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MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG Midget and Sprite Technical - More cooling issues

I thought I had this cracked, after I got the dizzy timing sorted by H&H Ignitions. But the hot weather shows that I haven't. Last week I wondered if it might be running weak, so I tweaked it up a bit on the HIF44. It then ran about 10ºC cooler. Great thought I, that was the problem. While I had the plugs out for a visual check I fancied the gaps looked too small and I was right, I had got the conversion factor wrong last time. So I reset them correctly, and while I was at it checked the idle timing again. Somehow it was back at 5º BTDC when it was 7º before. So I reset that and checked it again after locking the dizzy. And yes, I did do this with the vacuum advance disconnected and the port blanked off on the carb.

I did a 20 mile run first thing this morning and back late morning. On the second leg a brief burst at 70 put the temperature up to 95C. This means the electric fan is on most of the time.

I have been running A series engines since 1967 and normally they seem to be overcooled rather than under. I do not know how to fix this. The radiator has been recored twice in the last 20 years, and I have recently cleaned it with Prestone twice. The mixture strength is I think OK, from a plug test. I have tested the thermostat and it opens at exactly 85C.

I know you were all going to say get it on a rolling road with an expert, but here in Salisbury that seems to be impossible. I have used the one at Janspeed but they have no expertise on these engines now and the session was done by a young lad who was quite knowledgeable but to my mind not enough. I need somebody who knows these engines inside out, and has for example a stock of carb needles so they can experiment. I used Brian Slark years ago but that business has moved to Bristol. I wasn't greatly impressed anyway. Peter May would be the best I believe, but I really can't drive to the Midlands.

I think I have shown that it is possible to get this engine to run at a reasonable temperature, but I can't work out what has changed since then so that I can reproduce it. I suspect that the mixture is weakening at about three quarters throttle, but that is just guesswork. Today the weather is so hot that the engine boiled after turning it off. It really should be able to cope with varying weather conditions.
Les Rose

Having chatted to my race engineer friend Dave, it seems an alloy rad might be the answer. The original style aluminium one for the Frogeye is hugely expensive - £500 + VAT from Peter May. But May also says that Metro alloy ones are used on race Spridgets, and they are only £50 + VAT. I'm seriously tempted. I would need a remote header tank of course. Has anyone tried this?
Les Rose

Les, I forget, have you changed from 4 to 6 bladed fan?
GuyW

I had an overheating problem and I ended up having a new core fitted to my original rad.
On my 1965 it came with 66 channels and I paid for Arrow Radiators in Bristol to upgrade it to a 99 channel core.

Before this I’d flushed it so many times with all sorts of things as well as water. Checked the timing, thermostat, water pump, coolant mixture. The list goes on. Nothing made a difference. Just kept getting hotter and hotter, in traffic over 212F

Since I’ve had it done it doesn’t overheat at all. It works in perfect sync with the thermostat. I took it out for over an hours drive in the heat and it didn’t get hot at all. I was even stuck in a bit of traffic and it rose to 195 max, but immediately cooled as soon as I started moving again.

It cost me £270 to have the work done that includes a little welding, rebuild with new core and painted and pressure tested.

Moss sell the original 66 core for £240 and as you say the aluminium one is over £500.

The guys who did the work said the channels get furred up and there is little you can do to properly clear them out.

They also said the 99 channel core increases the efficiency by about 30%.

I’m not planning on racing hard, but now I don’t worry about it overheating anymore.

Also I’m running the four blade belt fan, so no electric.
James Paul

I have no engine driven fan, just the electric one. I have run the car with this for nearly 20 years, and only saw the temperature rising last year. That was with the old engine, but it's the same with the new one. Presumably the change to 66 core will only be for later crossflow rads? Mine is of course vertical flow.
Les Rose

Les,

when you say the old engine did overheat and the new one to0 then my guess would also be the radiator/thermostat as first suspects.

I had an alloy rad for my Kseries engine in my midget and wore two out by corrosion (wintersalt?)
My rad guy said aloy only cools better on high speed,
so my new(3rd!) is and standard(copper/bras?) one but with bigger core.
Standard temp is a wee bit(2/3C) up now then with the alloy.


My heating problems are different.
Never had problems when driving despite some heatfull conditions (heatwaves, trackdays and so on)
But when in realy slow moving conditions or trafficjam is slowly creeps up to 110 - 115C.
Cools down again when moving to normal speeds.

Second engine the same (or both engines had blocked coolchannels?)
3rd raddiator now a brace one
Several new thermostats since
2nd coolfan bigger/stronger one.
Added louvres to the bonnet for better loss of heat when standing still.
even changed to Evans coolant

Frustrating that temp still runs up so easely despite all the changes ive done over the years.
Should be fine now but isnt so thinking of getting more stronger/better fan but a spridget leaves not much room for bigger radius fan.

Someday it will be solved, im not giving up, some day! LOL!!

A de Best

How about an Ally rad from these people? 167 quid plus vat. Or have them redo yours with a larger core.

https://www.coolexperts.co.uk/motor-vehicles/classic/

https://www.coolexperts.co.uk/product/mg-midget-healey-sprite-1964-1974-aluminium-radiator-high-performance-42mm-core/#spec






anamnesis

Les,

I clean my cooling system by dissolving a washing-up block in the cooling water (without antifreeze) and driving for some time. Then I rinse the radiator with a garden hose in the reverse direction. Please note that this method is not suitable for a cooling system with aluminum parts. Water wetter also lowers the cooling temperature slightly.

Flip
Flip Brühl

Not Midget related but I agree with Flip. Or nearly. Instead of the dishwasher tablet I used the dishwasher powder that I cadge from the local hotel.
The advantage is (as Flip will probably confirm) that dishwasher soap is designed not to produce foam.
Transit Connects with the 1.8TDI engine are notorious for blowing oil coolers so that the coolant system is fouled with oil. Dishwasher soap flushes it out all right, plus all sorts of other crud.
Veering slightly off topic... sorry fellas, as you were...
Greybeard

Thanks Anam, but I suspect these rads are only crossflow and I need vertical for a Frogeye. I can't remember the change over point - was it later than 1964? If I have to change to crossflow I might as well go for the ultra-cheap Metro rad.

Flip - good tip, but the thermostat elbow is aluminium and subject to corrosion. Mine corroded right through, in the absence of any unusual chemicals.
Les Rose

My 99 core is fitted to my vertical flow 1965 MKII


James Paul

I also tried the dishwasher tablet and it did remove a good amount of crud, but not enough to stop the overheating.

As said the 99 core has made a massive difference.
James Paul

I've emailed Coolex because they don't show what the rad looks like. They appear only to offer one type. Can someone tell me when the factory changed to crossflow?
Les Rose

1968 ISTR
Do you not have a local radiator specialist in your area who can recore your unit as James did ?

I have also used Arrow radiators in Avonmouth to clean a contaminated boat diesel tank and had good service.

R.
richard b

No, the nearest radiator specialist is 25 miles away, and I can't have the car off the road. We used to have a good one here in Salisbury but that was 40 years ago. It is rather an automotive backwater now.

Odd that Coolex only offers one type, they don't say what it is, and if it's 1964-74 it could be either.
Les Rose

Les. Then the 99 recore that James had done by Bristol, seems the best solution.
anamnesis

Hi Les,

Arrow radiators only took a day to do the work.

Drop off Wednesday afternoon, picked up Friday.
Just got back from a 40 mile round trip to the pub. Ran like a dream!
James Paul

Another vote for Arrow radiators at Avonmouth. He re-cored my Frogeye original rad.
Bill Bretherton

Are you running an oil cooler?

In the sub-tropics here in Australia, it is essential to have as a minimum a 10-row oil cooler on a standard 1275. With any level of performance upgrade (fast road cam), I find it necessary to have a 13-row oil cooler.

For race engines here, it's not uncommon to run 16-row or larger oil coolers.

The oil carries away as much heat as the water in an A-Series engine (around 11% each). Both systems need to be uprated for sustained highway speeds or you will see the temperature rise gradually until it gets out of control.

Electric fans are of no help if road speed is above 15MPH and may actually reduce airflow through the radiator at highway speeds.

BTW - all 1275 Midgets sold new in Australia were fitted with a 10-row oil cooler as standard equipment.

I have owned and tuned my own 1275cc Midget since 1983. I run lean needles and hotter plugs and 10deg BTDC static with a re-graphed Dizzy to compensate for higher density "modern fuel" (designed for fuel injected engines).

The attached diagram is NOT an A-Series engine, but you are looking at very similar values in a A-Series.

Tony
The Classic Workshop
Black Mountain QLD
Australia



A L SLATTERY

"Electric fans are of no help if road speed is above 15MPH and may actually reduce airflow through the radiator at highway speeds. "

I've often thought that might be the case.


"BTW - all 1275 Midgets sold new in Australia were fitted with a 10-row oil cooler as standard equipment. "

Interesring. I didn't know that. Where did the factory fit it?
anamnesis

I don't think that statement applies only to electric fans. Above 20 mph the air flow through the radiator is by forced airflow - the cowling around the 'upstream' side (front) adding considerably to the efficiency of this. Forward movement of the car forcing air through the rad. Anything in the way reduces this, including the fan blades of either electric or engine driven.
I asked earlier if the fan had ben upgraded from 4 to 6 blades. My suspicion is that adding the extra blade may well improve its pulling power (!) at lower speeds but then eventually at higher speeds it could start to be a greater obstruction than a 4 blade.

I would also imagine that although an electric fan would obstruct the air flow, the fan will then spin quite freely and create less of an air brake effect than a belt driven fan off the engine.

I think some of the later 1500 use a viscous clutch fan but I don't know why or what that does.
GuyW

Guy
The Volvo 200 and 700 series cars had viscous coupled fans. AIUI the fan slowed down as revs increased because, as said, the "air ram effect" takes over at speed.
Bill Bretherton

Tony, I have a 9 row oil cooler. My engine is 998cc and putting out about 70 bhp. I have had this setup for at least 15 years, and only noticed overheating about 2 years ago. Today I put a dishwasher tablet in the rad, if that doesn't help what about descaling with vinegar? The heater doesn't do a great deal, so I suspect that is scaled up also.
Les Rose

Les,

I'd keep an eye on any aluminium components in your cooling system, water pump and thermostat housing, as they'll react with alkali materials and dissolve and produce hydrogen gas which will pressurise your cooling system.
David Billington

I just spoke to Coolex. They don't have any in stock as they have to do another production run. This will take at least 6 weeks, and they only seem to produce crossflow units. Generally they seem very clueless, as a crossflow rad will not fit a 1964 car as they claim. They don't maintain their website and they don't answer emails. To be honest £200 is a lot for a simple crossflow rad when a very similar Metro one is £60.

Google told me about B&J Radiators Salisbury. This is a lie, they are not in Salisbury they are in Manchester. Their website has pasted my location everywhere it possibly can just to suck me in.

Google also found Car Radiator Repair Andover. This is also a lie as they are just a garage. They don't do any repairs they just replace things: "Book the car in and we'll tell you how much it will cost".

So it's down to a Chinese one at £200 or convert to the Metro one for about half that. No doubt the Metro one is also made in China - what isn't these days?
Les Rose

Video of classic radiator being rebuilt:

https://www.aaronradiator.co.uk/video-page/
Tim Carter

Les
Salisbury has very hard water apparently - but I guess you know that! Do you use normal tap water in your radiator? You said it had been re-cored twice in the last 20 years so I'm wondering if limescale is building up very quickly. Or do you have a water softener?
Bill Bretherton

Yes Bill, having lived here for 53 years I'm well aware of how hard the water is. And yes, I usually use tap water but I don't think I should. You really would think that an expensive cleaning product like Prestone would deal with limescale, but it doesn't. This is why I thought about descaling with vinegar.
Les Rose

Hi Les,

I've spoken to Arrow in Bristol and they said if you post it to them they'll upgrade it and post it back within the week. Shouldn't be more than £10 using a courier.

Failing that they said to try Rayson's in Yeovil who might be able to collect it and return it.

https://raysons.co.uk/#repairworkshop

James Paul

Les,

Maybe pick up a donor radiator cheap and get that reconned/upgraded by the specialists mentioned.

Somebody on the board must have a spare old vertical flow in a shed somewhere ?

R.
richard b

Thanks James and Richard, but I have bitten the bullet and ordered the Chinese aluminium one at £190. I am simply not going to pay £500 for a very similar product. Yesterday I pulled out the heater matrix and filled it with vinegar, mainly as a test for lime scale. There was no fizzing, so I remain unsure that scale is the main problem. I'll report back shortly.
Les Rose

You seem to have focused on the radiator as being the problem.There is some minor discussion about having an oil cooler, but no discussion about whether it may be plugged and itself in need of a good cleaning so that it operates effectively. There is talk of a rebuilt engine, but no information about how the block was cleaned and prepared before the reassembly started.There is mention of a thermostat, but only that it is open (to what extent not noted) at about 85 deg C. No real discussion of what is being run as coolant, nor what may have been added to it to make it operate more effectively. There is talk of the distributor being "sorted", but no information about whether it is been fully tested after mounting to the engine.

Thermostat. This controls the lowest possible operating temperature. When the engine has reached full operating temperature, it should be no lower than the rated opening point of the thermostat. If it is, it indicates some form of over cooling situation, something that was common during the winters when I lived in Germany, but seldom encountered now that I live in the desert. The thermostat should begin to open at its rated temperature, as measured in a pan of water using a good thermometer, and should be fully open ten deg F beyond the initial opening point. You have to check to ensure it is fully open and not impeding the flow of coolant. A lower opening point thermometer may, or may not, lead to a lower overall operating temperature--its only function is to set the minimum operating temperature that the coolent operates at.

The coolent can be mixed at other than 50%-50% mixtures. Water has a cooling value of 1 while the common anti-freeze has a coolent value of .6--it is only 60% as effective in transfering heat as plain water is. Only distilled or otherwise purified water should be used as part of the coolant. Scale is only one of the things that can be caused by the use of tap water. If using less anti-freeze, you need to ensure the block is protected from freezing. Tables can be found that will show the levels of protection available at different mixtures. The use of "Water Wetter", a flow modifier, is often a good thing regardless of the exact coolent mixture.

The block, both the water passages and the oil passages, should have been cleaned out before the new engine was reassembled. If not, there may be scale and "crud" which insulates the coolant from physical contact with the block. This reduces the ability to cool the engine, sometimes quite significantly. Removing the brass oil plugs and inserting either new ones or brass plumbing plugs is more work, but the better results make it worthwhile.

Distributor. If the engine is relatively standard, the standard advance curve of the factory distributor should work well. If the engine has been modified, a modified advance curve may well be required and this can only be worked out by actual testing on a chassis dynomometer (rolling road), then the distributor needs to be rebuilt to the required specification. After the distributor has been modified (or simply rebuilt back to original specification), it needs to be installed on the engine, then the advance curve needs to be plotted by using a tachometer (one more accurate than on the car) and a dial back timing light to verify, exactly, the way the engine is timed and what the advance curve is as compated to the specified (factory or custom) curve required. Both excessive advance and excessive retardation will cause the engine to run excessively hot.

One thing to consider when building an engine is to use a dial indicator (clock gauge) to exactly determine when the cylinders are at top dead center. Then, to compare this to where the timing marks are to see if there is a difference. This is especially necessary if one has a harmonic balancer which, over time, may seperate into two sections which have moved out of alignment with each other. After I have verified the accuracy of the timing marks on the perifery of the harmonic balancer, I run a single white line from the center to the outer edge--a visible indictor if it should start to delaminate. Unless you know, by testing, that your timing marks on the harmonic balancer are correct, you are, at best, guessing as to your timing.

One more common thing that could cause the engine to run hot, especially after being run for several miles at road speed, is the fuel mixture. There are portable fuel/air analyzers, called a "four gas meter" or a "five gas meter" which can be used to determine mixture strength while the car is in opeation on the road. An excessively lean mixture will cause the engine to run hotter than a richer mixture would.

There may be no single cause of the problem discussed. Rather, there may be several components that, together, are causing the problems that are observed. Through diagnosis is needed, to define what the actual causes of the problem may be, before throwing money at the problem in a random manner.

Les

Les Bengtson

Les, the reason I am looking at the radiator is that the engine setup generally has not been changed significantly in the last 20 years, and the overheating only arose recently. But to answer your questions....

I fitted the oil cooler about 15 years ago because the temperature went up on track days in the summer. It was not needed most of the time, so for general road driving I don't think a blocked cooler would make much difference.

The cylinder block was prepared by a very reputable company, and they confirmed that it had been thoroughly cleaned in their degreasing and descaling tank. They cleaned out the oilways and fitted taper plugs.

I normally use blue antifreeze at 30%.

I tested the thermostat and it fully opens at 85 degrees C.

In the absence of adequate rolling road expertise in my locality, the best I could do was to consult renowned A Series tuner Keith Calver and have the distributor modified and tested with his sports advance curve.

When I built the engine I checked all the piston heights with a dial gauge and machined the pistons appropriately. I reset the TDC timing mark on the damper pulley.

I have only been able to check the fuelling via the plug colour, which is not at all ideal. Two years ago I did have a rolling road session, and the technician found the mixture was correct across the whole rpm range. However he didn't have the expertise to do anything to the distributor, which is why I've had to find a solution for this myself. I would be interested in a fuel/air analyser which I can use on the road.

Les Rose

Well the new aluminium radiator arrived. It is very well made. The welding is really neat, the material looks good quality and the filler cap and drain tap are much better quality than original. The problem is that of course it doesn't fit. The core is much thicker, so it's impossible to insert the radiator between the chassis stanchions and the steering rack. The item was advertised as suitable for a Frogeye Sprite, which is clearly wrong. I thought all the vertical flow radiators were the same. Am I wrong? Do later cars have more space in front of the steering rack? I would need another 20 mm to get this thing to fit.
Les Rose

There's several negative comments about Coolex (Nottingham) which is understandable if their communication was found to be poor but myself and several other local MASC members have purchased aluminium rads from them without any issues.
But being local it was easy to call in and explain my requirements and collect a couple of weeks later when produced, it was a bit awkward to fit on my 1500 as size slightly different but it sorted out my overheating problems and still happy with the results several years later.
Tim Lynam

I'm sure Coolex products are fine if they actually had any in stock, and they were made for my car.

Tim, would you do me a favour please? Just measure the gap between the rad front and the steering rack. On my car it's 70mm.
Les Rose

Hi Les,

On my MKII 1965 the gap from the form of the radiator to the steering rack mounting bracket is 70mm.

But it’s a little more than that to the actual body of the rack, more like 80mm.


James Paul

Thanks James. So the space available is exactly the same as on my Mark 1. The new rad measures 84mm from front to back of the core. But it never gets that far as the lower hose spigot sticks out too far and catches the main body of the rack. The only way to fit is would be to remove the rack, but then with the rad in place you could not refit the rack or the hose.

This radiator is supplied by at least 10 retailers, they all say it will fit all Sprites and Midgets from 1958-1957, and it appears it won't fit any of them. I am baffled as to how they have sold so many. Looks like an almighty cock-up at the factory.
Les Rose

Les, the distance from the front of the rad to the steering rack is only about 50mm but on a 1500, the hight of the rad is much shorter than the steering rack so if I have understood your issue correctly it sounds like the rad is too tall?
Tim Lynam

Les, just a thought but have they possibly supplied the wrong rad? Have you contacted the supplier to check?

Trev
T Mason

No Tim the rad is not too tall it's too thick and won't drop into the space between the chassis stanchions and the rack.

Trev - I sent the supplier this photo and all they did was approve the return. This is not out by a little bit, it's 20mm too thick.


Les Rose

I just found this one from MCCS. £408 inc delivery and VAT.

https://www.mccsraceengines.com/product-page/mccs-aluminium-radiator-sprite-and-midget

Odd that it didn't come up when I searched the other day. Pricey but better than the £500+ other UK makers are asking for. Highly reputable company, so I think I will go for it. But of course out of stock! More coming in a week or so. Installation looks very nice.


Les Rose

Les,

Have you considered a later crossflow radiator and cowl, it what I've used on my frogeye for the majority of its time on the road. I never had the original downflow one it would have had. The cowl also has a useful panel below the radiator where an oil cooler can be fitted so it's not in front of the radiator itself.
David Billington

Yes Dave, I have considered a crossflow. But I would have to replace all the plumbing. Looks like a lot more work and expense, even though I can get a cross flow radiator cheaply. Remote expansion tank is £75, lower tube £30, cowl £168, and I would need new hoses (just replaced them!) and thermostat elbow.
Les Rose

Not so expensive to convert Les.

Buy used.

"A tidy used coolant expansion tank part no. ARH 250 to suit a Midget 1275 , MGB with electric fan 09/76 onwards, TR7 and others A few very little dents on the back" £29.00+ £5.00 postage.
https://www.ebay.co.uk/itm/386107689258

-----------

"GOOD USED RADIATOR ASSEMBLY FROM AN MG MIDGET 1500"
"MG MIDGET 1500 - RADIATOR ASSEMBLY
100% Positive feedback.
£35.00+ £10.00 postage
https://www.ebay.co.uk/itm/204457244616

Even if the radiator isn't so good, you get the bracket for less than 50 quid.

-------------

Make your own lower cross pipe from domestic plumbing copper. Very cheap to make.



anamnesis

I was thinking the same but that 1500 shroud assembly looks rough compared to the 2nd hand radiator and shroud I bought and I didn't realise the 1500 radiator is different to the 1275 crossflow.
David Billington

Yes second hand is always an option, but frankly I can't be ar*ed. All the bits will have to be cleaned and restored. I will then find something that is broken or doesn't fit, because I don't know enough about what should fit. I am getting beyond all this. There was a time when I enjoyed restoring parts, modifying them and making them fit.

Meanwhile now the weather is much cooler the car is not overheating, so the pressure is off temporarily.
Les Rose

"-- frankly I can't be ar*ed. ".

"There was a time when I enjoyed restoring parts, modifying them and making them fit."

Les, I completely agree with you. Me too. I'm all in for the easy way now; even if it costs more to do. And that's from me, for who saving money has been raised to an artform, and one of life's highest aspirations. 🤣🤣🤣

I suspect it has something to do with the onset of receipt of the state pension 5 years ago. Lol. Nothing like advancing years to focus the mind.😏


anamnesis

I have just cancelled my third order for an aluminium radiator. To recap....

After the Chinese one from eBay went back for a refund, I ordered one from SC Parts. That also turned out to be Chinese and didn't fit. They had simply added £135 to the eBay price. Waiting for a refund. I then ordered the one from MCCS, on condition it was not made in China. They say they have factories in China and Germany, but - you guessed it - they only have Chinese ones in stock. And they charged twice the price of other Chinese rads. It really is a chaotic company. Appalling communication. Their excuse is that they are moving premises, but if they can't process orders and respond to enquiries then they should not say they are open for business. So that's another refund I'm awaiting.

As I said, pressure is off now as weather is cooler, and I'm thinking about the crossflow option again.
Les Rose

Les
What a palaver! I know James and I have mentioned Arrow radiators at Avonmouth a time or two but I can't help thinking your re-cored rad would have been back by now and he'd have done a good job. Still an option surely but ignore me if it isn't!
Bill Bretherton

You haven't mentioned if you've had the temperature gauge calibrated. I assume you have the standard dual gauge but they have been known to over read.
f pollock

I agree Bill. Either a recore, or convert to the later rad'.
anamnesis

Yes I know I can send it away for a recore, but that puts the car off the road for a week. OK, it's laid up now for a few days while I replace the big ends, and if I'd planned it better I might have got the rad done at the same time. The advantage of the crossflow is that I can get all the parts prepared and do a quick change-over.
Les Rose

I forgot to say that the dual gauge is new, and I checked it in boiling water. Not exactly a calibration, but it clearly works across the range that matters.
Les Rose

Eventually I took the easy and expensive way out, and bought the ally rad from Coolex. £480 all in, made to order. Quite a lot of fiddling to get it in. Bottom hose spigot was about 5mm too long. It is also very slightly lower so getting the hose on is even more difficult than usual. Core is thicker so I had to file the steering rack brackets and some of the welds on the rad. At least the fixings were in the right places.
Les Rose

This thread was discussed between 06/09/2023 and 04/11/2023

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.