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MG MGB Technical - Expansion Bottle

Coolant was squirting out the expansion bottle, checking it the spouut is split. Anyway I had two more surprises a, they are £60! and b, the one that's on there, and has been on there since I bought it 25 years ago is for a midget!!
I'm thinking of getting a scrap one off another make of car, anyone got any recommendations.
c cummins

It would appear that the same tank was used on B and Midget.

Can you have it brazed?

Try your local radiator repair shop.
Dave O'Neill 2

It's plastic. Part no ARA 326. Used on the Triumph engined Midget, no longer available.
c cummins

It was also used on the Rover SD1 - that's where mine came from.
Mike Howlett

Metal ARH250 available (V8 and 4-cylinder according to the Parts Catalogue), about the same price, but at least they are repairable.
Paul Hunt

ARH250 was used on 1275 Midgets.

The plastic version, as fitted to Midget 1500s, was very similar to that used on the Austin 11/1300, although you probably won't find many of those in the breakers.

Dave O'Neill 2

Somewhere in the back of my mind I recall them being fitted to Leyland Daf vans.
Regards
Mark
Mark Dollimore

Gentlemen. Please note that the brass expansion tank will, over time, work harden and crack. The cracks take place within two subsystems of the device--the solder and the sheet metal.

Cracks in the soft solder may be carefully repaired by resoldering. Make sure that all of the areas to be resoldered are clean and properly fluxed.

Cracks in the sheet metal may be cleaned and have a line of solder spread over them to provide a temporary fix. But, once the body of the tank begins to fatigue crack it will only get worse and replacement is the only cure.

The tank is under cooling system pressure when hot, nominally about 14 PSI, but the actual pressure will depend on the radiator cap being used and its pressure rating. (Later models used higher pressure ratings because each one PSI raises the boiling point of the coolant by 3 deg F.)

When purchasing a used brass expansion tank, it is a good idea to fill it half full of water, run a rubber hose (with clamps) from the neck to the input tube, and use a radiator pressure system tester to ensure the tank will both hold pressure and does not leak from either the soldered seams nor the brass sheet metal.

I have tested several used tanks over the years and have found almost half of them not capable of holding the rated cooling system pressure. Check before you buy.

At various times, both plastic and brass tanks have been available from various suppliers. But, they are always snapped up quickly. About time for someone "in the business" to reproduce the tanks and have a supply of new ones available to ensure many years of motoring joy.

Les
Les Bengtson

Gents, I've found the attached from Rimmer Brothers for a TR7 1975 - 1978. It would probably make a suitable replacement for the MGB expansion tank, but probably not a lot cheaper by the time you buy all the fittings etc. The pressure cap is 15 psi

Andy


Andy Robinson

Have you tried Andy Jennings?
Pat Gregory

There are a lot of second hand ARH 250's on e-bay at about £30 they are the metal ones.

Graham
GJ Barker

The 326 is similar, but not identical to the RV8 one which is the same as the Morris Marina/Ital.
Allan Reeling

I like my plastic one because I can see at a glance the level of coolant. A metal one could run dry without you knowing.
Mike Howlett

I realise now that BL raided what ever parts bin available, for all I know the Midget bottle may have been Factory fitted, or at least at a MG dealership.
Anyway there seems to be decent looking alloy ones from performance equipment suppliers.
In the mean time I visited a local breakers and picked out a header tank off of a Renault Megane and lashed it up so I can drive it.
c cummins

This thread was discussed between 12/07/2015 and 13/07/2015

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