1999 Chevrolet Silverado water leak

I have a 1999 Chevrolet Silverado extended cab with a 5.3 liter V-8 engine and an automatic transmission. First I would like to say that this has been one of the most trouble free vehicles I have ever owned. I bought it with 77k miles in April 2004, and all I have had to do to it is change the oil, oil filter and air filter.

The problem I am having (a very frustrating problem) is that there is a leak of water into the inside of the vehicle. The water always puddles on the front driver side floor and soaks through the carpet from underneath. There is no other indication that there is a leak. Nothing else gets wet. There is no water on the inside of the windshield or the dash or under the dash or near the pedals or on the side forward of the door under the dash. There is never water on the passenger side floor. I thought it was from the windshield but I was told by a windshield guy that it was not the windshield.

1. At first I thought it was caused by a leak from the windshield wiper washer fluid reservoir or from using the windshield wiper washer. I emptied out the reservoir but the next time it rained the floor was inundated again. Nevertheless I have never refilled the reservoir.

2. Now here is the frustrating part. THE %&#@*!# LEAK DOES NOT HAPPEN EVERY TIME IT RAINS. Sometimes when it rains it leaks and other times it doesn?t.

3. I removed the plastic grill from underneath the windshield wipers and inspected inside. We ran water from a hose inside that area but no leak. Also we could not see anything inside that area under the windshield wipers conducive to a leak into the front cabin floor.

4. Fact which may be relevant: The heater hasn?t worked since I have owned the vehicle. I bought the truck in April when it is dry and warm in south Florida and did not try the heater. I did not discover that the heater did not work until the next December. The hoses going into the core get warm. I have been told that the core needs to be replaced.

I can live without the heater in so. Florida. But because of the frequent heavy rains down here, the leak is more problematic. Any ideas or solutions?

Qustion #1 is - does the water on the floor smell like coolant? If so, then it is likely the heater core or the hose to the heater core leaking. If you don’t need a heater, then just loop the heater hose under the hood to bypass the heater core.

Could it be related to the air conditioner? AC drains often get plugged up. Finding the drain hose under the center of the car and poking a wire up it or sucking on it with a vacuum cleaner often helps clear it.

Does the car have a sunroof? The hose that drains the sunroof can shrink and pull up out of its exit hole, discharging the drainage into a body cavity .

Could the water be coming from the door? Water leaking past the rubber wiper at the base of the window can be more than the little drains at the bottom of the door will tolerate so will overflow out beneath the door inner panel onto the carpet. Try hosing the door for an extended period.

Other leaks can happen at seams in the firewall, or where the wiper motor penetrates the firewall (if the motor is inside the car) or anywhere that a cable penetrates the firewall.

I am having the same problem and starting to tear into the dash. I am curious if you ever found the problem.