Compression Results for GTD :( - page 2 - IDI Engine - VWDiesel.net The IDI, TDI, and mTDI source.

• #15 by wil892 on 18 Apr, 2011 02:24
• Thanks mark, would it be possible to run with stuck rings for 15k miles then? I have run 5w40 synthetic for all those miles surely this would have unstuck them?
  
  Ideally removing the head and pistons and honing would be much more cost effective than replacing the bottom end, something I think would be easy enough for me to do.
  Are stuck rings common on these? I'm wondering if the other pressures are ok and it is just no3 cylinder with the stuck ring. As i mentioned the original honing marks were all clearly visible when I had the head off last and no ridge.
• #16 by Mark(The Miser)UK on 18 Apr, 2011 05:23
• Quote from: wil892 on 18 Apr, 2011 02:24

  Thanks mark, would it be possible to run with stuck rings for 15k miles then? I have run 5w40 synthetic for all those miles surely this would have unstuck them?
  
  Ideally removing the head and pistons and honing would be much more cost effective than replacing the bottom end, something I think would be easy enough for me to do.
  Are stuck rings common on these? I'm wondering if the other pressures are ok and it is just no3 cylinder with the stuck ring. As i mentioned the original honing marks were all clearly visible when I had the head off last and no ridge.
  

  
  I believe synthetic is renowned for unclogging crud, and is definitely too slippery for decent break-ins. But does it remove genuine 'coked on' matter, I dunno.
  
  Don't tell anyone, but I use multigrade Wilko special which coupled with the worn out rings, probably contributed to the stuck rings.
  
  When I first had the engine, they were all reading the same 300psi, so as I had no starting issues I had put it down to my homemade adaptor:
  40000 miles later, and after only a month of intermittantly hard starts, the readings were 160, 200 200 and 270. But with those ring results maybe the readings were fairly accurate. .
  
  Since August's rebuild I'm barely using any oil, the dipstick shows semi translucent, rather than completely opaque and the oil baffle is definitely nolonger 'greasy'. I'm running injectors out of a Ford  1.6, and they are set to 125bar IIRC
  
  I've just done a run pure A38 stuff today. Half journey with family loaded and half ditto but with three 15ft dead apple trees on the roofrack chopped into 10ft lengths with all twigs on, 50 to 80mph going, and 50ish with trees and my mileage is.... 56.2mpg. 
• #17 by BigVWman on 18 Apr, 2011 07:15
• I think the reason the book doesn't advise the use of oil in diesel compression testing is the potential for hydrolock if you get a little overzealous with quantity. keep it small quantities and should be fine.
• #18 by Vincent Waldon on 18 Apr, 2011 07:19
• The MK2 Bentley says that the reason not to use oil during compression testing of diesel engines is that it can ignite (just like diesel fuel does), damaging the compression tester, causing bodily injury, etc. etc. etc.
• #19 by R.O.R-2.0 on 18 Apr, 2011 08:35
• Quote from: Vincent Waldon on 18 Apr, 2011 07:19

  The MK2 Bentley says that the reason not to use oil during compression testing of diesel engines is that it can ignite (just like diesel fuel does), damaging the compression tester, causing bodily injury, etc. etc. etc.
  

  
  the starter would have a tough time bending a rod or doing any kinda damage from a hydro lock..
  
  but, having a compression gauge blow up in your face would kinda suck..
• #20 by Mark(The Miser)UK on 18 Apr, 2011 13:40
• Quote from: R.O.R-2.0 on 18 Apr, 2011 08:35

  Quote from: Vincent Waldon on 18 Apr, 2011 07:19

  The MK2 Bentley says that the reason not to use oil during compression testing of diesel engines is that it can ignite (just like diesel fuel does), damaging the compression tester, causing bodily injury, etc. etc. etc.
  

  
  the starter would have a tough time bending a rod or doing any kinda damage from a hydro lock..
  
  but, having a compression gauge blow up in your face would kinda suck..
  

  Sounds nasty, but unless you were cranking for ages, and even then I doubt it could happen. How do you hydrolock from a few ccs of oil when you have the large  prechamber and the injector tester?
  Perhaps limit the oil to half prechamber volume. Naturally, don't do it unless compresson results low anyway. 
  When cranking you should only need do it for say 5 or 10 revs, and watch the pressure rise as you are cranking, for comparison purposes.
• #21 by R.O.R-2.0 on 19 Apr, 2011 10:43
• Quote from: Mark(The Miser)UK on 18 Apr, 2011 13:40

  Quote from: R.O.R-2.0 on 18 Apr, 2011 08:35

  Quote from: Vincent Waldon on 18 Apr, 2011 07:19

  The MK2 Bentley says that the reason not to use oil during compression testing of diesel engines is that it can ignite (just like diesel fuel does), damaging the compression tester, causing bodily injury, etc. etc. etc.
  

  
  the starter would have a tough time bending a rod or doing any kinda damage from a hydro lock..
  
  but, having a compression gauge blow up in your face would kinda suck..
  

  Sounds nasty, but unless you were cranking for ages, and even then I doubt it could happen. How do you hydrolock from a few ccs of oil when you have the large  prechamber and the injector tester?
  Perhaps limit the oil to half prechamber volume. Naturally, don't do it unless compresson results low anyway. 
  When cranking you should only need do it for say 5 or 10 revs, and watch the pressure rise as you are cranking, for comparison purposes.
  

  
  but if you are taking compression readings on a hot engine, like you should, then it is COMPLETELY POSSIBLE for the oil to ignite in the cylinder, if you are using oil at all..
  
  another thing, if you take a compression reading thru the glow plug hole, be sure to disconnect the power to the fuel solenoid on the top of the pump. then no fuel is injected (compression gauge wont blow up that way)
  
  and even if you did have enough oil in a cylinder to hydro lock it, the starter would come up tight against the oil, the rods and bottom end would be fine. you can not bend a rod with a starter, unless its a starter from a tug boat or something..
  
  even if you did get a hydro lock, you would just have to let the oil out, then start the engine and let it burn the oil out of that cylinder..
  
  only way i see it possible to hydro lock an engine and damage it, is driving (hitting a huge puddle) down the road. or driving into the river/creek/ditch on accident, lol..
• #22 by wil892 on 23 Apr, 2011 02:29
• Just had a thought. I thought I saw some years ago on here that the chinese 1.6 head castings actually had the 1.9 precups installed. does anyone know if this is true, if so it may explain why my compression is so low and my timing has to be set at 1.25mm to have the car running properly.
  Thanks
  Will
• #23 by R.O.R-2.0 on 23 Apr, 2011 08:54
• as compression lowers, the engine wears, and needs to have advanced timing..
• #24 by vdubspeed on 24 Apr, 2011 05:33
• warm, hot, draper, or harbor freight...those numbers are low. End of story.
  
  As for rings resetting. Can't say I agree. That motor is just tired. I pulled a rabbit diesel out of field that sat for 18 years and it fired up with fresh diesel and a new battery.
  
  Time for a replace or rebuild.
• #25 by the caveman on 24 Apr, 2011 10:11
• After reading about putting oil in the cylinders to try to diagnose bad rings etc, i realized that i don't know if i've every personally done it. Good point about the hydrolock and/or igniting. Too many gassers i guess