Blowing head gaskets

Discussion in 'Mechanic and Repair' started by dfor, Nov 15, 2001.

  1. khouse

    khouse LawnSite Bronze Member
    Messages: 1,465

    I agree with you BigJames. If you fill the bores up with oil and put the bolt in then you may break the bore out. Also the guy who put silicone in the bore was probably trying to seal the bolt on a water cooled engine. This can also blow the bore out. On the small air cooled engines you should have a clean bolt and have ran a tap in the bores to make sure all is clean. Then blow out the bore and put a coat of engine oil on the bolt threads only. Then put a small amount under the bolt head. This is the correct way to do it with no problems. If working on a water cooled engine where the head bolts are wet (penitrating into the coolant) then clean as said and apply copper coat to the bolt threads only and a touch of anti-seeze under the head. If it is a dry bolt then treat it like it is an air cooled engine. When in doubt check your manual.
  2. Bill Kapaun

    Bill Kapaun LawnSite Senior Member
    Messages: 964

    After you replace the gasket again, try this.
    After each heating/cooling cycle, re-torque the head bolts. Repeat until the bolts no longer turn when re-torquing.
  3. khouse

    khouse LawnSite Bronze Member
    Messages: 1,465

    When retorquing loosen the bolt 1 turn before torquing. Also squirt a little oil under the bolt head. This will give you the best results. Once a head bolt has been torqued it is kind of set hard. It may take more torque to break it loose in tightening then the torque value. This will make you think that they don't need to be torqued - but it will fool you. So loosen a little and then retorque. Try marking a line on your bolt and head to show where the bolt is now. Then loosen and retorque. Note the difference. Then do the same on another bolt but this time don't loosen it. You will see a lot of difference.

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