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But not in a classic car during the summer, thank you very much! Here’s how to keep your cool and avoid overheating and some nasty repair bills

Chances are that when you see a fellow classic car owner by the roadside this summer with the bonnet up, it will be because it has overheated – along with driver and any passengers no doubt. Some think that it’s part-and parcel of the joys of old car motoring and yet there’s no reason to suffer from it – after all, they kept their cool when new! So it’s case of regular maintenance and improvements to bring back those good old days – here’s how.

1. Hot headed

Does your car inherently suffer from overheating or have known problems? A specialist or owners’ club should be able to point you in the right direction here along with suitable causes and cures.

2. Back to basics

Because your classic may not be used much, it’s easy to neglect the basics, such as checking coolant level before setting off, looking for leaks (anti-freeze is great at leaving a trace where it is getting out), that sort of thing. And yet it’s a prime time to sport early dangers, as is the temperature gauge registering slightly higher than usual. Don’t procrastinate!

3. Maintenance matters

This is the key to sleep easy reliability. Start with hoses; check they are okay and not ageing or bulging past their clips (which should also be in good order and preferably proper ‘Jubilee’ type designs and not the nasty wire sort). Just because a hose looks okay, it doesn’t mean that it hasn’t collapsed internally, so remove and check, if in doubt. Naturally, ensure the fan belt is in good condition and properly tensioned.

4. Cap it all

Now, check the radiator cap plus its spring and rubber seal – replace it if it looks past it. Is the cap the correct rating for the engine? It’s not unknown for carmakers to change specifications during a model’s production run so check you have the correct one for your model, engine and year.

5. Go with the flow

With the engine up to temp, remove the said rad cap (very carefully to avoid scalding) and check that the water is circulating, indicating that both the thermostat and the water pump are okay; the latter should give a vigorous but even flow. If this isn’t the case (and it may also mean a blockage in the system), consider replacing both.

6. Flushed with success

A good flush through of the system with a hose at the same time, in conjunction with one of the numerous de-scaling additives that are widely available, is a sensible ploy every couple of years. Also, remove the radiator and play a jet of water through the ‘honeycomb’ rad fins (both sides) to remove a build-up of debris, road muck, dead insects etc (the transverse-mounted rads on BMC cars suffer badly here). If you can, compare your rad with a new one and we’ll bet you that your old one weighs a couple of pounds heavier simply due to the build up of scale in there…

7. Facts on stats

Thermostats aren’t just open and shut cases; they are constantly operating, and so they age and deteriorate. A new ’stat can work wonders, and you can even change the operating temperature by fitting a ‘winter’ one, which opens at a higher temperature, and so makes the engine run hotter, if desired.

Don’t be clever and be tempted to run without a ’stat thinking that it will halt any cooling woes since, on some engines, it forms part of the circulation route and the lack of the ’stat upsets the flow, leading to greater overheating – even seizure!

8. Not just water

Change the anti-freeze at the same time and keep it in the engine all year round as today’s brews lower the icing temperature of water in the winter and yet raise the Centigrades when hot, to reduce the risk of boiling. Critically, anti-freeze contains a corrosion inhibitor to prevent furring up of the waterways. Some enthusiasts run a 50 per cent mix of anti-freeze, and change it yearly, to keep trouble at bay; cheap insurance, it has to be said…

9. Locked out?

Airlocks, usually identified by poor heater performance are easy to trap (possibly due to incorrect filling) will also cause overheating. To check for one, remove the highest positioned heater hose and run the engine; water should gush out at an even rate, but if it stops, then that’s the air bubble that’s causing all the trouble. It can sound like a toilet cistern once the engine is switched off – but it can also signify early signs of impending head gasket failure; have a pressure or chemical test at garage (around £30) to determine the culprit.

10. Keeping good timing is a must

Keeping your car’s engine in good tune is important as an over-weak fuel mixture and/or the incorrect ignition timing all cause an engine to run that bit hotter. If the carb or fuel injection system is faulty, or the distributor worn out, these will all need to be addressed.

11. How to become supercool

There’s no harm in making your classic’s cooling better than new and there’s no shortage of ideas and products available. Start with an uprated radiator, because it’s the heart of the system We’re strong advocates of uprated radiators, sporting larger, more efficient cores from the likes of Radtec, NAR and Aaron. Radtec, as an example, offers two stages of upgrade: Stage One provides up to 25 per cent extra cooling while Stage Two (more aimed at motorsport) offers no less than a 50 per cent improvement.

Older vehicles that use thermosyphoning, rather than a water pump, are prime culprits for overheating as the rads aren’t up to the job.

Uprated radiators are good value starting at around £200-300 but if you can’t run to one, even a new standard replacement usually reaps rewards as they do gum up over time which no flush will cure; it’s reckoned that you should consider replacing or having a rad overhauled every 7-10 years.

You can cheaply update by simply opting for radiator from an other, bigger-engined or export model that you own – consult an owners’ club or specialist here.

An electric cooling fan is a wise fit because a standard engine-driven fan is a wasteful device, as it does little at low speeds when the air ram effect is minimal, yet screams blue murder at high revs when you least need it. Revotec has a full range of dedicated kits along with electronic fan controllers (go to for the majority of classics.

If you’re a stickler for originality, have a look at overseas versions of your classic; in many cases they featured items such as larger cooling fans (and radiators).

There’s a number of useful special pour-in coolant additives that claim to make normal water ‘wetter’ (if you see what we mean) and so improve its efficiency, by giving superior surface contact between the coolant and metal surfaces it protects. At least 10 per cent gain is spoken of, plus it can be mixed with anti-freeze. However, in our view, such additives should be regarded as a little extra help, rather than a total solution to an overheating classic.

There’s no shortage of additives and tonics for cooling systems and this now includes really effective head gasket repairers, some claim to be permanent. Is it worth pouring in as a preventive measure (MGF owners take note!)? We can’t say, but given the cost of having a head gasket ‘pop’ it might be worth taking a chance, but speak to the manufacturer (they have helplines) first. There’s no excuse for losing your cool this summer, just ensure you service the cooling system now.

Aqua advantage

Why rely on water when there are better alternatives? Evans Waterless Coolants has a higher boiling point than water and effectively eliminates overheating, and after boil. As there’s no water, there’s no water pressure to build up and, being waterless, there’s no corrosion and erosion worries for the internals, so it is ideal for classics in storage – the product is used by Beaulieu’s museum for this very reason.

At £100, for a typical large engine, it’s not cheap, plus you’ll need to keep some in extra for top ups. On the plus side, it lasts a lifetime and in our experience works extremely well, with the only disadvantage being its ‘searching’ properties which are greater than anti-freeze, meaning it will search out the tiniest of leaks.


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