hey mate,

I havent read all of the posts so if i have repeated stuff or if it isnt relevant ignore it

there are few things that can cause an engine to overheat that arent actually associated with a cooling system at all.

One: (to do with cooling system) If it tends too over heat at night time or under load ie) at high RPM, if you have a million speakers and a 20 lights on your car you can overload your alternator causing the fan belt to slip. Thus reducing the flow of air through your radiator and also minimising the heat being lost through convection.

Two: As cush said having a lean mixture could also do it

Three: If your brakes are dragging

Four: If your timing is retarded this can also effect your engine temperature.

Lack of oil also

Also,

Get your multimeter and put the negative to a good earth on the car and put the positive into the coolant in the radiator. To look for stray currents. This can corrode your radiator and cause blockages. It is often caused by a poor earth strap connection or after market/modifications additions to your car which arent earthed properly. if there is a current there should be less than 50 milli-amps.

Also is your thermostat stuck fully open? Or is it partially closed/open? You check the temperature at which it opens on the stove. Chuck it in to the pot get a thermometer and see when it opens.

Are you losing coolant?

Have you pressure tested the system and or radiator cap?

Have you thought of fitting a thermo fan?

Maybe run an oil cooler

Maybe get a heater core and put it in the direct flow of air ie mount it on thegrill You can get some out of alfas that fit well and are a decent size

But if your coolant is boiling there is obviously a problem internally ie a blockage or stopping the coolant flow or a slipping fan belt

Boiling is serious problem so i suggest you dont drive the car until you get it fixed if this is practical

Best of luck and I hope i was of some help.

Matt

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To correct the above which is pretty precise I might add, is that oil coolers will not affect water temp at road driving conditions. I'd say you have a blockage, my cooling system is very inefficient but still works, I've tracked mine down to radiator blockage and retarded timing. Curing both of those shoulf fix it all. As said above if it's boiling don'
t even let it get that far...you don't want a cracked or damaged head now do you?

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1964 Morris 850, 1330 Supercharged - 81.8hp atws.
1975 Leyland Mini S 1100S powered - Nice and reliable.
1977 Leyland Mini LS - Project LS-T

Or overly retarded at some point -

That's my case ^^ my dizzy is so old and thrashed that it has flat spoits with no good advance picks up then dies, I got 50.3 HP on the dyno at 6000rpm but was 48hp at 4500.... Due to total lack of advance, new dizzy sall prepped ready to go in next weekend I think.

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1964 Morris 850, 1330 Supercharged - 81.8hp atws.
1975 Leyland Mini S 1100S powered - Nice and reliable.
1977 Leyland Mini LS - Project LS-T

True but at the moment his engine is cooking itself. Any loss of heat will be better than nothing. Oil coolers do work best on racing engines. This wasnt a neccessity item to fix your problem just another option once you get this engine right to ensure that it doesnt happen again. You cant do as much damage to an engine running cool as you can when you over heat it



Or block, or radiator, or any other component in the engine and cooling system

When the coolant boils it cannot tranfer heats aswell when it is in a liquid form. It is much more inefficient.

Heat moves much more effectively through convection rather than radiation

When the air.fuel mixture is combusted the heat produced in the combustion chamber is transfered to the coolant. When it boils this heat can melt heads as the heat is not dealt with effectively (if they are aluminum obviously not as related to a mini) but still it gives you an indication of the temperatures. It can also warp heads among other things.

Air pockets in a cooling system can cause hotspots which occur in many places including the cylinders. they are usually indicated by a blue ish (kind of like the colour of the surrounding areas of a good fresh weld)

If there is an air pocket behind your thermostat, your engine temperature will read normal but when in reality the engine is cooking itself.

Have you got a jiggle valve/bleeder valve in your thermostat or do you have a hole drilled in your normal thermostat to allow the air pockets to escape. This is really important.

Is your fan belt stretched and or unservicable?

I will have a think tomorrow as to what else it could be

Matt

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Thanks for all the posts Guys,
I will try the electronic Dizzy and then work back through what I have already done. Im not losing coolant just boiling it. There is nothing worse than a great car that I cant take on a decent run.

Jim

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1975 Mini SS converted to a Mini Miami
1978 Clubman S
1965 Mk1 Cooper S
2005 BMW 318i (Well at least its a real BMW)
"Dont take life to seriously, you may never get out!"

Something else that is often overlooked is the little bypass hose that runs from the head to the waterpump. I have seen a few of these caked up with so much crap that no water could possibly pass through them. I realise you said you changed or checked the rad hoses but as i said this little bugger is easy to overlook.

Cheers, bryan

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1964 Morris 850 and some!!

yes that little bypass hose i got brand new ish from my local parts shop they found 2 in the bottom of a drawer along with a copper gead gasket...

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why does everyone want a Cooper S when you ca have a better Clubby

Before you spend on an electronic dizzy take yours out and get it serviced - rebuilt and tell them what motor its for, $120 or so and it may fix your heating issues. When the tappets and timing was touched on Saturday was the mixture adjusted at all???????

Steve

Nope - between the tuning and the banging (of Betty) somebody kept saying "put the spanners down"

It may be the ignition is a bit too far advanced - that will give overheating as well but it sounded fairly crisp while we weere fiddling with it.

I think the secret here is to sort out the dizzy one way or another (reco or electronic) BEFORE chasing the tail any more.

It was nudging 40 degrees here on Sunday, we went to the local car club chrissy party and then coming home mid afternoon after climbing our long steep hill both our mini and Morris 1100s were running hot and the mini never runs hot. Just the day.