mackrmodel686st Posted September 12, 2023 Share Posted September 12, 2023 The company I work for has a 1993 ch613 mack with a 400 mack engine. Every 6 months or so a head gasket blows and starts using coolant and overheating. We replace the fire rings when we do the head gaskets but still keeps happening. Does anyone havevany ideas why this keeps happening? Thanks. Quote Link to comment https://www.bigmacktrucks.com/topic/73293-blowing-head-gaskets/ Share on other sites More sharing options...
Joey Mack Posted September 12, 2023 Share Posted September 12, 2023 Did you check the deck with a straight edge, to see if it's flat. No more then .005" is allowed.. also, where is the leak? Same spot?? Have you checked the liner protrusion? Needs to be within .002" to neighboring cylinder,. The limits are .023"-.029"... 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73293-blowing-head-gaskets/#findComment-538717 Share on other sites More sharing options...
fjh Posted September 12, 2023 Share Posted September 12, 2023 I second the liner protrusion! That era of engine had liner protrusion set too low! for the horsepower! the spec got change in later years from low spec ~ 19 to 23 if you can achieve 25 or above is best! 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73293-blowing-head-gaskets/#findComment-538726 Share on other sites More sharing options...
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