How to store your beloved classic car from a mechanical & engineering point of view!

Winter is approaching fast and therefore the questions on how to store your car the best way is coming up. Many of you are putting their beloved classic car away during the cold, salty winter months – a wise decision!

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So things need to be taken care of before storing your car away for a longer period of time. I will try to point out the most important things one needs to consider from a mechanical point of view.

First up are the tires. In order to store a vehicle correctly without risking damage on the tires to options are available. The first one is to lift the car off the tires, for example on a lift. Here you are less flexible regarding moving the car around and if you do put it up a lift a potential working space is blocked. However, the second and easier one is to keep it on its tires but you will need to add more pressure up to 3 bar. Ideal would be if the vehicle would additionally be moved every month to also help minimizing ozone cracking in the bulge area. As Rubber has a time depending creep- and relaxation behaviour it can easily lead to a flat spot if not handled with care.

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Next up is the generically known climate problem. High quantities of humidity in the air (ideal 45%) can lead to corrosion in various places, such as the engine.

The biggest problem area will be the inner parts of the engine as it is blank metal, no paint or other sorts of surface protection is applied to prevent corrosion. If the engine is running or frequently turned on the engine oil will provide a protective surface internally on cylinder and engine block walls. Once the car is put away for months, the engine oil will unpreventable run down and fill up the oilsump – gravity sends its greetings.

Knowing this and the fact that the engine will 90% not be fully closed as one of the valves is usually open, there is a high possibility of risking engine corrosion. Not only through humidity itself but more likely caused by formation of condensate on the cylinders surfaces. This happens due to simple temperature change from day to night. The cold cylinders & walls will not adjust to the outside temperature as quickly and therefore the the humidity in the air will condensate on the cold surface. Similar to a cold bottle of water from the fridge. On these warm summer days where nothing is better than a cooled drink from the fridge you are experiencing the same effect. The bottle will immediately formate condensation of water on the outside surface as the temperature difference is too high.

Having this effect inside your engine walls will leave substances of water behind. The water will lead to surface corrosion of the material, often to be found on the cylinder walls. Corrosions means that the surface is damaged and the material usually expands in these areas. If the engine will then be turned later in time, the cylinder won’t be able to runs smoothly and a piston seizure is provoked.

In order to prevent these risks climate control is necessary. An ideal humidity of around 45% is wanted, to lower the risk of corrosion. Ideal is a garage with air flow and if one wants to store a cabriolet it is recommended not to close the roof entirely. Recommendable are also machines such a dehumidifier.

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Talking about corrosion not only humidity can cause corrosion but also the combination of various materials. This phenomenom is galvanic corrosion and is essentially a eletrochemical process in which one metal corrodes when it is in contact with another. Dissimilar metals and alloys have different electrode potentials, and when two or more come into contact in an electrolyte, one metal acts as anode and the other as cathode. The electropotential difference between the reactions at the two electrodes is the driving force for an accelerated attack on the anode metal, which dissolves into the electrolyte. This leads to the metal at the anode corroding more quickly than it otherwise would and corrosion at the cathode being inhibited. Commonly known at cylinder walls when for example aluminium cylinders run in a steel block. Also piston and oil rings are affected, usually made of spring steel a corrosion of such in combination with the cylinders. In extreme cases, there are seizure marks all along andaround the piston.

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The battery can cause difficulties too and therefore needs to be on your radar. If a battery is not disconnected there is a possible risk for it to be discharged in a short amount of time, which means destruction of the battery and a new one is needed. Especially with classic cars small amounts of electricity are often running through the system or even worse a small consumer is sucking up energy. As the battery is not running and loading it will effectively run low. So what does discharged of a battery really mean? A typical lead battery holds 37% sulfuric acid. During the process of discharging the relation of sulfuric acid to water in the electrolyte is slowly changing to more water and less acid. A chemical by-product of this process is a lead sulphate which covers the battery plates in every cell and reduces their surface. With a smaller surface of the active material which is available to the production of electric energy in a cell the stream is also reduced. If the discharging process continues, even more lead sulphate on the cell plates deposits, until finally no more chemical process is possible to the stream production any more.

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Further the risk with having water rather than acid in the battery case is destruction of such. If temperatures drop, which is usually the case over winter, the water can freeze and turn into ice. Adding to this process is also the expansion of the liquid / ice a matter which is can now destroy the casing from the inside, break the shell and the battery would be destroyed. This risk isn’t given with sulfuric acid as the aggregate of state change is not happening around zero degrees as with water. To avoid and take remedial action the use of an electronic battery charger is to be recommended.

Remember when I talked about the rubber which creeps, the same situation we can find at the windscreen wipers. If these aren’t lifted off the glass or newspaper is put underneath a risk of breaking the rubber is a given. Due to the pressure of the wiper itself to the windscreen and the creeping process the rubber can build up suction to the glass. Once the wipers will then be used again the surface of the rubber will be destroyed and are therefore non usable.

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Next up are rubbers from one end of the car to the other, door over trunk as well as steering rubbers and such are to be taken care of. Talcum or glycerin can help to avoid cracking and as a clever side effect freezing of the material is avoided. Best to apply with a small brush shortly before storing the vehicle.

Now we come to the fun part before storing your beloved car – go out for a long drive. In order to avoid chances that water and fuel are located in the engine oil, it is necessary to heat up the engine and all other units of the car to full running temperature. When a car is frequently used for small turns around the block the operating temperature is never reached. All engine parts have been designed and constructed optimal fitting while operating temperature. Therefore, when running in colder temperatures combustion gases can make their way past the pistons into the crankcase. As the gases are not complete and burned fuel and water can collect in the engine bay. Now, especially the water can cause trouble again, this time at the oil sump. As oil floats above water, the water in the engine oil will be pushed to the bottom and onto the oil sump wall. Classic cars are often equipped with thin sheet metal oil sumps, which doesn’t leave much material to stand against the corrosion process.

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The easiest way to check up on the water / fuel level in your engine oil is the following: fill up the engine oil to a maximum and check it every few weeks, if it seems to be getting more it is because fuel / water are adding to the engine oil.

Last but not least it is recommended to fill up fuel and oil and obviously clean & polish before storing your beloved classic car.

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