what will replace R 134 refrigerant
No.
You will have to replace the refrigerant, but not the engine coolant.
When vapor refrigerant is pulled out of a cylinder the vapor is reduced and the liquid boils to replace the vapor that has left the cylinder.
R-134a is the only refrigerant approved by the automotive industry. It requires conversion to be used in an R-12 system.
One refrigerant that is chlorine free is cfc-22. This refrigerant has gained popularity in the past few years in many homes.
The need to take off the refrigerant.
You would have to replace the orifice tube, accumulator or receiver-drier (which one you have depends on what type of AC system you have), as well as remove all of the R12 refrigerant, and you'd have to replace the compressor oil with PAG.
Remove and contain the refrigerant; if you suspect the compressor motor has a burnd-out; treat the refrigerant as contaminated. Disconnect the lines from the compressor, including electrical, replace the filter, and compressor, purge the system, check for leaks, vent the nitrogen, do a pull down below 500 microns, replace refrigerant, and oil. do a run up check pressures, and temp.
Have a CERTIFIED PROFESSIONAL - who will know what they're doing - recover and replace the blended refrigerant. AC system work - whether at the home or on a motor vehicle - is NOT a "do it yourself" task, and it seems now that you have a better understanding of why that is.
Buy a kit at Wal-Mart or auto parts store comes with instructions
you will need a conversion kit to use r-134a refrigerant (i belive) but if it has lost refrigerant suddenbly then it likely sprung a leak somewhere have it tested and the leak repaired before recharging it.