Can Diesel Knock Damage the Engine? Reasons and Fixes

Diesel knock is just a normal thing and it doesn't damage the engine in any way. Diesel engines should knock but you have to distinguish between normal and bad knock. If the engine changes the way it sounds and works, you should immediately consult with a specialist. But if it knocks just as always, you shouldn't worry.

Diesel engine problems highlights

• Level of importance:Medium
• Commonreasons:Age and mileage, aggressive driving, poor maintenance
• DIY inspection:In most cases, impossible
• DIY repair:Impossible
• Price for repair:$650 - $1,500
• Can you drive?Depends on the issue
• Ways to fix:Replace the worn-out parts, professionalrepair is usually possible only

Distinguishing between good and bad diesel-knocking sounds

You may know that diesel engines sound differently from gasoline ones. They usually knock when they work and sometimes it may seem that they even vibrate much more than a gasoline engine. In some cases, you may think that the knocking is not normal and may suspect that the engine is dying.

This is especially common for inexperienced drivers who open the hood when the engine is working. While from inside of your vehicle, you may not hear anything bad, after opening the hood you clearly hear that something is probably wrong with the engine.

Here's how you can say that there is actually a problem:

• the engine is vibrating heavily - you clearly see that it jumps to different sides in the engine bay;
• the sound has become much louder than it was before - this is a clear sign of problems with a diesel engine;
• the sound seems to be chaotic, not rhythmic, this usually means that the engine needs your help;
• the engine changes its behavior - it seems to be less powerful and the fuel mileage drops heavily;
• the weird sounds become much clearer when you press the gas pedal in your vehicle.

But overall, you need to understand that the diesel engine will anyway knock. It means that the engine will make some weird sounds and will work much louder than any gasoline engine. The question of how you can differentiate between normal diesel sounds and knocking which means problems with the diesel engine is too hard to answer.

The thing is that different diesel engines have different normal sounds and when you are driving a new car or you are driving your vehicle in new circumstances (for example, the first time on the highway), you may notice that something is wrong. In most cases, it's OK and this special knocking sound doesn't damage your engine - this is just how it works.

The knocking is weird - what should I do?

Even though I tried to persuade you that diesel engines knock and it's OK, you may still feel worried about the vehicle. That's fine, this is how you should react to something that you don't understand. The knocking sound in the vehicle may actually be a sign of bad problems that need your immediate reaction.

If you suspect that something is wrong with the car, here's what you should do:

• first of all, stop the vehicle and make sure you don't make things worse;
• secondly, find the nearest dealership or repair shop that can help you figure out all the problems;
• you may carefully drive to this place or, if things are too bad, find another way to get your car there;
• ask professional mechanics to check if there is something wrong with the engine;
• engine diagnosis is not that fast, so you will need to leave the vehicle for several hours;
• after you get the information from mechanics, understand if the problem is serious;
• ask them what are the best solutions in your situation.

Sometimes, the problem is as simple as contaminated oil that changes the way the engine works. But bad knocking may mean problems with expensive and hard-to-reach parts in your diesel engine. This means that the engine will need some complicated repairs and a lot of investment. And this thing should be investigated much better than just a quick diagnosis in a shop.

Be careful and always double check what mechanics say. Sometimes, they may add some problems that your engine actually doesn't have. This makes the final price for the work much higher than it should be.

Most common reasons for the knocking diesel engine

Once again, I want to underline that certain knocking is OK for the diesel engine and you can use it without any repairs or problems. The rhythmic knocking is just the way the diesel engine should work and it doesn't destroy it and doesn't pose any risks.

If the knocking is suspiciously loud or bad, you should visit the repair shop and have the vehicle diagnosed. But what will you learn after the specialist inspects your car? In most cases, the problem may be connected with such issues:

• bad lifters - diesel engines also have valve lifters and they may fail, very often they are the source of additional knocking;
• destroyed valve - one more issue that can cause loud knocking is the problem with one of the valves that can be bent or misshaped in any other way;
• bad piston - the piston may knock in a diesel engine because it's old and destroyed or damaged by something;
• issues with the timing system - when the timing belt or chain jumps a little, the engine may still work, but it will knock like crazy;
• overall wear and tear - older diesel engines tend to knock a lot and this sometimes means that they are almost dead.

Although it's hard to differentiate between normal and bad knocking, you may do that by adding knowledge about the common issues that cause bad knocking. In a diesel engine, there are quite a lot of units that can knock and cause problems. Unfortunately, nearly all of them are hard to repair and even inspect, so engine repair is not going to cost you a little money.

I also have to say that very often diesel engines just get louder after they reach some mileage or age. And it's OK, you just need to care about them and maintain them properly to let them live some more time.

How can you prevent diesel engines from knocking?

It's impossible to stop the diesel engine from knocking. Because its nature is to knock. But you can also overlook important symptoms of problems and eventually see the engine dying. So, even if it just seems to you that the engine is not feeling good, you should immediately plan a visit to one of the trusted repair shops and have the vehicle diagnosed.

A certain attention to the engine is important, so you should obviously have it inspected when something is wrong or just regularly.

Here are some ways to prevent a diesel engine from knocking:

• maintain the engine at least using the intervals that the manufacturer recommends;
• as the engine gets older, reduce the oil change intervals;
• get good fluids and parts when you maintain the engine or repair it;
• always make sure that mechanics who work with your engine have enough experience;
• plan a visit to the trusted repair shop once you feel that something is wrong;
• never ignore problems with your engine and never drive it if it has a serious issue;
• check the oil levels and keep the level at least in the middle between MAX and MIN marks at all times;
• never overheat the engine by overloading it or ignoring problems with the cooling system.

These are important factors that will make your engine work better and longer. I can't say that they will help you drive 500K miles, but if you follow these simple rules, you will most likely have more chances to prolong the life of the engine and not hear those bad knocks.

Also, such an attitude towards your engine will help you experience fewer problems with it. It's important to remember that ignoring issues is the direct way to the overhaul or even replacement of the engine.

Final thoughts

Your diesel engine is going to knock anyway just because it's the diesel engine and knocking is its nature. But if it starts knocking loudly or has changed its behavior, you should pay attention to the condition of the engine. It's important to understand that the engine is a complicated unit that isn't going to work for a long time if it malfunctions and has some problems.

So, the best thing you can do if you hear the engine knocking is to go directly to the repair shop or dealership and find the reason for this knock. If this is just a simple diesel knock, the experienced mechanic will tell you this and you will be able to drive further without any suspicious ideas about engine damage.