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Old 9th September 2006, 11:46   #16
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Quote:
Originally Posted by SLK
Removing water for once?.... how about... putting the car in say 3rd+ gear and pushing the car backwards manually... ...

*just a thought...
Ok ok agreed but atleast answer my question..if some little amount of water is sucked in air intake...willl it do nay harm?
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Old 5th November 2010, 00:36   #17
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Hi,
I would like to know the extent of damage to a Multi Cylinder Diesel Engine in two situations.
  • The vehicle is wading through water logged road and the water is ingressed into the engine.
  • The entire vehicle is inundated while it was parked.(Engine switched off) but later cranked without flushing the water out of the cylinder/s.
Regards,
Sudhir
Quote:
Originally Posted by falcon View Post
Hi,

The following is an excerpt from the site
"http://www.car-forums.com/archive/t8933.html"

Its an interesting write up on Hydrostatic locks... It describes what
could happen if we go thru water thats high enough to get sucked into the air intake.

###########################################
"Water lock" is the familiar term for the condition known as hydrostatic lock. As referenced in your question, it occurs when water is ingested by the engine in a certain quantity. The specific quantity necessary varies by engine. The problem is one of basic physics -- liquids are non-compressible. Water, of course, is a liquid.

Your engine is a four-stroke-cycle engine. The four "strokes" are intake, compression, power, and exhaust. Note that compression directly follows intake. The intake stroke occurs during (generally) downward movement with the intake valve open. This causes an air-gas mixture to be drawn into the cylinder. At the bottom of the intake stroke, the cylinder volume above the piston is at its greatest. During the compression stroke, the piston moves upward, reducing the cylinder volume above the piston until the piston reaches its upper travel limit. At this point, the cylinder volume is at its smallest. Under normal conditions, the air-fuel mixture is basically gaseous in nature and is therefore compressible. But... what happens if the cylinder is contains liquid instead of vapor? In this case, at the point when the cylinder volume is reduced to where it is approximately the same as the volume of liquid in the cylinder, the piston will no longer be able to move upward. This is the "lock" point.

Depending upon specifics of operating conditions, engine design, and general engine health, this sudden stopping of the piston by a non-compressible mass can cause damage such as a broken piston, bent or broken connrod, shattering of engine castings, or even breakage of the crankshaft.

As to the question of how much water is needed? Not much -- when the engine ingests into any single cylinder a volume of water greater than the cylinder volume above the piston at TDC, the piston in that cylinder will be stopped on its compression stroke when the cylinder volume above the piston matches the volume of ingested liquid. The smaller the engine (displacement), the less liquid is needed to get to this point. That amount can be roughly calculated for any given engine, so long as the bore, stroke, and compression ratio are known.
###########################################

My question....

The air intake of the diesel engine in my contessa is placed pretty low down behind the right headlight. As a result, I am afraid of the possibility of it sucking in water with the air when I travel through submerged areas.. and there are a lot of them on my way to work... Marol is among the worst!!!

Now in the case of a petrol engine, assuming I did not break anything... I could just remove all the spark plugs and crank the engine. This would eject all the water out of the cylinders. A lil spray of WD40 into each cylinder, put the plugs back in and I could drive my vehicle back home or to the garage.

Diesels don't have any spark plugs.... so... is there any way that we can get the water out of a diesel engine without having to take the head off ???
What about the glow plugs... has anyone ever replaced them ? if we remove them, does it open into the cylinder chamber ? and how easy is it to get them out ?

Regards,
Ashley
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Old 14th October 2014, 10:14   #18
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Default An idea to prevent Hydrolocking!

Well, this is not a discovery nor an invention, but just an idea (application of an already existing solution from another industry into automotive industry).
Every year we see that during monsoons our water logged streets turn into death traps for a variety of automobile engines, be it two wheeler, cars, jeeps, etc. Water is sucked inside the combustion chamber, water being incompressible, either the engine shuts down without causing any damage, or (in the majority of the cases)the mechanicals inside bend and warp beacuse of the build up of high pressure (the engine faces a catastrophic failure).

My idea is very simple, we all have seen pressure cookers in our homes. It employs a safety valve, which is made of an alloy which melts and releases the pressure, once a predetermined pressure and temperature threshold is breached.
A similar safety valve (pressure release valve) can be screwed into the cylinder (like a glow plug/spark plug), just near the top. For easy serviceability, this has to be a screw on type, with an alloy or something like that, that will melt or just blow out when the pressure inside the cylinder breaches the normal operating range. This threshold would be breached ideally, only when water gets inside the cylinder. In such a situation, what will happen is, the valve will pop open, the engine will lose all compression (with a loud hiss sound), the vehicle would stall and thats it. The vehicle would have to be towed to a service centre, the safety valve would be opened, any traces of leftover water removed from the very opening, new safety valve plugged in and the vehicle is ready for action. It should not cost more than a few hundred bucks.

But, i doubt car manufacturers will implement such solution on their own, because it will rob the service centres/manufacturers a major source of revenue. This has to be enforced upon by the authorities.
The industry in which i work do not deal with IC engines (leave aside turbines) otherwise maybe i could have got some cash benefit from such an idea, but i am open to recieving some percentage of cash benefit, if somebody from our forum (in automotive industry) decide to present it as an idea and claim monetary benefits. I even won't mind if this valve is named after me.

On a serious note, what do you guys think about this idea, is it feasible and would it really be helpful?
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Old 14th October 2014, 12:43   #19
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Default Re: An idea to prevent Hydrolocking!

Sorry to disappoint you chaudh2s, but your understanding is a little off the mark. Hydrostatic Lock occurs not because the piston builds up more pressure than it can handle, but because it tries to compress water in liquid state which cannot be compressed.

Under normal operating conditions, the gaseous mixture of atomized fuel and air, which can be compressed, is compressed by the piston, and as the volume(space in the cylinder) occupied by this mixture reduces due to compression, the piston moves and takes up that space. Now, when there is sufficient amount of liquid(water) present in the mixture, it offers infinite resistance to the compression being created by the motion of the piston, which in turn tries to stop the motion of the piston. The force that causes the piston to move now starts showing its effect on the conrod which buckles/bends/breaks.
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Old 14th October 2014, 13:05   #20
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Default Re: An idea to prevent Hydrolocking!

I don't think the safety valve mechanism will work in this case. A typical common rail diesel engine operates at 1000-2000 bar. Because pressure is directly proportional to temperature, it generates sufficient temperature to burn the diesel when injected.

In case of a hydrolock, water is not compressible as air. Pressure is inversely proportional to volume. Volume of water is not reducing here as it's not getting compressed. It's impossible to reach the air level pressure on water. In this case water compression produces backpressure on piston failing connection rod, crank or piston.

Safety valve will not get fused; invariably not stopping engine failure. Piston head design is very complex as it has to accommodate 4 valves and other mechanisms. Space is at premium.

Instead what I can think of is placing some kind of porous material like Silica gel filter at the air intake which will absorb water content as well as water in the sucked air before in enters into combustion chamber. This filter will give an alert to ECU when clogged.
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Old 14th October 2014, 13:06   #21
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Default Re: An idea to prevent Hydrolocking!

Dear PreethamB, I think my understanding of hydrolock is spot on. You need some more detailed understanding.
Let me explain. Say, the piston in it's bottom most position has 500CC of volume above it. When fuel air mixture is fed into cylinder, this 500CC volume is reduced by up moving piston, based upon it's compression ratio.
Let's assume compression ratio of engine is 10:1. That means the 500CC volume would be compressed into 50CC volume at top most extent of piston.

Now, if there is presence of 20CC of water inside cylinder, which is incompressible, the piston (along with the connecting rods, etc) would have to compress 500CC into 30CC. This make compression ratio 16.67:1. This increases the pressure inside cylinder. If the conrods, etc are not designed to sustain pressure due to 16.67:1 compression, it will bend, because the momentum of the vehicle will make the piston to go up, up and up.

Now, I am a civil engineer (not a mechanical engineer), this is what I know/understood from my one semester of thermodynamics (in engineering) and common sense. I may be wrong, expert please comment.

Last edited by chaudh2s : 14th October 2014 at 13:08.
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Old 14th October 2014, 14:51   #22
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Default Re: An idea to prevent Hydrolocking!

Quote:
Originally Posted by chaudh2s View Post
Dear PreethamB, I think my understanding of hydrolock is spot on. You need some more detailed understanding.
Let me explain. Say, the piston in it's bottom most position has 500CC of volume above it. When fuel air mixture is fed into cylinder, this 500CC volume is reduced by up moving piston, based upon it's compression ratio.
Let's assume compression ratio of engine is 10:1. That means the 500CC volume would be compressed into 50CC volume at top most extent of piston.

Now, if there is presence of 20CC of water inside cylinder, which is incompressible, the piston (along with the connecting rods, etc) would have to compress 500CC into 30CC. This make compression ratio 16.67:1. This increases the pressure inside cylinder. If the conrods, etc are not designed to sustain pressure due to 16.67:1 compression, it will bend, because the momentum of the vehicle will make the piston to go up, up and up.
Quoting from Wikipedia,
Quote:
Hydrolock occurs when a volume of liquid greater than the volume of the cylinder at its minimum (end of the piston's stroke) enters the cylinder. Since most common liquids are incompressible the piston cannot complete its travel; either the engine must stop rotating or a mechanical failure must occur.
Now applying that to your example, hydrolock would occur if the volume of water present in the cylinder is greater than 50CC.

I do believe that automobile engines are built with enough tolerances to sustain, occasionally, a momentary increase in pressure beyond normal. In your example, the presence of 20CC of water would probably not cause the engine to hydrolock at all.
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Old 14th October 2014, 18:40   #23
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Default Hydrostatic Lock - Water inside the engine

Quote:
Originally Posted by PreethamB View Post
Quoting from Wikipedia,





Now applying that to your example, hydrolock would occur if the volume of water present in the cylinder is greater than 50CC.



I do believe that automobile engines are built with enough tolerances to sustain, occasionally, a momentary increase in pressure beyond normal. In your example, the presence of 20CC of water would probably not cause the engine to hydrolock at all.
Don't believe that please. You can not compress water, it wont give. Either your piston is able to move around, or there is literally one drop to many and then it will just stop and something needs to give. The cylinder head, a con rod whatever. Either you have a hydrolock situation or not. It is digital, due to the fact water does not compress.

To simplify even further, this is one where better safe than sorry really applies. Make sure you don't have water ingress at all!

Jeroen

Last edited by Jeroen : 14th October 2014 at 18:47.
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Old 28th June 2015, 00:04   #24
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Default Compression testing and Hydrostatic lock

The recent Mumbai rains took a toll on my car :(

Story in short:
Car wasn't in too much water, BEST bus passes from the side and splashes water, car stops working.
Car in this case is a BMW X1 with the 20d engine.

Situation at Service centre
Service center does the following:
1. Flushes out intake and exhaust of any water.
2. Flushes out oil and puts in new oil.
3. Checks compression on every cylinder

Now, they revert back saying the engine is not rotating and hence they need to open the engine.

My question is:
How did they even check the compression on the cylinders if the engine wasn't rotating?!

Something doesn't feel right.
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Old 28th June 2015, 00:20   #25
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Default Re: Compression testing and Hydrostatic lock

Quote:
Originally Posted by jalsa777 View Post
[
Now, they revert back saying the engine is not rotating and hence they need to open the engine.

My question is:
How did they even check the compression on the cylinders if the engine wasn't rotating?!

Something doesn't feel right.
I agree, I doubt very much your engine need opening up. When engines stop due to heavy rain, it is nearly always an electrical problem of some sort. A connector, a sensor etc.

Get it hooked up to an OBD reader, see if you can get any codes

Jeroen
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Old 28th June 2015, 00:44   #26
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Default Re: Compression testing and Hydrostatic lock

Quote:
Originally Posted by Jeroen View Post
I agree, I doubt very much your engine need opening up. When engines stop due to heavy rain, it is nearly always an electrical problem of some sort. A connector, a sensor etc.
Thanks for the quick reply. I realized that I should have added some more information in the post above. But its too late to edit and hence making a new entry.

----------------------------------------------------------------------------------
Here is the updated version of the story described above:

Car wasn't in too much water (probably half of the tires submerged), BEST bus passes from the side and creates a wave (car bonnet momentarily under water), car stops working.

The driver was alone in the car. We know what happened only from his description and hence no accurate first hand view. It seems he then tried reversing the car, which means the car did not immediately stop. I am sitting in a foreign country so a communication gaps exists. Will update this thread if I find any more significant information to aid with the analysis.

----------------------------------------------------------------------------------

Thus, now I doubt it is an electrical issue. Or else the car would have stopped immediately, wouldn't it?
Also, the service centre did perform an OBD scan as mentioned in the bill. I will have to find out what the error codes (if any) were.

Last edited by jalsa777 : 28th June 2015 at 00:46.
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Old 30th August 2017, 19:54   #27
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Default Re: Hydrostatic Lock - Water inside the engine

In case of emergency where one has to leave the car in a flooded zone will covering the air intake and exhaust with plastic bags etc help prevent water from getting inside?
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Old 30th August 2017, 20:54   #28
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Default Re: Hydrostatic Lock - Water inside the engine

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Originally Posted by sumeethaldankar View Post
In case of emergency where one has to leave the car in a flooded zone will covering the air intake and exhaust with plastic bags etc help prevent water from getting inside?
Only if the bags form a water tight seal around the air intake and exhaust which is difficult to verify. On many flooded streets, the exhaust is already submerged and water may already be present in the system. Best not to start the car till all water is manually drained out from the intake and exhaust.
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