue light goes off after a mile or two of driving in temperatures in the teens to 30's. I don't know how much outside temp affects it.