Name that sound....
 

when i start my car, or just turn the key on without starting i hear a ticking humming,clicking.. not sure what to call it, coming from under the brake fluid reservoir.
also after the car runs for a few minutes there is a soft rumbling, ticking something noise that you hear inside the car. seems to be coming from about the same area.would this be the same noise? and what in the heck is it.

OK....I'll play......Do you have one of them there new fangled automatic a/c units. Ya know, ya just set it and forget it!!!??? I'm just guessing here but I'll bet my burro it has something to do with the a/c controls. Possibly something to do with whatever it is that controls the flaps which direct the air to the floor/vents/defroster??? So am I warm or cold on this one???

Does a 90 have the self leveling suspension? It could be the compressor.

Ya know, now that I think of it, you might have nailed this one. I had an Olds Tornado that developed leaky bellows(or whatever they were) in the air shocks and the compressor would run most of the time. I just disconnected the connection to the air compressor and replaced the shocks with the "normal" (non-air) units.

Charcoal canister?

When you turn your key
The fuel pump relay clicks and the fuel pump runs untill pressure is up
Self leveling rear shocks will, click their relay and compressor will run untill up to ride height.
If you have anti lock breaks there may be something going on there, I have no experience with this. Do you have antilock breaks ?

sorry i havent been to the site for a while to reply.
i think it may be the solenoid for the canister.... good guess fuddyduddy,

but i do have anti lock brakes and since my brother in law replaced the pads the light comes on and they do not work anymore (i guess you do get what you pay for sometimes :( )

dont know anything about self leveling. im sure i dont have that.

thanks for all your ideas!

do you have the inflator in the trunk? if you do, then you have the rear level ride control.

Are you sure about that??? I think the inflator you're thinking of is a tire inflator. The air compressor for the shocks(if a car has the self-leveling system) is usually located on the left side of the engine compartment.

The trunk inflator uses the compressor under the hood.