Analyzing and Repairing Leaks on RV Windows


What is a leak? - A leak is: water infiltration between the stationary glass and the window frame or water running down the inside of the ventilating pane or when water accumulates in the windowsill, overflows, and runs down the inside wall

The following are not automatically leaks:

  • Water in the windowsill - Ventilating windows will often admit water; this is true when subject to direct high pressure flows. They are designed to manage water that comes in during storm events & normal vehicle washes. They cannot withstand submersion, nor extraordinary flow velocities. All ventilating sliding windows & many awning-type windows are provided with "weep slots". These allow water coming in, whether through bypassing the opening pane, or from condensation, to drain out, rather than be trapped inside the vehicle.
  • Water running down the inside wall - If water appears between the window frame and the clamp ring, there is an installation leak, or the water is coming through the wall. Installation leaks occur when the window flange has not been properly bedded; when the frame bedding has become brittle or has been breached, such as by racking of the unit wall; improper hole cutouts, causing insufficient coverage by the mounting flange; & walls curved, preventing a continuous seal under the flange; water leaking through the wall may originate in several areas, often remote from window. Examples are: improperly sealed clearance lights and seams in sidewall skins.
  • Loose glazing vinyl - in most cases, the glazing vinyl is cosmetic only and does not seal. Look for gaps in the bedding under the glass, if present, they should be lightly caulked, allowed to set up, & the vinyl replaced

What can I do? - Window replacement is not always the best option when leaks appear. Removal and replacement will cause new anesthetic problems, which the vehicle owner may not be satisfied with. Things to check for are:

Is the window properly closed? -- Sliding window latches usually include & interlock so the sliding pane and the mullion fit together tightly. If either is bowed away from the other, the parts may by-pass, precluding a tight seal. Pushing outward when sliding the window closed can check this. If the vent stops earlier than previously, the seal has probably been restored. Often, the bowed part can be gently bent back into the proper position. Torque or awning windows may not seal for a variety of reasons: if the operator knob is stripped or cracked, the panes will not close fully. The vent seals are subject to deterioration over time. Replacing them, if indicated, will improve vent closure-Most vents have an adjustment feature. If the vent has a ""triangular" pivot brackets, be sure that the bottom adjustment hole is used. This will tighten the vent closure.

Can the water evacuate? -- Most sliding windows have sloped sill & weep holes. These holes are baffled or otherwise disguised on the inside to minimize wind noise, often, dirt or debris will accumulate over time, blocking the drain. to fix this condition: from the outside window, unsnap the weep hole cover, keep them for reuse. Use a stiff wire to probe the weep hole & scrape out debris blocking the sill. When you are sure that the area is clear, reinstall weep hole covers.

 Where is the water entering? - A process of elimination is used to isolate the leak.  If the leak persists, the water is entering elsewhere.  If the leak stops, isolate the leak by removing one piece of tape at a time until the leak reappears.  Depending on the leak source, various strategies can be employed, such as caulking, re-bedding, vinyl replacement etc.

Is The Window Installed Correctly? -- Radius windows are usually installed with an inside clamp ring.  This part is screwed together with the window frame, clamping the wall between them.  The clamp rings vary, depending on the wall thickness specified by the manufacturer of the vehicle.  This wall thickness must accommodate the actual wall materials, plus whatever sealant is used under the outside window flange.  If the clamp ring used is too thick, the window will not clamp tightly to the wall.  When this happens, the flange seal can be easily breached and a leak occurs.  If the window flange is not snug to the sealant around the outside, and the clamp ring not snug to the inner wall, you should order a replacement clamp ring.  In general, a clamp ring is better if slightly to thin for the wall, rather than too thick.

Air Leaks and Wind Noise: -- Unless the window also leaks water, wind noise should not be assumed to be a true leak.  Excessive interior noise may be a function of vehicular design.  A contributing factor can be the shape and placement of outside accessories such as mirrors.  Replacement of the window will not affect wind noise when this case applies.