22 replies to this topic

[Rubbershorts]

Hi everyone. I've discovered my Rio has a radiator expansion tank. There are liners under the wheel arch and it was hidden behind that. I took it off to clean all the wax oil from it and discovered it leaks at one of the rivets holding the bracket in place. I've read this needs to be fully sealed to do it's job correctly, so in theory this would be useless if it were needed. It's fully sealed, as in there isn't a top cap or anything, and a search on line draws a blank on a replacement. Does anyone know where I might find one? Or can an alternative be used to put back under the wing? Can it be fixed? If not, can it be deleted? Cheers, Daz.

Attached Files

•  instasize_251008195422.jpg   51.77K   2 downloads
•  instasize_251008195445.jpg   50.01K   1 downloads
•  instasize_251008195501.jpg   28.02K   1 downloads

[smurfomatic]

Available on eBay but not cheap!

 

https://www.ebay.co....tm/256974127982

[Rubbershorts]

Available on eBay but not cheap!

https://www.ebay.co....tm/256974127982

Cripes😱

I suppose the the delete or repair questions are more important now.

Edited by Rubbershorts, 08 October 2025 - 08:07 PM.

[cal844]

I deleted mine, along with the charcoal canister, car passes mot no problems

[Rubbershorts]

I deleted mine, along with the charcoal canister, car passes mot no problems

Cheers Cal. Did you just run the overflow from the rad down the inside of the wing towards the floor?

Interesting that you've deleted the canister too. Where did you run everything from that (tank breather, carb overflow etc)?

[Ethel]

I'm not sure it'll matter much. I believe it's main function is to stop you dumping antifreeze in to the environment. If the pressure in the rad returns to lower than the bottle it'll siphon back. I guess the black bung thing is a pressure relief valve anyway.

 

Can you figure out anything about the rivets? If they just go right through the poly you could try drilling them out & replacing them, with an added seal. Polythene is very unsticky, but it can be welded with careful use of a soldering iron. Googling HDPE kayak repair might chuck up something useful.

[timmy850]

Double check what kind of radiator cap you’ve got. A normal cap allows the coolant to expel but not draw back (which is what you want with no overflow tank)

A recovery type cap allows it to draw back in when the system cools and the pressure drops

[Rubbershorts]

Double check what kind of radiator cap you’ve got. A normal cap allows the coolant to expel but not draw back (which is what you want with no overflow tank)

A recovery type cap allows it to draw back in when the system cools and the pressure drops

Thanks Timmy. Just checked and I seem to have the 15lb none return. It's on Minispares as up to 1992. My car is 1993, so maybe not the correct cap for the return feature, but the right cap if I were to delete the tank? Or preferably, as Ethel pointed out, keep the tank as somewhere for coolant to blow out into to avoid leaking into the environment. It won't matter if it doesn't work fully as the cap doesn't allow it to anyway. Daz.

Edited by Rubbershorts, 08 October 2025 - 09:35 PM.

[mab01uk]

Mini Expansion Tank - They are now available again from 'Classic Minis Japan'

"Discontinued some time ago in the UK, the expansion tank is part of the cooling system found on all injection models. Located within the near-side wheel well, the tank is fixed to the inner wing with a single bolt, and designed to fit snugly on the suspensions mounting bracket. Connected to the radiator by a thin rubber hose, the expansion tank maintains an equilibrium [of pressure] in the primary cooling system by absorbing excess coolant when hot."

https://classicminis...expansion-tank/

Edited by mab01uk, 08 October 2025 - 10:37 PM.

[cal844]

I deleted mine, along with the charcoal canister, car passes mot no problems

Cheers Cal. Did you just run the overflow from the rad down the inside of the wing towards the floor?

Interesting that you've deleted the canister too. Where did you run everything from that (tank breather, carb overflow etc)?

All we did with the charcoal can was remove the pipework from the engine breather Y pipes (bung them with bolts and a jubilee clip to prevent running issues) leave the fuel tank vent pipe open to atmosphere and fit the earlier type vacuum advance pipe (direct from dizzy to carb)

[Rubbershorts]

I deleted mine, along with the charcoal canister, car passes mot no problems

Cheers Cal. Did you just run the overflow from the rad down the inside of the wing towards the floor?

Interesting that you've deleted the canister too. Where did you run everything from that (tank breather, carb overflow etc)?

All we did with the charcoal can was remove the pipework from the engine breather Y pipes (bung them with bolts and a jubilee clip to prevent running issues) leave the fuel tank vent pipe open to atmosphere and fit the earlier type vacuum advance pipe (direct from dizzy to carb)

Mine's dormant anyway. No cat, dizzy vacuum connected directly to the port in the carb as you suggested. The breather at the Y plugged. So did you remove the canister from the car? What did you do with the fuel over flow from the carb? Daz.

Edited by Rubbershorts, 09 October 2025 - 11:21 AM.

[Ethel]

The carb & the tank both need atmospheric pressure to work properly.

 

The correct rad cap will have 2 rubber seals. One to the very top of the filler neck plus the usual, spring loaded one.

 

Cunning botch plan - spread some sealant around the bracket & create a vacuum in the bottle to draw it in. 

[Rubbershorts]

The carb & the tank both need atmospheric pressure to work properly.

The correct rad cap will have 2 rubber seals. One to the very top of the filler neck plus the usual, spring loaded one.

Cunning botch plan - spread some sealant around the bracket & create a vacuum in the bottle to draw it in.

Third paragraph in particular deserves it's own thumbs up Ethel👍

Edited by Rubbershorts, 09 October 2025 - 04:32 PM.

[viz139]

The hole in the rivet is normal, it will allow air in and out of the tank. The tank is not pressurised and should be only half full. Pre '92 minis have air at the top of the rad but this tank ensures there is always water up to the cap when used with the correct cap as stated above. I have seen minis run hot in fine weather because the wrong or faulty  cap is fitted

[Rubbershorts]

The hole in the rivet is normal, it will allow air in and out of the tank. The tank is not pressurised and should be only half full. Pre '92 minis have air at the top of the rad but this tank ensures there is always water up to the cap when used with the correct cap as stated above. I have seen minis run hot in fine weather because the wrong or faulty  cap is fitted

Interesting Viz. I will say, when I removed the tank it did contain liquid that when the tank was inverted leaked out from beneath the bracket at the point where the rivet nearest the fixing is located. It didn't come out of a hole in the rivet so definitely looked like something was amiss. It's currently back in the car as a temporary fix. It's empty and I still have the above mentioned cap on, which I believe is wrong, but has been running without any issues for a few thousand miles whilst we've had the car. If I change the cap, half fill the tank and fully fill the rad, do you think this will be okay and correct? Thanks, Daz.