* Failed Trunk Seal/Weatherstripping: This is the most common cause. Over time, the rubber seal around the trunk lid deteriorates, cracks, and loses its ability to prevent water from entering. This is especially true in older cars exposed to the elements.
* Clogged Drain Holes: The trunk often has drain holes (sometimes hidden) to allow water that collects to escape. If these become clogged with debris (leaves, dirt), water will accumulate and find its way into the trunk.
* Damaged Trunk Lid: A dent or rust damage to the trunk lid itself can create openings for water to seep in.
* Rust and Corrosion: A 1990 car is likely to have some rust, especially in areas prone to water accumulation like the trunk. Rust holes can allow water ingress.
* Tail Light Seals: Water can leak in through poorly sealed tail light assemblies. These seals can crack or deteriorate over time.
* Broken or Damaged Trunk Latch Mechanism: Less common, but a compromised latch could allow water entry, particularly if accompanied by a poorly sealing trunk lid.
* Improperly Installed Accessories: Aftermarket accessories like spoilers or anything that interferes with the trunk's seal could cause leaks.
To diagnose the problem, you should:
1. Inspect the trunk seal carefully: Look for cracks, tears, or areas where the seal is pulling away from the body.
2. Check the drain holes: Try to locate and clear any drain holes you can find.
3. Examine the trunk lid and surrounding areas for rust or damage: Look closely for any holes or compromised areas.
4. Inspect the tail light seals: Check for cracks or damage.
5. Test the trunk lid seal: Have someone spray water around the closed trunk lid while you're inside to pinpoint the leak's source.
Addressing the leak will depend on the cause. Replacing weatherstripping is often a relatively straightforward DIY repair. More significant rust or damage may require professional bodywork.
