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MG MGA - Hot MGAs again

I have read a lot of good info on this problem but would like some more clariication in particular fitting a shroud. What is this made of and where and how is it fitted? Can one buy one ready made? Also I see in MGCC mag that someone has fitted a 7 bladed plastic fan. Where can I get one? Lastly I have an oil cooler sitting on the apron in front of the radiator. Would this be interfering too much with the air flow to the radiator. If I put it underneath I guess it wouldn't get much airflow itself.
H L Davy

Moss sells them; they fit behind the radiator, are very easy to put on. But are really only helpful when going slowly, may actually hurt air-flow at highway speeds. I removed mine. Be sure you have the two air intake tubes on eather side of the radiator as well as felt strip that's glued to the bonnet over the radiator.
David Werblow

Can't answer your questions, but living just across the road from you does make me wonder why you need all this. You should not be running hot in these climes. My 1800 engine has sat at 175, creeping up to 180 on the hottest days all this summer with an absolutely standard MGA configuration.

What is the history of your radiator? I firmly believe that incorrect radiator cores are the source of so many MGA overheats.

Steve Gyles

When you say it is running too hot, do you mean too hot all the time, or just when idling at traffic lights, ètc., or what. It does make a difference to possible solutions although super cool Steve is of course right that the radiator is perhaps one of the most important things to consider.
General opinion seems to be that the oil cooler doesn't cause a problem. I have one and it hasn't caused me any problems.

Regards, Graham
g Victors

I agree with the above two comments.

Mine did run hot, with a 1622 engine, but this was because I chose to have the cheapest possible re-core of the radiator.

I also fitted an oil cooler - I hoped it would fix the hot running.
It didn't.

Three decades later, I had a proper radiator repair outfit calculate the heat dissipation of the current 1798 engine and fit a more appropriate core.
It's now rock steady at 200 in all weathers.
(Shame about the oil pressure)

D Brown

With my similar set up to Steve's I have never really had any problem with overheating, even when crawling along on traffic. (My car has a Bob West radiator fitted like Steve's)

My car would always run between 175 and 185 when I first got it a few years ago, the only time it overheated and began to misfire in traffic was when one of the the cool air intake pipes fell off in front of the radiator and obstructed it a little. (Once I was moving again the temp came down to normal even with the pipe laying in the air duct)

A couple of years ago I bought and fitted a six blade injection moulded fan supplied by NTG Services in preparation for a summer trip over to the Continent.
It has a much more efficient bade design and is almost an inch greater in diameter than the standard metal fan.

I noticed an immediate drop in running temperature of 10 degrees with this fan so now the car runs between 165 and 175 degrees. It really shifts a lot more air than the old fan however, it howls like a banshee at over 3000 rpm and it does get a bit annoying after a while.
I have heard that the latest Moss plastic 6 bladed fan runs much quieter but still does a good job of improving the cooling.

If you do fit a plastic fan I would advise that you space the radiator forwards by 5mm or more as I have seen where some plastic fans tend to flex forwards a little in very high ambient temperatures and the tips of the blades can rub on the radiator core.
Spacing the rad forwards a little will prevent this.

I am about to experiment with the fitting of an electric fan to replace the plastic one to see if it can keep the car as cool as it is now.
It would be great to get rid of that howling noise.

But, overall, I would definitely recommend fitting a plastic fan.


Colyn Firth


That looks like a big fan, I'm surprised the car doesn't take off and fly!
J Bray

I too believe that a good radiator core will solve overheating problems. I bought a new Moss radiator a few years ago, and the car ran a little hotter. The radiators were constantly developing leaks and I got fed up of changing them under guarantee, so I got my money back and had the original radiator recored. On being asked if I wanted a high performance core, I said no, just a standard one please. The result is that my car runs at 50C on a cold day, 70C on a normal run, and last week as I was speeding up through France on the way to the UK, it ran at 75C even though the air temperature was 36C.

I still run the original steel fan, have an oil cooler, do not have any radiator shroud or electric fans. I do have a radiator blind for cold days ( a roller blind in front of the radiator that I can operate from the drivers seat).

I did have a spot of hot running recently, but traced that to a defective cap, where the seal had moved off centre, so the system was not under pressure. Recentering the seal solved the problem.
dominic clancy

David W.
Your comment about shrouds is the first time I have seen anyone mention that the car ran hotter at highway speeds.
Was this just your experience with it, or have other folks mentioned this?
I was under the impression that the shroud increased air flow through the core at all speeds.
Edward Wesson 52TD

My car has been very hot recently and I have bought a new radiator cap. Although it is the longer 1"one, I am not sure that it actually fits against the step in the radiator neck; there is no resistance at all.
Secondly, when tightening the cap it grips, but if I continue tightening it, it comes free again.
The radiator was off during the winter, and cleaned etc.
Any ideas what my problems are?
Nigel Munford

Here's a picture of mine
If I lay the cap on its back, the overall height to the top of the black spring loaded seal is 31mm.
The larger black seal, recessed in the metal of the cap, is 2mm thick. Do you have this second seal? How thick is it?

D Brown

Dominic - I know the standard thermostat is 74 degrees but for better thermal efficiency I would be inclined to run with an 82 or even 88 degree thermostat.

If the engine is not loosing water then is isn't overheating in my book.
Chris at Octarine Services

Thanks. My cap is the same size as yours externally, with the distance from the spring loaded seal to the inside of the cap one inch, which corresponds with the distance to the lip inside the filler neck from the top. Barney confirms that this is one inch on one of his papers. I do not have the second larger seal.
My cap came from the MGOC.
I think the fault is with the top of the filler neck.
Nigel Munford

That second seal isn't standard
I put it in when I added an expansion bottle - prevents rad water spraying the underside when I fill the rad as per the handbook. :o)
But it does mean the cap doesn't rattle about
Can't remember the last time I needed a top-up
D Brown

Davy: My plastic shroud is fitted between the radiator and the fan blade--as most are. I use a 6 bladed plastic fan. But Barney (the MGA guru) says he switched to a 7 bladed fan because it reduced fan noise. Both items are available from Moss.

My shroud made a huge difference in the cooling of my car, especially at idle and stop and go traffic. And at speed, the temp gauge stays pegged at the thermostat opening temp--no overheating at speed, unless climbing a long mountain grade and then it only barely moves up a little.

But everybody is right about being certain of the radiator design and condition. That was the first thing I did before moving on to the shroud and fan.
JM Morris

Someone told me today that one solution is to fit a fan that runs "in reverse" - that is to say it sucks hot air out of the front of engine bay and through the radiator. Thought he was pulling my leg, but he assured me it works well.
Has anyone heard of this?
g Victors

Only works with transverse engines that have the rad exhausting into the wheel arch like the Mini, 1100 & 1800.

You can't blow air through the rad in reverse in a MGA unless the car is reversing too!
Chris at Octarine Services

Having driven MGA's for over 30 years my cars have the same problem. The only way out I have found is to get the radiators rodded out every four years or so.
Barry Bahnisch

Rad caps - 7 psi is all you can get. I always fit a standard height neck if I overhaul a radiator (or fit a spacer ring in the bottom of the neck if I don't) so I can run a standard 12 psi cap.

Temp - people get flustered if the temp goes above 200 F. Most cars today run 200-230 F. by design. It isn't going to hurt anything as long as the coolant doesn't boil.

Cooling in general - is usually only an issue due to old rads with clogged cores. Get a modern optimal core in your rad and you should have no issues even if you don't bother with other add ons like radiator shrouds.

Don't foreget that fat felt seal that should be glued to the underside of your bonnet - that is an important bit of shrouding from the factory often missing.

FWIW on the Twin Cam race car, I went to a double thickness core (full width of the top tank) and moved it right up against the bonnet latch crossmember (not for street use as it requires modification of the front horizontal pan). I run no thermostat in the engine and often have trouble getting it UP to operating temperature without taping off part of the core.
Bill Spohn

Bill could you please explain the shape/size of fat felt and where it fixes on bonnet?
H L Davy

Take a look athe picture on this thread, it will give you the idea but I dont think it is in right position!,1128883,page=1

g Victors

In fact its on Barney's site
g Victors

I have to agree that Barney's site, referenced above, has it spot on.
From my 100,000++ miles in my own MGA, his meticulous documentation is well thought out.
The only point which might arouse some discussion is the orientation of the fan - the original workshop manual, the parts book, and Clausager have the manufacturer's ideas. Barney's reasoning, however, is interesting.
Shroud? Well UK temps don't really go above 100F, so I can't comment. Surely MG did some 'hot 'n hi' testing?
D Brown

My car has no felt, and it does not overheat at all
dominic clancy


Should not need much discussion on the orientation of the fan. Barney is spot on in his description. Look at any any helicopter blade, jet engine compressor blade or aircraft propeller. Basic aerodynamics.

Steve Gyles

Of Course!
I got to Barney's stuff after a little too much refreshment, and read wrong as right.
D Brown

I have just bought a new cap, for a MGA, from the MGOC. It is 1 " long, but as Barney says in his article above, it should be 1 1/8", to allow the spring to compress.
As I am having trouble getting a new cap, I wonder if any one has a second hand one I could have. I am obviously willing to pay. Apologies if this request breaks any rules
Nigel Munford

My 3 main 1800 1960 mga still gets hot in lineups when it's been run on the highway then stopped somewhere like border crossings where it can take a while to get through.
Plastic fan, oil cooler, air inlet pipes all connected, new moss rad when the car was restored, and a fan shroud. It takes longer now than before I installed the fan shroud and the overflow tank, but it'll still get up past 220
R emgeeaa

R emgeeaa
Is your Moss Rad specified for an MG 1600 engine, or for an 1800? The 1800 will generate more heat.
My rad was re-cored with the 1800 engine in mind.
D Brown

This thread was discussed between 05/08/2013 and 18/08/2013

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