Diagnosing and repairing an automotive water leak can be quick and straightforward or drawn out and complicated; there's no way to tell until you roll up your sleeves and go to work. Here's an example of what's required when it's difficult to identify the source of leak. Finding the pesky water leak in this F150 required removing the seats and stripping the interior all the way down to the floor pan.

Once everything was removed from the truck's interior, we were able to run new diagnostic tests and track down the source of the leak. It turned out to be a pinhole crack in a rear body seam.

A couple of pine needles in your open sunroof may not seem like a big deal, but beware. A stray pine needle here and a twig sliver there — pretty soon you've got a pile of debris wedged inside your drainage conduit. If your drainage conduit is plugged, rainwater backs up into your trunk or passenger compartment.

The same thing applies to convertibles. Check out the pile of debris (above) we found when installing a new convertible top. The drainage lines in this Miata were half-plugged with pine needles. We found the mess just in time. Another few months and the car would have sprung a leak.

Car stereo shops promise flawless installations. But, every once in a while some nitwit screws up an installation by drilling holes in the wrong place. In this case, a misguided installer ran wires through a van's rear access panel causing a water leak. The shop tried to repair the leak with a spot of silicon caulk. It didn't work, so they tried another fix.

Long story short, the second repair attempt caused even more damage: a cracked seal and a broken bracket. By the time the leaking van arrived at Mac's, the owner was fed-up. Fortunately, we were able to permanently fix the leak by "repairing the repairs", then properly sealing the damaged access panel.

After a few days in the garage, the carpet in this leaking Land Rover LR3 appeared bone dry. But, appearances can be deceiving. When we inspected the interior we discovered the padding beneath the carpet was still soaked. And that wasn't the worst of it. We found bundles of wire bobbing in about a quarter inch of water under the floor board.

Repairing a leak is only half the job. Hunting for hidden pools of water and then thoroughly drying the interior is just as important. Trapped water is dangerous. It can do significant damage to a vehicle before it eventually evaporates.

You'd be surprised how often a parking lot fender bender results in a water leak. It doesn't take much force to nudge a door panel out of alignment. At first you might not notice the damage because a cracked seam can snap back after impact. But after a few months of road vibration the crack re-opens. Before you know it, rainwater is dripping down the wrong side of the windshield.

We suspect a minor accident spawned the water leak on the driver's side of this 2006 Eclipse. It's difficult to see, but there's a tiny crack where the "A" pillar is welded to the roof. It also appears that some trim fasteners have snapped off; further evidence of a fender bender.

If a vehicle has been in a traffic accident, large sections of its body may be compromised. Even if a car looks good on the outside, a damaged vehicle may spring water leaks later.

The owners of this 2002 Hyundai Tiburon knew before buying the car that it had been damaged in an accident. It looked fine on the outside, but there were water leaks all over the place.

After running tests, we determined that the passenger side door, a roof seam and the right hand tail light all needed attention. Fortunately, the damaged sections were only slightly out of alignment. The sunroof was in good shape. After drying the interior of the vehicle, we removed the damaged seals and assemblies.

On projects such as this, identifying the source of the leak is usually the tricky part. Fixing the problem is relatively easy; apply a special sealant to the affected areas, then put everything back together. That did the trick.

Repairing a BMW is notoriously expensive. A dealership would've charged the owner of this X3 roughly $2000 to fix the damage caused by an interior water leak.

They charge an arm and a leg because often times this sort of repair requires replacing the entire floor cover. Rather than replace everything, we limit repairs to the damaged section.

This is a great example of how vulnerable modern cars are to water leaks. Electronics, computer components, and speakers are often located right next to conduits – in this case a red cleaning fluid hose (above right). Water from the leaking hose damaged the speaker.

The owner of this vehicle chose not to repair the speaker, so we diagnosed and repaired the leaking hose then sprayed the area with a special anti-fungal solution. After drying the interior, we custom-cut and installed sections of foam to replace the damaged ones, then refitted and attached the carpet. Our repair was effective and much less expensive than a dealer fix.

When is a trunk leak not a trunk leak?

The case of "The Phantom Trunk Leak" illustrates how tough it is to diagnose and fix an automotive water leak. The owner of this Volkswagen Jetta complained of a trunk leak. But, after repairing all the leaks in that section of the car, there was still water in the trunk.

We stripped the interior and spotted the problem; most of the water in the trunk was actually coming from the other end of the car. It turned out the drainage channels for the sunroof were clogged. Debris in those lines caused water to collect in the trunk area. We had to repair a sunroof leak and clear the drainage system. Along with a few other tweaks, that did the trick.

Often times we have to disassemble entire sections of a vehicle to identify the source of a water leak. What this customer thought was a simple trunk leak, turned out to be far more complicated and systemic. A do-it-yourself repair would have been a waste of time and money.