© By: Dwight Smith, MOG NORTHWEST
Formatted for the Morgan Web page by: John T. Blair (WA4OHZ)
Originally written: circa 1995
Last update: June 16, 2009 - Reformatted page and corrected my email address.
(Thanks to Ben Hodgkiss (email@example.com) for submitting the following.)
Freightliner Truck Manufacturer's engineers take a hard look at
the Morgan and Dwight Smith of Northwest Morgan Group draws some
conclusions that might make your summer a bit happier!
Freightliner builds its large semi-, over-the-road trucks in Portland,
Oregon, trucks made to withstand something like a million miles of the
hardest year-round driving possible, while pulling a 70M cargo. Their
cooling systems must be able to stand up to the extreme heat of the desert
and then, two days later, cope with the ice and snow of the frozen north.
Presumably, Freightliner engineers know a bit about engines and their
cooling systems! At the request of a MOG NW member who worked there, the
engineers took a close look at a '72 Plus 8, analyzing the radiator size,
number of tubes and vanes and the system capacity. Most important, they
also studied just how air flows through the radiator and engine compartment
when the car is on the road. Surprisingly, their first conclusion was that
the radiator, while not excessively large, was big enough to cool the
engine, if working properly. This conclusion is backed up by another MOG NW
member who has been building radiators for the last twenty years, even
though most Morgan owners think first of recoring their radiator and
increasing its capacity as the first remedy to overheating to attempt!
But if in fact the radiators capacity is sufficient, what is the problem?
The trapping of air in the radiator. Take a close look at your radiator from the side, as it is in place in your car. If you have a level, use it to see for yourself how the radiator shapes up. Note first that the radiator cap has a rubber gasket on the bottom and that it fits! down about 1 1/2 inches into the neck of the radiator filler. The level of water in the radiator will be right at the level at which this gasket seals. Now, use your level or another straight edge to draw a line parallel with the ground, from the bottom of this gasket seat across the radiator top tank. Not all Mogs are the same, a bit of news which will astonish you, I'm sure!, but if yours is typical, there will be a 1 or 2 inch space above the water level at the top of the tank. This area, unless you found a way to stand the car up on its grill, rather inconvenient at the local gas station, will never fill with water, but will remain a trapped bubble of air. Since air expands faster than water, as your engine warms up, this air bubble will pressurize and inevitably displace some of the water below it in the red. When you stop, the last bit of engine heat rises quickly into the radiator. Its temperature will quickly rise, the air will expand further, and up to a pint of coolant blows out the overflow tube like Old Faithful. Nature here is working the same way as does an Expresso coffee maker, but not at the time you want it to and against the efficiency of the system.
Retaining The Water
The cure is quite simple. Fit a recovery bottle. Most auto supply stores carry them, and a particularly compact one is carried by Volvo parts dealers, about the size and shape of a thermos bottle, an important consideration in the crowded engine compartment of a Morgan. Simply mount the plastic recovery bottle to the engine compartment wall and run the overflow tube (which is attached to an outlet next to the filler neck and runs down along the side of the radiator) to the inlet/outlet at the bottom of the bottle. You most likely will have to replace the rubber tube with one of the same diameter but longer, in order to reach to where you have mounted the bottle.
You now fill the system through the recovery bottle; the cap on the original filler opening remains in place at all times. You have created a sealed cooling system, which many contemporary cars are now fitted with. If you have trouble finding the right cap for such a sealed system, any cap will do if fitted with an additional rubber gasket on its inside where it seals on the mouth of the filler opening. Radiator shops can supply such a gasket. Do not exceed a 4-pound pressure cap; with more pressure than that, Morgan radiators will spring a leak. Be sure also to buy a cap for the recovery bottle, and remember, it is through this opening that you fill your system with coolant.
Not only will this addition increase your system's capacity, it will
also allow the system to eliminate that trapped air bubble that was causing
you overflow problems. Now when the engine heats up, the air will expand
and be forced through the tube into the recovery bottle, where sufficient
space is left for it to fill. After two or three trips in the car, water
will have replaced the air in the radiator top tank, effectively making
your systems capacity one pint larger. (You have eliminated the annoying
run off, sealed the system to prevent the almost constant loss of coolant
and increased the system's capacity and hence efficiency, all at the
expenditure of comparatively little time and money).
The best design for this simple air dam we've been able to come up with uses a 12" x 27" piece of rubber floor matting available at most hardware stores. This is fixed in place with bolts that hold the radiator to the frame beneath it. The rubber matting, after it is bolted on, can be draped over the steering rods, and will not interfere with their operation. It must be long enough to extend the bottom of the frame; 12 inches should do the trick, and 27 inches should be sufficient horizontally. As the air hits this dam, it will force it into place in front of the suspension frame just behind the radiator. Above 25 m.p.h., this system will really work. The relatively low pressure inside the engine compartment pulls air through the radiator and down and under the car. Side benefits include:
One other additional change is a good idea: a plastic fan. For example, Ford Cortina engines which can, and most likely should, switch to a Capri 1600 water pump, of higher capacity than the one installed, requires a Capri 1600 pulley and plastic fan, available at many junk yards for under $10. The plastic fan came along some 15 years ago, when the price of copper, used extensively in radiators, was going up. While looking for a cheaper way to make radiators, firms took a hard look at the total system. The plastic fan is one result. It is light, unbreakable and can be set at a higher pitch, which will pull more air through the radiator at slow speed. Due to the flexibility of the plastic, the fan's pitch will be reduced as engine speed increases, lessening the drag on the fan and increasing gas mirage. Above 35-40 m.p.h. there is enough air blasting through the radiator most radiators that is! - that the fan does not really contribute that much. So the plastic fan pulls more air at slow speed when it is really needed, then bends out of the way when it is not! I have mentioned the Ford engine, but I'm sure that a plastic fan can be adapted to the Plus 4s and Plus 8s. In fact, the Factory should be able to supply a plastic fan, as I would think the new Plus 8s would come with one, as do most new cars, including the 4/4.
If you are looking into this, the important things to remember are:
distance between pulley and the frame behind the radiator; the bolt pattern
and center locating hub of the pulley itself; diameter of the fan being
considered. It can only be as large as the hoses and engine parts in the
vicinity will allow. It might surprise many 4/4 owners to find that they
can fit as large as 12 inches. With the many plastic fans fitted to
British cars in the 70s, most of which followed similar design patterns,
you should be able to find one suitable to your Morgan. A good wrecking
yard can help.
Dwight Smith, MOG NORTHWEST
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