I haven't received message in a bottle on level 31

Since you haven't provided any info on what this is or what is leaking kinda hard to help you.

Sometimes the only fill cap in the system is on the "overflow" bottle. Which is actually called a "Degas" bottle, as long as it has a pressure cap on it. If you are getting a message for "low coolant" on the information display on your dash, and the coolant isn't very low, then you need a new Degas bottle because the coolant lever sensor is stuck down thinking it's low. Sometimes you can tap firmly on the Degas bottle with a mallet, and the sensor will free itself temporarily.

This indicates a low level of coolant in the coolant bottle/resevoir..... this symbol represents the radiator or coolant system liquid level.

Warning comes on to warn of coolant level too low.

When the engine is cold...remove the cap and check level. Add 50/50 antifreeze/water to level indicated on the side of the coolant bottle or tank.

Reservoir Bottles/tanks are usually transparent and you can see the coolant level through the plastic.

When coolant topped off to correct level, lamp will go out automaticly...no need for scanner or shop to turn it off. It will come on as a 'self check' when you turn on the ignition and if level is okay will go out when engine starts.

Brake Pads wear,caliper pistons extend out
further & the fluid follows & level goes down

Been that way for 100 years

So you haven't been checking the level

all right, I reccommend you to clean the throttle body with Carburetor-throttle body cleaner the one in autozone it is really good and not expensive follow instructions on bottle and replace air filter if you haven't good luck!

The light is a message from the computer that maintains one of your monitored systems. You can just go to one of your local auto parts places and they will go out with a scanner and check to see what the message is for you. The computer has detected a problem and while the problem exsist the light will stay on.

If you change the position of the height sensor on the front of rear, the aircompressor should kick on.

I have a 1996 Lincoln Mark VIII that has a fuse in the trunk labeled RSS (beside the on off switch) and if that blows the entire air ride system stops working. But I can't remember whether the self test was gone through or not.

Unfortunately, since the car is not doing a self test when you start the car or getting an error message it sounds more like the computer for your DeVille.

if the freon level is to low or to high the compressor wont work properly your best bet is to put a gage on it and find out how much freon is in the system.

you have a bad head gasket, best cheapest fix, is Blue Devil. its a great sealer and its pretty permanent. I have used this on at least 3 Subarus' and I haven't had any problems again.

Just be sure to follow the instructions to the FULLEST and VERBATIM, how ever you don't need the whole bottle, i usually keep the other half for a year then throw it away, if I dont use it before then, also it is 100% money back guarantee. so no loss there anyway...

remove the sensor in the coolant bottle and shake it a plastic ball inside sticks