My Engine Is Blowing Smoke! What Does It Mean?

My Engine Is Blowing Smoke, What Does It Mean?

So, you put the pedal down and a cloud of smoke can be seen. That’s not good. But what does it mean? Well it depends. Some small amount of smoke may not be a fatal sign in your motor, but too much can be sign things are not well.

Let’s deal with petrol or gasoline type motors and consider some of the symptoms that will help us tell how bad things are.

Firstly how much smoke is your vehicle blowing? When did you notice it?

  •  If you noticed the engine smoke in the rear view mirror. Then it can be a very bad sign. Generally there has to be quite a bit of smoke for you to see it in the rear view mirror! If it wasn’t you that noticed it and someone else has seen it and alerted you, or you saw your own car under heavy acceleration blow some black smoke, it can simply be over rich mixture. This will usually be a puff of dirty black smoke which only really shows up under heavy acceleration. The injectors or carburettor are pushing more fuel into the engine than can be easily burned all at once. This may be no real problem.

What colour is the smoke?

  • If it is blue or blue-white in colour, then it can be another not so good sign. If there is blue in the engine smoke, that means it may be produced from burning oil. Whereas if it is more of a black smoke it may be over rich mixture under heavy acceleration as outlined in the previous point.

 When did you notice the smoking motor?

  • If it is at any time the vehicle is under load or accelerating then this once again may be a not so good sign. If it also seems to get worse as the engine gets hotter. This is also not so good

How is your engine oil holding up?

  • If your oil needs topping up often and there does not seem to be a lot of fresh drips of oil on the ground after parking your car for a while. Then this is a pretty strong indication the oil is going somewhere else than on the ground.

Does the engine seem to be a bit lower in power than it used to be?

  •  If the engine seems to not quite have that same ‘zing’ as it used to, then it could be re-enforcing our oil burning concerns. An oil burning car engine will lose power generally. This can make the car feel sluggish, especially under load. Often this is most noticeable up a decent sort of hill. If it is really feeling like the vehicle is working hard getting up a decent hill, then it is a sign something is not right.

Is the engine running a bit hotter than it used to?

  • If you have a temperature gauge and it seems to have crept up from where it used to be by a few degrees then again this can be a sign we have a tired engine on our hands. Once again this heating will be more pronounced in the up a decent long hill type scenario. If you notice the gauge creeping up as you climb, when you have not noticed it before then this is a sign the motor is not performing well under load.

Is the motor making more noise than it used to under load?

  • Once again, we are on that hill and the motor seems to be clattering, or making more noise than it should every time we push it.  The smoke is there and the rattle is not good.

Does the engine fume when you open the oil filler cap?

  • This can be a good test. But of course it is not wise to do this with a hot engine. If you are not confident to do this step leave it to a professional. Start the engine up and leave it to idle. Loosen the oil filler cap gently. Then remove it completely. If you notice a lot of fumes and pressure coming out of the cap this is also not a good sign. If the fumes look contaminated with smoke too then its a very bad sign. Basically there should be very little ‘fumes’ blowing out of the motor in a motor that is in good condition. There will always be some, but there should not be a lot. Remember to fit the oil cap back in place and clean any spots of oil that may have come out with a rag. Note that the engine may stumble a little bit as you open the cap as the pressure change may affect some controls hooked up to the engine.

 How many miles or kilometres has your engine done?

  •  If you are noticing some of the other signs listed previously and your engine has done a lot of kilometres then this is a big re-enforcer to our diagnosis. If the vehicle has done quite a few hundred thousand kilometres, or a couple of hundred thousand miles. It will surely have wear. If the kilometres are under 100 thousand or under 60 thousand miles and the vehicle has been well serviced; never run out of oil, then it would be very strange for it to have an oil burning issue. If your vehicle has done a lot of work and is showing other signs mentioned then it may be at the end of its life.  It is important to note that you only have to let the engine oil run low once to cause catastrophic damage to the motor.  This hardly seems fair.  But it is the case.

 What will a mechanic do to test and confirm my concerns?

  • A mechanic has a device that can test the compression of a motor or engine. Basically the compression tester goes in one of the spark plug holes and as the motor is cranked by the starter motor it will show the pressure build up in the cylinders. A loss of compression from the standards laid down by the manufacturer for the motor in your vehicle, will tell the mechanic how badly worn things are. This is usually pretty accurate as far as a test of the engine wear goes.

To sum up, let’s say that our engine is blowing blue smoke under acceleration, it does seem sluggish up hills and seems to be getting hot too. When the oil filler cap is removed there are visible fumes blowing out with some pressure. Ok, so now with this set of questions answered we can pretty safely say, we have an oil burning engine on our hands.

Why does the engine or motor smoke?

The engine relies on very precise tolerances between operating parts. It needs oil between all these moving parts too. This avoids the motor seizing or locking up due to friction. But you can imagine that if over time, due to wear, the gaps between these parts gets a bit too wide we can get an issue where oil ends up where it should not be in large quantity. Such as in the combustion chamber. You can imagine that if we put oil on a fire we are going to get smoke! So what happens is the oil in a worn motor is allowed to pass by things like valves and piston rings. This allows it to get into the combustion chamber and with each firing of the fuel air mix the excess oil gets turned to smoke. The harder you work the motor the worse this gets. It can often be called bypass. Not only does the oil bypass the seals, but also the pressurised gas. This also means that the pressure can flow back into the crank case and up into the rocker covers. If you did the check of removing the oil filler cap. Then you may have seen those fumes. The ones that bypass the sealing engine parts such as the valves and pistons.

The two illustrations below show in very simple graphic terms where the oil and pressure bypass the worn parts.

Oil Bypasses Worn Rings And Valve Stem Seals

Oil In The Engine By-Passes Seals And Piston Rings
Oil In The Engine By-Passes Seals And Piston Rings

Hot Gasses Bypass Worn Valve Stem Seals And Rings

Hot gasses bypassing worn rings and valve stem seals
Hot Gasses Bypassing Worn Rings And Valve Stem Seals


What can I do about this problem?

It is possible through diagnosis to find that the valve stems are worn according to the graphic but the piston rings seem ok.  Or vice versa. Some mechanics may advise getting the head reconditioned as a cost effective option. This can be a very short term fix. What can happen is that the reconditioned head which now has the full seal back pushes the pressure right up to where it should be. But due to the bottom end and rings not being put back to standards, the extra pressure now starts to bypass the old rings. Even if it was not doing that before. This is due to the old rings not really bypassing that much under the low pressure of the worn and tired valves keeping the pressure extra low. So often what happens if one part of the motor is re-built is that the other will fail due to the extra pressures being placed on it by the reconditioned parts. The best options are to either recondition all parts of the motor. Or alternatively get a replacement used engine that has plenty of miles/kilometres left on the clock.  Here is a great place to buy used engines with plenty of miles left on the clock.

Anything short of these two solutions will usually come back as another problem in the near future. Please also see the section on fitting a replacement engine for other useful tips about the cooling system etc.

Having tried many short cuts over the years, I can vouch for how much money I have wasted not doing the job correctly from the start. If the motor is showing that it is an oil burner then it is really a terminal engine and is needing to be replaced or given an extensive reconditioning.

Why not just keep driving?

Well often you can for a while. But remember the EPA (Environmental Protection Authority) or RTA (Road Traffic Authority) may think otherwise. In many states, it is encouraged to report offenders. So it is probably only a matter of time before you get caught and end up with a fine.

Beside the penalty for being a polluter there is also the issue of pollution to the environment at a real and moral level. The more people that make sure they have an engine in good working condition in their vehicles, the less pollution we have. This will help us all minimise damage to our shared air quality and cut the detrimental effects to human health. So consider all these things when you are working out what to do with your old smokey.

If you put a replacement power plant in, you will often feel the joy of driving a fully powered vehicle again. Often we don’t realise how much power the old work horse has lost. With a freshly replaced well performing engine, driving can become a joy again. Not to mention avoiding having to stop constantly and check that fast diminishing oil level!

Share on Facebook+1Share on LinkedIn

Diagnosing Car-Auto Motor-Engine Knock Motor-Engine Pinging For Your Car-Auto. Do I need a new motor-engine?

Replace My Car Or Auto Engine / Motor? Understanding Pinging, Knocking & Other Sounds in my engine.

This post is applicable to petrol and gas / LPG  engines.  (The diagnosis of diesel engines is different and will be the subject of a further blog post.)

So there is a strange noise in your car-auto engine or motor?  Perhaps you had heard it before but wanted to ignore it?  A noise like this can be very annoying.  It is possible to diagnose what is going on, with some understanding of the the sound and what the various sounds may mean.  Let’s go through some of the noises and their possible cause and solutions.

So what does the engine-motor noise sound like?

Not all engine knocking sounds are the same.  It’s a little bit like when your doctor listens to your chest for the sound of the heart.  It’s exactly the same principle.  The doctor is listening for tell tale sounds that may indicate the heart mechanics, including valves, are not opening and closing as they should be.  How amazing is that?  A skilled ear can make quite an accurate diagnosis!  So what does a skilled ear listen for when diagnosing an engine knock.  If you imagine that there can be a tonal scale to the knock and its like tuning a piano.  There are keys that are high pitched and there are low pitched or deep sounding keys.  With various problems in a motor that cause a knock there is also the very high pitched metallic sound right down to a dull hard knock.  We are going to categorise these sounds into two possible categories and keep this at the basic level:

  1. Knocking

  2. Pinging

Knocking implies a much stronger sound.  A mechanic that might say that an engine has an ‘engine knock’ is referring to a strong sound almost like you were hitting a very solid metal object with an equally hard metal hammer.  If the sound is like that; very low in tone, it could be a very bad sign.  This indicates that the engine has something possibly going very wrong.  An engine has a lot of moving parts, they are covered in a film of oil where they come into close contact.  The parts must also have the correct tolerances to function properly.  If something starts to fail, it will usually be associated with some kind of warning sound.  Here are some of the possible points of failure in an engine that will often cause a ‘knock’:

  • Big end bearing failure

  • Engine oil pump failing

  • Wear gets to a point that engine oil pressure cannot be maintained

  • Valve sticking and hitting the piston

  • Broken piston or valve

  • And of course many others

So as we can see there are lots of points for failure.  Any one of these, will generally be associated with a pretty definite engine sound.  Usually something broken will sound pretty loud and become more pronounced under revs even with no load.  Usually getting much, much worse as you pedal the accelerator.  Of course there is cases where these sounds are not so pronounced even in a motor that is failing.  But generally they get worse progressively and without too much time.  If you start hearing a dull, deep knocking sound in any motor the first thing you should do is look for any engine warning signals on your interment cluster.  Immediately stop the motor.  Once stopped, you should check the engine oil level carefully.  If you are driving, of course pull over where it is safe to do so.  The procedure for this is important to get a good reading of your oil level, don’t short cut it as it is possible to think your oil is good when it is indeed low:

Stop the engine

  1. Pull the dipstick

  2. Clean it or all oil, with a lint free rag (Observe the high and low points on the stick for future reference, they are usually stamped into the stick)

  3. Insert the dipstick and count to 10

  4. Pull it out again carefully without touching any part of the car or your hand on the reading end

  5. Check the low and high points for oil mark

If the oil is not bang on the high point, add oil in small amounts to get it to the high point following steps 1-5 until it is exactly on the right mark.  NEVER over fill the engine with oil!  It can damage the motor.

If the engine oil was too low, it can cause the knocking noise.  It can also do major damage to the engine.  So if that was the problem, you need to get the engine checked out for the following:

  • Leaking gaskets

  • Wear, creating bypass where the oil gets burned up or blown out in smoke

If the oil level is ok and the knock is still there.  Then there may still be some other major problem.  If the knock is getting progressively worse or perhaps is worse under load then these may also not be good signs.  It is best to get the engine checked out by a professional.   If you are pretty sure that you need a replacement engine then you can check out our preferred suppliers on our partner page to get some help.  This company has a lot of low mileage engines car parts and are happy to help.

What if the sound is not so loud and is not so low in tone?  If it almost sounds like the hammer is a much lighter one and it is tapping very fast on aluminium.  If this sound is also not always there, but can be heard under load or high revs.  It can be something quite different.  It may be ‘pinging’.

It can be a big mistake to over react to pinging.  So let’s summarise the sounds and conditions of pinging.

The sound is more like a higher pitch tap of light metal on metal.  It can even sound like something is rattling or lose in the motor.  It can be much worse under higher revs and under load.  It may be completely non existent at low revs with no load on the engine.  The sound may also get worse as the engine runs in very hot conditions.

So what is pinging caused by?

The pistons in the engine are forced down in the cylinders by the explosion of fuel within the cylinders.  The idea is that the triggering of this explosion at the right time is critical to the motors proper functioning.  You can imagine what would happen if the explosion happened too soon?  It causes the rising piston to hit a wall of gasses.  This is called pre-ignition.  In simple terms causes the piston to ‘rattle’ in the bore and slap the sides of the metal bore as it rattles.  It results in pinging.  What causes this?

Here is a picture of what is going on inside the motor.

Pinging caused by pre-ignition

In general a couple of things:

  1. Poor quality fuel

  2. Bad engine timing

How much of an issue is poor quality fuel?

Well it’s a big one, if you are located in Australia like me.  The quality of fuel we get is massively variable.  This can be a clue to your problem.  If you recently filled up your fuel tank, then very close to this event the ‘pinging’ started; it is a dead give away.  Often we get fuel that has been sourced from lower quality sources.  These fuel sources may have lower ‘octane’ levels than what your car can handle.  This can lead to pinging.  The other thing can be accidentally putting the wrong fuel into your car.  Some cars are mean’t only to be run on the higher octane or premium fuels.  This will cause these higher specification engines to have difficulty adjusting to the lower octane fuels.  (Octane level is in simple terms how much explosive force in the fuel.  The higher the octane, theoretically the higher the energy output for the same amount of fuel.)

Not all engines are the same.  Some are far more prone to this engine pinging issue.  For example, I have a BA Ford Fairmont and this vehicle is very prone to the affects of pre-ignition or pinging, when it gets bad fuel and when its a very hot day.  This combination seems to really bring on the issue.  It is nearly impossible to accelerate and put the car under load without hearing some pinging.  The car has been for multiple tune-ups and it seems that the engine is not able to adjust its computer enough to correct the ignition to the right point.  Ideally pinging should not be left unattended to.   Obviously if your pistons are rattling in the bores constantly there is damage done to the motor.  The engine will also not be developing full power.  So get the engine looked at by a professional mechanic. Or of course change your fuel if you think that could be the cause.  I would also encourage you to experiment with various fuel providers.  If you have a vehicle you think may need high octane fuel, make sure you give it only that.

Share on Facebook+1Share on LinkedIn