Not sure what to do at this point took the van on a drive to Pa last weekend went about 90 miles and the car overheated there was no fluid in the back up or radiator. Filled with fluid after it cooled my husband then changed the thermostat still overheating after high idling for 20 minutes or so. Had a mechanic flush the radiator, clean heating core and apparently it was not running hot anymore my brother in law then went to drive it home for me got about 80 miles overheated again took it to a gas station and they replaced the water pump and apparently the last mechanic did a head gasket pressure test and it was fine. Picked up car today in NJ made it 60 miles before it starting creeping up again made it home and now fluid half gone in radiator but resevoir still full. No visible leaks that we can see also heat works for a few minutes then it does not no water in oil and very little water condesation coming out of tailpipe. Any suggestions one hose is very hot the other is not coming from the radiator are they both suppose to be hot not sure what to do since there are no visible leaks not sure where the fluid is going?

I have a 1996 Jeep Cherokee Sport (62,400 miles) and was told by the mechanic that I needed an oxygen sensor. He said the sensor and labor would be about $200 + $97 for the initial diagnostics. Does this seem like a fair price? Thanks.