Coolant level in my 1960 Austin Seven Mini

[Chapmag]

Hi all, I seem to be losing coolant but not overheating. I fill the radiator so that the coolant sits just on top of the fins. I then go for a 20 - 25 mile drive and when the engine has cooled I remove the radiator cap and there is no coolant on top of the fins. If I try and top up the coolant it only takes 1/4 pint to submerge the fins. I can see evidence that coolant has been coming out of the radiator overflow hose. Question is, should I be concerned or is the fact that the car is not over heating reassurance enough? Thanks in anticipation of your expertise and experience. G. P.S. Forgot to add I have a new ARP2000 radiator fitted.

[Exminiman]

What rad cap are you using, if water is escaping past the cap without obvious boiling then sounds like a faulty cap or low pressure cap

[Chapmag]

Hi Exminiman, I have a 7lb short reach radiator cap which I thought was correct for a 1960 850 mini? Would you advise swapping it for a 15lb cap or maybe another 7lb short reach one in case the one I have is faulty? I've tried a long reach cap and that won't twist shut. TIA, G.

[Peter Laidler]

On the other hand, if you're absolutely sure that the rad and system ain't leaking, you could always just change the fluid to waterless and forget the pressure caps as it ain't going to boil in any case.

Been using it in my Rover Cooper for 20 years now

[Exminiman]

Hi Exminiman, I have a 7lb short reach radiator cap which I thought was correct for a 1960 850 mini? Would you advise swapping it for a 15lb cap or maybe another 7lb short reach one in case the one I have is faulty? I've tried a long reach cap and that won't twist shut. TIA, G.

It sounds as if something isn’t sealing, it’s the age of the radiator, not the age of the car, if you see what I mean.

Could you have a later (long neck rad) fitted with a short neck cap ?

[Chapmag]

Hi Exminiman, I have a 7lb short reach radiator cap which I thought was correct for a 1960 850 mini? Would you advise swapping it for a 15lb cap or maybe another 7lb short reach one in case the one I have is faulty? I've tried a long reach cap and that won't twist shut. TIA, G.

It sounds as if something isn’t sealing, it’s the age of the radiator, not the age of the car, if you see what I mean.

Could you have a later (long neck rad) fitted with a short neck cap ?

Thanks, the ARP2000 rad was new in 2022. It has a short neck. I see now that Mini Spares recommend a 15lb rad cap for this rad, so it looks like that'll fix my problem. Thanks for your time and patience. G