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MG TD TF 1500 - TD heater system

I'm spending some time planning my heater hose rebuild while waiting for the last items on my convertible project.

There is an old Arnolt heater in my 51 TD. Currently it uses big hoses which snake around all over the place.

On the thermostat, the takeoff goes to a Y connector, half of which runs to a fitting on the rear engine plate. The other half goes to the heater.

Underneath, the connection between the radiator and the water pump also has a takeoff which goes to the heater.

So, there are two hoses to the heater and one hose to the rear engine plate. Does this sound reasonable?

I'm looking to add a valve to shut the system off. Where would be the best placement on a TD?

I'm going to use steel pipe and route them under the manifold.

So: my questions are: Does all this sound kosher as is? Where to put a shutoff valve?

I've already bookmarked several of the great pipe routing jobs by other owners and will be using some of their ideas...

in the photo below you can see both thermostat and water pump fittings



Geoffrey M Baker

In this photo you can see the connection to the rear of the engine and the firewall hoses

Geoffrey M Baker

and here is the Y connector that splits the hose from the thermostat, one going to the rear engine and the other to the heater

Geoffrey M Baker

I have more questions than answers. You have a line from the thermostat housing, which is hottest water and under pressure, and that combines with the water from the back of the head, warm, and also under pressure. These supply water to the heater, but you don't show where it returns to the engine.
Does it dump into the radiator circuit from the bottom of the radiator to the suction port of the pump?
You can lose the hose from the back of the head. It contributes warm water and compromises the water temp.
Also, what do you have for a thermostat and where exactly is it located within the housing?
JRN JIM

My guess is that it returns water from the heater to the lower radiator junction. I have the standard original thermostat in the original housing.
Doesn't water have to return to the head through the fitting in the back? That's what I assumed it was there for.

Does the water pump pump water INTO the engine from the lower radiator, or does it pump water OUT of the engine? I've never really studied how the water circulates, and how this heater should fit in. I've always assumed that it was working correctly, however it was set up (but I've never yet tested it to see if it puts out heat!).
Geoffrey M Baker

Geof,
There are quite a few articles in the archives about this subject,, but I think the best place for you to start is this explianation of the flow through a block,,
http://www.ttalk.info/XPAG_Cooling_System.htm

Hope this helps
SPW
Steve Wincze

Thanks for the link, Steve, that helps explain it. So water is pumped from the radiator into the engine and up into the head via the water pump.

So in a cooling system with no heater, where does the elbow off the thermostat connect to? Does it have a purpose?

All I'm really looking to do is replace the current setup with pipes instead of hoses. AND, if possible, add a shutoff valve to the heater line.
As far as I can see, my system looks much like a lot of others out there. The heat is drawn from the thermostat elbow to go to the heater. It is returned from the heater to the lower radiator hose that goes to the water pump. A Y is included in the line off the thermostat, to send water to the back of the head, which is unnecessary according to JRN.



Geoffrey M Baker

It goes back into the 'Branch Pipe"
http://www.mossmotors.com/Shop/ViewProducts.aspx?PlateIndexID=32736
PJ used some really 'slick lookin" aluminum pipe for his heater,,,
Steve Wincze

AHAH! So the purpose of the elbow is merely to recirculate the water when the thermostat is closed. I think I've got it.
Yep, I like PJs setup. I plan to do something similar in black steel, run under the manifold (I think, unless it obstructs removal of the manifold nuts significantly).
Seems like many people don't the connection to the back of the head, because they feel it's cooler, and a more efficient system is the arnolt bypass where both heater pipes come off the same connector mounted below the thermostat. So the heater both draws and returns water from two points on the system only an inch apart? Seems less than ideal to me.

Has anyone done temp tests to compare a system that has a connector to the back of the head? Just curious.

So why should my system not just cut out the Y that splits water to the heater and the back of the head, and just go to the heater instead? So there is a closed loop going from Y just below the thermostat elbow, out to the heater, then back to the lower radiator hose? Will that work OK? Why would someone connect to the back of the head at all if they are already connecting to the thermostat elbow?

Digging around a bit more, I see that Laverne and others have some great shutoffs behind the heater, with a cable to an under-dash pull lever. Nice.
Geoffrey M Baker

Geoff,

The Arnold Heater takeoff system is really good as it takes water under pressure directly from the pump - where it is hottest - and delivers it to the heater. The return goes to the radiator return (point of low pressure) as this is the return to the pump. Water cannot flow directly to the bottom of the rad via this connection because of a restrictor in the adaptor pipe. See attached.

LaVerne does this and many others as well.
It helps to have a shutoff valve as in the summer your cockpit will get rather warm if you don't. The restrictor is to allow some water to pass to the block without going through the Rad when the thermostat is closed. This is to get the engine warm quickly. Once the stat opens the least path of resistance is via the Radiator. Note, when the heater path is open the water is going to circulate to the heater rad with the stat open or closed getting the car warm quickly too. Some valves allow you to regulate the flow but in all the years I have had mine (without a valve) it does not bother me at all.

Rod



Rod Jones

Does anybody know if these arnolt heater bypass pipe units are available anywhere as new items or NOS?
Geoffrey M Baker

Geoffrey, here is a reply I had from Kevin McLemore the other week that answers your question

Kevin McLemore, Pennsylvania, USA

Cliff, et al, you can get the exact fitting that Rod has shown from Ben Corsden, an Arnolt Heater expert - he's restored over 100 of them. I just bought one from him the other day. He charged me $39.50 for the bypass fitting with the correct size restrictor hole and $10.50 for an ARNOLT decal for the front of the heater box, including postage. You can get hold of him at sculptart on the hotmail - dot - com system.
Cliff Harvey

Does it make the slightest difference if the unit has the pipes pointing up or down? I'd prefer down as I want to route everything under the manifold. Can't see why it would make a difference, but perhaps someone else might have a theory about it....
Geoffrey M Baker

I'm thinking that there is a better solution than the arnolt bypass: just put in a pipe junction into the base of the elbow beneath the thermostat, as Gordon Lawson did (see pic below).
No need to worry about whether the thermostat is open or shut, it will work in either position. Just return the water from the heater to the lower radiator line, nothing else should be needed (except a valve, if you want one).
I would put the hole on the other side, though.

Geoffrey M Baker

Geoffrey, I totally agree with you on the installation. I figured that the factory thought it was the best place when they provided a tap on the TFs elbow. I went a bit farther than Gordon because I thought the elbow wall was too thin for many threads. Mine has a simple pipe coupler brazed into place and made smooth with some body filler. No regrets.

Jim Merz

OK, so a pipe let into the elbow below the thermostat, running to the heater, and a return let into the lower radiator hose. It will work with the thermostat in any position. Simple and uncomplicated. Does anyone see any problems with that setup at all?
Geoffrey M Baker

Geoffrey, I used a simple ball valve and sweated on two short copper pipes... then I placed the valve directly behind the heater, connecting it to the right-hand pipe connection to the heater with a short length of 1/2" rubber hose. It's nicely out of the way and easily reached from within the cockpit (so there's no getting out in the cold to turn on the heat like in my Triumph Renown's factory setup).



Kevin McLemore

As for the plumbing setup, I wanted to go for an original-appearing setup, so I installed it the way Arnolt showed in their advertising literature, with 1/2" rubber hoses and the bypass fitting that Arnolt supplied as new.



Kevin McLemore

... and an overall shot of the hose routing.

Kevin McLemore

I guess I am much lazier than Kevin because I took the easy way out of controlling my heater output. I installed a NAPA inline coolant flow valve just behind the heater that is cable controlled via a knob on a panel I made. I also am using a variable electric rheostat switch to adjust fan motor speed. So, I can obtain just the amount of heat I need in the cockpit without much effort. See what old age will do for you?

Jim Merz

The control panel.

Jim Merz

I like it, Jim. I'm even lazier. I'm looking for a 12v controlled system - no worries about cable installation, just a switch.
http://www.thermotion.com/topic/19-automotive-heater-control-valve.aspx $54.
Geoffrey M Baker

Geoff, you might want to study that spec. sheet a little bit closer. I use the same adjustable valve as Jim. Bud

Bud Krueger

Yeah, it's not high temp enough. How about this one... good to 266F... $47

http://www.ebay.com/itm/3-4-Electric-Solenoid-Valve-12VDC-VITON-STAINLESS-S21V-/300716214166?pt=LH_DefaultDomain_0&hash=item4604154796

Geoffrey M Baker

Well,
I don't know where you guys drive but up here in Maine the heater is normally on winter or Summer (nights) and there has been no need for any on/off valve or thermostat control unit. With the hood down (The only way to go) the only thing the heater will heat is the drivers left leg (RHD). This does help combat the draft coursing through the gap around the door.
When all the weather gear up and in place. There is a few degrees change from outside but not enough to stop your breath ice developing on the inside of the windscreen. Again the warmest place is the driver’s leg. The reason for this is the Smiths heater has a port for the demister (seen on other cars but not on a TD) and it points directly at the drivers left shin :)
When I was in Germany serving with the RAF. I rigged up an old Oxygen hose to that demister port and taped it to the mirror stand to clear the ice on the inside. Now I don't have to drive on those days when Jack Frost's fingers make your bones ache.
Heater? Oh yes, great accessary. But keep it simple.
JMHO
Rod.
Rod Jones

Living in AZ, I'm more interested in having a valve so that the heater isn't putting out heat when it's already too dang hot out here...
Geoffrey M Baker

Good point.
Can't somehow imagine that ever happeniing up here :)

Think also that if it gets that hot, runnign the heater in Summer will also help cool the engine water a tad.
With your hood down. windscreen folded forward, nice breeze in the face. Heat in the cockpit won't be that much of an issue.

Rod
Rod Jones

There is this little vlave that might work, if you feel you need one. Placed like Kevin McLemore it would be out the way and easy to get to?
Rod.


Rod Jones

Without a valve, that box will generate 160-180 degree temperatures, winter or summer, whenever the engine is turning over, as the water is constantly pumping through it under pressure. That will set your leg burning on a hot day!
With a valve, it will stay nice and cool and at ambient air temperature.
Geoffrey M Baker

The hose is a 1/2" hose, so unless you're going to use adapters you'll need a 1/2" ball valve. The nice thing about the brass one I installed is that it also has a drain plug so you can both bleed and (fully) drain the system. You can see the drain plug in my photo.
Kevin McLemore

My hoses are 5/8.
??
Geoffrey M Baker

I think the barbs on a Smiths round heater are for a 1/2" STD hose.
I did find this little puppy at the NAPA site. Looks like its the right size but would have to see one with my hands to be sure.
$11.99
Nice and small and neat. They have the same think in a right angle too.

Rod.

Rod Jones

I believe those spec sheets indicating a max operating temp of 180deg is for the electrical operating device not the water temps. The description describes the exact use we are discussing. I have found this cable too and plan to use it as well. They have two types: power on valve closed and power on valve open. I plan to use this valve in conjunction with a solenoid to turn the water flow on only when the fan is on. I've also done the tap into the tstat housing (for a TF). Unfortunately, time hasn't allowed the rest of the project though.

Alex
Alex Waugh

Yes, I agree Alex; it struck me as odd that the device was described as being for automotive heater core water transfer and yet said the operating temp was only up to 180 degrees. I'll send them and email and ask.
Geoffrey M Baker

Geoffrey, one of the posters here, years ago provided numbers of the water temps at various points in the system. The max temp differential between the "hottest" point in the cooling system a(thermostat housing" and the coolest point (rear of head) was 7C. It was not worth it to me for 7C to modify the thermostat housing, run a heat dissipating hose run to the firewall for 7C when I could tap off the rear of the head and have a very short, very clean hose run. Regards, tom
tm peterson

Tom, very interesting point! I had been so busy thinking about how to tap into the front of the engine that it never occurred to me that tapping into the back might be even simpler... I'll probably do that instead... An even cleaner and simpler solution!
Geoffrey M Baker

I'd like to see that one again. I suspect that was a measurement of the external engine surfaces at various locations. Bud
Bud Krueger


Bud,
Gordon Lawson posted this pic some time back. As you say, it is temps taken from the surface of the metal, but that still gives a good idea of where the temp is and how much. For the sake of 8 degrees it makes sense to remove all that plumbing.
Rod


Rod Jones

Thanks, Rod. Turns out that I had it in my Gordon folder. Bud
Bud Krueger

Tom (tm peterson),

If you take the water from the rear of the head, where is your return going to be?

Gene
Gene Gillam

Well, Rod, looking at Gordon's photo it looks like taking the flow off the thermostat's bypass is where the highest heat is. Perhaps that's why Arnolt inserted their heater pickup at that junction? I've found that my heater (using the original Arnolt-style bypass insert) gets plenty hot... indeed, it can roast my right leg!
Kevin McLemore

Gene, the return should be the same - to the lower radiator hose...
Geoffrey M Baker

The return needs to be at the branch of the steel tube that runs from the bottom radiator hose up into the pump.

The plate at the back of the head sees water that comes from the radiator and through the external block channel from the pump BEFORE it picks up heat from the head & block. It is not nearly as hot. It is at pump pressure and not suction, so it cannot be used as a return. Ignore it completely.
JRN JIM

I intend to return water to the junction on the lower radiator connection. As the PO has already tapped into the back of the head, I think I will use that as the supply to the heater and see if that produces sufficient heat. If so great... If not I will tap into the thermostat elbow. I'll report back on how it works out.
Geoffrey M Baker

Alex Waugh: Thermotion responded to my email about their control valve, and as you suggest, they are referring to air temperature: "We prefer the actuator to be in an ambient environment of less than 140 degrees Fahrenheit to operate at its most optimal efficiency. The actuator will operate at temperatures at 180¢ªF, however, the return stroke time is much greater due to its being a thermal unit. The water temperature is good to 250¢ªF.
"
Geoffrey M Baker

This thread was discussed between 23/10/2014 and 27/10/2014

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