So as everyone knows I did a piston soak on my Saturn well I've done 5 now I think. When i first started doing them the first time the cylinders stayed full except the 3rd one. Well now it has gone to the 3rd holds fluid for about 2 hours before empty and the others leak down before i check on it at the 14 hour mark. Before they would all ne full.at 12+ hours except for cylinder 3 but it would hold fluid for more than 5 hours that I'm sure of. Why is this? Are they clean so they leak down now? Just curious. Thanks guys.
piston soak leak down question
- Thread starter Dakota1820
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Compression is 196 195 194 196
If it were mine I'd soak #3 one more time and then call it, compression numbers are good. Reality is, though, it's not the compression rings that cause issues on the S-Series it's the oil control rings that coke up.
I know its the oil rings but why would the cylinders leak down if compression is good? Thats what's losing me i guess.
I posted a similar question back in June/July and got conflicting advice as what it means.
Even the compression rings have a small gap in them so they are "spring loaded" to press on the cylinder walls. The fluid leaks through these gaps.
Piston rings are staggered around the piston approximately 30 degrees apart. The rings have an end gap (there are zero gap rings but they are not common) to allow expansion and contraction of the ring as the engine warms and cools.
This staggering allows the piston to create and maintain pressure during the compression stroke, if the piston was stopped under pressure it would eventually bleed down through these gaps. It also keeps oil from reaching the combustion chamber, if all gaps were in a straight line the piston could not build much pressure and oil would get into the combustion chamber.
With a clean piston the liquid you put in to clean the top end will leak through this gap on the top ring and flow down through the other rings end gaps into the oil.
If the piston is dirty the gap between the rings may be full of carbon and deposits preventing the liquid from running through to the next ring.
These deposits can also stick rings in the piston ring grooves, meaning they no longer expand tight enough to build maximum compression. They are still tight enough to hold a liquid with no pressure and if there is build up between the rings it may hold the liquid for a long time before bleeding down.
Good compression while allowing liquid to bleed past the rings end gaps would indicate there are few deposits between the rings.
I hope i explained this in an understandable way.
This staggering allows the piston to create and maintain pressure during the compression stroke, if the piston was stopped under pressure it would eventually bleed down through these gaps. It also keeps oil from reaching the combustion chamber, if all gaps were in a straight line the piston could not build much pressure and oil would get into the combustion chamber.
With a clean piston the liquid you put in to clean the top end will leak through this gap on the top ring and flow down through the other rings end gaps into the oil.
If the piston is dirty the gap between the rings may be full of carbon and deposits preventing the liquid from running through to the next ring.
These deposits can also stick rings in the piston ring grooves, meaning they no longer expand tight enough to build maximum compression. They are still tight enough to hold a liquid with no pressure and if there is build up between the rings it may hold the liquid for a long time before bleeding down.
Good compression while allowing liquid to bleed past the rings end gaps would indicate there are few deposits between the rings.
I hope i explained this in an understandable way.
Trav: that made a lot of sense. So I guess if they all leaked down in a 14 hour time span they are probably pretty clean now?
I would like to see HOW the pressure increases/builds up with your compression test.
I mean after 1,2,3, and 4 revs/cranks.
Also, leak down of fluids is affected by WHERE the piston is.
[At the worn top or the relatively unscathed bottom of the bore.]
I mean after 1,2,3, and 4 revs/cranks.
Also, leak down of fluids is affected by WHERE the piston is.
[At the worn top or the relatively unscathed bottom of the bore.]
^ I would think so. If it still burns oil after this, then chances are, the oil control rings are worn, but the engine is otherwise healthy.
Yes i would say so.
I must make a correction to what i posted, the stagger must be within 30 degrees (MAN diesel spec) but you got what i meant.
It would be unusual for the just the oil rings to wear out, i would try Kreen in this engine for a couple of OCI if it still burns some oil. Now the rings are somewhat clean the product may have have a good chance of cleaning out whatever crud is left.
If you can get the oil usage under control maybe an oil with some good cleaning abilities would help keep it clean.
Personally i might try Mobil 1 0w40,PU or Rotella T 5w40 in it.
I did this to an old Toyota, the Rotella T cleaned pretty darn good and the engine runs smooth and quiet.
Economy difference is so negligible its not worth talking about.
I must make a correction to what i posted, the stagger must be within 30 degrees (MAN diesel spec) but you got what i meant.
It would be unusual for the just the oil rings to wear out, i would try Kreen in this engine for a couple of OCI if it still burns some oil. Now the rings are somewhat clean the product may have have a good chance of cleaning out whatever crud is left.
If you can get the oil usage under control maybe an oil with some good cleaning abilities would help keep it clean.
Personally i might try Mobil 1 0w40,PU or Rotella T 5w40 in it.
I did this to an old Toyota, the Rotella T cleaned pretty darn good and the engine runs smooth and quiet.
Economy difference is so negligible its not worth talking about.
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Originally Posted By: Trav
Yes i would say so.
I must make a correction to what i posted, the stagger must be within 30 degrees (MAN diesel spec) but you got what i meant.
It would be unusual for the just the oil rings to wear out, i would try Kreen in this engine for a couple of OCI if it still burns some oil. Now the rings are somewhat clean the product may have have a good chance of cleaning out whatever crud is left.
If you can get the oil usage under control maybe an oil with some good cleaning abilities would help keep it clean.
Personally i might try Mobil 1 0w40,PU or Rotella T 5w40 in it.
I did this to an old Toyota, the Rotella T cleaned pretty darn good and the engine runs smooth and quiet.
Economy difference is so negligible its not worth talking about.
Trav:
In this particular engine, the issue is that the oil control rings lose their tension. It is a design flaw
Yes i would say so.
I must make a correction to what i posted, the stagger must be within 30 degrees (MAN diesel spec) but you got what i meant.
It would be unusual for the just the oil rings to wear out, i would try Kreen in this engine for a couple of OCI if it still burns some oil. Now the rings are somewhat clean the product may have have a good chance of cleaning out whatever crud is left.
If you can get the oil usage under control maybe an oil with some good cleaning abilities would help keep it clean.
Personally i might try Mobil 1 0w40,PU or Rotella T 5w40 in it.
I did this to an old Toyota, the Rotella T cleaned pretty darn good and the engine runs smooth and quiet.
Economy difference is so negligible its not worth talking about.
Trav:
In this particular engine, the issue is that the oil control rings lose their tension. It is a design flaw
Oh i didn't know that, i thought it was a problem with the piston design which allowed excess deposits to get to the rings. I guess if it doesn't stop a ring job with improved oil rings or pistons eh?
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Originally Posted By: Trav
Oh i didn't know that, i thought it was a problem with the piston design which allowed excess deposits to get to the rings. I guess if it doesn't stop a ring job with improved oil rings or pistons eh?
Yup. A guy recently posted a few pics of his. They have "the suck"
Oh i didn't know that, i thought it was a problem with the piston design which allowed excess deposits to get to the rings. I guess if it doesn't stop a ring job with improved oil rings or pistons eh?
Yup. A guy recently posted a few pics of his. They have "the suck"
I believe its both. They don't have drain back holes so they coke up but also lose tension all around bad design
Before I bought my Saturn my brother had a 94 SL1. I was aware of oil consumption. I really wanted a Corolla. Later I found out some of them had worse oil consumption than my Saturn. Saturn is not the only company that had a bad design.
Most definelty not. Saturns are good cars. And the oil issue probably wouldst evee happen if they run Full Synthetic 10w30 it whole life and changed oil every 5000 miles
Originally Posted By: Trav
If the piston is dirty the gap between the rings may be full of carbon and deposits preventing the liquid from running through to the next ring.
These deposits can also stick rings in the piston ring grooves, meaning they no longer expand tight enough to build maximum compression. They are still tight enough to hold a liquid with no pressure and if there is build up between the rings it may hold the liquid for a long time before bleeding down.
Great explanation! Also agrees with my experience where there was standing MMO in 3 cylinders after soaking overnight the first time, but not anymore on a second soak. Now, this is in Corolla. The thing is no consumption after couple of 1000 miles after the soak and then it slowly comes back. But there is clearly improvement.
If the piston is dirty the gap between the rings may be full of carbon and deposits preventing the liquid from running through to the next ring.
These deposits can also stick rings in the piston ring grooves, meaning they no longer expand tight enough to build maximum compression. They are still tight enough to hold a liquid with no pressure and if there is build up between the rings it may hold the liquid for a long time before bleeding down.
Great explanation! Also agrees with my experience where there was standing MMO in 3 cylinders after soaking overnight the first time, but not anymore on a second soak. Now, this is in Corolla. The thing is no consumption after couple of 1000 miles after the soak and then it slowly comes back. But there is clearly improvement.
Originally Posted By: chevyboy14
Most definelty not. Saturns are good cars. And the oil issue probably wouldst evee happen if they run Full Synthetic 10w30 it whole life and changed oil every 5000 miles
Knowing what I know now, I wish I used only synthetic in my car. I thought 4000-5000 miles OCI (every 6 months) on conventional oil were OK in Corolla. Mind you the manual stated 7,500 miles OCI.
Most definelty not. Saturns are good cars. And the oil issue probably wouldst evee happen if they run Full Synthetic 10w30 it whole life and changed oil every 5000 miles
Knowing what I know now, I wish I used only synthetic in my car. I thought 4000-5000 miles OCI (every 6 months) on conventional oil were OK in Corolla. Mind you the manual stated 7,500 miles OCI.
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