17 replies to this topic

[Efini611]

Hello everyone! Since summer began (And summer here in Spain is really hot with more than 35C) I have a “minor niggle” with my ‘72 Authi Mini…

 

Everytime I stop the engine after a ride, it burps a little bit of coolant from the rad’s overflow hose…

 

The cap is fine (It’s an aluminium Fletcher rad with no expansion bottle) The coolant level is always fine as I can’t see the fins and the car doesn’t overheat (It runs between 85 and 90)

 

Is this normal or do I have a big issue lurking around?

[cal844]

The cap isn't fine if it's burping coolant.

You ideally want to get the coolant checked for exhaust gas content. If none, change the cap for a new item and also fit a coolant expansion tank at a minimum

Edited by cal844, 12 July 2025 - 05:42 PM.

[Spider]

If you are filling the Radiator to the very top, this is normal. The recommended fill level is about 3/4" (or 20 mm) down from the bottom of the filling neck. Ideally, an over-flow tank should be fitted, this will keep all air out of the system and that in turn will allow your coolant to last longer and also greatly reduce corrosion and rust in the cooling system. It's an oddity that the Minis didn't get one of these tanks until very late, all the other cars in the BL / Rover lone up had one. It's something I've fitted to my Minis and has greatly helped them.

[Steam]

This is usually a sign of a faulty cap.

[Efini611]

Took out a little bit of coolant from the rad and went for a spirited drive…

It didn’t burp out any coolant this time… Maybe I overfilled it a bit as my radiator doesn’t have any maximum mark or ring like the original one… And with this temps out here it burped out (Summers here in Andalusia are boiling hot!)

Anyway… I will keep an eye on things and if it still burps out I will go to my specialist to fit a new cap and an expansion tank…

[68+86auto]

The cap is a cheap part that you can buy at an auto parts store.

[JXC Mini GT]

If you are filling the Radiator to the very top, this is normal. The recommended fill level is about 3/4" (or 20 mm) down from the bottom of the filling neck. Ideally, an over-flow tank should be fitted, this will keep all air out of the system and that in turn will allow your coolant to last longer and also greatly reduce corrosion and rust in the cooling system. It's an oddity that the Minis didn't get one of these tanks until very late, all the other cars in the BL / Rover lone up had one. It's something I've fitted to my Minis and has greatly helped them.

The other bonus of fitting an expansion tank, is that you can check the coolant level without the risk of scalding yourself when removing the cap.

[bpirie1000]

Is your fn on the right way and everything else working g properly like the water pump etc..

[Efini611]

Alright I’ve just taken the car out for another ride… It’s 33C outside and not a single drop (Nor burp)… Possibly I overfilled the coolant a little bit…

[Efini611]

[UPDATE]

It burped again since yesterday… Lowered the coolant level and still burping… I’m considering replacing the cap as it might be faulty and not holding pressure

[cal844]

[UPDATE]

It burped again since yesterday… Lowered the coolant level and still burping… I’m considering replacing the cap as it might be faulty and not holding pressure

Cap or thermostat imo

[Efini611]

Did a test yesterday… Started the car with the cap off… The radiator bubbled like a jacuzzi… I’m suspecting a faulty thermostat stuck closed (As I noticed the gauge creeping up slowly to “H” in slow traffic) or worse… Combustion gasses from a failing head gasket…

[gazza82]

Did a test yesterday… Started the car with the cap off… The radiator bubbled like a jacuzzi… I’m suspecting a faulty thermostat stuck closed (As I noticed the gauge creeping up slowly to “H” in slow traffic) or worse… Combustion gasses from a failing head gasket…

More likely to be head gasket than thermostat

[tmsmini]

Dont mean to take the thread off track, but what is the car that the plastic expansion tank was sourced from? I have seen metal tanks in the same shape, maybe from a MGB, but they have gotten expensive.

[Efini611]

I think it’s from a Rover SD1