Loud rattle in motor on my 1999 honda four trax

pull serp belt could be waterpump if it goes away look for bad part spin all pulleys by hand to see whats bad if you start it with no belt and it still knocks you killed motor get lookin for new one

Heat shield on manifold, manifold, Exhaust system loose, bad motor mounts.

Are you referring to the blower motor inside the car? If so, they get leaves in them which puts them out of balance and makes them noisy. Just take out the blower, 3 screws, and clean it. That's the cheap answer. It can be a bad blower motor.

sounds like a trip to the dealer, thats what warrantys r 4

Usually it is a loose rusted exhaust heat shield or shields.
Slide under and tap the exhaust system and shields from front (on the engine )to back.......there will be at least one rattle heard.

IT COULD BE A EXHAUST HEAT SHIELD ALOT OF TIMES IF THAT IS WHAT IT IS I JUST REMOVE THEM IT WONT HURT ANYTHING CHECK ON TOP AND BOTTOM OF YOUR CATALYTIC CONVERTER

this is caused by the forward clutch pack in the trans being worn out, if u pull the service pan u will find it full of what looks like mud, in any event u will need to overhaul or install a rebuilt/remanufactured transmission

clucth may be bad on compressor

is your ac compressor located on the left side as well and also try your ac if its not blowing to cold the rattling could be your ac clutch on the compressor if that is you will have to get a new clutch kit from your local auto parts store to fix it

This is telling you a electrical fault in the 4X4 engagement has occurred, most likely the engagement electric motor, pull it out and test the motor.