Dry and wet compression number help

[Shaman]

My car is at 140K miles, and as I am considering selling it, when I heard what was I thought an exhaust leak, I brought it to the local shop for a compression test, with new plugs since they would be out anyway. I was told that cylinder 2 was 110 psi dry and 175 psi wet. Compression numbers were 200, 110, 225, 200.

My understanding is that this points to a ring problem, but there have been comments about it possibly being a valve, or piston problem. I don't understand how a wet compression test numbers going up would point to the piston or valve. Can someone help me understand this?
Also, I know that there is not alot of information above, but is this a park it and don't touch it or you are going to die problem, or a get it fixed soon?


The car is a 2005 Saturn Ion Redline. I haven't done a leak down test, but I know that any fix is going to cost more than the car would sell for with good compression.

 

[bdcardinal]

Normally at that point a leak down test would be performed to isolate the source of the compression leak.

 

[Trav]

Did it have an exhaust leak? Does this engine have mechanical lash adjusters and did they check the clearance? A leak down test is 100% in order.
A slightly tight valve that just moves the valve very slightly off the seat by less than a hair may raise the numbers with oil also. A burned valve will pass oil and not raise the numbers by any significant amount.

This is not likely to happen if it has hydraulics lash adjusters but a leak down test will tell you if its the rings or in the top end. If its the rings on that one cylinder I would inspect the bore with a boroscope and if not scored do a hail Mary piston soak if the off chance its a stuck ring.

 

[A_Harman]

Originally Posted by Trav
Did it have an exhaust leak? Does this engine have mechanical lash adjusters and did they check the clearance? A leak down test is 100% in order.
A slightly tight valve that just moves the valve very slightly off the seat by less than a hair may raise the numbers with oil also. A burned valve will pass oil and not raise the numbers by any significant amount.

This is not likely to happen if it has hydraulics lash adjusters but a leak down test will tell you if its the rings or in the top end. If its the rings on that one cylinder I would inspect the bore with a boroscope and if not scored do a hail Mary piston soak if the off chance its a stuck ring.


I think by 2005, all GM OHC engines had hydraulic lash adjusters.

 

[Shaman]

Originally Posted by Trav
Did it have an exhaust leak? Does this engine have mechanical lash adjusters and did they check the clearance? A leak down test is 100% in order.
A slightly tight valve that just moves the valve very slightly off the seat by less than a hair may raise the numbers with oil also. A burned valve will pass oil and not raise the numbers by any significant amount.

This is not likely to happen if it has hydraulics lash adjusters but a leak down test will tell you if its the rings or in the top end. If its the rings on that one cylinder I would inspect the bore with a boroscope and if not scored do a hail Mary piston soak if the off chance its a stuck ring.


After the 110, I didn't even think about the exhaust leak. But the tick, coming home tonight, seems to be gone, or the car wasn't up to temp enough.

I will see if the shop has a boroscope when I get the leakdown test done. I am running water methanol injection, so I am not sure that a stuck ring would be very likely.

These are the lash adjusters

https://www.thatgmpartsguy.com/p-lnf-lsj-lash-adjuster-12572638b

 

[Trav]

Yep hydraulic. With water/ methanol injection i suspect damage, seen it before.

 

[andyd]

Yep hydraulic. With water/ methanol injection i suspect damage, seen it before. Trav could you please expand on water injection damage. I locked up my first 528e by sucking water into the intake. I was sweating bullets as I spun out the plugs. #6 had water and the engine fired up and ran another 75K. TIA

 

[Trav]

i played with water injection a lot years ago and it works great but too much of a good thing can mechanically damage the pistons. I found the bubbler systems to be the safest but the least amount of power increase. If you are looking for a smoother idle, no carbon deposits and a slight increase in mpg, its just the ticket.

A friend of mine was running water/methanol injection it on a Kawasaki with a water supply in a tank bag, It made lots more power so he kept bumping it up till it cracked a piston near the ring lands.

 

[Shaman]

Originally Posted by Trav
i played with water injection a lot years ago and it works great but too much of a good thing can mechanically damage the pistons. I found the bubbler systems to be the safest but the least amount of power increase. If you are looking for a smoother idle, no carbon deposits and a slight increase in mpg, its just the ticket.

A friend of mine was running water/methanol injection it on a Kawasaki with a water supply in a tank bag, It made lots more power so he kept bumping it up till it cracked a piston near the ring lands.


Water methanol injection has been running for three years. 2 gph before the blower, and 5 gph before the intercooler on a progressive kit. A few weeks before installation of water-meth, pulley drop, ported blower, and E85 switch, compression was 195 185 195 200.

I think at least from a secondary standpoint water meth in a cold engine might have caused some of it though.

 

[Shaman]

50% leakdown, and dipstick popping out during the test.

 

[bdcardinal]

Ya that's not good. You are creating too much crankcase pressure.

 

[mattd]

Time to pull the engine and go through it. I would ditch the water meth

 

[Trav]

Originally Posted by Shaman
50% leakdown, and dipstick popping out during the test.


Don't be surprised if you find a piston broken or cracked in the upper ring land area and cyl wall damage. With pressure water/meth systems it should only kick in at WOT and all systems inc the bubbler should use a low engine temp cutout switch. On some of the older that used vacuum temp switches for emission controls it was easy without one electric is the way to go.

 

[HangFire]

Ion Redline? If it still has the Recaro seats you can get more for the pair then for the entire busted car.