Identifying water leaks

Utility Land Rovers are well known for letting in water, but they can be made totally watertight. The rst job is to accurately identify the leak paths, as Alisdair Cusick explains

How to find leak paths

WE all know the symptoms: opening the door, the car smells a little musty. After a few minutes driving the windows start to mist up, only it isn’t raining. After a sudden downpour when the truck is parked, we notice the windows are suddenly misty. All of these subtle pointers evidence the fact there’s water inside our Land Rover. The problem isn’t specific to the Defender and pre-defender Ninety and One Ten models; Series Land Rovers have similar issues and much of this feature is relevant to them, too.

It is an old joke, and an ever-present issue throughout Defender and earlier production, that water will find its way inside the cabin. Principally, this is down to the design based on many separate body panels requiring joints that have to be correctly sealed to be watertight. When you realise that body joints can be up to 10 mm apart, it’s obvious there’s ample potential for water to enter the interior.

Sealing methods

Typically, joints are sealed by rubber strips, either fixed in position where panels fit together, such as bulkhead to screen seals, or door seals which fit to one side of an opening and work by creating a pad for another panel to push against. Some joints additionally use sealant to keep moisture out, like windows and roof joints. Sealant needs to be gap-free to be water tight. Equally, for a seal to work, the rubber needs to be plump and under pressure. Aged rubber can dry out, crack and shrink or compress from memory, allowing water to ingress. So the weather seals have a relatively finite lifespan. The factory also used Dum Dum putty, and butyl patches. These age too, and can be missing if panels have been separated in the past.

The fixes

Locating, curing and preventing further leaks in your Defender needs no more than a weekend. Many seals identified as having failed can simply be removed and replaced. Larger panel joints will entail more committed approaches. A roof, windscreen or hardtop may need to be separated or even removed if it’s necessary to replace a seal between panels. If the majority of a seal is in good condition it may be possible to effect a repair using a suitable sealer. We’ll come on to this in the second part of the feature, but this month we’re going to look at how to locate the sources of the leaks.

There’s a caveat before we start, in that we’re dealing with rubber seals allowing water ingress. We assume the bodywork of the vehicle to be in good, solid order. There’s no point investigating leaks if there is corrosion in panels, poorly-executed repairs or misaligned bodywork. If you have any of those, congratulations – you’ve probably found your leak source!

Rain, condensation or coolant?

Water in the vehicle comes from three sources. We know about rain, but any bare metal surface, such as a roof, allows condensation to form. If left in suitable conditions, and for long enough, large volumes of water can accumulate, eventually running down roof pillars and silently soaking into carpets. You can identify this as a source by removing an interior light to get a finger behind, feeling for a sweaty metal roof interior. Coolant can leak from a failed heater matrix, but coolant feels sticky, is coloured, and typically has a sweet odour. In this two part feature, Britpart’s Steve Grant show us how to identify failed seals, then how to deal with issues found.