Fixing the leaks
Last month we investigated our leaking Defender, pinning the blame on failed seals. This month Alisdair Cusick shows how to make the truck fully watertight
Having pin downed the source of your leaks, here’s how to fully waterproof your truck
WITH nothing more than a hosepipe and some time, last month we were able to exactly pin down the leaks on our sample Defender, editor Patrick’s 1998 110. The source of water ingress was evidenced primarily as failed vent seals, but around the car, Britpart’s Steve Grant also spotted a number of door seals that were either torn, perished, or otherwise defective.
Our test mule, at 22 years old, tells a typical story of aged rubber. Just as you wouldn’t expect two decade old tyres to be any good, so it is with rubber weather seals. Older Nineties and One Tens will likely also see original windscreen and alpine light seals as having perished. Due to the age now of any Defender model and the likelihood of modifications, those passing years may have involved seals of various qualities being used, or indeed all manner of bodges.
Body alignment can also create issues. On the production line, one particular assembly process involved physically pulling the upper door frame if alignment was unsatisfactory. Older cars present even more opportunity for variance, be that from the door simply not being true, off-roading or slam damage, or corrosion. So adjustment of the Defender bodywork itself can be necessary for good weather sealing.
The jobs list on our sample car involved simply swapping the seals for new ones. If you have side window leaks on riveted-in windows, it can be possible to re-seal the edges of those without removing the frames from the car. Beyond that, the cost and hassle of identifying the relevant failed internal seals and removal of the frames on those units has to be weighed against simply replacing them with completely new aftermarket window units.
Alpine light and rear quarter light seals use a compression strip inserted into the seal. The windscreen seal involves feeding string into the seal recess and pulling the string out as you offer the seal to the bodywork, which holds the seal lip over the body. A fiddly job, it isn’t too tricky for the average DIYER but needs patience.
Britpart’s Steve Grant walks us through the job list on Pat’s 110, and offers tips for how to make sure the new seals work as intended.
Off with the old
1 The rear tail door seal simply pulls off the body frame flange. Pull into the middle of the door aperture, not backwards, which can bend the mounting flange.
History revealed
2 Steve holds the butyl tape which bridges body joints on the seal flange, but you may find sealer, too. The orange colour is sand on this ex-south African car.
Eyes down
3 The tail door lower seal is held to the body by a metal strip. Steve removes the screws and seal. Any corroded screws may need drilling out.
Clean back
4 Remove the existing butyl joint tape. Steve uses a scraper to dig into the material without touching the bodywork. Gentle heat may help stubborn bits.
Spit spot
5 The seal lip needs to be as clean as possible as we want the adhesive to stick on the new butyl tape. Steve uses panel wipe on a cloth to chemically clean the lip.
Spotless is best
6 Wipe around the whole lip, cleaning back to a spotless surface. Take care not to damage the factory sealant on the adjacent roof joint.
Top tip
7 Carefully use pliers or grips to align the sealing lips across the body joints. They need to be true for the butyl tape to work effectively.
Vital seals
8 The inexpensive butyl seal tabs come on large sheets. These are for the straight joints, there are a few different shapes for joints that aren’t straight.
Bridge the gap
9 The tabs work by fixing to each side of the body seal lip, effectively bridging the gap between the joint. Each side of the lip needs a seal.
Mind the gap
10 Despite a butyl seal, there may still be a gap in the corner of a joint. Steve injects PU sealant into it. No gaps for water ingress now.
Get it on
11 The new seal is tapped onto the body lip using a mallet. Start at one end, compressing it around the lip. Avoid stretching, which would damage the seal.
Don’t cut it short!
12 If you reach the end and have seal spare, go back and lose some length by compressing it lengthwise around the flange. Never trim it, because seals shrink.
Acceptable cut
13 The only acceptable cut is when trimming around an interior panel, as here. Note, only the mounting ridge is trimmed. The seal profile should remain untouched.
Lower body seal
14 A new plump seal is fitted to the rear edge of the load bay to seal the door bottom, held by a smarter bright stainless steel retainer plate.
Common leak point
15 It’s a similar process for the side door seals; in this case the front passenger door. These have more joints to bridge: the main culprits for water ingress.
Bodge fest
16 Removing the seal reveals this festival of previous bodges. There’s factory sealant, silicone, adhesive and poster putty, doing nothing but making a right old mess.
Check the joints
17 Clean back the edges, as before, with panel wipe. Note this gap: a measured 10 mm between bulkhead and windscreen flanges. No wonder leaks can occur.
Do it right
18 A butyl tab goes on the outside face, and a second on the inside face. A narrow blade can help get the back tape into just the right position.
100 per cent sealed
19 To seal it fully, Steve injects PU sealant in the gap between the tape and the foam windscreen seal. Otherwise, water would still flow behind the door seal.
Fit the seal
20 As before, the door seal is tapped into position. Two upper corners need to be located, and there are body curves to deal with lower down.
Rear doors
21 The rear passenger door seals are fitted similarly. Notice the right angle butyl tape used for the body corners (using two layered straight pieces would permit a leak).
Same drill
22 As before, a butyl patch goes on front and back side of the flanges, with a touch of PU sealant if needed. The door seal’s corner joints are located first.
Proper job
23 The final result shows nice plump seals, compressed by the closed door. Note the door may need a firmer slam to compress the new seals.
Down low
24 Don’t forget the lower door seals, fitted to the door itself. These are riveted on, so are removed by drilling out the rivets. You may be surprised to find corrosion, too.
Riveting
25 The new one is pre-made with holes. Line them up, and rivet the strip on the door. Notice the lip being lower now, which will help keep Pat’s carpet dry.
Spanners out
26 The vents need removing to change their seals. Fxings are removed with two 7 mm spanners. Be aware that they can be corroded in – ours are fine
Vent off
27 An 8 mm bolt then holds the vent to the opening mechanism. Go steady, it can be tricky to access. Not a fixing to round off using brute force.
Seals off
28 The foam seals just pull off the vent. Any glue, sand and accumulated muck left behind needs cleaning off before the new seals can go on.
Is that a shine?
29 Panel wipe removes the old flaky adhesive and tape residue. We also unearth the only bit of gloss paint on Pat’s 110. Patina is the buzzword, isn’t it?
Fit the new
30 The new self-adhesive seal is formed of two sandwiched layers of differing foam densities. Make sure you get it to the outer edges, so it seals when closed.
Tight again
31 Refitted to the car, Steve tries the vent. It should feel tighter and close well. The final notch can take some force to close with new seal fitted.
Fillers
32 With the nozzle cut to a suitable size for your work area, inject sealant around any gapped joints. Be neat, but don’t apply too little sealant.
Clean back
33 Using a small plastic scraper (to avoid scratching paint), scrape excess sealant from around the joint, but also working it into the joint as you go.