1998 Cadillac Catera location of MAPmanifold absolute pressure sensor.

SOURCE: coolant leak

You should be able to, so yes. If you have a coolant leak the pressure will build and slowly decrease or it will not get to the correct pressure. Unless the leak is in the radiator cap itself as the pressure tester generally uses a different cap.

SOURCE: I have a 1998 Cadillac Catera and the speedometer

ok your cable for the speedometer,odometer may be broken is the radio stock or aftermarket

SOURCE: have a 2005 cadillac deville, get error code

the mapp & barometric sensors aren't doing the job in performing the correct mixture of hydrocarbons to pass through your exhaust

SOURCE: where are the hoses that run to radiator to

I don't have a diagram, but your problem is the oil cooler underneath the intake on top of the engine. Remove the intake, and the cooler is right there in between the heads. Easy to change once you get the intake off. This is a VERY common problem on Cateras, and the symptom of it is oil in your coolant. I have a 1998 Catera and had the same issue.

SOURCE: I own a 98 cadillac catera and

Like someone said before, I think you have a bad heater valve. If the leak is towards the firwall / back of the engine, then you want to replace the heater valve. Just look behind the planum, at the rear of the engine, you will see a black cylinder with 3 hoses, that's the heater valve. To verify that it is bad, start the car and you will see the coolant oozing out of it. They go bad every so often. They are easily replaced, if you are handy with tools you should have no problems. One suggestion though: In removing the hoses from the bad one, and also replacing them on the new one, your work time will be cut in half if you have a pair of needle nosed pliers with bent nose. You will thank me for this tip :).