Few mechanical breakdown events engender as much dread in a car owner’s heart as a blown head gasket. Located between the engine block and the cylinder head compartment, this mechanically-essential seal is responsible for containing the internal combustion process, plus all of those explosively rising and falling cylinder parts. It’s because of these stress factors that this gasket doesn’t leak, it blows. What are the causes of blown head gaskets?

What is A Head Gasket?

As we briefly explained a moment ago, this is the all-important engine seal that contains internal combustion stress. When the engine block is mated to the cylinder head, this geometrically complex gasket is fitted between the two core engine parts as a seal. If you were to look at it, you’d see a row of cylinder apertures, plus an accompanying series of smaller holes. The latter array of openings exists to deliver the engine lubricant and a coolant. If this primary seal were to be breached, what would happen? Well, engine compression ratios drop like the proverbial stone if the gasket leaks. Furthermore, the once isolated lubricants and coolants leak and mix. From here, the engine overheats, it spits out clouds of smoke, and there’s an increased risk of permanent engine damage.

The Causes of Blown Head Gaskets

If we know the causes, we can avoid them. For instance, those two engine halves are forged from strong alloys. Still, even the smallest manufacturing difference can alter the way one of those segments reacts to stress. If combustion cycles do produce heat, the thermal energy is making the metal expand and contract. Mechanical creep hits the head gasket hard, especially if it’s made from an overly rigid material. The result of this expansion effect is head gasket fatigue, which means a blown head gasket is imminent. Head bolt overtightening is the other culprit here, with the bolt pressure over compressing the head gasket material. Engine assembly expertise rectifies this latter problem by applying the correct torque to each bolt and installing each one in the right sequence.

Substandard head gasket materials don’t react well when placed under pressure. The segment marrying stress, perhaps done out of sequence, over compresses the seal and introduces a weak spot. Meanwhile, a poor lubrication fluid or low coolant level causes rapid expansion and contraction cycling, a repeating event that’s felt as a mechanical creep effect. Have the engine serviced by an expert, someone who will install a high-quality head gasket correctly. On top of that provision, avoid high-temperature cycling effects by using a superior lubricant and a properly topped coolant reservoir.

Strong chemicals will eat into poorly selected gaskets, make no mistake about that. Sure, that joint seal has been designed to handle high temperatures and intense pressures, but the clock is ticking. The deteriorating material will fail. A chemically resistant gasket doesn’t suffer from such issues. It retains its toughened outlines and its sealing duties, no matter how corrosive the chemical attack. Still, not all corrosion-resistant gaskets are created equal.

Chemically Compatible Gaskets

The following elastomers and metals are robust substances, but that durability factor doesn’t necessarily mean much, not when the reactive properties associated with a particular chemical compound are known to target that particular material. With that fact in mind, the correctly selected gasket type uses a compatibility model to avoid corrosive action, as imposed on a pipe or fitting joint. Just to illustrate that point, most oils and fuels are seemingly harmless. If someone rubs an oil drop between two fingers, no harm is done. However, those same oils have a very different effect on rubber gaskets. Seal deterioration is likely, as is the likelihood of a nasty leak. Nitrile, EPDM, and Viton gaskets are designed to counteract that material deterioration effect.

Chemical Resistance Charts

Material deterioration effects progress differently, depending on the composition of the chemical medium. Fuels corrode certain elastomers, as do the oils we mentioned earlier. Even vegetable oils and vehicle lubricants can corrode non-compatible gasket rubbers. Hybrid materials, including elastomer-bonded cork seals, are one solution to this best gasket selection puzzle, but the preferred approach is to use data sheets and chemical resistance charts. Like a unique fingerprint, these substance resistivity documents provide details on which rubbers and metals work best with particular fluid stream types. From dust ingress protection to strong acid and alkali protection, the information assures seal compatibility.

A Chemical Compatibility Primer

If nitrile gaskets perform well when aggressive hydrocarbons are carried in-pipe, then EPDM is the next favoured member of this synthetic rubber group. Ethylene propylene diene monomer, is an excellent outdoor chemical seal, with its UV-resistant polymer base acting as a superior open-air pipe jointing product. Nitrile, on the other hand, is every bit as popular as EPDM, but its chemical resistance fingerprint makes the material a preferred gasketing solution in vehicles, in the car engines that carry corrosive hydrocarbons. Curiously, of all the singular materials on the market, few are rated to handle every conceivable chemical type, which is why special bindings and coatings are making headway into every engineering branch, even those that add high temperatures and pressures to the fluid mix. One example of this approach is a PTFE (Polytetrafluoroethylene) coating, a synthetic fluoropolymer that maintains chemical resistance while allowing the base gasket polymer to retain its mechanical traits.

A medium-grade flexible gasket compresses well and handles high temperatures, but it may not resist a certain acid or fuel type. Bonded with a PTFE coating, the hybrid product gains a newly augmented measure of chemical resistivity. Meanwhile, tried and true synthetic rubber gaskets, nitrile and EPDM among them, target nominated chemical compounds as long as the correct chemical resistance chart has been properly interpreted. Finally, tough Viton gaskets and spiral wound metal composites excel when pressure extremes drive those caustic fluid streams, although the latter product must use a ring alloy that doesn’t chemically react with the chemical medium.

Gaskets divide into two discrete classes when they’re employed in automotive applications. There are the passive areas where the seals protect passengers and driver. They’re the door gaskets and window seals, products that are formed from extruded lengths of weatherized rubber. What about the active seals, though, the common gaskets that manage engine and exhaust fluids?

Extraneous System Seals

The coolant in a car lays dormant. When the ignition circuit sparks life into the engine, that fluid rapidly heats as it recirculates around the engine and absorbs mechanically-generated heat. It’s in here that water-glycol resistant seals withstand the heat without ageing prematurely. Meanwhile, the gruelling conditions throughout the oil distribution system generate a corrosive environment. Fortunately, cork and cured nitrile automotive gaskets resist the impact of aromatic hydrocarbons while creating a formidable barrier that blocks oil leaks.

Engine Gasket Solutions

Head gaskets are one example of the automobile engine seal, then there are intake manifold seals, exhaust manifold gaskets, seals for the engine block, the oil pan, and much more besides. Compressed by torque-heavy tools, the engine segments clamp tightly down on these parts so that the internal combustion chamber maintains its explosive cycle. If that measured air/fuel mix is to be compressed and combusted, this rugged seal family needs some heavy-duty sealing characteristics, just like the super-tough industrial pipe gaskets we’ve been describing in other articles. With that thought in mind, expect a head gasket and its associated engine seals to be manufactured from thin layers of heat-treated steel. More accurately, those bonded layers are likely fabricated as composite parts, as die cut inserts that are layered with an elastomeric coating.

All around a vehicle, common gasket types fill every conceivable application. They’re in the electronic control modules as cable protection inserts. Oil-bathed transmission systems use cork gaskets and compressed fibre seals. Whatever the application, the material exists to meet the need, be it a super-hot coolant stream or a channeled supply of engine oil. Down in the depths of the engine, geometrically shaped gaskets allow the passage of cylinder heads, so they’re die cut and manufactured from layers of composite material, from steel, copper, and from a wear-resistant rubberized coating. Of course, should a weatherized window seal crack, the extruded material simply leaks rainwater. However, if that engine head gasket fails, the combustion cycle is compromised, plus there’s a possibility of a nasty fluid contamination scenario, which is why even the most common vehicle gasket is built according to a stringent manufacturing methodology.

A correctly selected gasket performs as a key mechano-elastic component in all sorts of industrial applications. Selected according to the following factors, that sealing element absolutely prevents fluid leakage. No matter the pressure, the temperature, or toxicity of that fluid, the properly selected and installed gasket endures. Of course, if we’re to properly establish sealing proficiency, there are some important performance factors to follow, beginning with the fluid’s conveyance characteristics.

Gasket Selection: Assessing Media Characteristics

When we talk about media conveyance, the term is referring to the fluid carried in the pipes. The high or low temperature, the pressure confined inside the conduit, even the caustic nature of that liquid or gas, all of these factors require evaluation. Clearly, if the temperature climbs above 100°C (Water’s boiling point) or below 0°C (Water’s freezing point), certain dynamic media state changes occur. Aggressive steam discharges and layers of expanding ice come to mind, obviously, but these events become complicated by other fluid types and the pressure variances that exist in many industrial processing lines.

Dynamic Loading Effects: The Consequences

Chiefly, then, the gasket materials are subjected to expansion and contraction events. Already compressed by a pair of flanges and a ring of fastening bolts, the factor covered here involves strength and pliability. Mechanical strength gifts the seal with structural integrity, even when the compressible forces reach epic proportions. As for the expansion effect, the durable seal needs a measure of elastic pliability to endure under these conditions. Finally, those baking temperatures and arctic lows will bake or embrittle a gasket if the material isn’t rated as a temperature proficient gasketing substance, so do diligently evaluate this essential criteria effector.

A Study in Gasket Installation Procedures

The selection of a semi-metallic seal or an alloy-corrugated variant also relies on the application area. Is this a heat exchanger vessel? Is the usage domain a pump or valve flange? Then there are the subzero cryogenic and boiler room temperatures to gauge. Finally, when the application and the fluid medium has been accounted for, we address the installation stage. It’s here that the faces of the coupling pipe sections are inspected and cleaned. Certain surrounding equipment assemblies or pipe channels may need to be removed, perhaps due to access considerations.

When the prep work is properly concluded, the gasket is installed. A sealant paste is a potential part of the installation phase, with the compound acting as a corrosion-resistance aid and a seal facilitator. As the opposing flanges come together, ensure they align properly, then add a little lubricant to the face bolts so that the integrity of the joint is assured.

Cracking and drying problems trouble certain elastomeric gaskets. The affliction occurs when the seal dries, becomes brittle, and the material develops hairline fissures. It’s patently obvious here, as these cracks spread, that the gasket has been rendered less than reliable. Unless action is taken, a conveyed fluid will discover the tiny channels and there will be leaks. Here’s a list of tips that are designed to prevent gaskets from cracking and drying.

Low-Pressure Domestic Scenarios

An empty home hibernates. There’s silence in every room, the electricity is turned off, and there’s no water in the pipes. In this residential example, the elastomeric gaskets dry out because they’re unused. Avoid seal cracks by allowing a small trickle to flow. A smart homeowner can also sidestep this issue by asking a neighbour to run the taps occasionally so that the seals are kept wet.

Prevent Ultraviolet Aging

An exposed gasket ages when it’s exposed to UV light. Shield the products by storing the seals in a dark space, not some construction site where they’ll lay under the sun. Better yet, select a gasket material that’s rated to handle ultraviolet light. Incidentally, ozone, another outdoor threat, also causes seal cracking. Ozone occurs naturally, but the otherwise inactive gas is also produced by electrical equipment.

Eliminating Temperature Cycling Cracks

Hot fluids bake elastomers. The constant thermal cycling causes gasket embrittlement. The temperature changes then shrink the product. Bereft of its pliable nature, the seal cracks. Install materials that are rated to endure these temperature extremes. If the conditions are reversed, perhaps by an arctic climate, then the material must be capable of retaining seal integrity when material contraction occurs.

Meeting Mechanical Challenges

Joint expansion and contraction is one thing, but what about vibrational problems? Again, an elastomer that exhibits a matching set of vibration-dampening characteristics is the solution. Reinforce that solution by using a gasket adhesive that incorporates a similarly pliable material base. Additionally, a series of vibration-isolating hoses, as used on hydraulic equipment, will further prevent mechanical noise propagation.

As we can see, many conditions steal gasket pliability. The material hardens, becomes dangerously brittle, then the cracks break out. Prevent gasket cracking and drying by employing the tips we’ve listed above. As for the drying part of this sealing conundrum, a domestic water supply should be kept wet. Otherwise, use a cool, dark area to store the seals, and consider using a paste-like compound as a supplemental gasket lubricating aid.