Q: I own an older Subaru (I think it’s a 2003). Twice a year for the past couple of years, I have driven up to Oregon with friends. I stop approximately halfway to get gas, and each time I have done this, I have seen what looks like smoke or steam coming from under the hood.
The guys at the station always check my fluid levels and say they cannot find anything wrong. When I came home the last time, I took my car to three different repair shops and no one could find a cause for the smoke/steam, which only seems to happen on long trips. I have been told a couple of times that my coolant needs to be topped off.
Should I just ignore this appearance of the smoke when it happens?
A: No. Your vehicle is trying to tell you something.
You have not told me if the vehicle engine temperature gauge indicates that the engine is running too hot or too cold. Probably the most important piece of information is that you occasionally have to top off the coolant. It is important that the engine coolant level is kept at the correct level and is in good condition. Coolant does deteriorate over time in all vehicles. When the coolant goes bad, it turns acidic and will cause damage to the cooling system components.
My suggestion is to have a competent repair facility check your coolant condition as part of a routine vehicle service. This testing can be done with pH strips, similar to the ones used in a school science class, or by using other special test equipment.
So, let’s hope that you have not been driving the vehicle in an overheated condition. That can ultimately lead to severe engine damage for any vehicle.
Now, to your vehicle in particular. The probable cause of what you believe is smoke or steam is the engine cylinder head gasket allowing the coolant to leak externally. That would cause the steam you are seeing (not smoke). The early Subarus, such as yours, are known to have problems with the cylinder head gaskets leaking in this manner.
The coolant seepage occurs at the corners of the cylinder head where it mates to the engine block.
Take your vehicle back to your repair facility and have them put it up on a lift so that they can look at the engine from the bottom. They need to examine the front and rear lower corners of the cylinder head, where it mates to the engine block. There are usually pipes and/or a wire harness in the way, so a careful look is necessary. If whoever performs the inspection sees wet coolant or even dry coolant residue, then you need to install new cylinder head gaskets.