My car began to overheat on the highway.Coolant was leaking from the cap. I let it cool down and checked the coolant and oil. The oil was empty and the fluid was a little low. I filled the oil and drove about 20 miles on the highway at 50 mph to make it home without the car overheating.I took it to the mechanic and they said I had a bad radiator cap and replaced the cap. I took the car on the highway again and about 30 min into the trip it started to run very hot again. I slowed to about 50 mph to keep the temp down but when I got to the toll booth the temp shot up almost into the red zone but as soon as I would move again the temp would lower. Made it home from that trip ok.Took it back to the mechanic and they said they couldnt get the car to run hot. Said I needed a new head gasket and it would be a 1500 dollar repair. Took it to another mechanic for a second opinion they removed the thermostat and replaced with a test thermostat.I ended up taking 2 long highway trips with the car like that and there were no problems with running hot.The temp gauge stayed down in the very low range.The mechanic said I just needed new thermostat so he did a chemical flush and put in a new thermostat. I took the car on a highway trip and it is doing the same thing again. After about 1 hour the car started to run really hot and when I would be at a red light the temp gauge would almost go into the red but as soon as I would move it would go back down to a 1/2 to 3/4 of the way. The car would usually cruise with the temp gauge between the 1/4 to 1/2 mark before all of this(thats what I consider the normal mark for this car) I have owned the car for 5 years and it has 170,000 miles on it.There is no white smoke coming out of the tail pipe to indicate a bad head gasket, alsoSince the last trip to the mechanic it seems that the heat is not connected. When I put the heat on cool to warm air comes out not hot like before.
The part about the oil being “empty” really scares me. How often do you check the oil? How often do you change it? You can have a bad heasd gasket with the gas going into the cooling system, and not into the engine cylinder. That would give you a clean exhaust, but an overheated cooling system.
You likely have a bad head gasket, and it would pay you to get it fixed properly. Since you took some long trips after it was supposedly fixed, have it thoroughly inspected when the head is off. The problem with your A/C and heater may or may not be related, but, again when was the cooling sysytem last flushed and the coolant replaced?
How many miles are on the car now?
the second mechanic installed a hollow body thermostat to see if the problem may be a bad thermostat…the first mechanic had never thought this could be the problem. The car was running below normal temp for a couple of 300-400 mile road trips with the hollow body thermostat so the mechanic put in a new thermostat assuming that was the problem.When I took the car on a long trip again it had the problems again. I check the oil regularly and have it changed usually around 5000-6000 miles. The car has 170,000 miles on it.
One, start to check your oil level once a week. Changing every 5-6thou is good, but you need to top it up more often than that, because your engine is burning some oil. Check it every 500 miles and carry a spare quart in the trunk.
Over heating can also be caused by little bits of crud from the cooling galleries clogging up the radiator, and flushing, or backflushing which is better, will not always clear these. But the possiblity of a bad head gasket is strong here, and it would be a good idea to have a compression check done to see if this is the problem. You do not say you are losing coolant, but the fact that it gets hot when you come to a stop, such as at the toll booth indicates very poor flow of coolant. I suspect clogging of the system, also because of the heater not putting out heat, which can be caused by clogging of the heater core. One other note, if the impeller on the the water pump has come loose, that can cause the flow of coolant to slow way down. Next time it overheats, stop, get out and squeeze the top hose, you should be able to tell if there is coolant in it, and if it is flowing, do this with garden gloves on to protect your hand from the heat.