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Hello: I need help! My 1984 F-150 is overheating after running about five to ten minutes. The radiator was bad so I replaced that, I also changed the thermostat, new hoses,put a 7lb pressure release radiator cap on and it still overheats. The timing is fine, it will start right up and run good...it still runs good when it overheats, but I know that overheating is not good for my engine...I don't see any leaks anyplace....so I can't figure out what the problem is! The water pump isn't leaking, but I'm wondering could it be the problem? Please help me! Thanks! KB!
P.S. The truck has a 300 straight six engine.
Answer -
If you can do it safely, touch the front of the radiator to see if it is warm top and bottom, side to side. This will tell you if the water is flowing good. Also feel upper and lower radiator hoses, if the top one is cooler than the bottom then something is blocking the flow. My first thought is maybe the water pump impeller is worn away and not pumping.
Are you judging by the gauge, or is it boiling over? Perhaps the gauge or sender is faulty. I am not sure about that 7# cap, sounds kinda light. Most modern engines use one in the 12-16# range. Are you running a coolant mixture or just water? A 50/50 coolant mixture will boil about 247F degrees, as you know water boils at 212F
Thanks for your reply! I have felt the radiator top to bottom and side to side...they remain cool for a while and then they heat up...the bottom hose remains cooler than any other area...while the top hose gets very hot and also swells...I thought that the thermostat might not be working properly,so I removed it and got the same results...initialy I was using antifreeze(one gallon) and toppping it off with water but that got too expensive so I began using water...the overheating occured basically about the same time irregardless to what fluid I was using...the radiator on the top and bottom, side to side eventually got warm and then hot...the bottom radiator hose stayed pretty cool, but the top hose became very hot and it even began to swell, so I thought that the thermostat might not be functioning properly so I removed it and got the same result. As far as the 7lb pressure release cap...I took the old radiator to the shop to have the tanks repaired and the radiator rodded out...the technician repaired the tanks but could not rod the radiator out...he stated that I would need another radiator but in the meantime try a 7lb pressure release cap so I did but to no avail...I got another radiator and still got the same results...either something on the top side is clogged or the water pump isn't working properly...at this point I'm really not sure what to do...this is becoming very expensive and I'm on a limited income...so please help! Thanks! KB!
P.S. I'm not only using the gauges but you can visibly see the steam coming out of the overflow tube on the radiator as well as here the pressure building up!
AnswerI think you better remove the water pump and have a look at the impeller. If the thermostat was sticking, the lower hose would get hot but not the upper. With the water pump being ineffective, the boiling water will rise, but the pump is not drawing it thru the lower hose to circulate it.
A partially clogged radiator could have a similar effect, however you would most likely find cold spots at some places on the radiator.
