Question:
Thermostat has been changed. We had a coolent leak, but they put a seal on it, and hasn't leaked again since it was fixed, yesterday. The truck is a Ford F-150 1999. 4.6L The very first time this occured, we had to get it towed to Canadian tire, there was coolent all over engine, and flames coming out of tail pipe, and heater turned off. They said it was a head gasket needing done. We got Midas for a second opinion and they said Head gasket was completly fine... still saying this too. The truck usually fixes itself if we catch it on time, like the heater cue. When cold air blows out we know its time so when the temp increases (fast too), we pull over and turn it off. 5 min. later its fine and it usually wont do it again for that day (if not sitting too long) What is wrong? PLEASE help.... is it a head gasket? Anything I can do before taking it back to the mechanic to tell them they still have not fixed my problem? Thanks guys (oh the flames out of the tail pipe only happened once)
Answers:
First remove the radiator cap from the radiator.
Next crank the engine.
If water shoots out of the radiator like a geyser, then you have a blown head gasket, the compression from the piston where the head gasket is leaking will shoot the water out of your radiator like a geyser.
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If the head gasket turns out ok, next check your thermostat. With the radiator cap still off, run the engine. The coolant should be sitting there for a few minutes. Once the thermostat opens, you should see the coolant start to flow. If the engine starts to overheat and you don't see the coolant flow, then the thermostat is not opening up.
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You have to realize that the heater is going to work unless there is no water in the heater core. The only way water would not be in the heater core is if it were blocked or if it wasn't there. Since your heater does work most of the time, the second theory of water not being there part of the time has to be the case. Hence, no water.....then overheating. If it were a thermostat, the hot water would remain in the engine (and latter parts in the circulation process......which includes the heater core......so this can't be the problem). By deductive reasoning, it HAS to be between the thermostat and heater core......circulation problem......yep........believ... it or not, your water pump is bad. It is probably broken in two which would work sometimes when it catches and not when it doesn't. That explains why the heat doesn't work because circulation stops at the waterpump and the heater core water goes back in the radiator. This could cause a bad head gasket though if you don't fix it. BUT, a head gasket in itself would not cause the problem intermittently. A bad head gasket would leak out water into either a piston hole (causing a foul smelling smoke out of the tailpipe and make the truck miss) or into an exhaust valve.....causing only the smoke and bad smell. It would not be intermittent as you would lose water......the truck would never recover until more water was put in.If the heater is blowing cold then it's out of water or low on water. If it's a head gasket then you would water in the oil.
I am having the exact same problem!! I have replaced the theromstat, water pump, hoses and power flushed the cooling system.... It happens everyday after about 5 miles from home. Once the engine is turned off for about 2 or 3 minuets, its fine all day untill it sits long enough to get cold........ I have not been able to figure this out.... I was told by a Ford mechanic/engineer that it has air lock... I flushed out the system at least 5 times and I dont believe there could be any air in the system.. I will post again once I find the problem......Ps.. the engine oil light illuminates when the temp hand moves (instantly to hot)
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