I have what I think is a Morris 1100 radiator expansion tank.

As my Mini pushes water out of the overflow I was thinking of adding this tank so the excess water can be returned to the radiator. Maybe it will help with cooling.

Any help would not go amiss.

That type is an expansion tank. It’s different to an overflow or recovery tank

The expansion tank is an extension of the pressurised cooling system. You have a flat cap on the radiator and a hose to the expansion tank. The expansion tank then has the pressure overflow cap. They are useful in situations when you need to raise the height of the filler neck

A recovery tank has a special recovery type cap which allows the coolant to get back in the radiator when the pressure drops. The hose needs to be from the bottom of the recovery tank in order for it to return

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There is a non expansion cap on the radiator and the radiator cap goes on the expansion tank. The expansion tank has a tube that goes to the bottom of the tank which allows water to flow both ways.

I am sure Morris 1100 owners will know what I'm on about.

This extra tank gives more capacity so hopefully keeping the Mini cooler.

What you have there is from a Moke a it is short and squat whereas the 1100 version was taller and thinner, imagine yours turned 90 degrees. While they were used as timmy says as an expansion tank they can be used as a recovery tank. the difference is which cap you use on the radiator. the expansion system has a blank cap on the rad whereas a recovery system has a recovery type cap on the rad. The problem is that no one makes a recovery cap for the long neck radiators. A standard cap will not draw water back from the tank as it is not sealed at the neck and will draw air,

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Cheers Dave.

If it’s pushing coolant out the overflow now, it’s either overfilled or there’s something wrong elsewhere. Adding the expansion tank is unlikely to help with cooling. While it adds a tiny bit of volume it’s not circulating through the tank or cooling

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There must have been a reason Morris 1100's & Mokes had this extra tank!

Here is what the workshop manual says. You can see arrowed the blank raditor cap. The tank has the standard cap but it is a short neck version.. Hope this helps.

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Cheers Dave.

99% sure those 1100/moke tanks do work as recovery tanks - the tube that goes in the top extends inside down to the bottom of the tank and anything that goes in there is sucked back in to the radiator when it cools down

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did I tell you that I won a trophy?

Totally does work very well on a temperamental cooling system. These have been a staple on my cars for decades, with the addition of a flat-cap to the radiator. I fit mine beneath the guard to keep some space under the bonnet.

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

Thought it would work. Would you be able to put up any pictures of your installation.

Sorry the engine is out at the moment for a inspection and refresh, so its not all together. The tank is held secure by a flat metal strap around its waist. This secures to the foot well/guard by two bolts that fit snug up under the dashboard tray. There's a hole provided by the factory on the inner guard just aft of the radiator cap, and this is where I plumb the hose through to the expansion tank.

Not recommending a buyer in particular, but this is the first link I found to the type of cap which suits the expansion tank you have in its classic use.
https://www.ausminispares.com.au/produc ... r-cap-flat

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

Here are some pics





Some extra info here -
viewtopic.php?f=2&t=49154
viewtopic.php?f=2&t=22171

Thanks for all your inputs. I think it may help if water is pushed out of the system and will be pulled back when cooling.

Oooh, I recognize those photographs! Thanks for remembering them.

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

When I did the ground-up rebuild of our 850 40 years ago, the modded 1098 I built for it suffered from the coolant expansion from the overflow issue.
I slotted a plastic bottle for the overflow next to the wiper motor and made a thin gasket for the inside top of the long-neck cap to seal it and this recovery system has worked a treat ever since.
Just before chrissie last year the radiator (which is still the original by the way) top tank seam started leaking, so I pulled it out and had it repaired.
As is always the case with ageing cars I decided to do the obligatory "while I'm in here I'll sort this out as well"...
Anyway when I was up in Melbourne buying all my bits n pieces, Joe at Mini Makeovers advised me to put in a 74 degree thermostat instead of the 82 that I've always run.
I sorted all the jobs out and good ol Oscar the 850 hit the road once more and all I can say is that the change in thermostat temp is brilliant!
Of course it's a given that the engine now runs cooler, but the really great thing is that the overflow system is no longer in use.
As can be seen in the pic the air bubble in the top of the tube from when I filled the system is still there!
This would normally be pushed into the bottle the first time the engine runs up to temp.
Very happy with the outcome!!!

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Cheers,
Rod.
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'63 Morris 850 (Old Secondhand CAR)