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MG MGB Technical - 4 core radiator

Does anyone know where can I source uprated 4 core radiator (early type with rear filler neck) for my 66 B? I have now 1950 ccm engine and last summer I had some problems with overheating on very hot days. I added electric fan but on long uphill runs it can not cope with extra load, so my next consideration is bigger radiator. Aluminum would be nice fitment but price is very frustrating, so I am thinking about 4 core bras - cupper radiator. I know that some shops offer recore service, but since I am from abroad, I am looking for outright purchase without exchange unit. Any address within EU would be helpful.

Tony - Go to a good radiator shop and ask the above question. There is a world wide company that make radiator cores, called Prolaince (formerly Modine). They make a 4 row, L type radiator core that works very well in the MGBs. The core will have to be ordered, but should be no problem for a good radiator shop. Cheers - Dave
David DuBois

I fit a 5-row core to my '67 BGT. It fits without modification, using the original upper and lower tanks.
Steve Simmons

I fitted a 4-row to my V8. It was advertised as '25% uprated' but that only refers to the number of rows. As far as increased cooling goes the law of diminishing returns comes into play and you get much less than that additional cooling. In the case of mine with electric fans as standard I beefed-up the fan electrics and got a much bigger improvement.

What 'overheating' did you get? The needle moving up the gauge isn't an issue unless it gets up the the H zone, and even then it still shouldn't be steaming or losing coolant. You can get coolant loss if the cap is faulty or too low a pressure (they went from 8lb to 15lb eventually). Maybe it's just the gauge that is reading high, although a 66 would normally have a capiliary gauge which normally read low when faulty. There can also be any number of engine issues contributing to putting out too much heat, or inadequate circulation, rather than the radiator not being able to get rid of it. Standard engines run in desert states with no problems, what sort of ambients are you talking about?
Paul Hunt 2

Hey Steve, where'd you get that 5-row rad made?

Most places I've shopped and checked will only
do a 3-row core, and (more rarely) a 4-row core

Daniel Wong

I have a 5 row radiator in my 74. The tubes 3/8" compared to 1/2" for a 4 row. There is 3/8" between the tubes on the 5 row and 1/2" on the four row. Like Paul said it is supposed to be 15%-20% better but I don't think so. I went to a local radiator shop they called the distributor in Atlanta and that is what they suggested. It just barely fits inside the stock tanks so it's a little closer to the fan than the stock radiator.

Clifton Gordon

Daniel, I'll look up the contact information for the shop for you when I get a chance. I'm on the road up north at the moment.

I'm also sending you an email with some local info.
Steve Simmons

Paul, thank you for detailed answer. Yes it is 66 with capillary gauge with dual water-temp/oil-pressure indicatior, on front of radiator is additional electric fan that starts at approx. 95 deg. C. Temp raise over 105 deg. C and would go higher, but I rather stop and cool down engine. I noticed this problem only on hot summer days with temperatures 32 deg. C and above, with long uphill runs where is needed a lot of torque. I use standard radiator and water pump, less that 2 years old, with 7 psi rad cap and I have also expansion bottle from later model. Radiator thermostat opens at 74 deg. C. As coolant I use 4 life radiator coolant mixed with distillated water and Water Wetter. My consideration is shall I go for bigger radiator or would be enough to try first with wrapping of exhaust manifold and addling fan shroud?

Toni - 32C/90F is way below where you should be getting problems, we get that in the UK occasionally, and desert states will exceed that regularly and by a huge margin. If you aren't getting coolant loss with a 7psi cap then it doesn't sound like you have a real problem anyway, just a high gauge reading for some reason. If you are losing coolant into the catch bottle with a 7psi cap then you can fit a higher rating. I was wrong when I said 8psi was the original, it was 7psi as you have (and not the 10psi quoted by Clausager), increased to 13psi or 14psi at various times and markets. 10psi, 13psi or 14psi should be fine for your system. 74C is the correct rating thermostat for hot countries but you do need to check it is opening properly at the rated temperature as a 'late opening' or only partially opening stat will result in a high gauge reading. The easiest way to check this is by getting the gauge up to a high indicated temperature, removing the radiator cap (*carefully*, it may genuinely be overheating which could result in scalding steam) and measuring the temperature of the coolant at the top of the radiator. This needs to be done with the engine running as there are some circulation problems that can result in a hot engine but a cool rad, but turning off the engine the rad will heat up to the engine temperature. Really a 'point and shoot' infra-red measuring device is best as you can measure at multiple points round the engine without removing the cap, engine running and stopped. You do need to get quite close with these though, as they have an 'aspect ratio' which means when you get a certain distance away (which can only be a couple of inches from a small object like the thermostat housing) it averages readings to lower than the hottest part.

I was under the impression that 4Life should be used *undiluted*, it is not a concentrate see

Water Wetter is pretty marginal I think, bigger radiator, fan shroud, exhaust wrapping are also marginal. With a puller fan a shroud is much less of a benefit than for a pusher due to the dynamics or air flow. The bottom line is that your engine *shouldn't* be overheating under the conditions you describe, although long uphill runs are subjective. I'd do more investigation before spending money.

Paul Hunt 2


Have you checked that there is a foam seal between the radiator and the diaphragm? Sounds silly, but I had similar problems until someone noticed that mine was missing - and now there's no problem. It cost a pound or so.

I took my radiator to a radiator specialist and asked for the biggest core he could fit inbetween the tanks. The cost was less than a 'standard' one from the usual suspects.

Is the fan working in the right direction?

Before this solution, I tried Water Wetter. It is impossible to tell whether it made any difference.

Wrapping the exhaust manifold lowers under-bonnet temperatures - the heat you can feel when you pop the bonnet - but I think it increases engine temperature. As it is not cooled by frsh air, the manifold gets hotter, which means that the heat is less inclined to transfer between the head and the manifold. I warped a Peco manifold beyond repair by wrapping it. And cooked a dozen spark plugs!

I would counsel against removing the cap when the temperature is at 'high' - I did it, carefully, and ended up with burns that required daily visits to the health centre for a month... If you want to check the gauge, take it off and do it in the kitchen!


Tank you for all inputs.

Neil: it is not silly question, looking for solutions we often overlooked small thing, but yes, foam is there and blower blows in right direction.

Paul: temp goes in summer up to 38, 39, but I avoid driving at that time just from fear to have overheating problems. And yeas I do loose water from the system and that is the reason why I installed expansion bottle. I have checked thermostat for opening and it works fine (I took it out and measure temp while cook it). Good Idea is to use Infra red temp gun, I know where I can borrow one, but I will have to wait for summer first. But what I noticed was that I have oil leak on left side of engine between head and block under the no 4 exhaust port. First I re-torqued head, but it didn’t solve problem so I left it for spring, when it will be a bit wormer, but maybe are both problems connected?

Neil22 makes a good point about the diaphragm seal. I have always had the rubber seal to the bonnet insulation, but only recently fitted the foam seal between the radiator and diaphragm and that has made a surprisingly noticeable difference to summer running temps.

Have you measured the cap pressure? A friends late model with 15lb cap used to lose coolant when the fans cut in. I measured the pressure it released at and found it was only about 4psi! Without an adapter that fits between cap and rad it isn't easy to measure on early models without the pressurised expansion tank, they are cheap enough so I'd replace it anyway, and with at least a 10lb if not higher as it will do no harm.

If you *only* have an oil leak from the oil-way to the outside world it shouldn't have any effect on engine temperature, but if you have that you could well have a leak between combustion chamber and water jacket. You should be able to detect this with a combustion leak detector such as On the later radiators with the filler on top you can often see bubbles in the coolant when this is happening, but with the early radiator with the angled filler port on the back it is less easy. Another thing you can do is modify a spark plug with a tyre valve and use that to pump air into each cylinder in turn to see if you get any bubbles in the coolant, but that would need to be done on a hot engine.

My V8 always used to lose a bit of coolant when switching-off which is why I had a catch bottle as well. It suddenly got worse and started bubbling a lot into the radiator which pushed coolant out the overflow all the time. A leak detector showed no combustion leak, so I had the heads off to see what I could find. I found nothing, but as a matter of course replaced the water pump and after that it stopped. I think the pump must have been sucking air in past the seals. I have also heard of the same thing happening if hoses have been loose, but in theory that should show itself as leaks, when a hot engine has been switched off at the very least.
Paul Hunt 2

Oh yes, I forgot to explain that has engine attached sticker for recording of temperature and this remember highest value, which is now 107 deg C, so temp gauge shows pretty good. I know that temp over 100 deg C does not mean that water boils, but what would be still acceptable temperature of water with 10 or 15 lbs cap that wouldn’t damage engine?
I also noticed that are available two types of water pump alloy and cast, is any benefits form one or another or is only difference price and weight?

Where is the sticker attached? Some parts of the engine block and head could well exceed coolant temperature, but I doubt that is the only issue.

A 67 should only need a 7lb cap, but under heavy usage in hot conditions you may get higher coolant temperatures and so a 10lb cap could be of benefit. It won't damage the engine, but go too far and you could well blow a hose (as I did with a 20lb cap on the V8). It won't alter the temperature of the coolant, just the point at which it will lift and start allow boiling and coolant loss.

From my experience alloy pumps are cheap versions of the cast iron. I also understand there are two different pumps for MGB engines, one of the engines accepts both, but the wrong one gives insufficient circulation, and hence inadequate cooling and a too hot engine. Unfortunately I don't know the details. However you should be able to determine if circulation is the problem because the engine will be hot but the lower parts of the radiator, with the engine running, will be relatively cool. If the engine is producing more heat than it should or the radiator can't get rid of it then the outlet will be relatively hot. In the latter case there will probably be cool areas in the radiator, caused by blockages, which can be seen with one of those infra-red thermometers.
Paul Hunt 2

I dont see if you mentioned this above...
do you have an oil cooler?...
do you still have the old 3-blade fan?
I recommend switching to the later fans (depending on which one you can get ahold of you might also require a different belt pulley)
If you have an oil cooler and your radiator with a newer fan all in GOOD condition along with seals around your radiator so that air will flow through and not around you should be in good shape....even without an extra fan on the front....which may be inhibiting air flow.... This worked for me in Arizona where it gets quite hot. Hope this is helpful and not a repeat of advice you already have.

It may be something so simple that nobody has as yet thought of it: A cheap radiator hose. Due to poor wall strength, they can collapse at high pump speeds and restrict the coolant flow to the coolant pump, resulting in overheating. To test the hose, reach down to the hose that supplies the coolant pump and give it a good squeeze. It should be very difficult to compress.
Steve S.

JJ makes a good point, the later 6- or 7- blade is much more efficient than the original 3-blade. Can't speak for American motors but I seriously doubt the pump on the MGB is capable of sucking the hose flat. It would have to overcome the pressure when hot, and if it could do that it would be very obvious just by looking when revving the engine when cold.
Paul Hunt 2

Thank you for all support and suggestions.
Paul: temp sticker is attached at the middle core plug
Water pump, water radiator, oil radiator and water hoses are all about same age - 2 or max 3 years old –so I assume that are in good shape. Since this is early type B is oil radiator installed in front of water radiator. I noticed huge improvement already when I bought new radiator and some smaller improvement after correct orientation of fan (wrong direction). Instead of original 3 blade fan I am using MGA 6 blade metal fan (it fits long nose style water pump).
After all suggestions I already ordered new 10 psi radiator cap, but I start to think that is maybe problem also hole for fresh air for cabs that does not have its function anymore, since is there now crossflow head.

This thread was discussed between 08/02/2008 and 23/02/2008

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