2nd ring on a M21D24 piston - IDI Engine - VWDiesel.net The IDI, TDI, and mTDI source.

• 2nd ring on a M21D24 piston by klang on 09 Aug, 2009 14:09
• Probably a stupid question, but I want to get this right.
  
  I pulled my BMW M21D24 IDI Engine apart 8months ago, and had everything lined up, balanced etc.
  
  Now, when I'm putting everything together, I'm not sure about the second compression pistonring (the middle one)
  
  I can be mounted in 2 different ways.
  
  The "groove" should be down? Is this correct? 
  
  
  Dont want to have to pull the engine apart again just because of stupidity 
  
  // Klang
• #1 by Rabbit on Roids on 09 Aug, 2009 15:37
• pretty sure the groove in the scraper ring is supposed to face up.
• #2 by Rabbit TD on 09 Aug, 2009 20:00
• Most rings that are designed to face a certain way have a mark on the flat surface right near the gap area.  Does yours have a small mark there, if it does it should be facing the top of the piston.
• #3 by Rabbit on Roids on 10 Aug, 2009 08:14
• oh yea, there are marks on the top of the ring. on the top edge.
• #4 by klang on 10 Aug, 2009 12:45
• Thanks for the answers.
  
  I checked the ring, and close to the gap I found "TOPC" written.
  
  So I mounted it that way, and the groove is facing down. (the letters up)
  
  The top ring had "PC" mounted on it, so I mounted that facing upwards as well.
  
  The oil ring had nothing on it, looked to be the same on both sides, so I just put them on 
  
  
  
  Hope I have compression later =)
  
  
  Thanks.
• #5 by Rabbit TD on 10 Aug, 2009 15:23
• Quote from: klang on 10 Aug, 2009 12:45

  Thanks for the answers.
  
  I checked the ring, and close to the gap I found "TOPC" written.
  
  So I mounted it that way, and the groove is facing down. (the letters up)
  
  The top ring had "PC" mounted on it, so I mounted that facing upwards as well.
  
  The oil ring had nothing on it, looked to be the same on both sides, so I just put them on 
  
  
  
  Hope I have compression later =)
  
  
  Thanks.
  

  If you have those letters facing up you have them on right.
• #6 by klang on 11 Aug, 2009 04:22
• Quote from: Rabbit TD on 10 Aug, 2009 15:23

  Quote from: klang on 10 Aug, 2009 12:45

  Thanks for the answers.
  
  I checked the ring, and close to the gap I found "TOPC" written.
  
  So I mounted it that way, and the groove is facing down. (the letters up)
  
  The top ring had "PC" mounted on it, so I mounted that facing upwards as well.
  
  The oil ring had nothing on it, looked to be the same on both sides, so I just put them on 
  
  
  
  Hope I have compression later =)
  
  
  Thanks.
  

  If you have those letters facing up you have them on right.
  

  
  
  Great!
  Thanks
• #7 by arb on 11 Aug, 2009 06:35
• Quote from: klang on 10 Aug, 2009 12:45

  
  The oil ring had nothing on it, looked to be the same on both sides, so I just put them on 
   
  

  
  That's correct, the oil scraper rings have no up or down... (the spacer accordion ring goes between the 2 scrappers)