Overheating marquis

I have a 1995 mecury marquis that it overheats.iIchanged thermostat, flushed radiator twice. DOES NOT OVERHEAT EVERYTIME when it overheats Iturn heat on high and it will run normal range

any suggestions

fan motor seems to be working fine

Do you notice a drop in coolant level? Is there a milky substance in the oil? Does the cooling fan work at the front of then engine? Are the belts in good condition and tight enough? Is the water pump in good condition? Is there air in the cooling system? Are there any leaks? Is the intake manifold in good condition, without any cracks? What about the manifold gaskets? Is the bottom radiator hose collapsing? Has the engine ever seriously overheated before? Is there the proper amount of oil, and does the oil pump work? Do you see/smell coolant being burned?

As you can see, there are a lot of reasons why the vehicle may overheat. More info, such as what you’re doing when it overheats, what you’ve checked (if anything) and type of driving conditions you’re in would be helpful.
Also, you may want to ask this same question to the people at www.crownvic.net as they may have even more ideas.

1995 marquis overheating in city and highway driving
no coolant leaks. oil is fine belts are fine I can drive 5 TO 50 + miles and not overheat and then car starts overheating fans all seem to be working (turning).also at first car was only overheating when ac was on NOW it overheats with or without ac on . thanks

If the overheating happens slowly, a slow, steady climb upward that is somewhat speed related (the faster you go, the worse it gets) replace the radiator, it’s plugged up or the fins are corroded and loose…

It could also be something as simple as air in cooling system.

Before you spend a lot more money, put on a new radiator cap. You’d be surprised how often this works.

If its air in the cooling system how do you remove it ?thanks

I think a good place to start would be to simply take it somewhere reliable and have the cooling system flushed, and replace the radiator cap at the same time. That could do the trick right there.

Just take off the coolant cap and let the car idle for a few minutes, rev it up a bit, and you’ll be set.
At any rate, it wouldn’t hurt to change the rad and/or overflow reservoir caps either. They’re cheap and might just do the trick.

When the engine overheats, let the engine idle and take the lid off the coolant reservoir. Are there bubbles coming up through the coolant? Bubbles are a sure sign of a leaking head gasket … the most likely cause of engine overheating.

You could inspect the radiator too. If a small percentage of the cross fins are rotted away, the radiator may not be able to cool the engine enough. You have to move the shroud away and check it from the rear usually. If you see a lot of white or green coloring, it’s a hint. Your car is approaching the right age for this to happen. If you get a new radiator, you may soon need a new heater core on a Ford/Mercury.