Water ingress via air intake plenum chamber

[Kevin H]

If you have water coming into the footwells on your V8 Bristol the likely cause is blocked drain holes in the air intake plenum chamber below the windscreen.

There are three drain holes in the plenum chamber, each of about half an inch, so they easily become blocked with debris falling through the grill near the base of the windscreen. The pipes from these drains are marked with red arrows in the attached photos.

The problem is, there a great big hole in the firewall above the heater tray, provided for the fan to draw in fresh air. The bottom of this hole isn't far above the bottom of the plenum chamber (marked by the line of rivets in the firewall), so the plenum is easily innundated with water when it's raining heavily or the car is being washed. The result being water spilling over into the heater tray. On my car there were several small holes in the heater tray through which the water will find it's was into the cabin behind the dash. On car with the original heater box fitted, it will also find it's way under the heater box where there is a large rectangular hole through to the cabin.

My personal view is that this is poorly designed and I believe some other owners have the same opinion. My intention is to partly close off the large hole in the firewall because it is far bigger that is required to pullin fresh air.

Note: The attached photo is of a 411 V8 heater shelf but I suspect is similar to other V8 Bristols. It will look a bit different from normal because heater box and fan which normally occupy this area have been removed to make way for an air conditioner.

[Kevin H]

Just doing some investigation of the plenum chamber beneath the windscreen on my (very dirty) 411 and I was wondering if what I have is original.

The attached photo shows the grill beneath the fins, which have already been removed. Unfortunately on my car the grill sections don't quite meet up, which allows slightly larger debris to get down into the plenum below.

The grill sections are fixed at the front (screws A & B - there are more across the width of the car), but at the back they are 'fixed' by some sort of black putty (for want of a better term), marked "C" on the photo.

I have now removed some grill sections and some of this black putty, which took the paint with it, revealing pink primer, which I presume is original.

Is the "putty" original? For that matter, is the grill original?

[408VIKING]

I have the same grill mech on my 408. Has to be the original.

Most damage (rust) on my car is on LHS of firewall. See pictures.

The sealant was in good shape (soft) and the where no signs of leakage between plenum chamber and fire wall. The only possibility I can see on my car is at the top left corner, where it´s attached with sealant only.

Per

[Kevin H]

Thanks for the photos Per. I suspect very few people have seen a 408 looking like that. It's interesting to see how it differs from the 411.

Any chance you could post a couple of photos from further back ? (not so close-up, so that those of us who are not familiar with a bare 408 chassis can get a better understanding of what we are looking at).

Regards,
Kevin