Cooling

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Here comes summer… as the old 50’s song goes – but for many classic owners that can mean becoming hot under the collar with overheating woes. But it needn’t be if you follow this advice on keeping your cool

If you see a classic broken-down by the roadside this summer, then the chances are that it has overheated – along with its owner no doubt! But while it’s a common occurrence, this needn’t be the case. After all, they didn’t boil over when they were new – so why should they now if the system is properly maintained? Here’s how to keep your cool. And your cash!

MAINTENANCE MATTERS

• Start with hoses; check they are okay, not ageing and bulging past their clips (which should also be in good order and preferably proper ‘Jubilee’ type affairs and not the cheap and nasty wire sort). However, simply because a hose looks okay, it doesn’t mean that it hasn’t collapsed internally, so remove and check if in any doubt.

 

• Now, check the radiator cap plus its spring and rubber seal – replace if the cap looks past it but do check it’s the right poundage as many engines had this revised over their production runs. As it affects the system’s efficiency as well as the water pump’s performance in particular, are you absolutely certain that the correct one fitted?

 

• With the engine up to temp, remove the said cap (very carefully if the water is up to temp) and check that the water is circulating, indicating that the thermostat and water pump are okay; the latter should give a vigorous flow. If this isn’t the case (and it may also mean a blockage) then consider replacing both to play safe.

 

• A good flush through the internals with a hose, in conjunction with one of the numerous de-scaling additives widely available, is sensible if it hasn’t been done for many years but follow the specific instructions for it to work properly.

OIL’S WELL?

Did you know that engine oil accounts for up to a third of an engine’s cooling performance? Well it does and as you can appreciate, it makes sense to use a top quality brew changed regularly. You can fit an oil cooler, but generally this isn’t needed unless you run a tuned engine that’s continually driven hard; in general terms, you don’t want oil exceeding around 80 degrees.

Be warned, however, that anything less and the oil will be too cool and lead to heavier fuel consumption and wear rates even though coolers usually have their own thermostats incorporated. One way of ascertaining whether you need a cooler is to drive the car flat out for 10 miles (legally, safely!) and note how much the oil pressure gauge’s needle falls, assuming you have one fitted.

AIR TO THE GROAN?

An air lock in the cooling system is the automotive equivalent of trapped wind – and is just as painful! Likewise, it’s usually caused by gulping things down, in this case large quantities of water, say after replacing a hose? Air becomes logged not allowing proper circulation and hot spots occur, this causing the engine to sporadically overheat.

To rid the system of an airlock depends on its severity and location. In many instances, simply running the engine up to temp with the rad cap removed and regularly squeezing the top and bottom hoses can do the trick, otherwise it’s disconnecting a heater return hose, running the engine until water (take care it’s not hot) stops flowing out before resuming evenly, signifying the air has been expelled.

Before any of this though, you must ensue that the car’s heater is fully on and the lever in the ‘hot’ position. This is how air locks can form here and if in doubt check that the cables and water valve are operating properly, otherwise you’ll never get rid of the problem. Similarly, before any major refills, set the heater to the ‘hot’ position.

FEELING FLUSHED WITH SUCCESS?

Play your cards right with this flush and you can cure all your overheating ills. There are two methods, a normal flush and a reverse one, which as the name suggests goes against the normal coolant flow. Some mechanics are opposed to this as any gunge can be forced back and clog the system elsewhere. First decide if you are going to use a special descaling additive; follow instructions fully. Flushing means removing the thermostat and replacing the housing and turning the heater to its ‘hot’ position.

Disconnect the top hose (if the rad is still in situ – plug the stub up but with rad cap removed). Insert a hose in the top of the radiator and fully turn on the hose – some advocate running the engine at the same time so pump encourages speedier flow. A reverse flush means you fill via the thermostat housing – consult an expert if in doubt.