BACKYARD MECHANIC: Full or not, gas-tank condensation unlikely

Hey there, time traveller!
This article was published 17/12/2010 (5755 days ago), so information in it may no longer be current.

QUESTION: I will be storing my car for the winter. My question is whether it is better to store a car with a nearly empty gas tank (due to the use of fuel stabilizer), or a full tank to prevent condensation.

ANSWER: The answer to this question depends on where you live, where you store the vehicle and how old it is. To figure this out, let’s look at some other items we have more experience with. All of us have taken a cold glass bottle out of the refrigerator and set it on a table, only to find a puddle of water beneath it later. The water formed on the outside of the bottle when the water vapour in the warm air came into contact with the colder bottle. Did water form on the inside of the bottle? It did if the bottle was open to the air, but what if it was sealed? Probably not, and if some did, it was very little.

Now let’s look at gas tanks. If you take a partially filled gas tank and subject it to temperature changes, it makes sense that water vapour will form where warm air touches the cold metal, but just like the bottle, this condensation will be on the outside. If the tank is sealed, and most fuel tanks since the 1970s use a sealed system, there will be very little on the inside of the tank. Perhaps the filler-cap seal isn’t perfect. Then you could get air into the tank and moisture would condense, but it would still be difficult for this air to be exchanged regularly when the vehicle is stored. You might get a little condensation inside the tank, but very little.

What about storing it with a full tank? All fuel tanks have a domed top or part of the tank above the filler-neck level. This allows for fuel expansion as the fuel warms up after you “fill” the tank. A full tank is never completely full, so it doesn’t make a big difference whether the tank is full or half full when storing it, as long as the fuel system is sealed. I prefer to have less fuel in the tank. That allows me to top it off with fresh fuel in the spring.

As for storing it in different parts of the country, vehicles stored in dry, cold climates don’t have problems with condensation. If you live where humidity levels are high and temperatures vary widely, this is more of a concern. Storing a vehicle inside a building, even if it is unheated, will slow the temperature fluctuations and reduce condensation. The biggest problem occurs with 1960s and older vehicles with unsealed fuel tanks that are stored outside. Filling the fuel tank will reduce the amount of air inside the tank and allow less condensation. For most of us though, it isn’t a problem.

QUESTION: I did a tune-up on my 1997 Honda Civic EX and I can’t seem to find where the PCV valve is located. Where exactly is it? I need specific directions. Is there a PCV breather filter as well, or does this system just use the engine air filter like it seems to? I’ve tried online forums regarding this question and I get different responses. It is a 1.6 D16Y8 non-V-TEC engine. — Chris

ANSWER: Honda’s 1.6 litre D16Y8 is a V-TEC engine. I am guessing you have the D16Y7 non-V-TEC engine in your Civic EX. The engine does have a PCV valve and it is located near the oil filter and coolant temperature sensor on the engine. You should be able to hear it click as vacuum is applied and released to the valve. As for a breather filter, many vehicles now use the air filter as the filter for the crankcase ventilation system and your Honda is this way. By ducting the vent back into the air-intake ducting, it reduces hydrocarbon particles from the engine oil evaporating into the atmosphere when the vehicle is parked.

 

Jim Kerr is an experienced mechanic, instructor and member of the Automobile Journalists’ Association of Canada.

kerr.jim@sasktel.net