Thread: Discovery 2 'plenum cover' (lower windscreen trim).

Originally Posted by Forged

Can i just ask, what is under this 'scuttle panel'? As the one on the Disco i just purchased has a crack straight down the middle and its been ****ing down with rain the last few days. Should i be concerned with how much water has entered into this space?

I'm just going to use black silicon to seal it up i think.

Hi Forged,
If you have not been getting water coming in on the floor in the front passenger-side footwell, then I don't think it matters how much water gets under the scuttle panel.
Under that panel are drains that lead to just in front of the front doors, one on each side.
Under the LHS (that is, the passenger side) of the scuttle panel, located above and behind the drain channel, is a raised air intake for the cabin ventilation. On mine, that intake was an open rectangular hole facing UP!
Water was getting into it and appearing on the front-passenger floor.
I fixed that by making a hood for the air intake out of heavy aluminium foil that I shaped by hand and glued over the air intake hole with silicone. Air can still enter under the hood, it just "roofs over" the intake hole.
Cheers, Andrew

Like a lot of D2 owners, my plenum cover is cracked right across the middle. See Pic 1.

As I am having my windscreen replaced, I decided to take the plenum cover out prior to that job and see if I could repair it before re-fitting.

The plenum cover doesn't bear any weight (doesn’t support anything else) and is only held in place by one scrivet near each end and a bolt through the centre of a plastic flange along the bottom edge.
I think it likely that over-tightening of this centre bolt down onto the plastic flange is what initiates the cracking.
In my case, part of the plastic flange adjacent to the bolt head had cracked and broken off.
The crack terminates (or begins) right at the bolt-hole there. Pic 2 shows this.

I decided to brace the plastic flange along the bottom edge of the plenum cover with a narrow sheet-metal strip to bridge the crack and hold the opposite sides of it together.
I cut this strip from a scrap of Colorbond fence sheeting.
The outer side of the plastic flange has a trapezoidal recess where the bolt-hole is, so I also cut a shape to fit in this recess as a sort of shim to level the surface up (Pic 3).

Pic 4 shows the shim and longer metal strip in position before fastening, and Pic 5 shows them (mocked up) prior to setting rivets to secure them.

Pic 6 shows the assembly after setting the rivets, with detail shown in Pic 7 (which also has the centre plenum bolt in place).
Pic 8 shows the setup from the exterior aspect.

I then spread Plasti-Bond over the crack on the underside of the plenum cover, and used "T-Rex" waterproof tape (courtesy of onebob) to cover the crack on the upper (visible) surface.
Also painted the visible part of the metal strip black, so it doesn’t draw attention to itself.

When the windscreen replacement has been done tomorrow, I'll (gently) re-install the plenum cover.
I notice that the scrivet holes at each end of the plenum cover are elongated rather than being circular.
This may be to accommodate lengthwise thermal expansion of the cover, in which case it is best not to overtighten the scrivets when installing them.
I think I'll even lightly grease the holes.

The wire strand that runs along the foam filter strip in some of my pictures is there to prevent air flowing through the filter foam from pushing it forwards into the plenum cavity, which I found was happening despite the retaining clips for the foam strip being in place.

I can add a couple of cautionary points for anyone intending to remove their plenum cover:

1) The plenum cover cops a lot of sunlight and heat, and at 15 years or of age more the plastic is very brittle. Handle gently!

2) The upper edge of the cover (which overlaps the bottom of the windscreen) is held in place by 4 hook-shaped plastic lugs, one of which is shown in Pic 9. These lugs tuck under the bottom edge of the windscreen glass. To release the 4 lugs, it is necessary (after removing the scrivet at each end of the cover and the bolt in the bottom centre) to tilt the lower edge of the cover (beneath the foam filter strip) upwards and gently pull back.

It is very difficult to do this without damage unless you unbolt the bonnet hinges and slide the bonnet forward FIRST.
There is an Atlantic British video which shows how to do this job.
You can find it in the sticky entitled "British Atlantic's DIY YouTube how to guides".
The specific video title is: "Atlantic British Presents: Installing Centre Air Intake Moulding – Discovery Series II".