Water ingress via heater box

[skysurfer]

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.

[Shsun123]

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,

[skysurfer]

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.

[Derek UK]

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.

[Ron Kwas]

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!

[Derek UK]

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

[Natedog]

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.

[Derek UK]

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.

[Ron Kwas]

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

[Derek UK]

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.

[skysurfer]

Many thanks gentlemen for the great diagrams and photos. As natedog lives very nearby, I think I'll go and check out his car whilst the heater is disassembled. It could be a relatively simple fix if the drain plug is blocked or perished, but it might be a good time to check the heater matrix and paint the heater housing at the same. Thanks again.

[Derek UK]

I took some photos and I hope you find them useful. Ron has asked if he can use these on his website https://www.sw-em.com/. Go visit for a lot of useful info, all written in a way most will understand.

[Derek UK]

Heater box 2

[Derek UK]

Heater box 3

[Derek UK]

Heater box 4.
Matrix sponge is shown with measurements. Anyone who is desperate for one can get one from me for £4 posted. Most of that is postage. At this point only ask if you have the need NOW, not for putting on the shelf.

[Derek UK]

Heater box 5
This is the top retainer bolt for the heater box. You have to pop off the intake grill above it to get to the nut. Prise off the grill with a plastic trim tool or a plastic spoon handle with a piece of thin card protecting the paint. This one very scruffy and I will replace it. A cheap and easy source for the conical rubber washers is the floor of any tyre shop. pick up a few of the ends from valves that have been cut off. The one shown is a small bore one, There is also one with a bigger bore Both can come in handy for other jobs.

[Ron Kwas]

Derek;

...in the first pix you posted, the rust stains certainly suggest there was a standing pool in the bottom of the enclosure due to a failure to drain (probably due to biomass blocking the path).

Compliments on the Heater Enclosure restoration and additional pictures...I started putting my notes together, but with that great selection of pix showing details, I'll definitely have to expand my notes, so this will take a bit more time.

Thanks as always for the kind remarks and reference!

Cheers

[skysurfer]

Wow....these are really helpful photos. Better than a Haynes manual in fact. Many thanks to both of you gents for posting them. An enormous help for me and to others thinking of rebuilding their own heater unit.....

[csm22]

Thanks much, Derek -- these photos will be most useful when I knock this off my To-Do list.

Did you use gloss or satin paint? Not sure what's factory spec.

[Derek UK]

I used UK market Simonize Tough Black which is a bit below full gloss. It is somewhat close to Eastwoods Underhood Black. The factory finish is poor with little or no primer. That's why the end up with the typical speckled rust coming through the black. The early grey ones were much better. The whole box was a bought out item by the factory as were the very similar ones supplied to Saab at the time for their 95/96 cars. If you like bling go to gloss. If getting a paint supplier to make up the paint in aerosols you could ask them to use low gloss thinners. That knocks a bit of shine off. Satin black is too close to matt to give a nice finish on this item. You can use what you like on the inside as long as it keeps the rust at bay.

[csm22]

Thanks, Derek... good info to have.

Aside from heat resistance, any particular details to consider in choosing the foam wrap for the heater core? Think the original was varnished cardboard or something similar.

[Ron Kwas]

CSM;

I would use some of the low durometer silicon based foam sheet material common in aerospace...these won't deteriorate like the commercial foams originally used. Derek may have more specific product recommendations.

I have collected several of Derek's excellent pictures in a tech note here: https://www.sw-em.com/Water_on_the_Floor_Notes.htm

Cheers

[Derek UK]

The original that I took to pieces had a foam wrap. Typically with age it was falling to pieces but not to bad as it had been hidden in the dark since new. If you look at the pictures you'll see what I used. I had a roll of what is called foam backed scrim I bought it to replace the foam that goes between the vinyl and hardboard on the doors. Unfortunately it was too thick. My guess was wrong and I never did get round to doing the doors before the car was sold. The new boards I'd made got sold on. The foam I bought was 6mm from here.
https://www.martrim.co.uk/car-trimming-supplies/scrim-foam.php You can see from the pictures how it fits. I have a big roll of it and that is why I offered it for anyone who was doing this job.
You should have no problem finding it in the USA. Scrim foam is what it says. foam with a layer of scrim, a sort of muslin bonded to one side to give it a bit more substance and stop it stretching and tearing.

[Derek UK]

Ron, you might like to mention in your article that a build up of water in the air intake which flows into the heater can be caused by the stubby drain pipe, which is part of the heater box, getting blocked. This outlet has a hose on it which goes down the side of the heater to the side of the coil in the engine compartment. It often goes a bit flat causing a restriction which means it's more prone to blockage. Don't rely on the mesh to keep all of the dirt out of the intake.

[csm22]

Thanks, Ron and Derek... that info should help in narrowing down the search for the right material.


Cheers,

Chris

[Ron Kwas]

Derek;

...right...good idea...I'll have to refamiliarize myself with location and how it ties into the Heater Box...but its a bit too cold at the moment...you don't have any nice pix handy do you...?

Cheers

[Derek UK]

Is the pic on message #24 not enough? It's the only one I had on hand.

[Ron Kwas]

Derek;

That picture certainly shows the drain tube, but is a bit busy...I think I will include third pic of posting 21, which shows tube it connects to in Air Box well...

Cheers

[Ron Kwas]

Derek;

I have rewritten notes to include the two part drainage design, and invite your review...see: https://www.sw-em.com/Water_on_the_Floor_Notes.htm#Reference%20Info

Cheers

[Derek UK]

Condition 2 - The drain hose from the side of the heater Part # 668807 is a black thin walled plastic tube which just pushes on to the pipe coming from the heater. It is a black tube, never clear unless an owner has used a tube like that. Black is original but of course any sort of pipe will work. It can find itself stuck to the pipe but it isn't normally stuck on with a mastic, just an easy snug fit. It is retained by a screwed on clip just below the sloped part of the bulkhead/firewall. If the clamp is a bit flat it can also flatten the tube. This in turn can cause a trap for dirt and debris. (I've found a blockage here but nowhere else.) Except for the tube being potentially stuck to the pipe it is easily removed for checking. It will normally just pull out from behind the clip as all that does is direct the tube downwards. After checking the hose give the short heater box pipe a poke around with a bit of stiff wire to check any blockage there.There is no need to remove the fan motor but you can go in check for leaves if you wish. If doing so it's a good time to drip some thin oil onto the bearing areas and allow it to soak in.

Ron, you can use or abuse any of that text as you wish. Yes the picture is a bit scruffy but it was the only one I had and was for interest only. Maybe someone can supply a pic of their neat and tidy one?

[skysurfer]

Took the air intake grill off and found that debris had been blocking the heater box drain pipe....along with two of the missing metal air intake grill retaining clamps! As Derek says, the hose gets bent and forms a further constriction. Cleared it out and flushed it through which seems to have resolved the immediate leakage problem However, I'm still going to strip down the heater to inspect the matrix, heater drain plug and get it painted. Derek - do you have any of that foam left for wrapping the matrix as I'm sure mine's going to disintegrate.....
Thanks

[Derek UK]

PM me your address.

[skysurfer]

Finally removed the heater box unit and matrix from my Amazon today. The 40 year old matrix is in good condition and just needed a good flushing. The heater box unit is also very sound with no major rust, so will just need wire brushing and a paint. I have bought a set of new foam seals from Brookhouse in addition to new drain hoses. The old foam has been bedded using a type mastic/sealant which has now been stripped back. Could anyone tell me what type or brand of mastic/sealant I should use when reassembling? It needs to be black to match the new paint on the unit. Many thanks.

[Natedog]

I’ve had similar agh with mine. I’m trying to get hold of black silicone but if I can’t get some black around now, I’ve got some clear.

[simon roberts]

Sika EBT....comes in Black....remains flexible.....good stuff

[Derek UK]

Butyl tape makes the job easy and neat. Search the Bay for sizes, both width and thickness. You don't need it very thick and you need double sided sticky.

[skysurfer]

Job now completed. I've fitted a new aftermarket Scandix heater control valve to replace the original and the heater now works a treat. Probably the first time it's been working for many a year and I can now switch the heater off to stop it getting too toasty inside.....

[sleek lemur]

I had water ingress which caused my foot to slip off clutch. Cause was leaking inlet tap, available from Brookhouse.