Coolant loss
 

I can only drive my car about 10 minutes before the coolant light comes on, and I can't find any external leaks. Is a cracked water jacket the only real possibility? I'd rather not replace the engine, but this doesn't sound good. I believe the 1990 convert uses the 13b engine, correct? If so, does anybody have a good source for a replacement engine? Thanks!
Jim

if your coolant reservoir is always full, then the radiator cap is unable to sustain the pressure. otherwise, you may have a leak somewhere. i've always work on pre-86 rx and not sure if the coolant level sensor is on top of the radiator or the coolant reservoir.

coolant sensor`
 

The sensor is at the top of the rad