Sinking feeling after leak down test

[Hitmachine101]

Hey guys/gals.

I ll get straight to the point here. 99k miles on a s52 out of a 96 m3. bought the car for parts because it didn't have a title. Got the car up in the air to look it over after purchase and found a turbo drain port drilled into the oil pan that was capped off and sealed. my heart sunk right there but did the compression test and leak down to see what was up. compression on every cylinder is 192 or better. leak down on every cylinder is 1% - 3% EXCEPT cylinder 4. It has 6% leak down on that one and the coolant res level rose and poured out the top when pressurized. took the bleeder screw out and did the test again and saw bubbles coming out of the bleeder screw port. but the level did not rise when I performed the test that way.

From what I can tell there looks to be coolant in the oil because the oil cap had moisture and coolant on it. oil level is right.

Motor runs strong and flawless. doesn't skip a beat.
We looking at a cracked head? or bad head gasket?

Is there any way to tell short of yanking the head and bringing it to the machine shop for them to go through the head and see if there is a crack.

My assumption from the oil pan having that port drilled into it is that this motor was turbo'd. Do not know if it over heated before my possession. Sat in the guys drive way when we went through it idling for about an hour and never overheated. Test drive was fine as well. Maybe he lifted the head with the force induction? Thoughts and ideas before I go down the tear down road

Thank you for the help

[AJLM34A]

You bought a parts car with an engine that runs, but might need a head gasket?

[Hitmachine101]

You bought a parts car with an engine that runs, but might need a head gasket?

something like that, bought the car to swap the drive train over to a 95 m3 and build a track car. Wish I did the leak down test before I purchased the car but live and learn.

[pbonsalb]

It's easier to change the HG and have the head tested now. You don't know the history. Could be cracked head or blown gasket or cracked ringland.

[Hitmachine101]

It's easier to change the HG and have the head tested now. You don't know the history. Could be cracked head or blown gasket or cracked ringland.

humor me but can you explain what a cracked ringland is? If its something to do with letting air past the rings then I would hear the air escaping out of the valve cover cap correct? or are you speaking about the block being cracked

[ScotcH]

humor me but can you explain what a cracked ringland is? If its something to do with letting air past the rings then I would hear the air escaping out of the valve cover cap correct? or are you speaking about the block being cracked

Ring lands are on the pistons ... happens with detonation usually. It would mean leaks past the rings, so you'd get air escaping into the oil pan.

1-3% leak is SUPER low ... even 6% is very low. But I guess we deal with race cars where the tolerances are looser But if you put pressure in the cylinder, and coolant rose, that's a pretty good indicator that air is getting into the water. That pretty common on the #6 cyl on ... the gasket fails there most often. Just change the HG, have the head checked and decked and you're good to go. Don't use the Victor Rinez gasket.

[Hitmachine101]

Ring lands are on the pistons ... happens with detonation usually. It would mean leaks past the rings, so you'd get air escaping into the oil pan.

1-3% leak is SUPER low ... even 6% is very low. But I guess we deal with race cars where the tolerances are looser But if you put pressure in the cylinder, and coolant rose, that's a pretty good indicator that air is getting into the water. That pretty common on the #6 cyl on ... the gasket fails there most often. Just change the HG, have the head checked and decked and you're good to go. Don't use the Victor Rinez gasket.

Fantastic information thank you. next step is the yank the head off and see whats going on
appreciate the education from everyone

[pbonsalb]

Ring lands are the machined lips on the upper piston circumference that sandwich the rings. On a turbocharged S52 with stock pistons a ringland could break from detonation if the engine ran lean or timing was too high. You would probably see some pitting in the piston top as well -- another sign of detonation. #6 for some reason has a reputation for being the cylinder to cause trouble.

[Ex36]

6% is crazy low. The variation you have across cylinders is not meaningful. You can see up to 20% on a cold engine. Unless you have specific other data suggesting a bigger problem, I'd be inclined to think you're over-reacting.

[hli]

Condensation on the oil cap is normal. I wouldn't worry about that. Those leakdown numbers aren't absurdly out of whack either. I would do another test to make absolutely sure that the coolant and oil aren't mixing, and if it checks out just put the motor in and run it.

A good way to check is to run the engine at operating temperature,, then open coolant reservoir cap after it has completely cooled down. If you hear a lot of escaping pressure then you probably have combustion gasses getting into the cooling system.

[Hitmachine101]

6% is crazy low. The variation you have across cylinders is not meaningful. You can see up to 20% on a cold engine. Unless you have specific other data suggesting a bigger problem, I'd be inclined to think you're over-reacting.

Yes I defiantly don't want to do a head gasket on this motor if I do not have to but I have never had the coolant overflow tank start pouring on the ground when doing a leak down test so something is not right there. air is coming through the coolant return line that runs to the bleeder. doesn't do it on any of the other cylinders when leak down testing them

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Condensation on the oil cap is normal. I wouldn't worry about that. Those leakdown numbers aren't absurdly out of whack either. I would do another test to make absolutely sure that the coolant and oil aren't mixing, and if it checks out just put the motor in and run it.

A good way to check is to run the engine at operating temperature,, then open coolant reservoir cap after it has completely cooled down. If you hear a lot of escaping pressure then you probably have combustion gasses getting into the cooling system.

when I was doing the testing, I had the oil cap resting on the injector cover face down. after completing the tests I picked it up and saw coolant on the cover where it was resting. Just to make sure it wasn't condensation I tasted it and yes sweet to the taste. Nothing like ethylene glycol poising lol

[pbonsalb]

Forced induction use has often resulted in pressuruzing the cooling system. If the motor had not been turbo, I would not worry about the variation. But since it was, you may have an issue. Metal expands when hot so the crack or leak may seal when the engine is hot and not running excessive cylinder pressures like it would under boost. That may be why there was no issue when you inspected the donor car. I'd rather do the work now than later, but thats my preference and yours may differ.

[AJLM34A]

I'd rather do the work now than later, but thats my preference and yours may differ.

This^^^^^^
Since you are removing the engine for a track car, why not spend a grand(maybe more) on machine work, gaskets, oil pump.......... while it's easy to do. Part out the items from the car to recoupe $.

[blckstrm]

I had relatively little experience when my head gasket failed. I did a lot (A LOT) of homework and things went very smoothly. If you bought a parts car and are planning to swap the engine, this is DEFINITELY within your capabilities. Those are pretty good compression and leakdown numbers, so I'd say it's a little more work than planned but certainly not the end of the world. I doubt the head is cracked, but even if it is, the machine shop should be able to find and fix it.

(It is also an easy excuse to upgrade to some cams while you have the head at the machine shop).