Leaks are often the first sign of problems beneath the bonnet of your car. From steering and braking issues to overheating, loss of performance or complete engine failure, if a leak isn’t taken seriously, the consequences can be costly. Leaks are a problem all motorists will likely have to face at some point, so it’s important to know exactly what’s leaking and why.
To help you identify the fluid that’s leaking from your car, here’s a brief guide on how to recognise leaks beneath the bonnet or on your driveway. Our guide includes a quick reference table to the different characteristics of each fluid, as well as useful tips on the best way to spot if your car has a leak.
What’s that Leak Quick Reference Guide
Use the table below to quickly identify the fluid that’s leaking from your car, or scroll down for more information on the characteristics of each fluid, and where they’re likely to be leaking from.
|Fluid Type:||Colour:||Consistency/Smell:||Areas Prone to Leak:|
|Engine Oil||Light brown/black||Oily; distinctive smell (check dipstick scent)||Timing cover; oil filter; oil sump; head gasket|
|Transmission Fluid||Pink, red, or brown||Slick/oily; clean or odourless scent||Axle seal and output shaft seal|
|Power Steering Fluid||Reddish brown||Thin consistency; sweet burning smell||Rack end seals on rack and pinion system|
|Brake Fluid||Pale amber||Similar to cooking oil||Master cylinders; flex lines; brake calliper seals|
|Coolant/Antifreeze||Bright green or yellow||Thin consistency; sweet odour||Water pump; radiator; hoses; freeze plugs; heater core; head gasket|
|Water||Clear||Thin consistency; odourless||Air conditioning unit|
The colour of engine oil depends on when it was last changed and the age of your car. New engine oil is light brown in colour, but can look black if it hasn’t been changed in a while. If your car is leaking engine oil, there could be a stain where the car has been parked. Engine oil will feel oily to touch (obviously), and won’t be easily washed away with water. Each brand smells different, so if you’re unsure, remove the dipstick and check the odour of your engine oil.
Oil can often leak from the timing cover, oil filter, sump plug and head gasket. A small leak (a few drops every week) may be usual on high mileage vehicles, so ensure you keep it topped up and check the levels regularly. Larger leaks should be fixed, so take your car to a professional mechanic if you suspect and engine oil leak.
Depending on its age and condition, transmission fluid can either be oink, red, or brown. As the transmission assembly is located beneath the car, you’ll probably notice a stain on the road if the system is leaking. Like engine oil, transmission fluid is slippery to the touch and can be mistaken for engine oil.
Leaks aren’t common on manual transmission cars, but are more common in automatics. Common areas prone to transmission fluid leaks include the axle seal and output shaft seal. If you notice a significant leak, it’s always best to have a professional take a look.
Power Steering Fluid
Not to be mistaken for transmission fluid; power steering fluid has a reddish-brown colouring and thin consistency. What sets it apart from transmission fluid is its distinctive smell, which is quite difficult to describe; we’d say it’s like something sweet burning.
Power steering fluid leaks are rare, but when they do occur it’s normally near the steering rack, specifically the rack end seals on a rack and pinion steering system. This may result in the system squealing or the steering becoming heavy. Top up the system following the manufacturer’s guidelines and monitor the levels. If the leak persists, have a professional take a look.
Brake fluid is characterised by its colour – in that it doesn’t have one relative to other fluids in the car. It’s clear or pale amber and resembles cooking oil.
Areas prone to brake fluid leakage are the master cylinders and flex lines, as well as the brake calliper seals. If you suspect a brake fluid leak, don’t drive the car! Check the level and top it up if necessary. Start the car and pump the brakes while stationary and check if the level has dropped. Have a professional check it out immediately if you suspect a leak.
Of all the fluids to spring a leak beneath the bonnet, coolant/antifreeze is the easiest to identify. This is thanks to its bright green or yellow colour, and its distinctive sweet odour.
There are many places around the engine bay where coolant/antifreeze can leak from, and any leaks are usually easy to find. Coolant/antifreeze leaks can occur on the water pump, radiator, hoses, freeze plugs, heater core and head gasket.
We won’t insult your intelligence by going into detail about how water looks, feels and smells. Basically, if you notice clear, odourless liquid dripping from your car — particularly on the front passenger side — there’s no need to worry. If your car has air conditioning which was switched on before you parked, it may be that the condensed water has drained from the conditioning unit, leaving a small pool on your driveway.
How to Know if Your Car Has a Fluid Leak
It can be tricky to determine whether your car has sprung a leak, and locate where it’s coming from. Here, we offer practical tips on how to detect a leak before it can become a serious problem.
- Place cardboard or newspaper beneath your car — This is an easy way to check if your car has developed a leak, and identify the fluid by its colour, smell, consistency – helping you diagnose the problem early. Once you’ve placed the cardboard/paper, leave the car stationary for a good period (overnight if possible), giving the fluid time to drip.
- Look for fluid on components beneath the car — If you’re having trouble finding the source of a leak, jack the car up and have a look at the components on the undercarriage. If one of the mechanical areas is leaking, the fluid may blow backwards onto different components as you drive. Move forward from where you spot the sign of drips, and you should find the culprit.
- Use white foot powder to trace the source of a leak — Once you’ve found the general area of where a leak is coming from, using spray-on white foot powder is a good way to work out exactly which component is faulty. Foot powder is great because it easily wipes off, and will highlight what’s dripping and where from. Spray the powder onto the suspected area, then run the engine for a few seconds. If you’ve sprayed in the right place, you should find drips in the white powder – helping you trace the leak to its source.
- Park on a flat surface when checking for leaks — It might sound obvious, but always remember to park somewhere flat when checking for leaks. If the car is on a slope, it’ll make it much more difficult to trace any drips back to the problem area. Not only that, but it’ll skew the levels on the reservoirs beneath the bonnet, so you won’t be able to get an accurate reading.
At Prestone we test our products in the toughest conditions so you know they perform for you every day on the road. To find out more about our products, visit the Prestone website
Image sourced via Flickr Creative Commons. Credit: Robert Couse-Baker, David Murray, brian gautreau, EvelynGiggles, Robyn Corps.