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MG Midget and Sprite Technical - Radiator Capacities and temperatures

My two sprites have different radiators because of their models: vertical flow and cross flow.
The Mk4 warms up very quickly (in around a quarter of a mile) but the Frog takes ages to get warm and at this time of year it doesn't seem to get above 160( deg F of course!).
THe Frog has almost twice the amount of water as the Mk4 which must have some effect - on the warm up time at least! The Frog has a new thermostat and this also has a 1275-based engine.
Is my experience in this the same as others? Both have mechanical fans.
Graeme Williams

Yep my vertical flow rad keeps my midget to cool aswell.
In winter I block 75% of the area with a piece of cardboard.

Get's the temp up to an acceptable level
Onno K

I had been wondering about that Onno. Had been trying to think of a more elegant solution but at the end of the day a bit of cardboard is nice and still and should stay there quite happilly. Wonder whether it will get wet and go soggy?

I also wonder whether an electric fan and removal of the mechanical fan might solve the problem?
Graeme Williams

My GAN6 Midget uses a Kenlowe fan with it's own thermostat. Warms up in minutes and guess what? The heater works great! It's actually better than the Boss's 4 year old Ford.
BTW, not cardboard. It does indeedy go soggy. Try kitchen foil. Worked great on my GT6!
RS Hughes

All self respecting hillbillies only use card board, if it does get wet, just replace with more card board

A piece of masonite works great also

Prop
Prop and the Blackhole Midget

I've used one of those plastic rally plaques before, seems to block off just the right amount on downflow rad on the Frogeye
G Lazarus

Graeme,

The other thing to consider of course is whether your vertical flow has it's temperature sensor in the header tank? You might expect to get a lower temperature reading from here in cold weather, compared with those cars that have their sensor in the cylinder head, which is, of course, on the hotter side of the thermostat.

Simon
SA Wood

These are good for anything but a frogeye. Easily attached and removed and has flaps that can be locked open or closed.


Ray Rowsell

Mine's the opposite. Vert flow rad in my '66 Sprite, engine warms up quite quickly. Cross flow in the '73 Midget, barely crawls over 160 in this weather, and often dips back below 160 even after half hour of driving. I'm even wondering if the stat's shagged.

Both mech fans. (Although the '66 also has an electric on a manual switch).
Lawrence Slater

If I were to think of blocking the rad air flow, I would want something more sophisticated and alterable from the drivers seat, than simply blocking the rad with carboard or fixed screens.

I've put an internal tap in my Sprite to control the water flow to the heater.

So I'd look to invent a means of installing a retractable screen or blind over the rad.

You can buy a small roller blind circa 12"W x 15"drop for as little as 10 quid. If not suitable as is, it would be easy to modify it, using maybe just the sprung mechanism, and using a different material. Control it with a long cable, similar to the bonnet pull, but with a longer pull action.

OR. How about modifying a small venetian blind? Closeable slats. Now that sounds good to me.
Lawrence Slater

Pity you can't get one of these.

Radiator Blind Kit
For quicker warming up, reduced fuel consumption and longer engine life, fit the appropriate variable setting radiator blind. Setting is easily varied as required from a facia panel control.
Part No 105E-18690 (Anglia saloon and estate cars)
Part No 307E-18690 (5/7 cwt vans)

But I bet you could make one quite esily. :).




Lawrence Slater

>I also wonder whether an electric fan and removal of the mechanical fan might solve the problem?<
as the engine fan runs even when the engine is cold replacing it with a temp controlled electric fan will allow the engine to warm up quicker

but it won't make any difference to the open road running temp however my Midget has run at around 160F or lower through the last 6 winters without problems and still gave hot air out of the heater vents (engine fan removed and electric fan with thermoswitch fitted for the last 5 winters)

you could check that the thermostat isn't stuck open but I doubt but I doubt that is the cause

you could change to a winter thermostat for a quicker warm up

I intended to try to make a rad blind last winter but the weather was so mild I didn't bother
Nigel Atkins

pity you cant get these anymore
http://www.ebay.co.uk/itm/1967-68-IMPERIAL-RADIATOR-BLINDS-PRICE-LIST-/380932331245?pt=UK_CarParts_Vehicles_Manuals_Litterature_ET&hash=item58b15616ed
mark 1500 on the road Preston Lancs

It seems you can Mark. it just needs a bit of alteration and attention.

http://www.ebay.co.uk/itm/Engine-Cooling-Radiator-Blind-from-Austin-A90-six-Westminster-needs-restoration-/371075391143?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item5665d11ea7

Or a slightly more expensive one for a faster car. lol.

http://www.ebay.co.uk/itm/Ferrari-Radiator-Shutter-Blind-Complete-NEW-/251715402323?pt=Vintage_Car_Truck_Parts_Accessories&hash=item3a9b683a53

Or a rear window blind much cheaper

http://www.ebay.co.uk/itm/New-Rear-Window-Sunblind-Rover-75-MG-ZT-Saloons-Genuine-MG-Rover-/301447307669?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item462fa8e195
Lawrence Slater

Nigel: your midget will have the later rad which on mine is the one which warms up quickly. Your problem may be down to excessive deep cleaning the water ways at some point. :-))

Graeme Williams

Graeme, for what it's worth, I have been running an MGA with just a Revotec thermostatically controlled electric fan (water pump fan removed) for more than 3 years and it is brilliant! Warm up time is quicker, no over-cooling in winter and the engine is noticeably more responsive with not having to drive that metal fan round when it is not needed.
P.S. I don't work for Revotec and I'm sure a Kenlowe would work just as well!
Lindsay Sampford

Graeme,
I know the rad on my Midget is later than the one you're referring to but on mine I didn't say I had problems I put it was without problems

nice of you to say I've got the cooling system cleaner than when the car left the factory :)

I'm suggesting you might not need to worry too much about the temperate reading and that a temp controlled (so no need for override switch) electric fan with engine fan removed will help you - I can't say I noticed any performance improvement fitting the electric system though - and also that you might want to consider checking that your present stat isn't stuck open and perhaps fitting a winter thermostat
Nigel Atkins

Okay since you did not ask I'll explane why there is a difference in warmup times between vertical and cross flow rads.

You need to look at the history of radiators.
Early M.G.'s had thermo syphon cooling systems, so just atmospheric pressure and no water pump.
This required a large volume of water to cool the engine. Max temp was 100 degrees.

To improve over the years a pump and pressure where added.
Increasing effeciency and raising boiling temp due to the pressure.

The older vertical flow rad is still a higher volume lower pressure type.
It needs the higher volume to cope with higher temperatures in warmer climates.
But the down side of long warmup times was not yet solved.

With the introduction of the cross flow rad they improved on the warmup time problem by simply reducing the volume of water.
And to keep the hot weather preformance the same they simply applied more pressure, raising the boiling point.

For both models warmup times can be improved up on by removing the mechanical fan for an electrical one. As was the next step in cooling system evolution seen on the rubber bumper MGB.
Onno K

The frog has a vertical flow rad with a later 1275 engine. Are you saying, Onno, that the water pump on the later engines has a higher flow rate than the ones fitted to the original smaller engines? In that case we have a combination of high volumes of water with a high pump throughput. I wonder what effect that would have?

Can someone tell me whether the correct Frog combination of 948cc and vertical flow rad warms up quickly?

It isn't all about warm up times - the frog runs 15/20 deg cooler although that could be the gauge.
Graeme Williams

I thought that concencus was, that the later cross flow rads stay cooler than the earlier vertical flow rads. That's certainly the case with my 2. Both have 1275 engines, the same pumps, the same stats, and the same mechanical fans.

So If Graemes Frog is running cooler, I reckon there must be a far better heat exchange going on due to more air circulation. Frog rads, aren't as boxed in as the later models are they?
Lawrence Slater

Hi, Merry Christmas to all who celebrate Christmas. Merry wishes to all those who don't.

Surely there are too many variables here to make a proper diagnosis.

The cleanliness of the cooling systems - radiators, engine blocks pipes etc., the thermostats, the engine tune, the grill openings in the bodywork and cowling - Frog verses mk4 sprite, the water pumps, the driving styles (is the Frog driven slower, less aggressively?), the temperature gauges, the amount and type of antifreeze, volume of coolant.
These can all make a difference to the engine warm up time and running temperature.

Dave
Dave Brown

I wonder if the differences are due to the condition of the cooling systems? I put a reconditioned rad in the frog in the summer and it ran cooler than previously. It used to run around 170F but struggles to get past 160F now. its a 1275 with an A+ water pump (no by pass)
Bob Beaumont

>>Can someone tell me whether the correct Frog combination of 948cc and vertical flow rad warms up quickly?<<
if you're asking this then you might as well also ask what temp the car runs at (taking into consideration Dave Brown's comments)
Nigel Atkins

Taking Lawrence's point, I would have though air flow through a frog rad would be less effective than on the later cars. THere is more opportunity for the air to "miss" the rad by going through the large spaces at the sides and above/below. The later models have the advantage that any air going through the grill can only really go through the rad.

As you say Dave, there are too many variables to conduct any serious analysis. It was just based on my observation that there is a BIG difference between the two vehicles and noting that since the radiators were different styles and very different capacities, I was wondering what effect that would have.

The 10 deg difference noted by Bob when he changed his rad is significant. Perhaps my horizontal flow rad needs a good poke out between the fins (but it has been flushed, Nigel).
Graeme Williams

Just made up a rad restrictor using the Owner's Handbook as a guide.
Graeme Williams

Graeme
Though there is a difference between pumps and yes the new cast deep impellor type is the most efficient it is not what I was talking about.
The point was volume and pressure.
The old M.G.'s I was on about are the pre-war's and T types.

Lawrence
Both should run at an equal temp with the rad in the same condition.
The vertical flow rads bigger volume just takes longer to get at that temp

Dave
Certainly not to many variables!
Just simple fysics combined with testing on both models.
Key to the difference in warm up times is the volume of water.
In both cases warm up times can be improved by deleting the engine driven fan and blocking the radiator.

Graeme
Airflow through both rads should be equal on non frog fronted cars

Onno K

Graeme,
my more thorough cleaning of the cooling/heating system includes gently brushing out of the rad fins on both sides (same for matrix) and a bit more as you know

when I brushed the rad fins this summer I was surprised at how many insect corpses there were and how much straw (from following a lorry for many miles that summer)

I can't say I noticed any change in the temp reading after cleans but on the second of three clean outs a lot more grit type muck came out than I thought would considering I'd cleaned out previously so these clean outs were still worth while as a preventative measure

plus with standard antifreeze you should be changing it every two years by the book so that would help clear some muck out just by draining

despite how it may seem I've only cleaned out the cooling/heating system on my car three times in 7 years and the last two times it was because the rad had to come out of the car to fit an electric fan and its upgraded replacement

looks like the good book has proved useful once more, again, and again . . .
Nigel Atkins

The "good book" was indeed useful although I think you may have misunderstood me. When I said I found it useful as a guide I meant I laid it out on a sheet of cardborad and drew round it to get a suitable rectangle to cut out and use.
Graeme Williams

lol.
Lawrence Slater

:-)
Graeme Williams

sorry, yes I did misunderstand you, I thought you meant you'd used the good book itself as as a rad blind - either way the Driver's Handbook has come in useful again - and it shows coolant capacity
Nigel Atkins

Superb put-down Nigel!
lol
Graeme Williams

I hope it was a little uplift with humour

. . . as well as a humorous put down :)

I know you appreciate the value of the Driver's Handbook and look for ways to get even more out of it :)
Nigel Atkins

This thread was discussed between 22/12/2014 and 27/12/2014

MG Midget and Sprite Technical index

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