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MG MGB Technical - Heater/Blower Installation

I am assembeling a 1973 MGB abandoned project. I am ready to install the heater/blower box but find it impossible to insert it into the opening. Any advice out there? Thanks, Tom
Thomas McNamara

I assume you're using the large, rubber heater outlet seal? That thing makes the job almost impossible sometimes. Folks have found a number of fixes for this problem:

- Some have found that lubrication works, like KY Jelly or Astro Glide (both of which are water soluable).

- In one post on another board recently, a guy shaved a bit of the rubber from the seal to make it fit in the opening.

- Others have just given up on the rubber piece and cut a foam-rubber piece to match.

- Brute force.


I'm sure you'll hear others....
Rick Stevens

There are a number of archive discussions on this. One around a couple of years ago canvassed a number of issues.

I know that on my 69 the so-called 'seal' in fact seals nothing at all. It does not seal between the front and rear compartments because any number of air routes exist between those two sections. Take a look through a heater flap, one of those located just above the tunnel and you will see what I mean. I worked this out by observation only after trying N times to fit the heater box with the seal attached without any prospect of success.

Neithet is the thing needed to secure the demister tubes to the heater box - a belief sometimes mentioned. Those tubes are well enough secured by shapings on the circumferences of the tube holes into the heater box. It should be noted however that to achieve the intended security of the tubes at the box face the rubber elbows at the other end need to be secured by locating the metal face plate (that which screws to the bulkhead) into the grooves formed into the elbows at the outer ends . The plate, when secured to the bulkhead, holding the tubes within the defined distance between the box lip and the point at which the elbows limit the insertion at the tubes.

Relying on memory here I think that beast of a thing only came into existance for cars somewhere in the 72-74 era. I once knew and posted the info into one of the earlier threads.

Regards
Roger
Roger T

Thanks guys, it appears that the rubber needs to be compressed but I can't do it. I will try tonight without the sealing rubber to see if the assembly can fit at all. Then I guess foam rubber of some sort. Regards, Tom
Thomas McNamara

Tom

I think the job you are attempting routinly comes up as one of the worst things to replace on an MGB.
Bruce-C

http://www.chicagolandmgclub.com/photos/b_heater/ is the usual reference for this swine of a job.
Paul Hunt 2

Thomas-
It may be that you have one of the poorly-made Malaysian reproduction rubber gaskets that has a too-small opening once it is installed. Where did you get yours? Don't despair, though, as a properly-dimensioned one can be had from MacGregor up in Canada. Click on this: www.macgregorukcarparts.com/
Steve S.

Or you can leave the block rubber gasket out and use the air tubes and 90 degrees bends like the earlier cars had. Makes a bad job much easier and makes the running of the defrost tubes more compact
gerry masterman

When I replaced my leaking heater core last winter I gave up on the rubber piece (more wasted $$$) and ended up using very thick foam rubber, cut to match. I thought then, and still do, that made me a future DPO.

What is that piece supposed to do, other than support the tubing?


Rick Stevens

It is a seal to prevent loss of air flow to the demisters and seems to have been on all years. Although the Parts Catalogue still has the demister vents for 77 on it doesn't seem list anything to connect them to the heater! Before that there were the angled pipes and flexible hoses mentioned (which still used the rubber block). Both eras also have two 'hose, heater' but where that was used I don't know.
Paul Hunt 2

I cut the rubber block as shown.

New uprated heater matrix and new uprated fan ex MGOC work very well.
R W Kerr

The one out of my 67 was thinner than the one I got from Moss. When I tried to cram that one into the GT, it actually started to bend the metal of the heater box.

I had to trim it to get it to fit.
Bruce-C

Last year when I did this, I re-used the original seal because I didn't think it was that critical to have a new one, even though it was developing cracks and showing wear. I still had to apply wheel bearing grease liberally to get it to slide into place. The seal was definitely not going in without grease, but went in really easy with it.

I suppose trimming a new seal somewhat, then greasing it would create a firm seal once it is in place.
Erick Vesterback

Thomas-
Sorry 'bout dat. Click on this: http://www.macgregorukcarparts.com/
Steve S.

Hey Steve and others, Can you advise me on the compressabiliy, ( is that a word)?, of the Macgregor product? Thanks, Tom
Thomas McNamara

I put mine in yesterday, with some help from friends and liquid dish soap. We decided the friction between the firewall and the hard rubber seal was too much to overcome. We could not fit even after shaving about 1/8 inch from the side. After we soaped it up it dropped right in (sort of). Anyway the heater is reinstalled. Check the Chicagoland MG club's site as mentioned above. There is a slot to cut to allow the cable to fit without kinking.

Good luck!

John
John Schroeder

After putting a lot of sweat on it (and some prayer) with no result, I put a coat of grease (Waxoil or something like that). It went right in its place with no efforts.

Good luck
M Gaudreault

Waxoil stinks when it gets hot ...
Paul Hunt 2

The OEM seal on my '71 B/GT was made of foam
rubber (= seat cushion foam) and is forgiving
and flexible and "squashable".

Don't get me wrong. Even with the softer foam,
installing the heater unit is STILL a major ordeal.

When (...and why) did they decide to go with hard,
solid black rubber?

Durability?
Daniel Wong

Probably the after-market took one out of a 30-year-old car, found that rock-hard, so made them that way!
Paul Hunt 2

About 5 years ago I put in the new seal on my 74B. I couldn't get it to go in dry, and I can't remember if I used talcum powder or white appliance grease, but after coating it with lubricant it went right in with no problem. I had a container of talcum powder left over from doing the rear leaf springs and that's what makes me think I used talcum powder. Either way, what you need is a lubricant and it will go right in.
Ken Thompson
1974 mgb roadster
Kenneth Thompson

This thread was discussed between 30/11/2007 and 13/12/2007

MG MGB Technical index

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