My 1999 TJ keeps overheating. I do not have any leaks in the radiator, and I have already replaced the thermostat. Does anybody know what I should do or look for to find what the problem is? Thanks in advance.
Check the coolant level in the radiator. Are both radiator hoses hot? Putting the heater on make any difference? Bottom radiator hose in good shape?
- dirty radiator maybe
- worn out water pump/impeller maybe.
2003 Jeep TJ Sport - 4.0L - 251,430 kms
2002 and 2007 Grand Caravans - Sport & SXT
Is it building pressure? After a drive squeeze the upper radiator hose to feel if the system has pressure in it. If there is no pressure in the system you have a leak, also if there is no pressure this means that the boiling point of the coolant is much lower than if the system was at the normal 18psi. Low pressure and boiling commonly leads to overheating.
A radiator cap can leak and you will never see a drip on the ground they just leak air pressure and a small about of coolant witch will end up in the overflow bottle.
If its building pressure I would then vote clogged radiator or bad fan clutch.
while i am idling, it stays around 210 like normal, but when i am on the highway, it starts rising and after a while of running it at about 55-65 mph it goes into the red and the check gauges light comes on.
Drop the coolant level down enough via the drain valve on the bottom of the radiator so you can see the top of the radiator core underneath the radiator cap. With a flashlight, look for telltale calcium deposits around the cooling channel openings indicating the radiator is becoming clogged with hard water deposits.
If you see mineral buildup inside, such deposits are caused by using tap water in the radiator instead of the required distilled water which is mineral free. At this point, I would suspect the radiator is getting clogged with those hardwater deposits. And while most radiators can be "rodded out" to get rid of such deposits, the TJ's radiator cannot be. Once it gets to that point, it can only be replaced because once it is taken apart to rod it out, it cannot be effectively resealed again since it is crimped together, not soldered.
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