405 Heater Box Removal

[peterf]

Hi forum,

I am in the process of removing the heater box from our 405, I would appreciate hearing from anyone that has actually under taken this process on a 405. I am aware of the steps as outlined in the 405 workshop manual and have completed all steps, up to the final instruction which says to “Lift out the heater box”

The last instruction can’t be completed because the two aluminum demister tubes which pass from the heater box through two holes in the bulk head into the cabin will not withdraw far enough to clear the bulk head. I believe this is because of the firewall reinforcement bar which the forward facing surface of the heater box comes into contact with.

If the aluminum tubes were shortened by approx 5mm -or a max 10mm this would allow the heater box to then be removed. So hence my question to any one that has completed the removal of the 405 heater box, is this what needs to be done? Or is there some other demon tweak?

Thanks for any experienced advice.

Cheers

Peter

[Geoff Dowdle]

Peter,
Easy , just scrap the whole car and buy a 400 !!!!!!!!!
Geoff

[peterf]

Thanks Geoff for the suggestion, the thought did cross my mind but what to do with all those bits of unwanted Bristol 405 ???? besides I would still want to hang onto the heater box as a memento!!

However with some persistence the problem is now solved and I have one heater box removed and the heater radiator ready for the tanks to be removed and the entire radiator and tubes cleaned.

For those interested here is how it was done,

Firstly It is important to understand that the demister tubes exit the heater box at a slight upwards angle.
The two holes in the bulk head that the demister tubes pass through are elongated upwards and towards the driver’s side.

The workshop manual says to disconnect the speedo cable, which would suggest that you remove the heater box from that side BUT this could not work because the oil pressure line is immediately in the way as is the auxiliary light socket and the hump for the steering column. No mention of removing the oil line or the light socket in the workshop manual.

Because of the tube angle when I cut the tube end off ( Straight ) with just a metal saw blade I ended up with one side being 3-4 mm and the other side being about 7mm, which as it turned out was pretty close to what I estimated should be removed (5mm -10mm) this amount would still easily allow the rubber elbow to be refitted. It was still a bit tricky to remove the unit via the passenger side where I disconnected the cable to the fuel mixture system and pulled it back through the firewall and partly through the bulk head so as to not impede the heater box movement at all. I had already removed the HMV radio power unit which is located immediately to the left of the heater box but that is a simple procedure. I taped up the edge of the bonnet opening to prevent any scratches and then finally I was in possession of one liberated heater box.

To make it a little easier to refit I will look at trimming the demister tubes a little more and perhaps work out a tube insert mechanism which can be inserted/withdrawn from within the cabin, Not that I think I should ever have to do this again.

The next step is to take the heater radiator to a radiator specialist for a tanks off cleaning and then I need to service the water valve. I hope this info assists someone else in the future.

Cheers all

Peter

[BRIGHAM G]

Thank you Peter,
I am just about to remove the box on my 405 and had no idea it would be difficult. Your postings are going to be a great help to me.
Thank you again,
Best wishes,Gerald.

[Stuart]

Just put mine back in....

There is a story that Bristol made the 405 by first hanging the heater box from the work's ceiling and then building the rest of the car around it.... Anyway...

One hint for removal re-insertion is to force the forward bulkhead forward about 6 - 10mm with a scissor jack, that's what I had to do to get enough clearance, didn't seem to damage the b'head....

I just took the heater assembly to bits, easy, then cleaned out the dead animal life from the air side, removed the radiator and hosed hot water through it with the radiator at various angles to get at all of it... I think there was more dead water life than air...

I didn't need to cut anything from the air vent pipes, however the rest of my car is in bits so it's fairly easy to get at most of it....

My water valve was stuffed so I got a similar one from the local MG spares guy, it's a common BL type... Don't forget the little O ring that seals it all...

I have pics of the heater controls setup and water valve if needed...

Have fun, Stuart

[peterf]

Hi Stuart,

Could you please post the photos you mentioned, I am looking to replace my water valve as well so could you also provide the specific part number and the model of MG car that your valve is from, all information very much appreciated.

Cheers

Peter

[devadmin]

This thread might be useful;

http://www.bristolcars.info/forums/8...ter-valve.html

[Kevin H]

If your heater valve has two control levers it is the same as that used on a Triumph 2000 (1963-69). I just checked in the Triumph workshop manual

[GREG]

Ashley Hinton - Manufacturer of Body Panels, Heaters and Accessories for MG and Austin Healey

This company stock the valve and many other parts for various Bristol's £28 on eBay

[peterf]

Hi and thank you to all those who took an interest in the 405 heater box removal.

Gerald (Brigham G), I think you may also find this useful, once I had the heater box out I decided to remove another 4-5mm off each demister tube so a good 10mm in total, so as to make the replacing of the heater box even a little easier by providing a bit more room for manoeuvring, without ripping or damaging the original felt insulating material that is attached to the bulkhead and firewall.

I then acquired some aluminum tube that would slip inside the existing demister tube, once the heater box was located back into position this length of tube, was, from inside the cabin then passed through the hole in the bulkhead into the demister tube. The rubber elbows were then attached as per normal to the new tube extensions. I am sure someone in another 60 odd years’ time will appreciate the ease at which they can now service the heater unit!!

My heater water valve which only has one arm (standard) was in pretty good shape with minimal corrosion, it was however seized. After separating the housing and then removing the diaphragm and after a week of soaking in CRC/WD40 etc. I then tried to gently heat the specific area behind were the diaphragm is located with some flame, careful not to end up with a blob of die cast aluminum at my feet. In the end the heat source that did the trick was one of those hot air heat guns that are used to plastic weld bumpers on modern cars; the type you can dial in the heat up to 900 degrees.

I sourced a rubber diaphragm from the local MG shop that happened to have a valve in pieces. A reassembly of the valve and attaching to the heater box on the work bench to test the operation and for any leaks before removing the valve and refitting the heater box to the car and then attaching the water valve again.

One point on the water valve removal, you will find that two 3/16 BSF single screw headed bolts are used.
One is located on top and the other below the valve body which is quite difficult to get undone, I replaced them with a normal bolt headed unit and cut two slots in the head (north- south and east west) now I was able to turn the head in quarter turns with a blade screw driver I also modified a spanner to allow it to get some purchase on it as well.

I am sure that you could use one of the later type water valves as described by others who have contributed to this thread but I was keen to see if I could continue with the original unit.
Job done, heater works a treat.

It was Stuart who said "Bristol made the 405 by first hanging the heater box from the work's ceiling" I tend to disagree, I think they liked the idea of starting with a ridiculous 3/16 screw head and seeing what they could add !!

Cheers

Peter

[BRIGHAM G]

Thank you again Peter.
I am making a careful note of all these good points.My car does not seem to have any felt in the heater/tool box area and wonder what type you use.
My immediate concern is to re wire the car completely.I have a wiring diagram but lack a layout for the looms to the tag strips on the right hand side and wonder if you have such a thing or indeed a good clear picture of yours which I could follow.
Best wishes, Gerald.

[peterf]

Hi Gerald,

The felt that lines the heater/tool box area on our 405 is still the original material, it is the same as what is used to line the boot. It is dyed black and quite fibrous, I have included a general photo of it on our 405.

Concerning the placement of the wiring loom, I am including a photo taken of another 405 that underwent an extensive rebuild that shows the loom attached to the frame with the front of the car removed - what a handy way to work on a 405 !! The same person also had easy access to his heater box as the firewall had been removed as part of the restoration of the car. Photo also attached.

If need be I could send you a small sample of the felt should you need it.

Cheers

Pete

[BRIGHAM G]

Dear Peter,
Thank you again for your most helpful reply.They say "a picture is worth a thousand words" which was the case for me. The picture of the wiring looms was spot on,it shows clearly that the fore and aft looms go in first followed by the midships one and lastly the one from inside.The felt should be easy to find now I know what I am looking for.
Best wishes,Gerald.