Water, Muffler & Car Engine Mystery

Usually, when you park your car for the night, the hot exhaust system cools down and atmospheric water condenses inside the pipe. By morning you have water vapor and liquid water lying inside those pipes.

When you start the car that morning, the hot gasses vaporize the water again and it re-condenses at the tail pipe, which is still cooler than the rest of the exhaust. So condensation and water droplets appear at the tail pipe.

Nothing to do with the engine's running condition, other than the car did start that morning, which is considered by many a blessing in itself.

There is no perfect engine (not even close), however, water dripping from the muffler is a normal by-product of the combustion, heat, and humidity in the air. The heat of the muffler works like a huge dehumidifier, basically drying out the air.

So The water dripping is a result of high temperatures and humidity in the air.

The next question is:Is this good?

If the water is fairly clean without:

- any oil residue, or

- Black or Bluish-white smoke accompanying it;

there is a fairly good chance the engine is in good running order (no guarantees).

Note

1. Water can cause corrosion in cheaper mufflers
2. An engine is designed to run at fairly hot operating temperature.
3. The heat is a result of friction, and friction = wear.

The more efficient engines will run a little cold and water will not be seen unless it is an extremely humid day. If you take the same engine and add something like Duralube to the crankcase, it will run quieter and cooler, and last much longer.

"The heat is a result of friction, and friction = wear."

Please correct me if I'm wrong, but I have always thought that the heat of an IC engine had something to do with combustion?

Yes some of the heat is from the combustion, however, most of the heat from the combustion goes out with the gasses and heats up the exhaust manifold, and the exhaust system. The friction of the motor heats up the oil and the engine block.

Excess wear, and heat from friction is generally what causes engines to breakdown.

Presumably, then, this friction heating must be down to the pistons in the barrels, as these are the only major linear (rather than rotary) sources of friction in the engine. If rotating components caused enough heat through friction (to need cooling), surely the gearbox would need a water cooling jacket?

Also note that it is only the cylinder block area that needs the additional cooling (more obvious with an air-cooled engine).

You may be right, but I'm not yet convinced.

I agree that a lot of heat is generated by the combustion (requiring cooling), however combustion and heat alone will not cause a engine to break down.

What causes engines to breakdown is wear and deposits.

Deposits in the combustion chamber will cause extra friction and can cause the valves to not seal properly.

Excess heat is simply one indication of excess friction.

Friction will happen wherever there is moving parts. That is why:

1. the cylinder arm bearings wear down,
2. the rings wear down
3. the CV joints wear down
4. the steering arm pivot joints wear down
5. transmissions will fail - Also the seals may be a problem
6. etc

The biggest problem is the inefficiency of the oil and grease that lubricates these joints. If we could make a grease that was as effective as the liquid in joints of animals, and we use a fuel that burns clean without deposits, IC engines would last a lot longer.

Water is 1 of the products of combustion.

Water can also indicate a broken head gasket or cracked block/head.

Yes, water can readily leak into the combustion system from a leaky head gasket, which results in water from the tailpipe. I would first check to determine whether there is a continuing loss of engine coolant; then if there is have a pressure check made on the coolant system to determine if this is the cause.

Water is a natural byproduct of any hydrocarbon combustion and has nothing to do with engine quality.

When a hydrocarbon burns in the presence of a pure oxidizer (O₂, for example) the only byproducts will be CO₂ and water. Since most real-world combustion draws the oxidizer from the atmosphere, you also get nitrogen byproducts along with the water and CO₂.

Tell your friend that any car will get a certain amount of water dripping from the tailpipe, regardless of how long it's been since the last tune-up or oil change.

Water dripping from the tailpipe of a properly running engine is just an indication that the car has not been running very long. Once the exhaust system warms up the water from the engine will vaporize long before it reaches the final exhaust pipe.

However, if the car has been running for a long time (and assuming the water is just the result of combustion and not leaking coolant) then perhaps someone has discovered a way of converting all of the waste heat of the engine into power, in which case that would be the best car with the perfect engine, and your friend would be correct.

One of the functions of the catalytic converter is to change harmful hydro-carbons to less harmful ones. Which water is one of them and not very harmful. A poorly running engine may emit more hydro-carbons from unburned fuel. This would mean more water produced in the converter. So the amount of water coming from the tail pipe is not and accurate indicator of the engine condition.

Tha catalytic convertor effects redox reactions on the normal byproducts of combustion in internal combusion Otto cycle engines, except for water, which is not affected.

The oxides of nitrogen are converted into N2 and 02 in the reduction catalytic chamber: carbon monoxide is oxidized to CO2 in the oxidation catalytic chamber.

The water that is seen arises from condensation on the cold metal surfaces, which is then blown out the tailpipe.

This is one reason why "short trips" which do not heat up the exhaust system are particularly harmful: the water remains in he exhaust and causes rust.

The great majority of the heat in a typical car engine arises from "waste" heat from the combustion proces, not friction.

Yours was the first answer that hit the button for me - short journeys!!

Thanks.

...particularly harmful: the water remains in he exhaust and causes rust.

I believe most automobile exhaust systems are being made of stainless steel in recent years, although your point is well taken.

What you say is true, but the replacement of an exhaust is still far easier and cheaper than replacing an engine due to blocked oil ways from sludge.....or just worn out because the oil was 50% water, which does not lubricate quite so well......

Hello SP:

Perhaps your friend has a car which "runs on water". (Joking, of course)

As the engine warms up, and the tailpipe (exhaust pipe) heats up, the water vapour still comes out the exhaust system, but the dewpoint of that water vapour is not low enough to condense as visible drips.....

each gallon of fuel burnt produces about a gallon of water

Really! I had no idea it was that much.

Thank you Guys for all your valuable advices & time.

have wonderful holiday season

Best answers are Garthh & CSMEngineer. Combustion of a hydrocarbon includes water as a by product. Unfortunately my chemistry is out of date and I can't write the formula for you, but maybe there's a combustion engineer out there who can. My recollection (dim as it is) is that your friend is right, more water, cleaner burning.

agreed!

hydro carbons are carbon and hydrogen methane is ch4, ethane is c2 h6 etc. Octane is c8h18. as the fuel combines with the atmospheric oxygen, each carbon combines with 2 oxygens to make CO2; And 2 hydrogens combine with each oxygen to form H2O. (As Oxygen is diatomic, its actually 4 hydrogens combine with each O2 to make 2 H2O's)

Thus water is an expected output of combustion.

whether or not its in liquid or vapor state depends on operating conditions, (Temperature) as water vapor will condense upon cooling, just like in a distillation process.

milo

having been a mechanic for over thirty years I must say in a nutshell: dont worry about the water dripping from your tailpipe and go for a nice drive in the country with your honey...

nuff sed

Hello Guest who was a mechanic for over thirty years.

I'm a bit puzzled by your turns of phrase.

I can just see it now, the car being driven in the country, a pot of honey being clutched by a small fluffy animal in the back seat and being followed by a swarm of

Who is in the nutshell, and why? Are they nuts?

Your guidance is urgently needed, thank you in anticipation....

Well, to put it simply, there is no need to worry about water dripping from your tailpipe. your honey is your girl (or guy). I admit that I am no Engineer but....

cute bear bye the way

happy holidays sparks

If water is dripping out of the tailpipe, this is an indication that the engine is seldom run warm for any length of time. Therefore that same engine will most probably have too much water in the oil, reducing the oils qualities and maybe causing sludge and foam (emulsion) that can block oil ways and cause an engine to die far earlier than it should!!

I feel an engine should get a 20 mile + run at least once a week......but watch the oil level, it can take a dive as the water is driven off.....use the best oil (synthetic) and change it as often as you would a normal oil, not wait for the extra miles that synthetic normally allows......

...or just count on replacing the engine at an earlier date than planned!!

God knows where your friend got the idea tat it was a good sign!!!!

Hello SP,

I don't really know about your water dripping, or what your car's tailpipe had to do with it.

We grew up on Bread and Dripping, and very tasty it was too.

Happy Christmas.....

STILL IS !!!

Germany has a similar product that gets sold at local Fetes etc, already spread on a piece of good bread, with a touch of salt & Pepper if you wish!!! I am sure it is not good for old hearts such as mine, but an occasional piece......by the way it is Pork Dripping here......

I grew upon a farm where we had our own home-cured bacon etc.

Our Dripping was pork dripping, and we sprinkled it with salt & pepper too.

Very tasty, home cured hams, bacon, black puddings, etc, even 50+ years later, I can still remember the exquisite flavour.

It was one of my jobs to sugar cure the bacon, rub it each day, ensuring the liquid did not go "ropy', in which case the bacon was ruined.

I still have the old family recipe for doing it.

Today bacon & ham is ghastly, it is just injected with enzyme, water and flavourings, not really cured at all.

Same with "smoked fish" - just dipped in chemicals overnight,the buyers have no idea what is going down the hatch.

Happy Christmas - here Christmas Day is nearly over.....