The German Car Blog

4 Reasons You Shouldn't Leave Your Diesel Engine's Water Separator Undrained

9 July 2019 by Yvonne Carter

Diesel engines come with plenty of advantages, including superior efficiency, added torque and lower maintenance requirements. However, one drawback is that diesel fuel can become contaminated with water more easily than gasoline because it absorbs water more readily. This is why many diesel engines are fitted with a water separator that takes water out of the fuel. You'll usually find it near the fuel filter.

Of course, you'll need to drain the water separator whenever it gets full. If you don't, it will not work as well, so most vehicles have a sensor that tells you when it's time. Here are just four reasons why you should always drain your water separator when it's full.

1. Water Leads to a Loss of Lubrication

Just like any other engine, a diesel needs plenty of lubrication to prevent friction when parts move against each other. Without the proper lubrication, overheating can occur, and engine parts can quickly wear out. When fuel contains too much water, it wears your engine's lubricants away, making future breakdowns more likely.

2. Water Leads to Clogging

When a compound starts to break down due to an interaction with water, the process is known as hydrolysis. This is exactly what happens when diesel fuel interacts with water. As diesel fuel breaks down, you end up with a darker fuel that develops sludge and solid material. Once this happens, that sludge and solid material will start to build up and form clogs, which often leads to the need for extensive and expensive repairs.

3. Water Leads to Excessive Smoke

As soon as you notice smoke coming from your exhaust, you can be sure something is going wrong within the powertrain or exhaust. If your diesel fuel contains too much water, you'll often notice heavy black or white smoke exiting the exhaust during engine operation. This isn't pleasant for you or for your fellow road users, and excessive smoke can damage parts of the exhaust.

4. Water Leads to Erratic Driving

Plenty of people think it's fine to keep driving as long as their vehicle is still behaving as it should. Unfortunately, leaving your diesel engine water separator undrained is soon going to make driving harder. When your engine is forced to use fuel that's contaminated with too much water, it often cannot fire properly. You may notice erratic idling and unpredictable performance. It's common for the engine to cut out unexpectedly, usually while you're accelerating.

If you need to service your diesel engine, visit a local car service.

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