what is the action when a engine cooling fan goes bad
If the cooling fan at the rad never,ever,ever comes on then your car will over heat if the temp gets too high. Mine don't kick on until about 100.
The fan will get noisier over time. There may be an electrical burning smell from the front of the car. Turn on your AC with the engine running and the Hood up and see if the fan is running at all. It's a common failure. The fan will always run with the AC engaged and only come on otherwise when the engine needs it.
If your fan is coming on and making weird noises then you need a new one. If it never comes on (or you never see it come on) then the fan,the power circuit and the switch circuit can all be inexpensively tested right in your driveway.I tried to put this simple testing into words but I think the written explanation is a bit wordy . In other words you either know how to do it yourself or I'd need to stand there and point to stuff for you to unplug and test and plug back in and unplug something else and test and plug back in,etc. Search that youtube thing - somebody probably is showing one on this. Maybe dandyoun will join in with one of his handy web addresses.
Or, one could hook up an advanced scan tool and command the fan on in its different modes and speeds and actually see if it operates properly. Unknown to most amateurs: While only two wires supply power to your fan, the power is conditioned by a fan module. It contains large capacitors and other circuitry to quiet the fan's operation, both audibly and electronically. You can bypass the circuitry and make the fan run - be careful, it is a powerful fan. Bottom line is that it's a High Powered multiple speed fan that is electronically controlled by the PCM. The PCM uses the input of the Cylinder Head Temperature Sensor to determine when to activate the fan. You cannot bypass a switch and make the fan run - there isn't one.
A owner asking about a 1999 probably doesn't own an advanced scan tool! In a 1999 I'd look for the temp switch connected to the thermostat that runs a wire to the fan. Maybe by 1999 that type of set-up was gone but I'd see that when looking.
I thought there would be a video out there - googled:car cooling fan repair and beholdith a picture of a guy who has a tube video of exactly what I said to do, no scans-just d.i.y.. So er_clara -just ignore Tracy and watch the guy on the computer video, it's very simple to do.[ I will;however, agree with Tracy on standard caution about moving parts. But, I'm from an era where the manufacturer didn't have to print a 10 page warning label telling the consumer common sense things like don't use your electric appliance in the bath tub.]
Looking for a Used Grand Marquis in your area?
CarGurus has 1,506 nationwide Grand Marquis listings starting at $999.
Search Mercury Grand Marquis Questions
Mercury Grand Marquis Experts