MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG TD TF 1500 - Arnolt Heater Installation Sequence

I've done, at least, three Arnolt Heater installations, but I'm stuck. They were all in the previous century. I've decided to re-install my heater in Lazarus. I took it out seven years ago when we moved from Massachusetts to Georgia. I've now decided that I want/need to re-install it for the sake of cooling in parades. It's not a problem when the cars are moving along. It's when there is a tendency for paraders to stop and go when the temperature gauge is approaching the oil pressure reading.
Other than the screw that attaches it to the underside of the battery shelf, there are three major components in the Arnolt Heater, the casing containing the working parts, the mount, and the plumbing. The Arnolt is designed so that the casing fits neatly into the mount which fits neatly into the space under the battery (with just one screw) and the plumbing goes onto the back of the casing.

I have forgotten the sequence for assembling the components. Can one attach the plumbing onto the back of the casing with the casing attached to the mount and slide the whole thing into the tub with the plumbing protruding through the firewall?

Or, should one install the mount in place and then install the casing and plumbing?

How about connecting the casing and mount and attach the assembly to the firewall and then connect up the plumbing?

Granted, having just passed birthday #88 I'm no longer as flexible as I was back in the 20th century, but I should be able the get it in there.
Anybody remember how it was done? TIA Bud
Bud Krueger

I have no first hand information. Many others here can give you tips I am sure.

Here is all the instruction manuals I have for it.

https://www.mg-cars.org.uk/mgtd/mgtd_radiomobile_manuals.htm
Christopher Couper

Thanks for the info, Chris, but it doesn't sem to do much for installing a a heater. The best info that I have is http://www.ttalk.info/Tech/Arnolt.htm. And, it doesn't handle the installation part. Bud
Bud Krueger

Hah. What a screw up. Not sure where my mind was. :-)
Christopher Couper

I put mine in with the bracket, then the heater, then the hoses, but I can't say that is the easiest way.

I can't see why the heater could not be put onto the bracket and all that put in . The bracket just hooks on the edge of the tool box and then the bolt goes on.

Depending on your hoses, you still may need to get behind it to hook up the hoses.
Bruce Cunha

Okay, it's in!! I fiddled with every combination and ended up bolting the heater to the mounting plate and then located the combo in place and secured it with the screw through the battery tray. The setup was to give me room to tighten down the mounting screw.
I first attached a piece of hose to the leftmost tube on the back of the heater. It's long enough to go through the firewall and reach about half way down the engine. I also attached a short length of hose to the other tube on the back of the heater. This allowed me to reach the bottom of the securing bolt and tighten it down. I then attached my open/closed valve onto a length of hose and fed it through the firewall from the heater side. I then attached the end of the valve to the short piece of hose already attached to the heater. A pull cable, easily reached from the seat, allows me to open/close the valve while driving.
My main purpose for reinstalling the heater down here in Georgia is to have it as a source of cooling when the water temperature starts approaching oil pressure numbers. I opened a thread about the trouble that I've found in locating rubber 90 degree hoses to use when installing such things as an Arnolt adapter. Bud
Bud Krueger

A PROBLEM -- HOSE SIZE!! The Arnolt Adapter is designed to fit inside of the hose that connects the Thermostat Elbow to the Water Branch Pipe. The hose is nominally 6 inches long and the Adapter replaces the center 2 inches of it. The problem is that the hose i.d. is somewhat smaller than the adapter's o.d. and the hose material is too thick to squeeze it around the Adapter. I had to attack the hose with a heat gun to soften it enough to insert the Adapter after smearing it with generic K-Y Jelly (no wise cracks). Moss and A/S sell that hose as part of a set of hoses for the TD. The hose is labelled as 7/8". I'm curious if a generic 7/8" hose can be easily installed in that location (with the Adapter). I'd hate to get caught out on the road needing a heat gun in case I had to remove the Adapter. Bud



Bud Krueger

Bud,
I know that story. The answer-use silicone hoses. When I installed my Smiths heater, the return goes to the bypass which is made up of a copper t-Piece, a 90° bend and an orifice all soldered together. The t-piece is a standard 22mm copper pipe fitting. The outside diameter is 24.2mm. This is easily attached to 25mm ID silicone hose which fits the bypass perfectly. No heat gun required.
That was my problem solved

Regards
Declan





Declan Burns

Declan, you have a fantastic way of solving these issues. I have already tapped the water outlet manifold to function as the water source, ala TF. A single return then handles the system. The copper parts are readily available, but I'll have to hunt for the silicon hoses. Any chance of an image of your source plumbing? Thanks, Bud
Bud Krueger

Bud,
Here you go.

Regards
Declan





Declan Burns

Here's a top view
Regards
Declan
Declan Burns

Very clever, Declan. But what else would we expect from you? I think I'll stick with the return on the carburetor side using your single aperture. I'm still in the 'solder the fittings' days. Thanks. Bud
Bud Krueger

Declan, the orifice puzzles me. Your 'adapter' is connected to the elbow of the thermostat housing. I have a modern thermostat in the housing and a 5/16" aperture at the elbow. I think that is sufficient flow for when the thermostat is closed. I don't see a need for another orifice inside of the adapter. Besides, I don't have the facilities to make one like that. Bud
Bud Krueger

Bud,
Absolutely correct. No need. I have an original thermostat.
It is also possible to replace by using say a copper gasket with a smaller hole at the top of the bypass elbow-see pdf .
Regards
Declan
Declan Burns

Declan, you win. After fiddling around with the manifolds, and my vacuum takeoff for the power brake booster, I've decided to take my heater input line around the spark plug side with the return line. But, I'm running mine above the return line.

I looked into the cost of buying the tools required to use the copper press fitting technique, rather than soldering. That's an expensive change. If I were younger and doing some plumbing, I might consider it. But I'm well past that stage. Might have some images by tomorrow afternoon (wishful thinking). Bud
Bud Krueger

Bud,
Here you can rent the tools for the press fittings at the local DIY or borrow from a plumber which is what I did.
Regards
Declan
Declan Burns

Indeed, I committed to Declan's approach. But I had to use old-fashioned sweated joints. Learned that I could have rented the equipment for the modern technique, but I couldn't trust myself on the learning curve. Note that I chose to run my return line above my feed line. A classic one is that I had one leaking joint when I fired it up. It was the last solder joint of the whole project, seen in the above image. The one right in front of the valve cover. It gave me good pactice for testing my design that allowed me to remove either line in less than 5 minutes. No 90 degree rubber components were used. The 'adapter' used was Declan's as shown in a former entry in this thread. It's nowhere near as neat as Declan's, but pretty is as pretty does. And I think it's doing it's trick. Thanks Declan, Bud






Bud Krueger

Bud,
Looks fine to me!

Regards
Declan
Declan Burns

Went the way of least resistance. Works just fine.
I was always worried about the connection of the back of the head and the right-angle hose that perished. Very difficult to get to as well. Tried to keep the plumbing to a minimum. With an inline tap.
Rod





Rod Jones

I am confused, how do you get circulation with the heater flow/return in virtually the same place.
The only pumped circulation on an XPAG is along the transfer gallery and through the head. This by-passes the radiator when the stat shuts (on TD).
I may be missing something simple.
Ray TF 2884
Ray Lee

Ray, the entrance & exits are at the hottest (feed to radiator) and coolest (return from radiator) points. Note that Declan's 'adapter' has but one auxiliary connection, the return from the heater. The feed to the heater is taken from a tapped pipe fitting in the water outlet to the radiator (see image above). Bud


Bud Krueger

Yes Bud that is the way mine is.TF with tapping in the thermostat housing
I meant the first photo of Rods setup where both pipes are into the TD bypass pipe.
Ray
Ray Lee

The adapter shown in Rod's pic, if it's the same as mine, has a restrictor plate between the two branches so there is a pressure differential sufficient to cause circulation through the heater core.

Jud
J K Chapin

It May be a bit pedantic but a pressure drop across a restriction requires a flow.
When the stat opens on a TD there is no flow in the bypass pipe, (or very little)
On the late TF MG went to the expense of casting a new stat housing to fit a heater.
I have a KL heater and I toast in winter, OK not winters like yours.
Ray TF 2884
Ray Lee

The other option is to take the hot water from the rear of the cylinder head. This is how it was done by the factory on the Wolseley engines. I had stainless steel plates laser cut for those who want to go along this route. On my car I tapped the thermostat elbow.

Regards
Declan





Declan Burns

I originally had a Wolseley cast ally outlet.The transfer passage does not put a lot of heat into heater.You need to pick up heat from the head flow.
Ray
Ray Lee

Rod, I spent 1970-71 in Charleston, ME, driving a '62 TR-4. Its heater would roast you. Charleston is considerably north of Auburn and I'd regularly drive up to Katahdin and Millinocket. Now I'm in the south and the TD's Smith heater is on the shelf in my garage awaiting installation.

Anyway, do you know if your heater adapter has a restriction between the branches? Do you have an original or modern thermostat housing? Do you get adequate warm air in cold weather?

Thanks.

Jud
J K Chapin

Hi Jud,
The takeoff point has a restriction between the two outlets that allows for the water to be directed to the heater and maintains a pressure difference to assist it. Remember this is fitted to the Bypass Tube from the underside of the thermostat and the water pump inlet. I have one of Tom Langs SS Thermostat housings with a modern stat fitted 85C. For the 7 years I lived in Florida - Port Charlotte. I used the heater to assist in removing heat from the rad. Worked fine. Nights could be cold in the winter, so it is a good thing to have, either way.






Rod Jones

This will only work efficiently with a modern stat.
The original stat has a sliding port cover that blocks the bypass when the stat opens so little or no flow in that line.
Ray TF 2884
Ray Lee

Thanks Rod. That's the same setup as I have. Ray, I understand about the original sliding shutoff, Rod and I both have Tom's modern housing with modern stats so the adapter we have with the restriction should work. I hope to get mine installed this summer but I won't use it til December. I drive with the top off all winter but some heat on my feet and a bit for the occasional passenger will be welcome.

Jud
J K Chapin

Jud,
on this side of the pond I don't have to worry about cold feet. I have a very efficient foot heater known as the exhaust system.
Ray
Ray Lee

FYI, I have been using a 'modern' thermostat for quite a few years now, see http://www.ttalk.info/modern_thermostat.htm. I have a plate across the exit with a 3/16" hole in it. Bud
Bud Krueger

A puzzler -- went for a little spin to see how the cooling system was working and where any more leaks might be. Went about three miles to Home Depot and saw that the temperature gauge needle hadn't come off the peg. Continued back toward home and eventually saw the needle rather abruptly swing up to about 70°. I was beginning to think that I'd messed up the capillary tube. Once it warmed up (>70°) the readings seemed okay. On the way up the pipes felt warm. It probably has to do with the modern thermostat and modified housing with the small hole in the elbow. I'll dig out my digital IR thermometer and track the temperature. I think the thermostat is a bit ancient. Bud
Bud Krueger

As suggested by Declan, I increased the hole in the plate across the exit to 5/16". Made an appreciable difference. Bud
Bud Krueger

This thread was discussed between 02/04/2023 and 20/05/2023

MG TD TF 1500 index

This thread is from the archive. The Live MG TD TF 1500 BBS is active now.