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1985 Coupe DeVille

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Ok so she heated up and I left it cool down and was driving down the highway and it lost acceleration and I felt a pop and it shut off. We put a radiator in cause there was a hole in it. We replaced the thermostat and the upper and lower hoses. Now the overflow tank was filling up the whole way and it was bubbling. We flushed it to try and get the air out of the system and did everything we could think of hoping that's what it was. The light was also coming on and off. Now it's bubbling a little bit and so far the light hasn't popped off. We've done everything we can think of to get air out. I'm thinking maybe it's the head gasket but hoping it's not. If it is it will be too expensive and not worth fixing. The oil looks fine and it starts and runs. It doesn't run the best because it shudders a little bit but it stays running. I have never had this much of an issue with a car. Its got 125,000 miles on it I'm only the third owner and the body and interior is great. I'd love to be able to keep it but I cannot figure out what's wrong. I haven't gotten it to a shop yet afraid of paying more money if I can't keep it. I paid $600 hoping I could fix it up and clean it up and keep it or sell it gettin more money out of it to get something better on gas and cheaper to maintain and fix that will last me. HE

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As you say, head gasket problems are rare in the 4.1/4.5/4.9. If you felt it pop and shut off, it sounds like it threw a belt. The radiator had a hole so there was physical damage under the hood. Check the belt and water pump. Look for things that something in the road could have damaged.

Almost anything that causes overheating will allow steam pockets to form in the head and look like air in the system, fill the overflow tank, etc. Things to do about overheating, in order:

  • Make sure that the radiator is not clogged or blocked by leaves or road debris.
  • Check the coolant level, and make sure it's at least 50% antifreeze but less than 70%.
  • Make sure that the radiator cap is the exactly the right type for your car and is installed properly. Screw types must be screwed all the way down.
  • Make sure that the system isn't leaking. Do a pressure test if you're not sure.
  • Make sure that the water pump is turning (check the belt), and that it is pumping. Water pump impellers have been known to go away.
  • Make sure that the thermostat is exactly the right type and temperature for your engine, and is installed properly (not backwards).
  • Check the coolant for combustion products. There is a nose test that can help in most cases (see below).
  • Make sure that the bypass is working and not clogged.
  • Make sure that the radiator hoses aren't kinked or clogged, and that they don't collapse when the car cools off.
  • Make sure that the heater hoses are OK, not kinked or clogged.

Testing for combustion products requires that the coolant be in the car for about 100 miles of driving. If you have flushed the coolant, it may take as long as a week for a leaking head gasket to show in a coolant test.

If the head gasket is leaking more than a tiny bit, you can smell an exhaust odor in the bubbles in the overflow tank or radiator. Also, you can smell coolant in the exhaust; the coolant smell is strongest if you start it cold in the morning for a few seconds, shut it off, and smell it then.

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Well got her looked at and it's definitely a blown head gasket any idea what I'd be able to sell it for with the blown head gasket. It has a great body everything else works great it just needs a heater core and the power windows fixed. 125,000 miles on it. Decent tires,not inspected and not a spec of rust or wear and tear in interior or exterior. It really is a shame it was a good car. I just gotta get something out of it to save for something else asap.

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