Fuel and Coolant Leaks can be Dangerous and Expensive, yet Checking is not Difficult…
Kim Henson explains.
One way and another I spend a great deal of my time peering under bonnets of both new and old vehicles, and lately I have encountered a number of cars with potentially dangerous leaks of fuel and coolant.
Fuel weeping from a loose union or a split hose will ignite if it gets the slightest opportunity – for example if it comes into contact with a hot exhaust system/catalytic converter. Just this week I was working on a classic car and its owner was unaware that there was a small but significant leak from an inlet union on the mechanical fuel pump. The union was securely re-tightened in seconds, yet the car’s owner had never thought to investigate why, in the preceding few weeks, he could smell petrol.
Before tightening unions on older cars, ensure that the sealing washers (often, fibre types) or ‘O’ rings are in good condition; if necessary renew them.
While unions need to be tight, care is required… The mechanical petrol pumps used on many cars have aluminium bodies and care needs to be taken to avoid over-tightening unions, or the threads can easily be stripped from the pump body, requiring a thread insert to be installed, or the pump to be replaced.
On newer models the underbonnet pipework is often extensive and many of the pipes/hoses employed in the various systems (including cooling system hoses, also vacuum pipes) are made from brittle plastic which becomes more fragile as it ages, partly due to the build-up of heat within the confined underbonnet space.
I was reminded of this last week when a coolant hose stub, made of plastic, sheared off on the engine of a modern sporty hatchback just a few years old. The stub had broken because the plastic had degraded and was ‘rotten’. Ironically it broke when the coolant hose condition was being checked…
Leaking fuel or coolant can become very expensive… even more so if the engine is wrecked as the result of overheating due to coolant loss.
So, about once a week it is wise to visually inspect the fuel and coolant hoses/pipes/connections. Ideally do this when the engine is cold (note that if a coolant hose or union ‘lets go’ when the engine is hot and the coolant is under pressure, a dangerous shower of anti-freeze mixture will be unleashed…). If you see signs of a leak, take action to fix the problem; call a mechanic if you are unsure of how to proceed yourself.