What is the tightening order for the cylinder head bolts?
The value of all fastening elements in the engine is very high. This is an axiom. The tightening of the cylinder head bolts is no exception.
Features of tightening cylinder head bolts
Cause? And she is simple. Just think about what loads all the fasteners experience: constant vibration, crazy temperature changes. As a result of the research, a figure of 5000 kg was obtained. and higher. This is approximately the same tensile load at full throttle for each engine bolt.
One of the main conditions that guarantee the correct actions when repairing the cylinder head or when replacing the cylinder head gasket is compliance with the manufacturer's requirements. Different engine models have different cylinder head tightening torques. The tightening order of the cylinder head may also differ. There are recommendations in the manuals for each model, and they must be followed.
Having its own characteristics, in relation to different models, tightening the cylinder head bolts also has nuances that apply to the cylinder head bolt tightening procedure in general, and are the same for everyone.
And it is advisable for you to know them, since no one guarantees that the service will do it competently and as for yourself.
The tightening torque of the cylinder head is affected by:
- Lubrication of the threads of the holes and the bolts themselves. It is recommended to lubricate with non-viscous types of engine oil.
- The condition of the thread, both the hole and the bolt itself. Deformation and clogging of the thread before tightening are contraindicated, this can lead to a decrease in the compression force of the gasket with all the consequences ...
- New bolt or already used. A new bolt has a higher resistance and torque readings may be distorted. It is desirable that when using new bolts, the tightening of the cylinder head bolts is carried out after 2-3 cycles of tightening and unscrewing the bolts. It is recommended to tighten the bolts to 50% of the final tightening torque and loosen.
When tightening the bolts, special attention should be paid to the accuracy of the tool, namely the torque wrench. Dial indicator wrenches are both convenient and accurate. But, they react sharply to drops and bumps, like any precision instrument.
Recommendations for tightening cylinder head bolts
- Refer to the manufacturer's instructions for the exact torque and sequence for tightening the cylinder head.
- Bolts must be in perfect condition. Do not save, and in no case cut the thread. After all, you are doing it for yourself.
- Bolt threads and holes must be clean. Wire brush in your hands.
- In the case of a "blind" hole for the bolts, try not to pour oil into them, otherwise the bolt will not fully fit into place. And it would be useful to lubricate the threads with plastic sealant if the hole goes into the engine cooling system.
- TTY type bolts (usually used in engines with aluminum cylinder heads) are strictly forbidden to be re-tightened, as they may break. Their repeated use will also not be able to provide the necessary compression of the gasket, which means a leak.
- When installing a gasket, be sure to refer to the gasket manufacturer's specification for the tightening torque. If you have a past experience with changing gaskets, then forget about it. Each engine has its own specifics.
- Returning to the TTY type bolts, you need to emphasize that for them there is a clear degree, and not the tightening torque of the cylinder head bolts. That is, you will need a tool with an angle indicator.
- Tightening or broaching of bolts, if necessary, is carried out for engines: with cast-iron cylinder heads when hot, and with aluminum cylinder heads when cooled to room temperature.
Good luck with your DIY cylinder head tightening.
Often, the wells where the bolts are screwed become rusty or clogged with dirt; it is not always possible to clean them. It is strictly forbidden to pour oil into them, exactly, as well as to tighten the bolts into dirty holes, otherwise it is impossible to achieve the desired effort. Oil can only be applied to the threads directly on the bolts. Often there were cases when, when these tips were ignored, the well collapsed, and this threatened to replace the cylinder block, since it is not always possible to repair it.
It is impossible to tighten without a torque wrench, under no circumstances, tightening the bolts “by eye” is almost always done in excess of the allowable force, this leads to breakage of the bolts and repair of the cylinder block. It is also recommended to always use new bolts, even if your old ones look perfect, the fact is that they tend to stretch after being tightened.
