Stop the 'Head'-Scratching Over Head Gasket Replacement with Some
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SEALING IN QUALITY BY TOM NASH Stop the ‘head’-scratching over head gasket replacement with some useful information to help make sure the engine is sealed tight the first time. ylinder head gasket re- vising gaskets to successfully seal bimet- placement has given al engines has become a challenge for many a technician night- gasket companies. Gasket makers have mares. If not done prop- developed a wide variety of gasket de- Properly position a new head erly the first time, the signs, many invented for one specific gasket to avoid blocking the flow vehicle surely will make application, to overcome these prob- of coolant and oil. Always refer an unscheduled return trip to your lems. Some engines present a unique to the instructions and dia- shop. If the correct gasket isn’t used, combination of problems, making them grams packaged with the gasket Cproper techniques aren’t followed or even more difficult to seal effectively. to avoid installation problems. proper inspection isn’t done, the seal Photo courtesy Fel-Pro courtesy Photo won’t be right. Difficult Engines to Seal The head gasket must seal combus- GM’s 2.3L Quad 4, Chrysler’s 2.2 and block. The more times the engine is tion pressures up to 1000 psi in gaso- 2.5L and Honda’s 1.3 and 1.5L engines started and warmed up, the faster the line engines and up to 7200 psi in tur- are the ones that present gasket mak- deterioration. bocharged diesel engines. In addition, ers with the biggest challenge. Let’s Fel-Pro’s method of solving this the head gasket must withstand tem- take ’em one by one: problem is with its PermaTorque gas- peratures in excess of 2000°F. Given GM’s 2.3L Quad 4 engine. This ket, a “no-retorque” design. The appli- this severe environment, even the engine’s bimetal construction, high op- cation for the Quad 4 has stainless- slightest fault in a gasket will eventually erating temperatures and tight toler- steel armored fire rings and silicone result in its failure. ances created head gasket failures that beads top and bottom around the fluid The emergence of bimetal engines— resulted in the telltale white exhaust openings, and it’s coated with Teflon which use different metallurgical com- smoke of coolant being vaporized. on both sides. The result is a sealing binations of engine block and cylinder Since the coefficients of expansion design that allows the surfaces to slide head materials—has further complicat- for the cast-iron engine block and the on either side of the gasket while ed the situation. Most bimetal engines aluminum cylinder head are different, maintaining a seal that will contain in service today consist of a cast-iron the potential for trouble starts the mo- pressurized hot gases, coolant and oil. block with an aluminum cylinder head. ment the engine is fired up. The head Chrysler’s 2.2L & 2.5L. In these Since different metals and alloys ex- gasket can be literally “scrubbed” apart engines, small radiators and air trapped pand and contract at different rates, de- when the head expands faster than the in the cooling system can contribute to 38 August 2002 “hot spots,” which cause engine castings nation of epoxy coating topped with sil- graphite clinched to a perforated steel to expand unevenly, excessively com- icone helps ensure a secure seal at the core and a stainless-steel flange. A pressing the cylinder head gasket. metal-to-metal interface between the thicker gauge metal flange at the com- When these engines cool and the cast- gasket and the block. The graphite fac- bustion chamber improves the torque ings contract, the head gasket may be ing material is also coated to provide a retention in this most critical area. unable to recover its normal size and tight seal at the cylinder head. shape. And if that wasn’t enough, large Honda’s 1.3L & 1.5L. These en- Causes of Gasket Failure core holes in the casting contribute to gines present a different kind of prob- Here are some of the causes of gas- head flex and the engine is prone to lem. The so-called “siamese” exhaust ket failure that must be recognized detonation. All these elements combine valves on these engines create local- and understood in order to correct to allow combustion gases to leak. Even- ized heating that can cause head gasket the problem: tually, the leaking gases burn the gasket damage if the cooling system isn’t op- Hot Spots. A hot spot causes metal facing material, causing gasket failure. erating at peak efficiency. Poor coolant in a small area of the head and/or block Corteco’s answer to this problem is circulation can eventually lead to com- to expand excessively. This expansion its White Gasket technology, which us- bustion leakage between cylinders. can crush and damage the head gasket. es two layers of graphite facing materi- Victor Reinz’s solution is the Ni- As a result, the gasket may leak, erode al with a double steel armor envelope troseal replacement head gasket, and/or eventually burn through. to prevent crushing. A special combi- which is composed of Teflon-coated If a head gasket is replaced without August 2002 39 SEALING IN QUALITY coolant is added in order to provide even cooling. The thermostat some- times blocks the air, leaving pockets in the upper block and/or heads. In other cases, the configuration of the cooling system itself makes it difficult to re- move air. With air in the system, coolant does not circulate properly, so the engine doesn’t cool evenly. Air trapped in the system can often be found in the heater core. Little or no output from the heater when the engine is warm is a good indicator of air trapped in the system. Check the overall condition of the Photo courtesy Fel-Pro courtesy Photo cooling system. Make sure the thermo- A proper head gasket replacement job requires that warping and distortion stat, cooling fans, belts and hoses are in be corrected. Use a straightedge and feeler gauge to measure the surfaces good working condition. Check the of the head and block. Straighten or resurface the casting as necessary. hose clamps on the intake side of the water pump to ensure air is not being finding the cause of the hot spot, the the damaged spot, then compare the sucked into the system. replacement gasket will eventually fail, reading to other areas of the gasket. Consult a service manual to deter- too. Hot spots also cause additional If you find evidence of crushing, ex- mine cooling system capacity and stress to the head itself, resulting in amine the corresponding surfaces on make sure the full volume of coolant is cracking or warping. the head and block for damage. Use a added. The manual will also help you Hot spots have an even more dra- straightedge and feeler gauge to check locate any bleeder valve(s) and will list matic effect if the operating tempera- for flatness. If either surface is dam- any special refilling procedures that tures rise above normal. A severe over- aged or out-of-flatness, it must be are required. Front-drive cars and heating incident can cause castings to resurfaced to assure proper sealing minivans are more prone to having air distort permanently. when a new gasket is installed. trapped in the system because the The excessive crushing caused by Cooling System Problems. Air heater core may sit higher than the en- hot spots leaves head gaskets measur- pockets in the cooling system can gine. In some cases, it may be neces- ably thinner in the damaged area. Ex- cause head gaskets to fail. They can be sary to remove one of the heater hoses amine the failed gasket, using a mi- formed while coolant is being added. to let air escape from the core. crometer to measure its thickness in Air must escape from the engine as the Coolant-Related Problems. Sometimes coolant can be problemati- cal for head gaskets in bimetal engines. Corrosion inhibitors are added to many coolants to protect all types of metals. In bimetal engines, these addi- tives eventually form aluminum salts, which can form a coating on the radia- tor tubes, reducing cooling efficiency and possibly leading to gasket failure. A thorough flushing is called for in this case. In extreme cases of plugging or deterioration, radiator replacement may be the only answer. Replacing a radiator at the first sign of a problem is usually cheaper and easier than doing a head gasket job after the engine dam- age has been done. Casting Motion. This is the result Corteco’s White Gasket technology uses an epoxy, which surrounds the of the cylinder head trying to lift away graphite-based gasket, topped with silicone. This design provides excellent from the block under the pressure of sealing of rough surfaces and accommodates cold seals. compression and combustion. This 40 August 2002 SEALING IN QUALITY thinner than the block and the physical law that heat rises. Although severely warped heads must be replaced, some minor warping can be removed by clamping and heat- ing the head. This technique is recom- mended only for technicians with ex- perience in cylinder head work. Mini- mal warping and distortion can also be corrected by resurfacing. First, inspect the cylinder head and engine block for flatness. Place a straightedge lengthwise on the head or block and, using a feeler gauge, check for warping between the head and straightedge. The total maximum lengthwise out-of-flatness of head and block combined should not exceed Fel-Pro’s PermaTorque head gasket distributes the pressure and heat evenly .003 inch for 3-cylinder and V6 en- to avoid detonation problems and lessen the effects of “scrubbing.” gines, .004 inch for 4-cylinder and V8 engines and .006 for Straight Sixes.