* Sunroof Drain Clogs: This is a very common culprit. The sunroof has drains that can become clogged with leaves, debris, or even sealant that has broken down. If clogged, water will back up and overflow, often entering the car through the passenger side.
* A/C Condensation: While less likely to be a *major* pool of water, A/C condensation can sometimes drip onto the passenger side floor if the drain is clogged or improperly routed. This is usually more of a dampness than a puddle.
* Leaking Door Seal/Window Seal: Water could be entering through a deteriorated seal around the passenger-side door or window. Check for cracks or gaps in the seals.
* Windshield Seal Leak: Less likely, but a leak in the windshield seal, especially on the passenger side, could allow water to enter.
* Blocked Heater Core Drain: A less common cause, a blocked heater core drain could lead to water accumulation, though it's less likely to be a large puddle on the floor.
* Body Panel Gaps/Rust: Over time, rust or damage to body panels can create gaps allowing water to enter. This is often more noticeable after heavy rain or car washes.
To diagnose the problem:
1. Inspect the sunroof drains: Locate the sunroof drains (usually at the front corners of the sunroof opening) and try to clear any obstructions. You might need a small flexible tool or compressed air.
2. Check the door and window seals: Look for cracks, gaps, or deterioration in the rubber seals around the passenger-side door and windows.
3. Examine the windshield seal: Look for any signs of separation or damage around the windshield.
4. Check for standing water after rain: After it rains, carefully check the car for any signs of water entry points. You might need a flashlight to inspect crevices and seals.
5. Check the A/C drain: This is typically located under the passenger side dash. It’s a small hose or tube. Verify that it is clear.
If you can't identify the source yourself, it's best to take your Lincoln to a mechanic experienced with older vehicles for diagnosis and repair. They'll have the tools and expertise to pinpoint the leak.
