My mini sits at about 3/4 up the gauge in 35 degree temps, it has a new engine with new water pump, big performance 2 core radiator and fresh air heater fitted. Laser thermometer shows peak temp of 95 degrees for the top radiator hose. Is this too hot? Is there anything else to do to keep it cool?

Check the timing and mixture? Lean = hot.

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Its getting up there, but no its not too hot yet. As long as that's as bad as it gets. I have a 93 degree thermostat in my 1275, I've been meaning to drop a lower limit in but haven't had an excuse to open it up. I went for a drive today in the 38 degree heat and it was fine.

As it was 38, whats the chances it was just running hot?

Above 100 is where you start getting worried, and 104 is the usual limit.
The rad fan on my YZF1000 doesn't come on until 104 is reached when stuck in traffic.

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

Is there a radiator that is big enough to ensure it won't overheat under any circumstances?

no - you could probably fill the whole car with water and use it as a radiator, and if something was wrong enough, it'd boil all of it eventually

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did I tell you that I won a trophy?

Im not running a thermostat in my 1275 and have fitted a high fliw water pump and new aluminium 2 core radiator. It runs fine in any weather. Will have to out a thermostat back in for winter this year as it tskes for ever to warm up the engine.

Rodney

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The best part of fixing your mini is the test drive

Minis..

1976 van daily drive
1975 van
1968 deluxe in the shed
1967 deluxe high strung 1310
1959 austin healey sprite

I don't think anything is 'wrong' as such, the car doesn't boil coolant and it doesn't seem to go above three quarters on the gauge.

Will taking out the thermostat improve cooling?

Taking out the thermostat improves flow but you need the blanking sleeve too.

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The best part of fixing your mini is the test drive

Minis..

1976 van daily drive
1975 van
1968 deluxe in the shed
1967 deluxe high strung 1310
1959 austin healey sprite

A working thermostat is a lot better than a blanking sleeve or not running a thermostat at all.

Getting the water to move faster can actually reduce the heat transfer and cause it to run hotter.
Not running a thermostat can make the water just circulate mostly around cylinder 1 and the other cylinders get progressively hotter with number 4 overheating badly.
The temp gauge is located at the cool end of the head!

I agree morris remving the thermostat will make the water circulate around number 1 hence the need for the sleeve.

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The best part of fixing your mini is the test drive

Minis..

1976 van daily drive
1975 van
1968 deluxe in the shed
1967 deluxe high strung 1310
1959 austin healey sprite

When I had my engine stripped down to bare bones at the start of the rebuild I spent a week of evenings cleaning the water jacket with welsh plugs out - you wouldn't believe the amount of crud, casting sand, slag and bits of wire that came with a lot of poking, scraping and wire brushing - most from around the #4 cylinder too.

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David L


My greatest fear in life is that when I die my wife will sell my Mini and tools for the price I told her I paid for them!

If you engine is in correct tune (ign timing & carb mixture)

& as long as the fan belt it tight

& if there is no leak from the head gasket, nor crack in the head

& if , as you say, everything else is in good order

then it shouldn`t be running hot at all

but simply becasae you have stated all this already & it`s still running hot then -->

You can try the old trick of blocking off the original by-pass (btween water pump & cyl head)
& making a new one go from the back of the head & take it to the top tank of the radiator

we have a fitting welded into the top tank of the rad & simply use the std issue water outlet (normally for the heater) & Bob`s your Aunty

but,,, it seems to me that one or more of the above issue may still be playing with you

or your temp-infra-red thingy is not reading acurately

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No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.

You may have a new radiator, but how long has it been since the block has been flushed? There might be enough gunk inside to be restricting the coolant flow. I had to give mine a really good rinse with a radiator flush, because the previous owner had just been topping up with water - first drain and it was like mud!

Yes, taking out the thermostat can fix the problem (definitely better than overheating!) but really you're just covering an issue that shouldn't be there in the first place.

My suggestion would be to take the thermostat out and test at what temp it starts to open and when it is fully open. Just put it in some water on the stove with a thermometer and watch as it heats up. If it's fully open before 80 degrees, then seeing as you are getting 95 i would say you have a problem, but if it's fully open at 90 then i would say your engine is fine, but you might like to put in a cooler thermostat.

New engine you say. I would flush the radiator out before trying anything else. New engines have a habit of releasing a lot of pieces of crud/rust scale from the coolent passages when first started. Those pieces sit in the radiator cores and block them up, reducing water flow through the radiator.

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1963 Morris 850