Engine Cooling problem
1993 Honda Del Sol 4 cyl Front Wheel Drive Manual
engine overheats with no visible exterior leaks, there is a lot of white residue around the flange on the exhaust manifold, could the oxygen sensor cause this overheating or is this more serious problem
First thing I would check is to make sure you have enough coolant in the system and that is it PROPERLY BLED! I cannot stress how many times I have seen DIY'ers not properly bleed coolant and have their engine overheat.
Next check is your thermostat. With the car at operating temperature both rad hoses should feel about the same temperature.
Is your cooling fan coming on when its overheating? If not, then something is going on.