Mk 2 Leon, How to Seal the Bonnet Strip

[AlexAXP]

Does anyone have the photos from this thread as they are now expired?

 

[L1ON213]

This is a very straight forward procedure and requires no special skills

Tools required :
T-25 Torque bit
Pliers
Scissors / Knife
Cleaning materials

The Bonnet Strip is held in place by torque screws along the back and plastic clips along the front. Once the bonnet insulation is removed, you can see the underside of the clips. Just press the 2 legs together and push it through the hole. The 2 end clips can be awkward as they are behind the hinge plate. I used a pair of decorating scissors (long thin blades) to compress the 2 legs. The clip can easily be turned if it’s not in the right position to compress.

For those who haven’t yet removed the Bonnet Strip, this is a cross section (not to scale) of what it’s like underneath. There is a 13-14mm gap between the Bonnet Strip and the recess in the bonnet. The Bonnet Strip is quite thin and flexible, any sealing strip has to be compressed enough to make a good seal but not ask the Bonnet Strip to apply too much pressure or it will bow in between the clips. This will leave it proud of the bonnet, look bad, but worse still, air could get under it at speed and rip it off.

I did try putting a foam rubber strip as far forward as possible where the gap between the bonnet recess and Bonnet Strip was at its’ narrowest. Unfortunately, this meant putting the seal on the slope where the bonnet recesses. It did seal it but after a few days, it started leaking. When I took it off, the downward pressure from the Bonnet Strip had dislodged the seal. I moved the seal back where it would be on a flat surface so any pressure would be directly downwards and shouldn’t dislodge. This meant sealing a gap of 13-14mm and leaving more area in front of the seal where water could collect.

The seals I chose (both self-adhesive) were a 10mm wide x 5mm thick closed cell foam rubber strip and a 12mm wide x 10mm thick hollow ‘D’ profile ‘bumper’ seal. The bumper seal is very soft, requires very little pressure to compress it and forms a very good waterproof seal. As you can see from the photo, that is 15mm compressed down to 13mm and the seal is more than sufficient to withstand vertical standing water. These materials are readily available on the internet and, depending on the quantity you buy, should cost between £12-15.

Ensure the surfaces are clean and free from any grease. I placed the 5mm seal in the bonnet recess between the fixing holes for the clips and the slope. There is only just enough room for a 10mm wide seal. I placed the bumper seal on the underside of the bonnet strip up against the raised section for the clips. This position should enable the seals to be in the correct position to form a watertight seal. There is also a drain hole in the centre of the bonnet recess just where the 5mm strip is fitted. This should be sealed.

Water can also get in at either corner at the back of the Bonnet Strip. There is a cut out in the lip near the wiper spindle. Water tests on the windscreen showed water does get in here as well.

As you can see, it is a little awkward to fit a seal across the back as the fixings get in the way. The gap is again 13-14mm so the same seal will suffice. I found it easier to fit both seals to the underside of the Bonnet Strip, 5mm seal on the Strip and the bumper seal on the 5mm seal. It needs to be right up against the fixings (as far forward as possible) as the bonnet recess does not go back as far as the Bonnet Strip.

When re-fitting the Bonnet Strip, it is advisable to ensure all the clips are poking through the holes in the bonnet before applying pressure and engaging any of the clips.

To fit the seal as shown requires 2.3 metres of each seal. The eagle eyed members will see that I have a join in my seal. I ordered 2 metres but it came in 2 x 1 metre lengths. The join is only butted together and has not leaked. It has been constantly tested since fitting about 7 weeks ago and no water is leaking under the Bonnet Strip. The bonnet insulation is staying dry and no water runs out of the back and into the engine bay if you open the bonnet after it rains. The only water that comes out is at either end of the Bonnet Strip (the water that collects in front of the seal) but that runs harmlessly into the drain channel. Very little water runs out, less than I expected. That water will get dispersed if the car is used.

As a precaution, you may want to obtain some replacement clips, they can wear if the Bonnet Strip is removed a few times. I only replaced about 3 clips and my Strip has been removed 7 times in total

I am certain there are other methods to successfully seal the Bonnet Strip, I don’t claim this is the only way to do it.

A few key words to search for when looking for these strips are EPDM, D Profile and foam rubber. Google brings up a lot of manufacturers and bulk sales, E-Bay is probably better for smaller quantitie"

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