Why does my car overheat at higher speed?

Question

-I have a jeep cherokee 96 classic
-it over heats on hiways if i drive 75mph for about 15 min, its seems ok in the city though

-i changed my second water pump this year
and i got all new hoses, radiator, cap and coolant
-there is no thermostat
-it was fine before, i use to drive over 100mph for hours
-my A/C don't work, but all the fans do
-the water/coolant comes out of the expansion tank when i stop

any posible reason for this? plzz

Answer 1

first of all, there needs to be a thermostat in the system. IF you removed it thinking it would run cooler without it your wrong. There needs to be a restriction in the cooling system to slow the flow of coolant through the radiator. If there is no restriction, ie no thermostat, the coolant is passed through the radiator too fast to transfer any of the heat to the cooling fins. typically, if a vehicle overheats while driving and not at idle it's because the coolant is low. see above. when the engine is at idle the water pump is slowed way down so the coolant has time to transfer the heat off to the cooling fins of the radiator. also there is no load on the engine while idling. If you still believe you need to run your cooling system without a thermostat, then take the old thermostat and cut apart the wax pellet and discard. replace the rest of the thermostat back in the system to provide the necessary flow restriction. You can also use a flat washer that is the same diameter of the thermostat to sit in the housing. the hole in the center of the washer will restrict the coolant flow. this is the first thing I woult tell any customer of mine to do. if there are no leaks, the engine could be consuming the coolant internally. Or, you could have a cracked block or head allowing combustion gases to enter the cooling system and this is what you are seeing from the expansion tank. A good pressure test of the cooling system is in order. You can also purchase what they call a block tester. It uses a test fluid to check for combustion gases in the coolant. This will tell you if you have a cracked block or head, or a bad head gasket. check to make sure your heater core is not plugged also. both hoses should be hot to the touch, one slightly cooler than the other.

Answer 2

The thermostat would be the most likely problem. It should only cost about ten to fifteen dollars for the thermostat and gasket. If not you may have a clog in the radiator. Take the rad cap off and let the car warm up. Check to see that the coolant is flowing good. The last thing to check would be the fan. When it is at normal operating temp rev the engine and see if the fan comes on. If not the check the fuse and fan assembly. Good luck. EDIT: If the thermostat is new and you have good flow through the radiator, then I would go get the combustion gas test done.

Answer 3

Have you ever used any radiator or block sealer? Those can plug up the radiatior

Answer 4

Did you ever have the water system flushed? You may have some clogged and corrosive parts. Does your jeep have a temperature gauge? If it does, what is the temperature displaying in the city driving compared to highway driving? You may also need to use a better coolant or more of it.

Answer 5

Is the air flow to the radiator blocked? Did you have the radiator cleaned and boiled out at a radiator shop? That is about it for the cooling system.

The only other thing could be the timing, causing the engine to get hot, or maybe a restricted exhaust system, or the engine running lean. Good luck

Answer 6

Radiators clog easy.Or head gasket.
Neither one,does the automakers invest in good parts.

Answer 7

ur car sux srry but seriously its prob the radiator

Answer 8

its prob the radiator, you should get a cold air intake plus it will improve preformance