Is my Taurus engine toast?

Let me guess, you have a 96+ Gen3 Taurus with a 3.0L 2V vulcan engine?

These engines where notorious for built up brown sludge. There is a TSB on that issue.

I would do a compression check to see if all cylinders are close. If not, its probably head gasket time. If so, i would do a chemical flush and reload and see what happens.

Keep in mind if the system has a air leak, it will overflow too. mine had a leak at the heater hose bypass T

You also need to check your plastic degass tank for cracks. that will causes issues also

bob

Yes, this is a 99 3.0 engine. Thanks for the suggestions. A compression test was done with all cylinders l 105 or above. Cylinders 1 and 2 were somewhat lower than 5 and 6. The cooling system was flushed last summer but not since the intake gasket was replaced. The system has been checked for leaks a couple times. I have a new Ford filler cap on the tank. By plastic "degass" tank, do you mean the coolant reservoir? I have put an aftermarket tank in there which seems ok.

I have a '99 Taurus sitting out in the garage right now with a bad head gasket. Can't keep colant in it because the leak over-pressurizes the system and pushes it out of the coolant reservoir. Sometimes on start-up it runs on 5 cylinders until the coolant works it's way out of cyl. #1, and then smooths out. The heater also doesn't work well because the combustion leak puts air (combustion gas) into the cooling system. Any of that sound familiar?

Your description sounds real familiar. I had missing on #1 also and when the plug was removed I could see both oil and coolant on the end. But, if compression is good, there's no grey smoke out the exhaust, manifold vacuum is quite steady, it might just be the intake manifold that leaks. If it's the U engine with iron heads the odds of blowing a head gasket are low. Replacment of the intake manifold gasket appears to have ended coolant loss in my car but the hot engine odor remains. It's possible my wagon will need a top overhaul with rebuilt heads but a car that old is hardly worth the $1600 or so repair bill.