Hints and Tips - Overheating

From: C Knight
Sent: 12 July 1999
To: British-Cars Pre-War
Subject: Overheating

Does anyone have experience of using modern radiator cores on cars with no water circulating pumps? My recently acquired BSA Scout is overheating badly. Timing, valves, oil etc are all as they should be so I am left suspecting the radiator core efficiency. The car was fitted with a new modern radiator core by the previous owner. BSA Scouts have no water pump and rely on thermo-syphon for water circulation. As built, due to the fact that the engine is mounted back to front, it had no air fan either. My car has been fitted with an electric fan, despite which, it is incapable of going more than 20 miles before seriously overheating in our current hot UK weather. Does anyone know whether this could be due to the modern core, and is their anything I can do apart from saving up for a proper honeycomb core or waiting for winter to arrive again.

Any other suggestions would be welcome.

Thanks in advance


From: Brian Kelly
Sent: 12 July 1999
To: Cliff Knight
Subject: Re: Overheating

<< Does anyone have experience of using modern radiator cores on cars with no water circulating pump >>

I've had three years of hot S. Californian summers driving a 34 MG PA. The radiator has a modern version installed by a previous owner. {It's always the other guy!} This particular rad' has three rows of cooling tubes, driven without a water pump again on thermo syphon principles. Having heard of experiences with new rad's being fitted with two rows of tubes only the efficiency was too low, in this case it was a MG TC. There is a product I used out of California called "Water Wetter" comes in a 12 oz bottle good for up to twenty gallons of water. This product can be used in summer without the use of anti freeze. It reduces the temperature significantly, and still has protection for the cooling system. In fact in Cal' I used it year round. Perhaps you have a similar product in the UK. I've just located these pages www.4unique.com/cooling/redline.htm You can actually purchase it here. 8 dollars.

www.redlineoil.com This is the manufacturer.

The pages are interesting. Good luck!

Brian Kelly.

From: Ian Grace
Sent: 12 July 1999
To: C Knight; British-Cars Pre-War
Subject: Re: Overheating Cliff,

I could be wrong, but I seem to remember that modern cores are not best suited to thermosyphon action, since they are designed to have the coolant 'forced' through them.

Modern radiators also have far less coolant capacity, but yours should be somewhere near spec. if you have the original header tank.


From: Mark Roper
Sent: 10 July 1999
To: Brian Kelly
cc: Cliff Knight
Subject: Re: Overheating

A friend of mine has just tried "water wetter" in his 59 TR3a and it made no difference at all.......


From: Neil Sherry
Sent: 13 July 1999
To: Ian Grace; C Knight; British-Cars Pre-War
Subject: Re: Overheating

What may make a difference is which way the water flows. Many modern(ish) cores have horizontal flow, I imagine that a thermosyphon system would work better with vertical tubes. Could this be the problem?

'34 MGPA

From: C Knight
Sent: 16 July 1999
To: British-Cars Pre-War

Thanks for all the useful suggestions re the cause and for curing the overheating on my thermosyphon BSA Scout. In summary the ideas were:

Header tank may be too small
Capacity and efficiency of core - 3 tube type recommended on a MGPA, not 2 tube
Use Water Wetter
Some modern cores are designed for horizontal flow - needs vertical for thermosyphon.

My header looks to be original, the rad core has no less than 5 rows of finned tubes, and the flow is vertical, however, as someone suggested I think that the problem must be capacity/efficiency. The water capacity of the complete system is only 10 pints where the original manufacturers literature quotes 19 pints. I presume that a honeycomb has greater water capacity, and since it also has a greater wetted area presented to the cooling air I assume the efficiency is greater. BSAs have a very short rad as the front wheel drive occupies half the area behind the radiator cowl, hence the radiator is thicker than most cars. Despite the modern 5 tube core the capacity, and I assume efficiency, is much reduced. I suspect I will have to bite the bullet and buy a large capacity honeycomb core. Does anyone know a good maker in the UK?

Many thanks for help


From: Peter Thompson
Sent: 18 July 1999
To: British-Cars-Pre-War
Subject: Re: Overheating

If the water capacity of your current system is so much less than the figure quoted in the handbook, and the current rad. uses the same top and bottom tanks, then the reduced capacity can only be due to the core having much less capacity than the original. If the height of the rad. is the same as before, the reduced capacity can only be the result of reduced cross-sectional area of the water tubes. Not only would this cause more resistance to circulation, but there is obviously a lot less water sitting in the air stream getting cool. It sounds as though you had best replace the core with something with more, and bigger water passages; alternatively, you could try fitting a pump off some other vehicle, if you can rig it and don't mind unoriginality.

Incidently, if anyone can tell me why the water temperature on my 1930 Essex (OK, I know it's not strictly British, but it was assembled at Brentford) FALLS when the throttle is wide open, and peaks when I back off, I'd be pleased to know!

Peter Thompson

Home | Hints & Tips | Suppliers | Engineering Data | Links | Events | For Sale | Gallery | Books | Videos | About Us