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Compressions

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  • dave.unwin@btinternet.com
    Hi All, I recently noticed that when cold my compressions are quite low on two cylinders, but once the engine is warm all four seem pretty fair. I m going to
    Message 1 of 4 , Jul 10, 2013
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      Hi All, I recently noticed that when cold my compressions are quite low on two cylinders, but once the engine is warm all four seem pretty fair. I'm going to do a 'leak-down' test but was wondering if any of you had any theories? I suspect the valves.
    • Ray Leonard
      Valves don t tend to improve with heat. I d suspect the head / cylinder seal. Check head bolt torque. Are the low cylinders on the same side? Ray ... From:
      Message 2 of 4 , Jul 10, 2013
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        Valves don't tend to improve with heat.  I'd suspect the head / cylinder seal.  Check head bolt torque.  Are the low cylinders on the same side?
         
        Ray
        ----- Original Message -----
        Sent: Wednesday, July 10, 2013 3:29 AM
        Subject: [AirVW] Compressions

        Hi All, I recently noticed that when cold my compressions are quite low on two cylinders, but once the engine is warm all four seem pretty fair. I'm going to do a 'leak-down' test but was wondering if any of you had any theories?  I suspect the valves.



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      • Andrew Cilia
        That s typical for the VW. We had a few bright sparks here that didn t like the cold leak, tightened up the heads to something ridiculous and then wondered why
        Message 3 of 4 , Jul 10, 2013
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          That's typical for the VW. We had a few bright sparks here that didn't like the cold leak, tightened up the heads to something ridiculous and then wondered why they were pulling studs out of the crankcase when the engine was running. Thankfully, it wasn't in a plane.

          Is that two cylinders on the same side?

          I asked Steve Bennett for torque settings on Nikasil Cylinders and he said "We torque them to 22 ft lbs and re check every oil change.  They put a lot more expansive force on the studs than do stock steel cylinders".

          Only helps if your using nikasils.

          On Wed, 2013-07-10 at 09:29 +0000, dave.unwin@... wrote:
           
          Hi All, I recently noticed that when cold my compressions are quite low on two cylinders, but once the engine is warm all four seem pretty fair. I'm going to do a 'leak-down' test but was wondering if any of you had any theories? I suspect the valves.





        • Dave Unwin
          Thanks for the advice so far!
          Message 4 of 4 , Jul 10, 2013
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            Thanks for the advice so far!

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