Cylinder head gasket replacement
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I discovered my car, which wasn’t too old, had empty radiator fluid in the reserve tank all the time. The fluid will disappear in short while even I have it filled up. In the beginning, I thought the bottle was leaking, but I found it wasn’t. The radiator was always three quarters full. It will return to low level in few days after filled up. The performance of my car had not deteriorated at all. I just have to make refill the tank every few months. So I just ignored this problem for nearly two years.
Later on, I always hear some water bubbling sound near the heater panel. One day, I parked my car on the street. I wasn’t able to crank the engine again. So I towed it back to my garage.

I deeply believe my trouble is related to cylinder head gasket because of the water sound I heard, however, I did not understand why I could not crank the engine. So I thought the valves could have rusted to break and jammed the engine. On calling for estimation, the dealer wanted five thousand Canadian dollars to replace it with a rebuilt engine. The cheapest, estimation was two thousand dollars to replace the head gaskets by an independent mechanic. Through conversation with the mechanic, I realized the reason that I could not crank the engine is because of water filled up the cylinder during the engine cool down. To prove that it was correct, I remove the spark plugs one at a time and crank the engine after each removal. I began with the easiest to remove spark plug first. I had disappointed four times after five spark plugs were removed. For my last chance, I removed the spark plug, which is near the tension idler pulley, on the inner most part of the chamber, which is most difficult to access. On fifth trial, the engine cranked. I saw a spill of water on the ground. On installing the spark plugs back to position, I was able to drive again. The test had proven that there was no damage or jam on the valves. When my engine was stopped by chance with both exhaust and intake valves closed on that leaky cylinder. On cooling down of the engine, it created a vacuum in the cylinder. The cooling fluid was sucked in. When this cylinder on compression stroke cycle is filled with water, it created a high backpressure, which made the starter unable to turn. Water is not compressible as air.

I have no confidence to use this car any more. It must be properly repaired; otherwise, it could have same trouble again on the road. The parts required are only a few gaskets and seals. The labour is intensively high. Since technically is not that difficult, I had decided to do the repair myself.

This engine is a V6. It is horizontal mounted. The blown gasket is on the inner side. That is near the passenger compartment. The tight space has little room for hands to manoeuvre the tools, make repair job difficult and time consuming. Removing several screws could take me one night of work. The head gasket is laid between the cylinder head and the engine block. Engine block is where the cylinders located. The function of the cylinder head is to control the intake of gas air mixture, and the exhaust of combusted fume.

The first procedure is to remove the exhaust manifold. Second step is to remove the intake manifold. Then have to remove the belt that drives the alternator and air conditioner, because there is a tension idler wheel attached to the cylinder head. This wheel is besides on that troublesome water filled cylinder. On this procedure, I realized this must be an engine design trouble. This tension idler wheel vibrates on turning, eventually loosen the head gasket. The final procedure is to remove the head cover and the head. The bolts, which hold the cylinder to the cylinder block, are extremely tight. The first attempt to remove it broke the socket (tool). I finally have to use a half-inch shaft socket with a four foot steel pipe as lever to amplify the torque. The bolts removed can not be reused, because they had been stretched. These bolts must be removed in correct sequence as suggested in the service manual. Failure to follow correct procedure will corrupt the head. The procedure is usually loosening the outer most bolts by half a turn. Then, loosen the opposite side. It is repeated again on the second outer most bolts again. The final bolt to be removed is the centre bolt. The procedure is repeated again until all bolts loosen. To re-install these bolts, I have to use a torque gauge to adjust the torque first. Then tighten each bolt in sequence started from the centre bolt to the outermost bolts. The sequence must be symmetrical. The number of turns to tighten must be as specified by manufacturer. Failure to use correct sequence and torque and number of turns can distort the cylinder head.

On successfully removed the cylinder head. It was a dirty piece of block. The surface is filled with greasy soil. On carefully removing all the dirt, I discovered it is a beautiful piece of engineering. The metal is aluminium alloy. This alloy is hard and strong as steel. The valves after 120,000 Km are still in excellent shape. Hardly any worn out sign. I expect this engine can last me another 120,000 Km with no trouble at all.

Initially looks like a dirty piece of junk metal, under my careful examination, I found it is a marvellous engineering. I realized there must be an intelligent engineer designed it. In fact, in the natural world, there are billions and billions of marvellous engineering surrounding us. A piece of fallen leave fit only as compost. On careful examination, it is a complex engineering job. Every organ of our own body is also an ultra high tech product. When we mention an artificial satellite, we could say Lockheed Martin, GE Astro, Boeing, Eurostar, Chinastar or etc builds it. However, when we look at the moon, the sun, the Mars, the galaxies, and etc, have we ever thought of who made it? There must also be a great designer. Guess who He is?


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