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Rebuild my 1275 s and it seems to be running around 95-100 deg water temp with normal driving with the heater open with the fan running.

I have checked this by warming the sensor to known temperatures and measuring the resistance and then putting the same resistance throught the gauge to get a set of photos of the needle position for 80-100 deg.

I have got a new 11 fin per inch recored rad, 13psi cap, new hoses. Has a cooper s water pump pulley and a metal 11 blade fan, 75deg thermostat, 940 head with bypass, new minispares water pump, austin mk1 grill.

Carbs and mixtures have been set, have also checked dizzy setting. Engine performance seems ok to me, although have not yet rollered it.

Engine is only lightly tuned, ported head, 270 cam, 10:1, twin hs2. Head and block have both been skimmed. The engine at present only has plain water, no coolant so maybe that may make a few deg difference.

Is this fairly normal, I was expecting nearer 90 deg.

Thanks Dave

Actually, with a 75 oC thermostat I would expect the coolant to run closer to 80 oC than the 90 o that you mentioned. Is the thermostat new and known to open at its 75 oC rating?

I know you have done a lot of work to characterize the temperature sending unit and calibrate the gauge accordingly. However, for sanity have you tried either a thermocouple or infrared thermometer to measure the temperatures at the sending unit, the thermostat housing, and the header tank of the radiator?

Get a little prestone and a bottle of water wetter in it .................

Hi Dave,
A mixture of coolant that is too strong can cause overheating so usually 60% water to 40% coolant is about right. Maybe worth checking.

Al

My Black mk3 (1310, 286 cam, ported etc) with a 4 core rad, plastic fan struggles to get above 70, in fact im still running around with a grill muff on, temps measured with infa red gun and capilary guage

My 8 port has the same flamin issue, even at blyton we had half the grill blanked off

every other min i had was always a bugger to keep cool

pad

Start by replacing your 13lbs rad cap with a 15lbs one.

Raising the radiator cap pressure will raise the boiling point temperature but it will not lower then engine temperature.

Others hinted at this on your thread at TMF... check that your fan is on with the correct side of the blades towards the radiator.
Engine ----- ( ------ Radiator

I don't feel like weighing in on the thread at TMF. Suffice it to say that antifreeze is not designed to improve heat transfer as was suggested there. Water by itself is marginally better. Water with a surfactant (Water Wetter as suggested by Minimans) will help. However, all these changes are patches. You really need to determine if your bench calibration of the gauge was accurate and if the coolant really is running as hot as you think. You need to address the root cause of the problem, not mask it.

66S wrote:Hi Dave,
A mixture of coolant that is too strong can cause overheating so usually 60% water to 40% coolant is about right. Maybe worth checking.

Al

...yes I have noticed this when topping up in our other car... as far as a mini is concerned less is more !!mine never overheats... foxy52

I know I've mentioned this before on similar threads but dipping your castings always helps clean out the water jacket when rebuilding an engine and leads to cooler running.

Pete wrote:I know I've mentioned this before on similar threads but dipping your castings always helps clean out the water jacket when rebuilding an engine and leads to cooler running.

That's so true. There's a guy in Leicester (don't know the address but I could drive you there) who uses mega hot alkali dipping to remove casting sand from er.... pump castings. Chuck him a tenner and he'll throw your block in with a batch. 'Cannot believe he's still alive - the stink in that place must give a life expectancy working there of six and a half weeks! It's not totally perfect as it leaves the casting a dull grey that requires another cleaning process to get it ready for painting - but the main thing is it cleans out the crap left by the foundry in 1967. I tried dipping my subframes in there too but unless you neutralize the alkali, it's not good as you get salt deposits appearing from the seams for years afterwards that needs cleaning off with vinegar, lemon juice, etc.

Sorry - forgot the main OP topic......unfortunately, asking for tips on keeping your engine cool is akin to asking Swifty how he makes his engines so powerful - he won't say because keeping the water temp as close to 70degC as you can, gives max power!
What I can tell you is that it's lots of little things that amount to a lot!

Hi,

Thanks for the replies. I realise I need to get to the root cause rather than "patching over it".

I put a temp sticker on the top of the head as soon as I got home from brighton, before the engine had time to heat soak too much and that only just blew the 93, the gauge was just onto the H, which according to my bench testing was around 105. It was running cooler on the gauge when actually travelling and yesterday was very hot in the afternoon.

Played around on the way down to brighton, didn't seem to make much difference if the heater was on or off, or with the fan on.

I think I need to run another test on the gauge as somewhere along the line, i think that has gone wrong. Ill see if I can find some temp sensors to borrow, either a capillary or an infra one. I think ill stick some more temp stickers on and see what I get. I think initially I was too confident in my gauge after the tests, which put me on the back foot i think.

All the basics are there, head was clean, block was clean, new pipes, rad, thermo, so its not like it is full of 40years of crud. Water level remains constant and not "blowing". Cowling is good and the fan is round the right way, i believe, although the fan becomes useful below something like 30mph i thought.

Hopefully it is just a badly calibrated gauge and I was having a little panic over nothing.

To imply the obvious seem ridiculous, but obviously the heat from the engine is not transferring to the air blowing past the radiator.

Check air coming out the radiator. Is it hot? Is the bottom hose cool? Most importantly, is the water pump actually circulating the water? Is there a large temperature difference between what is measured at the outlet of the head and the top inlet to the radiator? Is the cooling water bypassing the radiator through the bypass hose or heater?

You can use a cooking thermometer to test the radiator top tank temperature.
You should see the water in the radiator tank flowing - rather fast at slightly raised engine speeds, say 2000 rpm.

Is the gauge powered up via the voltage stabaliser? I had one many years back doing the same and that's all it turned out to be.

I've also found in recent times that the current range of temp senders (transmitters) seem to have the wrong resistance and also show a Hot reading when all is well.

Hmmm. I had a 1340 with a 286 and a minispares 2 core rad and that ran pretty cool. It would barely break 3mm off the cold line. If I was stuck in traffic on a summers day, it would go to about halfway and that would be a "PUT THE HEATER ON AND OPEN THE WINDOWS" moment!

I never liked the standard electrical gauge. I prefer a mechanical gauge. I know it's not original but at least it will keep your mind at rest.

John Bull wrote:I never liked the standard electrical gauge. I prefer a mechanical gauge. I know it's not original but at least it will keep your mind at rest.

True. You may have to forgo originality for reliability

I've found both types to be as good / bad as each other. These days I run electric as surprisingly I've had fewer problems with them, maybe I'm just lucky. I do check the gauges though for repeatability as well as some semblance of accuracy. Then once fitted get to know how that gauge normally behaves in that car, generally ignoring the actual numbers. Then when it reads outside the 'normal zone', go looking.

dklawson wrote:Raising the radiator cap pressure will raise the boiling point temperature but it will not lower then engine temperature.

Shows what you know then doesn't it.

Smiffy wrote:

dklawson wrote:Raising the radiator cap pressure will raise the boiling point temperature but it will not lower then engine temperature.

Shows what you know then doesn't it.

dklawson is spot on here. If everything is right with the engine and cooling system, you can run without a cap (ie, non-pressurised).