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MG TD TF 1500 - MG TD Rad Expansion Tank

So I fitted an expansion tank to my TD this week and so far it all seems to work as intended.
I used a 32oz Nalgene Wide Mouth Rectangular Bottle to sit in the Battery box. Ran a nylon tube 1/4" id from the Rad overflow to the bottle and extended it to the bottom on the bottle. I have a rubber gasket in the Rad cap so that is now sealed to atmosphere at that point. Extended a new overflow [if required - hopefully not] from the lid of the bottle to the underside of the car which is open to atmosphere. So even though the system is not pressurized in any way, Fluid dynamics should allow the hot expanded water/antifreeze to escape to the expansion bottle and get sucked back into the Rad when it cools.

Only thing that caused a frown is - there is a bubble that forms in the hose at the bottle cap end. Everything seems to work just fine. Water goes to the bottle and partially fills it when hot, and it is sucked back into the Rad when it cools. The marked cold fluid level is maintained.
I have re filled the system a couple of times. Done by squeezing the bottle, thus filling the hose and the Rad to the point where it will overflow at the Rad and at this point put the cap on tight to form the full Rad seal. However after the next heat cycle, there will be a bubble in the hose at the bottle end. I have two right angle barbs of brass through the lid of the bottle and believe me they cannot leak at these pressures. There also clamps on the hose above and below the lid on the barbs.
The overflow Pipe in the Rad is about 1" down from the absolute top of the rad. So any residual air caught under the cap when fitting it - could not be the source.

Not sure if this is really an issue - as the system functions.
Total cost under $33.00

32oz Nalgene bottle $5.99
10’ silicone hose [500f] $8.99
2 x right angle brass barbs $7.98
10 x 3/8" Heavy Duty Double Gripping Nylon Hose Clamps. $9.79





Rod Jones

I have a very similar set up on my TF, connecting up to the overflow pipe just below the cap. No need to go to the trouble of filling the interconnecting pipe between the rad and the expansion tank and sealing everything up though. Just put an inch or two of coolant in the expansion tank, and the next time you run the engine it will fill the pipe. The coolant in the expansion tank may get drawn back into the rad if not completely full when cold, so if necessary top it up.
Dave H
Dave Hill

Good thought Dave :) I guess I just wanted to have the system primed to start. Not too hard to do. Real easy with two of you. I did start with 2 odd inches in the tank anyway. SO it probably would have just filled itself anyway. I do also believe a pint bottle would be more then enough and cheaper with less room needed. Judging by the meager levels it gets to when hot in this 32oz bottle. AT 85c it had only raised 2 1/2" in the bottle.
It certainly would not fill a pint bottle.
Rod Jones

Yes I agree - I've never measured it, but 1 1/2" sounds about right. The other positive thing is that you very quickly notice if you have a leak.
Dave H
Dave Hill

Mine - http://www.ttalk.info/Tech/Overflow_tank.htm Bud
Bud Krueger

A TF has a pressurized coolant system, where as the TD does not. This make a difference in how a coolant recovery system works. The TD, having a non pressurized cooling system, the addition of a coolant recovery system only catches coolant that is expelled from the cooling system and drawing some of the expelled coolant that is caught in the recovery tank back into the cooling system. Bud's addition of an external expansion tank basically turns the unsealed cooling system into a modern cooling system. Unless coolant is added to the external expansion, no coolant in lost. The external expansion tank that Bud is using, is from a late model MGB and in that configuration, the only place to add coolant in the external expansion, which will overflow just as happens in modern coolant systems. See the article, EXPANSION TANKS, COOLANT RECOVERY SYSTEMS AND HOW THE COOLING SYSTEM WORKS in the Other Tech Articles section of my Homepage at: http://homepages.donobi.net/sufuelpumps/ Cheers - Dave
DW DuBois

Rod,
,
Thank you for this brillaient idea!
I apologize for the stupide question: where did you put the battery?
C.M. groucho

C.M.
The expansion bottle sits beside the battery-here's a photo of mine.

Regards
Declan

Declan Burns

C.M.
It certainly is not my brilliant idea :)
There are I presume lots of folks out there who have coolant recovery systems. This is just the way I did it.
Not expensive and the nylon bottle is man enough for the job and small enough to fit in beside the battery. Similar the Declan's. I am sure you could find lots of bottles that will fit in your space. I do have a large battery and the room I had to deal with was only 3 inches [7.5cm]. The brass right-angle fittings were the easiest way to get the hose into the bottle and extend it to the bottom. I don't think the hose clips are rally necessary - But what the heck. The new overflow now starts at the top of the expansion tank bottle. There is no extension below the lid. I drew a line with a magic marker to indicate the LOW level about 2" from the bottom.
Rod.

Rod Jones

I copied mine from Declan's set up, and I've no doubt that he got it from somebody else, and so on.
Dave H
Dave Hill

I used a hot rod tank on my now departed TD.... I would like to see pictures of your set up Dave as I'd like to put one on the TF but have no idea where I could mount a tank. The space by the battery is taken up with an oil seperator/catch can.

L E D LaVerne

I mounted the expansion bottle right next to the battery, the same as Declan has. It a small windscreen washer bottle and fits the space perfectly.
Dave H

Dave Hill

Dave,
Correct. I got it from the Morris Minor guys.

Regards
Declan
Declan Burns

Thank you Rod, I will check if I have enough room besides the battery. Anyway I appreciate your input.
C.M. groucho

It may be too large, but the catch bottle from a 79 spitfire might work.

Bruce Cunha

In the unpressured system surely the added tank will not add any amount of additional cooling capacity. I imagine the purpose is to make filling up the radiator to proper level a bit neater?
D Wells

What it does is to catch coolant from expansion rather than expel it onto the road. This is then available to be drawn back into the cooling system when it cools (on a TF this works perfectly). It also gives a very good visual indication of any issues with the cooling system, leaks internal or external, etc. It doesn't give additional cooling capacity in any other way than keeping the system topped up.
Dave H
Dave Hill

The opening paragraph of http://www.ttalk.info/Tech/Overflow_tank.htm tells why I installed mine. Bud
Bud Krueger

Wondering if an unobtrusive overflow tank could be mounted low down behind the radiator? Say about 10" x 5" x 2" deep made from metal & painted black. This would be difficult to spot & the tubing from the overflow pipe would only be a few inches long. I can see why Bud & others have incorporated an overflow tank (see pic) but I'd like to go with a much less obvious install. Possible do you think? Any problems? Cheers
Peter TD 5801

P Hehir

Hi Peter,
The Stag originally had such a system and there has been a lot written (and I mean A LOT) on that forum on the subject of low level catch tanks versus header tanks. One argument against the original low level expansion tank is that, whilst it is fine when the system is new and perfectly airtight, any leak will result in a gradual loss of coolant as the coolant pushed into the low level catch tank when the coolant expands on heating can only be pushed back in again by atmospheric pressure when it cools. It is not 'sucked' back in.
As I understand it the TD system is unpressurised so I would expect that there would be no pressure differential to return coolant from a low level catch tank to the radiator. However, gravity will be on hand to save the day with a high level catch tank.
I decided to add a pressurised header tank to my Stag as it gives a tiny amount of extra coolant in a marginal system, makes filling the radiator easy (it's a bit like bleeding T type brakes otherwise) and allowed me to include a low coolant sensor with a warning light.
Chris
C I Twidle

Chris,

While the TD is not pressurized, it is sealed, except for the overflow port. The radiator cap contains a gasket.
Thus no matter where the tank goes, the difference in atmospheric pressure to the internal radiator pressure will force fluid back into the radiator as the collent temperature drops.

Gravity should not be needed.

Jim B.
JA Benjamin

Thanks for the clarification Jim. Does that mean that with the standard TD system one would expect it to lose a certain amount of coolant until the system reaches some sort of equilibrium?
With the pressurised Stag system the pressure cap is on the catch tank and the inside end of the overflow pipe is well below the radiator filler neck leading to potential air entrapment and difficulty in bleeding. All that in a system that is theoretically 20 years more advanced!
Chris
C I Twidle

Yes Chris,
Starting from a full topped off, condition, as the coo lent heats up and expands it runs, more or less freely, out the over flow tube onto the ground.

When the engine cools down the level will be below full. But it should stabilize at that level.


Adding a recovery tank, connected to the overflow pipe, the overflow liquid would be collected. When the coolant cools and returns to its normal volume, the pressure in the radiator will be reduced and the excess, now in the overflow tank, should return to the radiator.

One big improvement of the pressurized system is to allow the coolant to run at a higher temperature before boiling. This can improve heat transfer to the surrounding air.

Jim B.
JA Benjamin

Peter. If you hide the tank down below the radiator (no doubt possible, but certainly not easy), you lose the advantage of having a visual indication of the coolant level. Having the tank visible, but making the pipework unobtrusive would be much easier.
Dave H
Dave Hill

That's a nice clear explanation Jim and it applies equally to the Stag which certainly requires the extra cooling capaciity but from personal experience there are so many ways the integrity of the system can be compromised that I wouldn't go back to a low level system. Leaks around corroded 40 year old hose spigots, over stressed soldered radiator joints, head gaskets. Plus, for the Stag, an inlet manifold with water galleries that joins two angled heads creating innumerable opportunities for a leak.
I've seen Dave's TF system, it certainly doesn't look out of place unless you are up against a serious judge and it would be completely reversible.
Chris
C I Twidle

Mine is also a windscreen washer reservoir, mounted low down on the chassis back towards the stanchion.
It's reasonably unobtrusive, has a visible level, and leaves space next to the battery for a bottle of top-up engine oil.

Tim Wilkinson

Hi Tim,
I like the colour, is that by any chance Almond Green? I hope so as my chassis code is for that colour but as the rest is still largely a pile of bits and pieces with so many different layers of so many different colours I haven't found a single piece that I can say with confidence is original.
C I Twidle

No Chris, it's probably closer to Woodland Green. It's actually a BRG, Rover paint code HAA.
When I first restored the car years ago I wasn't confident of matching the original, possibly Almond Green, so chose a popular shade of the time. Maybe next time ...
Tim
Tim Wilkinson

Chris. I have an original paint colour swatch for all BMC colours of the era and it includes Almond Green (non metallic).
Dave H
Dave Hill

Tim. It seems a good place on a TD, but not a TF. I have far too many cables there and the bonnet side woukd make viewing the coolant level difficult.
Dave H
Dave Hill

I broke down yesterday and put a coolant recovery system in the Green Hornet. I used and old windshield washer bottle from some departed BMC product. I removed the overflow hard line this morning after verifying the new system is functional.

L E D LaVerne

Kind of a funky stand off but I didn't want the line resting on the hot surfaces.

L E D LaVerne

The bottle sits snuggly next to the oil vapor separator can.

L E D LaVerne

I filled it about a quarter full with fluid and took it out yesterday in the 95F degree heat and ran it hard for about 10 miles. The engine temp never got above 85 C. When I got home I checked and the bottle was now about 2/3 full of coolant. Checked it this morning and it was back to the 1/4 I started with. Pulled the cap and the radiator was plum full.

L E D LaVerne

Again, I did it my way


M Grogan

and


M Grogan

This thread was discussed between 15/06/2017 and 27/06/2017

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