Wow, that's crazy looking. Did you paint the light area of the engine? I looks like bear plastic to me.
I doubt the weathering is causing the cracks, it think it's just revealing them.
When I zoom in close it looks like the model iteself has cracked. Look at the rib where the crack crosses, you can see that the rib is offset on either side of the crack. What does it feel like when you run your finger across the crack?