Hey All,

When on long and hilly highway drives (100km/h over 1hr, many decent hills) my minis temperature gauge will read up to about 3/4. Normal 100km/hr temp is about 1/2, and idle temp is around 3/8.

The 998 is being cooled by the standard 11 fin fan, copper radiator, no expansion tank.

I've flushed the system, and it was pretty dirty in there.

What's the suggested next steps? Should I take a temperature reading while the car is driving? If so, where should I mount the probe and what temperatures should I be looking for? Or is it easiest just to upgrade to an ally radiator and an expansion tank? I see some for around the $100 mark on ebay, and $150 on minisport.

Thanks in advance for any advice

1/2 on the gauge should be around 80°. If it's reading 1/2 on normal driving then there's nothing wrong, don't be too concerned about 3/4 when you're making it work hard, it's still below 100°.

I have an ebay radiator, no complaints - been in for 7 or 8 years

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did I tell you that I won a trophy?

Check that your plastic fan is the right way around.
Smooth face towards motor..

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

I just changed my 11 blade plastic fan for the 16 blade metal fan from a Mk1. Runs a little cooler on city running here in hot NQ.

Sweet - that’s what I was hoping to hear! My coolant gets pretty dirty pretty quick, but doesn’t seem to be much of an issue in regards to cooling, but I was thinking an ally eBay radiator could be the go.



It’s pushing the air through the radiator, into the guard.



True? I thought more blades were moving less air? Or did you mean 6 blade? Did you notice any difference in power?

The fan pushes air into the guard either way around, but it blows better with smooth face of hub towards motor.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

You may still have a partially blocked rad, flushing is limited in the amount of grunge it can move, the only real way to clean a rad is to have it dismantled and profesionally cleaned, they can also advise whether a new core would be a better fix.

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Cheers Dave.

It’s pushing the air through the radiator, into the guard.



True? I thought more blades were moving less air? Or did you mean 6 blade? Did you notice any difference in power?[/quote]

No, I have not noticed any difference in power.
All plastic fans I have seen on Mk2 engines have ‘engine side’ marked on the centre part.

I run the steel 16 blade fan. It runs at 180F with or without the Matic fresh air heater installed.
But on the freeway it's a little cooler with the heater (aux radiator).
Radiator is the original Matic/Mini K 16 gills/inch, cleaned out by a radiator shop.
I used to have a white plastic fan on but it threw most of its blades off.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Certainly nothing wrong with an alloy rad, but it shouldn't be necessary and I don't know that it'd make a lot of difference. I put a thick one (55mm?) in for the extra capacity when I was running a supercharger.

I think you ought to keep flushing and see if you can get it to come out clean. Run plain water in it for a while (just to save $$) and flush often to see how clean you can get it. Mine is bright green with only a slight brownish tint - motor is about 5 years old and does a lot of sitting around.

When I have a radiator out of a car that isn't already clean I take the thermostat out and clamp the garden hose into the top radiator hose then run water through until it comes out clean... The other thing I do is half fill the radiator with water, put my hands over the inlet and outlet and shake it like mad, it usually dislodges a bit of crud though as Steam says it's worth getting the radiator cleaned out professionally - however the cost difference between getting a cleaning and an alloy one off ebay is minimal these days.

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did I tell you that I won a trophy?

The Minispares three core radiators are pretty good and still look stock.
When you are flushing out the system there is a plug on the back of the block just about the clutch slave cylinder. It is worth while removing and cleaning out the block

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1969 Cooper "S"
1967 Mini Deluxe
1973 Clubman Van (the fleet spare)
1978 ex 1275 LS ("Wizard" Eaton Supercharged)
2015 HSV GenF GTS(occasional drive & tow car)
2019 MINI F55 Cooper S

before you go mad, check your grill

I have seen an ex-japan mini that half of the grill was blocked off, presumably so it would run fine in the winter, this car ran way hotter than I'd like to have seen.
however the owner wouldn't cut the blanking part out, it was part of the frame that supported the chrome slats and could have easily been removed without compromising the grill structure

my car will freeze the carb on anyway that is below 15ºC, and therefore I have to use a grill blind to stop this from happening.
I used the competition 2 core radiator from mini spares au, and can flog the car on a 45ºC day and not over heat.

it wouldn't hurt to give your current setup a good flush, and check with another gauge, just to be sure you are actually overheating

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So after flushing the radiator a bunch of times over the last few days, I went for a big drive on the freeway and pushed it a bit hard and ended up boiling the water. I was already keeping an eye on the temp, so managed to pull over pretty quick and had a pitstop and replaced the lost water - haven't noticed any issues since, but I'm definitely considering a new radiator now.

Could my advance be set a little happy? I'm not getting any knocking at all, and it was set by someone who should know what they're doing (Mini specific mechanic).


Yeah - I might have to do that now. Especially the extra gauge part - where should I mount the probe?


I'll have to have a look - I've never done that before. Any chance you could take a quick snap and post it? I'll go have a look for it now.


Thanks everyone! Very much appreciated!

jdrin. I hope that you can solve the problem without needing major surgery.
There are several different radiator caps for different era Minis and radiators. The boiling point of water at 15PSI (a common radiator cap pressure) is well over 110 degrees C, (even higher with antifreeze added). This allows the engine to run at 100+ degrees without boiling.
If you have the wrong or faulty cap on the wrong or faulty radiator (maybe bent hooks inside the neck) then there will be no pressure build up and the water will boil out at 100 degrees. Get an infra red heat gun to check the temps of the cylinder head, thermostat and radiator. Mine are usually about 85 and up to 95 if pushed. These match the capillary gauge on the dash. Have seen 105 on the dash up a long hill on a 40 degree day.
Good Luck. Dave D

You and I both, Dave.



I think there's a few things at play in this scenario:

1. My radiator is dirty
2. I was flushing it a few times, so I was only using water, and not coolant
3. I'd just changed to an expansion tank type setup, and part of that was getting a cap let the coolant expand... I probably should do away with that setup.

Thanks for the help!