16 replies to this topic

[whistler]

A friend of mine has totally restored a 1990 mini except for the engine. It's from a 1275 Metro that has sat in the corner of his workshop for about 2 years.

He refitted it recently but it has started to overheat, with the temp. gauge going off the scale after a short drive. No loss of water, but overflow pipe is weeing on the floor. Run it without the rad cap and no loss of water. No bubbles.

Changed thermostat and sender; run it without thermostat, no difference. Removed rad and test, full flow. Removed water pump and that's in good order. No water in oil, no water or vapour out of exhaust. Only thing different is he has fitted one of those billeted thermostat housings with the flying engine steady bar to the bulkhead. Supplied by 3D Scan (used to be DSN). Can't see any reason why that item would make any difference.

The heater hose is fitted from head to bottom hose.

 

Any thoughts before he takes the head off?

[MiniMadRacer]

Has things like the timing, and the carb settings been checked, and have you "flushed" the block out at all. was it stored with or wthout coolant?

[whistler]

No settings been changed and block has been flushed through. Brown water then went clear. Just usual colours.

[Piero]

Radiator cap?

[Quinlan minor]

 

it has started to overheat, with the temp. gauge going off the scale after a short drive.

is there any other evidence that it is overheating?

Could the problem be limited to the sender, wiring, power supply or gauge?

Is a Metro sender matched to a Mini gauge?

Edited by Quinlan minor, 06 September 2026 - 12:59 PM.

[mab01uk]

Radiator cap?

 

I agree it is definitely worth checking the rad cap is the correct type, pressure, long/short reach? and is not faulty, if it is not correct and holding pressure the coolant/water will have a lower boiling point and come out the overflow pipe.

I have always found with 1275 Minis it is worth fitting an expansion tank to the rad overflow which the factory did with the 1990's onwards Rover Mini Coopers, etc under the front wheel arch.

Most other BMC/BL cars of the era like the ADO16, 1800, Maxi, Metro, etc had expansion tanks as standard and now most modern cars too. I used to fit the brass expansion tank from the 1100/1300 ADO16 (later plastic) as they were common to find in breakers yards, now usually some on Ebay. The BMC works Minis fitted the ADO16 expansion tank in the passengers foot well but I usually found a space under the bonnet on the bulkhead or inner wing. (Pressure cap on the expansion tank and blanking cap on the rad and upgraded hose from the rad overflow).

 

Faulty Radiator Cap?

https://www.theminif...y-radiator-cap/

Edited by mab01uk, 06 September 2026 - 02:56 PM.

[whistler]

 

Radiator cap?

 

I agree it is definitely worth checking the rad cap is the correct type, pressure, long/short reach? and is not faulty, if it is not correct and holding pressure the coolant/water will have a lower boiling point and come out the overflow pipe.

I have always found with 1275 Minis it is worth fitting an expansion tank to the rad overflow which the factory did with the 1990's onwards Rover Mini Coopers, etc under the front wheel arch.

Most other BMC/BL cars of the era like the ADO16, 1800, Maxi, Metro, etc had expansion tanks as standard and now most modern cars too. I used to fit the brass expansion tank from the 1100/1300 ADO16 (later plastic) as they were common to find in breakers yards, now usually some on Ebay. The BMC works Minis fitted the ADO16 expansion tank in the passengers foot well but I usually found a space under the bonnet on the bulkhead or inner wing. (Pressure cap on the expansion tank and blanking cap on the rad and upgraded hose from the rad overflow).

 

Faulty Radiator Cap?

https://www.theminif...y-radiator-cap/

 

Rad cap is correct poundage and is the long type but the problem is there when the engine is running without the cap being fitted, as I mentioned in my post.

[R32Egor]

Was it running ok and not overheating for a while and then started overheating?
If it was immediate after refitting - fan correct way round?

[whistler]

It was running fine when it was removed. Overheating since refitting. Fan is correct way round.

[Spider]

If it's been sitting around for a while. the cooling system is likely gunked up and needs a good clean out. When he had the Thermostat out, what did the cooling jacket in the head look like ? That'll be on of the better looking parts of it.

[Steam]

1275 A+ metro engines will overheat with the smaller Mini side radiator. I know because I went through this whole scenario years ago when metros were first launched. I finally fixed it by fitting a metro rad to the front of the mini, instantly solved the problem.
So, you need more cooling in the rad. Some form of upgraded better cooling mini rad may fix but basically you do not have enough cooling ability with the basic mini set up.

[68+86auto]

Check the timing and mixture throughout the rpm range. After sitting, it may not be working correctly.

[whistler]

The thermostat housing in the head is completely clear.

 

Going to check the timing when my friend returns from holiday. I don't have access to the car at the moment. I think that when he put the dizzy back in he used the old method of turn the dizzy until it peak revs were obtained but don't know if he backed it off a bit. Going to use proper digital timing light this time.

[pete l]

1275 A+ metro engines will overheat with the smaller Mini side radiator. I know because I went through this whole scenario years ago when metros were first launched. I finally fixed it by fitting a metro rad to the front of the mini, instantly solved the problem.
So, you need more cooling in the rad. Some form of upgraded better cooling mini rad may fix but basically you do not have enough cooling ability with the basic mini set up.

 

Why would it though ? it's exactly the same engine used in the mini.

[Spider]

1275 A+ metro engines will overheat with the smaller Mini side radiator. I know because I went through this whole scenario years ago when metros were first launched. I finally fixed it by fitting a metro rad to the front of the mini, instantly solved the problem.
So, you need more cooling in the rad. Some form of upgraded better cooling mini rad may fix but basically you do not have enough cooling ability with the basic mini set up.

 

Hmmm,,, that tends to suggest there was an issue with the Mini Radiator you were using.

From late 1979, it was the same engine as fitted to the Metro that was fitted to the Mini in the UK and our locally produced Mokes, even in 998 form from early 1980.