# How to Avoid Snapping Head Bolt



## Spokane95PU (Jan 14, 2017)

Hi All-
Am considering a head gasket project on my '95 V6. Anticipating possible problems, any good recommendations or best practices for avoiding snapping a head bolt, if that's even possible? 
Thx!


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## rogoman (Dec 16, 2004)

Most vehicle manufacturers use Torque-To-Yield (T-T-Y) head bolts, especially on engines with aluminum heads. They provide more consistent clamping loads across the entire head-to-block mating surface. Since T-T-Y bolts are designed to stretch, reusing them can cause improper or uneven torque and clamping force. Stretched bolts can damage threads in the engine, especially on aluminum blocks, and since the bolts are weakened, they may break if retorqued. *You should always replace the bolts*.

It's very important to follow the proper torquing sequence and specifications when installing T-T-Y head bolts. As with conventional bolts, T-T-Y bolts are tightened in a series of stages and in sequence. T-T-Y bolts are generally tightened in sequence to what is known as a snug torque value. This snug value is to ensure that the component, in this case say a cylinder head is firmly located on the block. Correct sequence tightening is essential to eliminate distortion. Torque is further applied in sequence through a series of motions only this time instead of torque load being measured, angle of rotation is measured by using an angle wrench. 

Follow the tightening specs as outlined in the FSM. Always clean the threads where the bolts pass through, any thread damage, corrosion or rust will create excessive friction giving you a false torque reading, robbing you of valuable clamping force. Using engine oil, lightly oil the threads and under the heads/washers on T-T-Y bolts unless otherwise specified by the FSM. Clean, oiled threads prevent binding, allowing for accurate and consistent torquing. Be careful not to over-oil the bolts, especially if they are threading into a blind hole. Too much oil will hydrolock the bolt and give false torque readings.


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## Spokane95PU (Jan 14, 2017)

rogoman, Thx for the quick reply and all the insights. What about any possibility of snapping an existing, stuck bolt that I'm trying to back out? Does that happen with head bolts? If so, what steps will minimize the chances? (Seems like I recall seeing a YouTube of somebody pulling the head off a Mazada and snapping two bolts in the process.)
Thx!


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## rogoman (Dec 16, 2004)

To minimize bolt breakage, before removing T-T-Y head bolts, allow the engine to fully cool. Removing the bolts while the engine is hot can cause cylinder head warp-age. T-T-Y bolts should be removed in the reverse order and sequence of which they are installed. If the engine has been sitting for a very long time without being run, spray a penetrating solvent like "liquid wrench" or "PB blaster" on the bolt heads and let it soak in for at least one hour or more; also tap the top of the bolts with a hammer lightly to activate a vibration that will help to loosen any oxidation on the threads.


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## Spokane95PU (Jan 14, 2017)

Thank you, rogoman! Very helpful.


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