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MG Midget and Sprite Technical - Aluminium Radiators

The temperature gauge on my 1500 quickly moves past'N' heading for 'H' when the car isn't moving, so driving in hot weather/heavy traffic can be a challenge...

BACKGROUND: I'm running a Kenlowe fan with Revotec thermostatic valve (with timed manual overide switch) AND a Revotec inline-fan blowing fresh air onto the carbs (when the Kenlowe fan is running) to help prevent fuel evaporation (that's the theory anyway) AND I have an thermostatically controlled oil cooler AND I've moved the number plate (onto the bumper) to increase air flow.

An LCB manifold hasn't helped... Also and the engine produces 85 BHP (thank you Peter Burgess) so that might be a factor too.

IS IT WORTH FITTING AN ALUMINIUM RADIATOR?

Any recommendations or advice gratefully received.

Thanks, Michael
Michael Davies

Hi Michael.

Yes if your current radiator isn't up to much or is clogged up with crud and if the ali rad has more cores tubes that the original and isn't expensive.

I might be wrong, or forgot, but I can't remember seeing anything to say the ali was better for cooling in itself, racers use them because of the weight saving.

A mate go a cheap Chinese (new or s/h I forget) ali rad and said they all look the same, perhaps all are the same, but for whatever reason he was very pleased with its performance on his modified 1275.

If there is any crud in the engine block and heater matrix that may not be helping with circulating the cooling (or heating).

Is the Kenlowe in front of the rad or behind it?

Have you checked it's turning the right way or facing the right way (to be efficient)?

Do you have an engine fan still.

Is your rad cowling standard, fully intact and not modified?

I offer a simple and thorough cleaning set of notes, most find them over the top and don't seem to bother or not fully but a couple have and even reported back with good results from them (all very simple stuff, just thorough). Just email me if you want a copy of the notes.

Needing a fan to keep the keep the carbs cool has me wondering, if your visit to Peter was before these issues -
are you running lean (on E10 petrol)
have any sort of exhaust partial blockage
brakes too tight or catching.

Two fans putting extra load on a worn alternator taking a bit of engine power and further warming the engine.

Nigel Atkins

Hi Nigel. Thanks for your thoughts. I was under the impression that aluminium radiators we more efficient - at least that's what various manufactures claim!

The rad is in good condition (clear of crud) but the heater matrix is the 46 year old original and I probably last flushed it (as in removed and flushed) 20 years ago. So that might be worth trying.

Kenlowe is in front and turning the right way. Original fan is still fitted. Cowling is standard. I use E5 (premium) most of the time. Post PB tune the engine runs richer at low revs so as to produce max power at higher revs (previously it was lean at mid to high revs). So it's now more sensitive to heat when ticking over; I have it set to 900-1000 revs because of the cam (Road 83). It's uneven at 700-800 (or less). But shouldn't increase the engine temperature - or could it?

Exhaust isn't blocked. I'll check the brakes, but this is a long term problem, so I'd be surprised if that's the issue.


Michael Davies

I had an aluminium rad in my MGB V8 and it was a disaster as it leaked from where the tubes enter the tanks. I took it to a radiator specialist in Glasgow and he said it was almost impossible to repair as the tubes are not sealed into the tanks in any way. They are just a good fit. He said copper/brass rads are better at heat exchange and can be repaired. So I swapped for one of those.
Mike Howlett

I found with the fan in front of the rad a very surprising amount of debris got held at the Revotec fan and its mounting brackets, even within a couple of years so a good careful clean out of the existing rad fins and around the fan could be helpful.

Any chance the Kenlowe fan is not working well with the engine fan? ((fairly) easy to do smoke tests)

Is the engine fan standard?

You appreciate overcooling and slowing warm up so once sorted you might want to consider removing the engine fan which may help a tiny bit with tick over.

Nothing wrong with 900-1,000 tick over if required, and do you know if your tacho is correct with that reading (or others) anyway.

If you get things sorted you may want to go the other way and remove the electric fan if you don't use the car in the winter (and miss some of the best driving days).

Have you ever cleaned out the engine block coolant drain hole?

If you run warm perhaps a better quality oil will help offer better and further protection and possibly run a tiny bit better too.

Are you sure you actually have an issue, is your gauge accurate and if it is H is just 'Hot' apparently you can get the needle into the oil pressure on the dual gauges (but I think best to have some margin).

I had a LCB manifold that had a bit of weld partially block the head port apparently not uncommon.

Got to go, tea time (or dinner if yer posh).
Nigel Atkins

Shouldn't really need it if your setup is in good working order IMO.

I drove my 1500, which has a standard rad, for two hours on the day when it was 40+ and the world was going to end.

When moving, temperatures were OK. When stopped it did start to get hot and the fan came on (a 7" electric "blower" and no engine fan) which was able to "maintain" temperature but not powerful enough to "cool" things, but once moving again it clicked off eventually.

However... I did have the heater on (blowing into passenger footwell) and have some small vents (six or so louvres) on bonnet and each wing, oh and no bumper! But it was a pretty extreme ambient temperature test.

Outright HP figure isn't that relevant unless it is a racer and you are driving full chat all the time. A midget with 200hp or 50hp will only be using 30hp to cruise along (random guesstimate figures! ) and chucking out a similar proportion of useful power as heat. Is it approx. 1/3 that is lost to the cooling system? I forget.

Hope this helps.
Cheers,
Malc
Malcolm

50% coolant + 50% water, and a deep impeller pump cured my cooling problems

Flip
Flip Brühl

Well I didn't get to if the bumper is removed or what is the coolant, got distracted and forgot the pump, but I'm glad Malc made the other points too.

Yeah about a third IIRC and a lot, lot less than 30hp if you're just steady on a level straight.

And I think there's something else I forgot but as I can't remember it I' don't know, pressure cap would loose coolant, so perhaps the dreaded.
Nigel Atkins

Hi Michael,

"The rad is in good condition (clear of crud) but the heater matrix is the 46 year old original and I probably last flushed it (as in removed and flushed) 20 years ago"

Even if it flushes clean, it doesn't mean the core is clear. My old vertical flow rad always flushed clean, but my Sprite began to overheat without using my electric fan. Turned out the core was partially blocked.

Recore was more expensive than a new one. So I converted to a crossflow (regular not ally) with a bigger core; and now I have to keep a 180 stat in all year round, and removed the electric fan because it wasn't amymore.

anamnesis

Michael
If you have the std fan, an electric fan x2 and it overheats idling there is something drastically wrong
my first thought is the thermostat has stuck or is the wrong heatrange-- it is supposed to be 74deg. same as an MGB
The other thing is-are you 100% sure your electric fan is blowing in the correct direction(towards the rear)
The arrows on the blades might say so but it depends on how it's been wired up---seeing as you have an override switch, just turn that on and make sure it's blowing towards the rear of the car, not out the front-
willy
William Revit

Hi Mike, you know my car.

Standard 1500 engine, maniflow 421 exhaust and K&N airfilters with richer needles. No bumpers.

I dont run an oil cooler, or an electric fan. Cooling system is standard with just the fan running off the engine. Standard radiator.

I dont have any problems with cooling. On one of the hottest days of the year, with the car idling the needle moved a little and stayed in the middle of the gauge. In my opinion the standard setup is adequate if its working optimally.

I would suggest giving the cooling system a really good flush first.
Chris Madge

Michael Davies, like others I too suspect your thermostat and defenetly your radiator!!
Or an airbubble...?

Like Mike Howlet I went from aloy back to copper/bras.
Two aloy rads started leaking by (salt) corrosion and they are unrepairable...
Copper/brass handel salt much better and its painted black so that "protects" too

My Radiator specialist explained that aloy cools better on high speeds but I never had heatproblems while driving normal or fast)

On photo my last aloy rad and my 1978 Jaguar xj6 radiator :)



A de Best

After overheating issues several years ago, I found clearing out the blocked water ways in the engine block made a good improvement on my 1500 as Id always flushed the pipes out missing out removing the bolt on the engine under the carbs and found this full of years of corroded rubbish.

Also adding an aluminium radiator made to order from a local company Coolex in Nottingham made an improvement, they can adapt the rad to your requirements and were very reasonably priced and I was safe in the knowledge that if anything goes wrong they are not 1000's of miles away in China.

On a slightly different but heat related issue, I had a new 4 to 1 Maniflow manifold coated in Cerakote hoping to reduce any fuel vaporisation issues which it may have done slightly but not as well as hoped.
Tim Lynam

Its a fact that the thermal conductivity of brass and copper is miles better that aluminium. So if a radiator has the same number of cores then a brass/copper will be superior (provided its not crudded up).
A former colleague of mine tested the comparison on his Stag in the wind tunnel And as expected the copper/brass provided much better cooling than aluminium.
As has already been said the reason aluminium is used on modern cars is cost and weight. The tubes are soldered into the end plates on both types. Horizontal tubes have proved less durable than vertical if the air flow across the rad isn't uniform top to bottom. (the tubes in part of the rad expand more than the rest).
Paul Hollingworth

Willy,
you remembered 74c but again there's the difference in countries and continents, we generally use 82c here or some run 88c in winter, or all all year round. 74c might be tried more in future UK summers.

I'm as always with you about prevention being better than cure by stopping the heat build up rather than trying to deal with it. Trying an 88c stat (twice) was the only time the needle on mine went above the 'N' other than on heat soak from switching the engine, even then even on warm days the needle would be near the 'C' after a stop for hydration.
Nigel Atkins

Lots of interesting thoughts - thank you - and many not what I'd expected; I thought everyone would be singing the praises of aluminium radiators... Unusually, whenever I visit this site it leads me to spending less money on unnecessary upgrades, and for that I am grateful.

I had the temperature gauge rebuilt ages ago, because it barely moved off C, and it behaved normally until I fitted the Maniflow 4-2-1 exhaust manifold (ceramique coated as is the inlet manifold), when it started to swing round to H when stuck in traffic. It returns to just below N quickly when the car is moving

The electric fan is definitely spinning the right way, and I'm sure the thermostat is 'standard' (82C), but I will check. The block is also NOS. The only really old part is the heater matrix, but it seems unlikely that that alone would cause the issue.

Perhaps all I need to do is fit a 74C thermostat??
It's certainly a lot cheaper than a (SERCK?) aluminium radiator!

Michael Davies

As Willy put you want to check the stat isn't stuck shut.

Putting a 74c stat in would be avoiding the issue rather than solving it. The 74c stat would be fully open at possibly anything from 80.5c to 86.5c coolant temperature so offering no control above this range.

Unlikely but perhaps crud from the matrix could migrate to clog elsewhere, what about as Tim said the engine block at drain point.

How is the coolant level and colour in the rad, any gases, HGF isn't always instant boiling or mayonnaise.

Ceramic coating on the inlet and outlet manifolds could this perhaps cause the cylinder head to hold more heat -
"I had the temperature gauge rebuilt ages ago, because it barely moved off C, and it behaved normally until I fitted the Maniflow 4-2-1 exhaust manifold (ceramique coated as is the inlet manifold), when it started to swing round to H when stuck in traffic."

Have you checked the temperature of the head compared to a non-ceramic coated manifold(s) head?

Nigel Atkins

Mike your last post doesnt mention your water pump?

Obviously it needs to function well as part of the cooling system.....
Chris Madge

Chris, that’s an interesting point! As far as I’m aware the water pump is the original item and the car had done 99,500 miles.

I clearly need to inspect every item…
Michael Davies

This thread was discussed between 30/08/2022 and 01/09/2022

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