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Originally Posted by ajmat
(Post 1110228)
As discussed, if this is a continuing trend then I will look at a Honda agian next time around going back to the water pump - the plastic impellor split. Although held together in the hosuing, the circulation presure weakens. What is a disaster is when the plastic beaks up into little bits and lodges in the water jacket |
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Originally Posted by razor4077
(Post 1110192)
Oh boy. Just when I had almost convinced myself to upgrade to a vRS. :( |
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Originally Posted by Jaggu
(Post 1110619)
Dont they have any other option with a metal impeller? Any swap from VW stable? |
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Originally Posted by prabhuav
(Post 1110677)
Hmmmm. the Elantra crdi seems to make soooooooooo much more sense now :) |
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Originally Posted by ajmat
(Post 1110637)
Inertial cavitation is the process where a void or bubble in a liquid rapidly collapses, producing a shock wave |
| Pumps and propellers Major places where cavitation occurs are in pumps, on propellers, or at restrictions in a flowing liquid. As an impeller's (in a pump) or propeller's (as in the case of a ship or submarine) blades move through a fluid, low-pressure areas are formed as the fluid accelerates around and moves past the blades. The faster the blades move, the lower the pressure around it can become. As it reaches vapor pressure, the fluid vaporizes and forms small bubbles of gas. This is cavitation. When the bubbles collapse later, they typically cause very strong local shock waves in the fluid, which may be audible and may even damage the blades. Cavitation in pumps may occur in two different forms: Suction cavitation Suction cavitation occurs when the pump suction is under a low-pressure/high-vacuum condition where the liquid turns into a vapor at the eye of the pump impeller. This vapor is carried over to the discharge side of the pump, where it no longer sees vacuum and is compressed back into a liquid by the discharge pressure. This imploding action occurs violently and attacks the face of the impeller. An impeller that has been operating under a suction cavitation condition can have large chunks of material removed from its face or very small bits of material removed, causing the impeller to look spongelike. Both cases will cause premature failure of the pump, often due to bearing failure. Suction cavitation is often identified by a sound like gravel or marbles in the pump casing. Discharge cavitation: Discharge cavitation occurs when the pump discharge pressure is extremely high, normally occurring in a pump that is running at less than 10% of its best efficiency point. The high discharge pressure causes the majority of the fluid to circulate inside the pump instead of being allowed to flow out the discharge. As the liquid flows around the impeller, it must pass through the small clearance between the impeller and the pump housing at extremely high velocity. This velocity causes a vacuum to develop at the housing wall (similar to what occurs in a venturi), which turns the liquid into a vapor. A pump that has been operating under these conditions shows premature wear of the impeller vane tips and the pump housing. In addition, due to the high pressure conditions, premature failure of the pump's mechanical seal and bearings can be expected. Under extreme conditions, this can break the impeller shaft. Discharge cavitation is believed to be the cause of the cracking of joints. Cavitation in engines Some bigger diesel engines suffer from cavitation due to high compression and undersized cylinder walls. Vibrations of the cylinder wall induce alternating low and high pressure in the coolant against the cylinder wall. The result is pitting of the cylinder wall, which will eventually let cooling fluid leak into the cylinder and combustion gases to leak into the coolant. It is possible to prevent this from happening with the use of chemical additives in the cooling fluid that form a protective layer on the cylinder wall. This layer will be exposed to the same cavitation, but rebuilds itself. |
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Originally Posted by siddartha
(Post 1110736)
hey prabhu , both these cars are out of production , so there might be a day when elantra spares may become rare and expensive , |
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Originally Posted by prabhuav
(Post 1110958)
Only difference being that Hyundai gets parts from Korea - and since the same engine is sold in 5 cars in India, I dont believe it will be that big an issue. having said that , engine parts are bound to be expensive in the diesel, but I am betting on the fact that they are built to last a lot longer. Vijay |
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