Water ingress via heater box
 

Just had some work done on my Amazon including the removal and reseating of the windscreen with a new rubber and trims using plenty of sealant. Turned the hose on it this morning and no leaks from around the windscreen. Great. However, I did notice a leak from the bottom of the heater box, so it would appear that water is getting in from the air intake vent somewhere. The chrome air intake vent grill is well seated and the securing holes filled. The water must be getting in from a broken seal somewhere, although I will check the water vent pipe first. Pretty sure its not the heater matrix as it only leaks when being hosed down. Think I'm going to have to take the heater box apart to check things out. Is this pretty straightforward? I'm going to fit a new heater control valve at the same time as mine is shot.....
Thanks for any advice.

All the seals are foam on the heater box and can be replaced with ease and are readily available, I have recently removed and renovated mine on a 1969 model , the hardest part of the job removing the washers for the control cables without damaging them , I would recommend if the paint work is tatty or surface rust to blast and re paint while removed and stripped,

Thinking of disassembling the heater to replace the foam seals and inspect the heater matrix. Also to fit a new after market heater control valve and paint the heater casing. Is this fairly straightforward from the engine bay and are there any problems that I'm likely to encounter. Cheers.

There is a small drain tube at the bottom of the box, inside the car. It drains through an adjacent hole in the floor. This is available from Brookhouse. It often gets broken off, so any water in the box then drains into the car. Note, if the tube is original it has a small plastic spreader bung in the grommet part to make a good seal. Make sure you retain this for use with a new tube as it isn't available new as far as I know. I don't even think it's in the parts book. The box can also rot out at the bottom which then leaks so yours might be a victim of that.

Skysurfer;

The Drain Hose (45) which drains rain water getting into fresh-air (cowl) vent into engine compartment, and which would not cause leakage into passenger compartment, is shown here: https://weblisher.textalk.se/gcp/20160201-027/ ...and I do not see the interior drain hose Derek speaks of shown, but I agree, that is likely the source of water in passenger compartment...have a closer look in that area.

Good Hunting!

Page 704 item #45 on that link. Click to go to the end, 800 plus pages and work backwards!

Hi neighbour. I’ve had the same thing on mine buddy. The drain hose was clearly blocked and water had gathered along the seam of the bodywork air scuttle and and the heater box itself and rotted out. I’ve taken all mine apart and are in need of some welding! We’ll go to the yard and take a look at mine if you think it’ll help, it’s still in pieces as I’m having the heater housing cleaned and painted in chi. I’ll be fitting a new heater motor and fan whilst it’s stripped.

One picture shows the drain tube and the other the hole in the tunnel that the tube goes through so it drains outside the car.

Forum;

Derek has once again gone the extra distance with those pix...! They show all one needs to see, and looking carefully at the exploded assembly diagram, one even sees the stub where Hose (45) is to be connected...

Cheers

Edit: Added graphic. See green circle!
https://www.sw-em.com/Heaterbox_Housing_Drain.jpg

I like to save useful pictures and pick them up from all over the net. Some are saved from this forum, and I hope the original posters don't mind me helping others by posting them again. I could say for a first step when looking for info do a search here on the forum but many earlier pictures will have been zapped by Photobucket. Google images always a good bet along with Flickr.
I have a lot more heater box pictures but most of them are less useful as they just show the black painted bits after resto.
A couple of tips. Make sure you rewrap the matrix in sponge, one that won't degrade quickly. The original sponge will be well past it's best. No sponge and a lot of the airflow will go around the sides and that air won't be heated. i.e. the air won't get as hot as it could. Secondly, take care when clamping the two sides together where the heater valve tube passes between them, you don't want to crush the tube or damage it so it leaks. Work out where it is going to fit between the sections and use a small file to make a small notch for it. Obviously best to do this before painting. You can make a larger notch if you wish and put a grommet in or use a small piece of tube (washer pipe is good). A grommet or tube will allow you to push/pull the pipe a little bit after fitting if needed. No notch and the two sections will lock it in place. I'd also advise not to the to take the cranked axles out of the doors when painting as it is a pig to get them clamped back in neatly and aligned correctly.

I'll get a pic up of the matrix with new foam. Also a pic of the drain tube and the plastic spreader.