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Thema: Overheating

  1. #11
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    03.11.2007
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    The most reliable indicator for a BHG is *continuous* loss of coolant together with air in the cooling system. Not having to add coolant once, but if you refill 5 litres on 500km, something is wrong. Usually -but not always- the leakage gets worse in some 1000km. This combination is 99% reliable on nearly all engine types.

    White smoke, dark coolant, rough idle, blocked starter motor, green colored spark plug... may occur sometimes but not on all machines.

    The colling system of the legend is hard to bleed. I changed the cooland twice. On the first change the heater did not go dry leaving lots of cooling in the system. The engine was cold and I turned the heater to max with the ignition on. I refilled the system, bleeded it and everything was all right. I also recognized that my radiator cap was defective as the cooling system was not able to hold its pressure. The car drove thousands of km wit a depressurized cooling system!!! I ordered an new cap and performed a second change of the coolant. That time, I had the engine hot and the heater on. In that condition, about 6 litres could be removed. I filled the radiator to max, opened the bleeder valve and had the engine in idle. During the first five minutes it was possible to remive air and to add about 0,5 litres. After that, the coolant level stayed constant and the fans started to run. The bleeder did not show any bubbles. After some additional minutes, the hot steam escaped from the bleeder and I checked the Temperature. It was one division higher than usual and I stopped the engine immediately. As it cooled down I was able to add nearly one litre of coolant and remove air through the bleeder. I started the engine again and it ran at normal temperature. On the next three days with 50km it draw a bit of coolant from the reservoir and since then, the system is absolutely stable.

    There are different types of head gaskets. Most reliable are the multi-layer steel, which may outlast the lifetime of modern (lo-cost) engines. These gaskets require a high quality surface of the head and the cylinder block. Even small scratches will not be tolerated. On the other hand, they withstand overheating much better and they are not prone to ageing like standard gaskets. Standard gaskets are swelling over the years and this is one major reason for their limited lifetime. Even if the car is not driven, these gaskets accumulate coolant and loose strength. Overheated once, the accumulated coolant converts to steam and disrupts the structure of the sealing material. That´s why I considerably prefer the usage of multi layer head gaskets. The Ford N9D Enine (2.0 DOHC 8V) is a typical example. The HG breaks down at cylinder 4 (hottest spot) after about 140.000km. New standard gasket will withstand about the same lifetime. Rework the surface accurately and use the multi layer steed gasket developed for the 16V (both engine types share the same pistons and engine block, the gaskets are compatible) and this problem will never come back.

    I was not able to find a multi-layer HG for the Legend! This would stop that issude for sure. Note that the single layer copper gaskets sold in the US market are *not* recommended. These are *not* able to meet the requirements regarding thermal expansion and surface finish.

  2. Themenersteller #12
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    07.04.2006
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    Daniel -

    Now that I think about it, my radiator was replaced about 2 years ago after a front end collision. The shop may not have bled the system correctly.

    It is possible that this was the 1st time that I had run the car hard in cold weather since the radiator replacement. Maybe it just took this long for air trapped in the heater core to get out?

    I have since bled the system carefully with the heater set on high and have not had to add coolant since. My temp gauge has not moved since this incident.

    Thanks again!

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