If you’ve been eagerly devouring the tech features here in DRO, (And if you haven’t, shame on you), then you’ll have noticed the attention we’ve been paying to those quiet engine sentinels, head gaskets. We’ve talked to you about the importance of keeping your head gaskets in trim, we’ve even shown you a sample of the veritable cornucopia of gaskets available. But perhaps you think this doesn’t matter. How would you even know if something was wrong? Well, that’s what we’re here to talk about. Whether it’s your daily driver or your ¼ mile monster, everyone should have the know-how to diagnose this problem, and potentially save yourself an engine. Because a blown head gasket can be murder on your engine.
The Butler Did It
Before you can learn how to diagnose a leaking head gasket, it’s important to understand the hows and whys of head gasket damage. Think of this as the motive and means of an engine’s death. And what good detective would investigate a crime without looking at that?
The head gasket creates a seal between the cylinder head and engine block. Now, most modern engines are bimetallic. That is to say that they are made of two metals, usually cast iron for the block and aluminum for the head, thus providing a balance between strength where it’s needed and lower weight where it isn’t.
However, with this construction comes an issue, namely that the two disparate metals heat and cool at different rates. Aluminum heats and cools faster then iron, and with that comes faster expansion and contraction. The engine then, is designed to run in a margin where the expansion rates between the two materials are similar. Even then, one will inevitably grow a bit larger then the other, and as it heats and cools it will stretch and rub the gasket. This is normal wear and tear, not something that can be avoided.
But venture outside those green fields of the optimal temperature range and the expansion rates of the two metals differ more and more. If the engine begins running too hot, the head can actually warp, blowing the seal on the gasket.
Even if you religiously avoid overheating your engine, you’re not safe. Minerals can find their way into a car’s coolant system, either from water added to the coolant, or from the block itself. As these mineral deposits build up, they increase the coolant’s electrical conductivity. The electrical charge will attack the rubber of the coolant hoses, eating away at them until they blow. Blown coolant hoses equal an overheating engine.
And that’s not all. Break out your high school chemistry for this one (or your pool care guide), because it’s time to talk ph. New antifreeze begins its life with a ph of 11. That’s a bit on the base side for us humans, but just right for your car. As it ages though, the coolant begins to break down, and its ph lowers, becoming more acid. Once it hits 7.9 (7 is neutral acidity), it’s too acid for the car’s coolant system. This can cause erosion of not only gaskets, but heads and manifolds as well.