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Windscreen Leaks

Leaking windscreens are a fairly common cause of leaks in cars, which can be fixed by refitting. While that sounds straightforward, there are a number of issues which deserve further explanation.

James shows us a windscreen removed from a Land Rover, in which it can be shown that the adhesive sealant was not bonded to the top of the screen. Videos like this can be used as evidence that a replacement windscreen company is responsible for the fault, although in this specific case, it is a known factory-fault.

On modern cars, windscreens are not fitted into a frame, they are effectively glued to the outside of the car. A generous bead of sealant is applied to the outside of the frame and the windscreen is pressed against it.

There are four main reasons this fails:

  1. When the windscreen was fitted, not enough primer and adhesive was applied, or the windscreen wasn't sufficiently pressed down into the adhesive. This problem is most common on replacement windscreens and may be caused by misalignment.
  2. The adhesive failed to adhere to one of the surfaces due to improperly prepared surfaces. This is mostly likely to be on the glass, which has a matt black finish on the back, which serves both to hide the fittings and form a surface for the adhesive to key to. If this surface is contaminated with oils or grease, or there is a manufacturing defect in the coating, it is possible it won't properly bond.
  3. Corrosion of the bodywork can occur under the windscreen. This will happen with age, but it can happen if there has been a replacement windscreen and the frame was damaged while cutting the adhesive from the old screen with a metal 'cheese wire'.  (How windscreens are removed).
  4. The adhesive fails with age. Cars can get very hot in the sun and this will cook the adhesive over time, heat and cold also cause the car to expand and contract. Car bodies will also flex and twist as they go around corners. With the adhesive suffering from the climate and the movement in the frame, it is possible for the seal to leak in older cars.

If the leak is due to an incorrectly fitted windscreen, then you may well have recourse with the company who fitted the screen, especially if it was done through an insurance company. In our experience, they will usually pay for the refitting of the screen and additionally repair of water damage and drying. If the carpets are wet on the surface, then they will be wet underneath and so proper decontamination and drying could be required to rectify the problem properly -- a valet and shampoo will not be sufficient.

Therefore, we advise going to an independent company to assess the problem and cost of clean up.

Written by . Last updated 26/10/2023 16:07