Search for leaks with car wash-like spray

Tag : Garage Door Seals

Q. Over the last two years, my 1998 Pontiac Bonneville hasdeveloped a large and persistent water leak – consistentlyafter heavy rains – that appears mostly on both sides in therear seat area, and to a lesser degree on the left front.I’ve had a competent garage work on it several times.They’ve replaced all four door seals, and have ruled out thefront drains from the sunroof. Drenching the lower portion of the Apillar leads to a small leak at the parking brake, but not enoughto explain it. Any ideas on what to try next? Would I have betterluck at a body shop?
A. You might have better luck at a collision repair shop, but sincewater leaks are notoriously difficult to find, your best luck willbe in finding someone who has prior experience with fixing them inthe Bonneville and its H-Body siblings.
GM bulletin No. 431003 describes how to detect and locate waterleaks from door seals on 1992 to 1994 Pontiacs, BuicksandOldsmobiles. Even though the bulletin doesn’t directly applyto your Bonneville, the principles (and for that matter, the modelplatform) are the same.
The bulletin recommends removing the kickpanels and the rear seat,then soaking the vehicle in a “car wash type of water sprayfor at least eight minutes” while inspecting for leaks with aflashlight.
The solutions offered by the bulletin vary according to where theleak is discovered, but range from applying a bead of butyl rubberaround the door openings to adding “supplemental waterdeflectors” to the insides of the doors themselves.
Postings in the “technicians only” portion of www.iatn.net list a panoply of possible causes for Bonneville water leaks:plugged sunroof drain tubes (front and rear); cracked body panelseams in the wheel wells, firewall or floorpan; leaking seals atthe rear window, trunk or taillights; and water wicking down awiring harness, hood release cable or parking brake cable.
If the leak occurs when the car is parked, suspect plugged sunroofrear drain tubes. If it occurs only during driving, suspect acracked seam or a bad seal. In this case, diagnosis might requiredriving the car with the carpeting and the rear seats completelyremoved for however long it takes to expose the leak. Chip Keen and his wife operate a repair shop on Puget Sound in Washingtonstate. Keen is certified in 18 ASE categories including MasterAuto, Master Truck, Master Machinist and Advance EnginePerformance.