Where to start and what to look for Liquid diagnostics
Sound structure
1 We’re looking for failed seals, not rust. Corrosion like this is a bigger problem than malfunctioning body seals. A solid car is the base we want.
Classic example
2 This is typical of how an aged seal fails, seen on a 1990 Tdi windscreen. The rubber dries out, shrinks or splits, and eventually allows water in.
They all do it
3 Any rubber seal can have the same issue. Note the rubber splitting along the side window. If the drains clog, too, water invariably finds its way inside.
Panels, too
4 Panel joints can also fail, as can corroded rivets. The rear waist seals here are ageing, but may not even be present if a car has been modified.
Hot tip
5 The heater intake has a drain, low down by the heater assembly. If this blocks with crud or leaves, water can be drawn into the heating system.
Flow chart
6 Look at how water flows off the Defender. Large volumes flow over the screen and down the A-pillar. A defective door seal allows great volumes to enter here.
How to do it
7 To check, spray water over the bodywork. Use a wide sprinkle to mimic falling rain, not driving water. Allow time for it to flow over the car.
How not to do it
8 Here’s what we don’t want to do – never aim a forceful jet square on to the joints. This can drive water under pressure past even brand-new seals.
One exception
9 The one place to spray a jet is on the front face of the car, mimicking driving rain. Even then, be sensible. You’re wetting down, not power washing.
Look inside
10 Check around the interior for any evidence of water tracks under windows, or staining on headlining and carpets. Have a good sniff, too. Does it smell damp?
Bulkhead exterior
11 Bulkhead to screen seals can perish, as can the screen bracket gaskets. Vent seals also fail, but many owners simply don’t close them far enough.
Main fail point
12 This joint is the classic water leak. Check the roof to screen seal is present, complete, undamaged, and the door seal isn’t split. Evidence of previous bodges is common.
What was I saying?
13 Pat’s imported South African vehicle has foam seals crudely taped to the door skins, possibly for dust prevention or failing factory seals. This trapped debris won’t help.
Eyes higher
14 Inspect roof joints and headlining. Roof joints can gape, allowing water ingress. If so, they can be sealed, then tapped closed, forcing sealant in.
Splits or tears
15 Check each seal for splits or tears. Common damage occurs to the waistline area, but can appear anywhere. How can a seal work if it doesn’t have a fixed location?
Roofline
16 The sealant in the roof gutters can crack, especially if a roof rack is fitted. The volume of water collected here means the slightest crack draws fluid inside.
Check the joints
17 Underneath the seals, butyl tape should bridge the panel gaps. This can crack, dry out or migrate under pressure. If panels have been apart, it may be missing.
Window pain
18 Side window drains can block and channel seals crack, allowing collected water to enter the cabin. These vertical seals are shot, but the horizontal ones crack, too.
Look inside
19 Check the cabin for evidence such as stains, mould spots or damp carpets. This staining under the window tells us we’ve had a leak for quite a while.
Lift the bonnet
20 Look at the wiring grommets and pedal box gaskets. Splits here can allow water in, not to mention the potential danger of electrical issues if left unchecked.
Bonnet, too
21 Even the bonnet has a seal, on the bulkhead. If missing or damaged, water can stream down the front bulkhead face. Later Defenders also have wing seals.
Look closely
22 Having wet the car, inspect the interior for water trails, then identify the source. This drip is from a vent seal. Be aware, opening doors will allow drops in.
Check small areas
23 Don’t be afraid to re-soak localised areas with an assistant watching. Here, Steve soaks the pedal box area to locate water running off the clutch pedal.
Jackpot
24 Soaking the pedal box showed no water. But wetting the bulkhead vents gave a steady drip onto the pedal again. An assistant is useful, and plenty of light.