My 2000 s430 is leaking on the passerage side from under the dash is that my heater core, if so can I replace the heater core myself...

 

leaking what? coolant? water?

your ability to do the heater core yourself is generally dependent on your ability as a mechanic.

 

Before you worry about the heater core (assuming it is water) you should check the drainage hole under the hood on the passenger side right below the wipers. May be clogged. Plenty of talk about that hole being clogged over the past couple of weeks.

 

There has been a lot of threads/posts regarding the well-documented plugged up drain hole in the vent intake. The plastic grill between the hood and the windshield on the passenger side is the intake for the vents and there is a drain in the bottom that is prone to getting plugged up. This generally causes it to overflow when it rains and flood the passenger side of the cabin. I would start there and if you can verify this drains adequately then you may be looking at the heater core.

Keith

 

It's not the heater


There is large plastic waffle grille located at the top of the engine compartment by the wipers



it covers a reservoir and "funnel" hole that gets clogged with debris and water collects, this water can then leak into your passenger compartment and cause thousands in electrical Damage

Either get a very long thin screwdriver or similar object like a chopstick down through the plastic waffle grille , and clear the drain hole at the bottom of the plastic reservoir

All the water should dump out under your car

I simply broke the tabs off the waffle grille and used my finger to clear the drain hole- water was pouring in my passenger footwell causing Damage