Water not staying in Radiator

You blew a head gasket no way a new radiator will fispx this issue !!!!!!!!

You have cooked the engine ,engine of story so now its head off and have it skimmed with a new gasket

Was the oil changed? Has the low pressure been verified with a mechanical test gauge at the oil pressure sending unit pressure port? Do that 1st before assuming the pressure is low.

It could be a blown head gasket. Check for water bubbles on the oil dipstick, and for oil in the radiator. Also, get rid of all that water in the radiator. and replace it with a quality anti- freeze / anti-boil solution. Then have a good tune-up. Check and replace , if needed, the spark plugs. Ensure that the gap is right. Same/same for points. Then check the timing. Those things should get you going again. Please don't forget to rate this answer.

YOU COULD HAVE A DEFECTIVE WATER PUMP OR THERMOSTAT ALSO RADIATOR PRESSURE CAP.MAKE SURE YOUR WATER PUMP IS BEING TURNED BY DRIVE BELT.NOT SLIPPING.MAKE SURE COOLANT SYSTEM HAS BEEN BLED AND YOU HAVE HALF ANTIFREEZE HALF WATER.CHECK YOUR CRANKCASE WHEN CAR COOLS DOWN.IF OIL STILL LOOK LIKE MILK SHAKE.YOUR NEW HEAD GASKETS LEAKING.THE MECHANIC WHO REPLACED HEAD GASKET DIDNT DECK THE HEADS.THEY PROBABLY NEED SHAVED A LITTLE SO HEAD GASKET WILL SEAL.

If you have coolant mixed in you oil you have blown a head gasket at the very least. You will have to pull the heads and replace the gasket.

The rust is probably in the engine. There are many little pockets, water ways, water jackets (around the cylinders), etc, so getting all the rust out without dunking the block and heads in a cleaning tank is about imposible. I would recommend giving it really good flush every 4 to 6 months. I would try flushing the radiator before replacing it because it is probably not rusted, even though it is full of gunk.

Several things can cause this overheating. Have you recently done a:
1. Check Hoses for Leaks
2. Check Radiator for Leaks --- Also, Change Radiator Cap ( can loose pressure there if
cap is bad)
3. Check Water Pump for Leaks. If Water Pump is bad, you will hear a loud noise from it
4 Complete Tune Up? Should be done at least 1x a Yr. Depending on how much you drive the Vehicle. Includes: Plugs, Plug Wires, Gas Filter, Air Breather Filter, PCV Valve, Adjust Timing,
Check Belts -- see if worn
5. Changed your Thermostat & Gasket and have the correct degree Thermostat in the Vehicle?
6.. Had your Radiator Rod and Cleaned out?
7. Temperture Sending Unit (located near Thermostat) could be bad
8. 02-Sensor (Generally located in the Exhaust Manifold - needs a socket with a space in it
to allow the Socket to fit over this top wire of the 0-2 Sensor )
9. Change oil and oil Filter.
10. Change Gas Tank Cap ---

Do all this yearly ( except the Radiator Rod & Clean ( do every 2-3 yrs), and you should not have
any over-heating nor stalling out, etc. and should pass emissions as well.

It could be your head gasket.

the only way for engine oil to get into the cooling system at such a high degree is if you have a cracked block. even a blown head gasket doesn't allow that much oil into the coolant system. if the block was cracked it would be the water jackets around the cylinder walls. even a cracked head would not allow for this to occure. now if you don't have engine oil in the coolant but transmission oil instead via the trans oil cooler this would mean that the radiator has a crack in the tanks along the side where the coils of the oil cooler runs through it,(this only applys to vehicles that have an integral trans oil cooler). another thing that could occure is that the heads are cracked and the coolant is mixing with the oil in the upper oil galleys in the heads and then getting pumped through the intake into the bypass. if this were to occure your vehicle probably would not start at all and even if it did I seriously doubt it would stay running. You stated that you just had the head gasket replaced. well if the heads them selves were warped or the block deck was warped and they were not planed then a new headgasket would not solve the problem to begin with. My suggestion is to take it back to the shop you had do it and have them do it again because i believe someone screwed up because you did not have this problem before so the mechanic did not do something right.