When replacing a head gasket:


  • Use the correct size and pitch tap to clean up the threads in the block. Make sure the tap is clean, free of burrs, and oiled, and do NOT continue turning it if significant resistance is encountered. A used head bolt with three grooves cut into it can substitute for a tap. You should be able to run it all the way down the hole with your fingers. Be extra careful in aluminum blocks because if the tap bottoms out, continuing to turn it will strip the threads from the hole.
  • Make sure the holes are cleaned and completely free of oil and solvent or liquid lock may result.
  • Clean the block surface with solvent or oven cleaner, a brass brush, and gentle scraping. Use lint free rags.
  • Have the surface of the head machined if the previous gasket was blown.
  • Ensure that the head surface is clean and that the cylinders are free of liquid solvent; otherwise when you go to place the head onto the block, the solvent will drip onto the gasket surface and carry carbon with it, compromising the seal.
  • Ensure that any guide dowels have been reinserted into the block and that the NEW gasket has been placed over the dowels before lowering the head.
  • Use a high quality assembly lube on the head bolt threads and between the bolt head and washer. If a bolt turns roughly, remove it, apply more assembly lube, and tighten it back to the torque for the current stage.
  • Allow the assembled engine to rest for 24 hours, then one by one loosen and retorque the head bolts.
  • If a bolt simply refuses to turn smoothly up to torque, do not “guess” at the torque. Bring another bolt up to the torque where the problem bolt begins to jump. Then count the number of turns that it takes to bring that bolt smoothly to final torque. Bring the problem bolt to the same starting torque, then apply that same number of turns to the problem bolt.
  • Find and fix the overheating or lean running condition that caused the gasket failure. Check factory service bulletins through ALLDATA to ensure that you have taken any steps necessary to prevent repeat head gasket failure.


  • Don't use a die on the bolt threads when reusing head bolts. Head bolt threads are cut differently than standard bolts (“J” cut). Clean the bolt threads with solvent and compressed air. If the bolts are TTY (Torque-To-Yield), where torque is specified with an angle, always replace them and be sure to install them with a torque/angle indicator.
  • Don't use Scotch Brite or similar abrasive to clean the block surface. On engines that use a MLS (Multi Layer Steel) gasket, this can disturb the OEM mirror finish that is required for the gasket to seal. On ALL engines, allowing the fine aluminum oxide particles to fall into the cylinders and/or oil passages will lead to bearing failure within a few thousand miles because the particles are too small for the oil filter to catch and are extremely abrasive to bearings. (This failure tends to be blamed on other things, like coolant in the oil from the leaking gasket, or that the head was removed without draining the coolant first and the engine started without changing the oil.) If you do this, ensure that all oil holes and cylinders have been covered and taped, and that afterwards you blow the dust off with compressed air before uncovering.
  • Don't use an uncalibrated ratcheting torque wrench. Don't use a torque wrench where the target torque is near the end of the torque range of that wrench. It is okay to use normal socket extensions on the torque wrench to reach the head bolts. Don't pay any attention to people who claim that the “twist” in the extension or the length of the extension somehow affects the delivered torque.
  • Don't use any kind of gasket sealer unless it is provided with the gasket or otherwise specifically called for. Don't remove the gasket from the packaging until it is time to install it. This keeps it from getting dirty, and some gaskets have built in sealers that begin to set up when exposed to air.

Leave a Reply