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Discussion Starter · #1 ·
Currently running a ForcedFed turbo kit on a stock motor running a very conservative 6psi of boost, with AEM EMS-4 for tuning. Put about 5,000 miles on it by now, up to 28K miles on the motor. Recently I noticed the engine chugging as if one cylinder wasn't firing right. Also started noticing white smoke coming from my crank vent catch can filter too.

So I opened the catch can and it was lined with milky white foam that dissipated into a watery residue when touched. Compression test showed around 210psi for three cylinders, with one (2nd from passenger side) down to 165psi.

Sounds like a blown head gasket right? Burning coolant, milky foam, white smoke from crank. So I pulled the head; both block and head weren't warped at all. Gasket surfaces didn't show any cracks or notable defects either. So I replaced the gasket with a Cosworth gasket and ARP head studs, and reinstalled the head. STILL BURNING COOLANT, STILL LOW COMPRESSION... :mad:

All I can think of is a cracked block / head somewhere internally. Thoughts?
 

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Did you ever get the car running right? I mean really and truly right? Drivability, dyno, AFRs, steady boost, etc?

I recall you were having a bear of a time getting things sorted out...

-Phil
 

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Discussion Starter · #3 ·
Did you ever get the car running right? I mean really and truly right? Drivability, dyno, AFRs, steady boost, etc?

I recall you were having a bear of a time getting things sorted out...

-Phil
I did finally got the drivability issues all sorted out (fluctuating idle/IAC, "fuel cut" symptom, AEM connectivity, ect) right before this motor problem happened. :rolleyes:
Tune was decent, solid AFR's, pulled very smooth, kept boost limited by wastegate at 5-6psi. Still had a few little issues though (ex. no knock control) but I haven't been driving it too hard (just daily driving to classes), so no real opportunities to overheat or do much damage.

Replaced the thermostat earlier this summer because coolant temps were pretty low. Temps still only high 160's, but the burning coolant and engine chugging (low comp) only started recently...
 

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Discussion Starter · #5 ·
I did a quick coolant leak check and it dropped 1psi over about 5 minutes. Would that be enough to signal a crack in the block?
 

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Discussion Starter · #7 ·
I haven't had a chance to tear it back down again, but the first time I borrowed a machinist scale that was very straight.

But if it WERE a head gasket, even if the head/block were warped even a little, installing a new cosworth gasket and arp studs would have improved the compression results even a LITTLE bit.

When I tear it down again I plan on having professionally checked, but given the straight edge I used the first time, it seems like the only reasonable explanation is a cracked block
 

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Discussion Starter · #9 ·
Normally I would think it'd be a piston/valvetrain problem, but it's still burning coolant, and only blows smoke when the compression check is done on that one cylinder. Strange...

Will have to pull the head again over thanksgiving break and look for cracks...
 

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What does your oil look like?
 

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It's always something simple... always...
 

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Discussion Starter · #12 ·
Oil came out with a bit of a chocolate milkshake resemblance, so definitely must be getting coolant into the oil.

Sure wish it was something simple... Pulled the head again and rechecked the cylinder for cracks and warping; no visible cracks in the combustion area, no warping around the cylinder even using the 0.0015" feeler gauge (going to find a shop on Monday to verify).

Even if it was a crack, it couldn't be in the block, because that wouldn't let coolant into the oil, just the combustion chamber. If it's not a warped cylinder, then maybe a crack up in the head back up behind a valve (even though there were no visible cracks around the intake ports.

If it were something simple, I don't think I'd have low compression in one cylinder unless there were two root problems....
 

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The fact that you have low compression tells you it's simple... When I say simple, I mean easy to diagnose/identify.

Whether or not it's simple to fix is an issue that will be relative to the one fixing it ;)
 

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Discussion Starter · #14 ·
And the coolant in the crank would make it even more specific (unless there are two separate issues) to a warped head or crack somewhere.

Had a local shop check the head and they said it wasnt cracked but it was 0.002" off. Would that be enough to cause a low compression nearly 40psi less in just one cylinder?
 

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Discussion Starter · #15 ·
Well I put the freshly decked head back on and it got worse... a LOT worse. Compression went from 205 202 165 205 all the way down to 205 175 110 175 :panic:

Managed to get my hands on a leakdown checker and when I pressurized the cylinders, I could hear the air leak echo out of the crank vent tube for all the cylinders, but mainly the lowest 3. I also noticed air coming from the exhaust valve on the lowest cylinder (probably explains the low compression... but not the coolant in the crankcase part).

Wish I would have done the leak down (pressure check) before I had it surfaced... Though I'm a little surprised it actually made it worse.
 

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Did your head-man Zyglo the head before he resurfaced it?
Coolant in oil is typically caused by one of 3 causes.
1. Most common blown head gasket, but you already checked that one.
2. Cracked head. Zyglo finds the cracks.
3. Cracked block. If not item 1 or 2, it is likely 3.
Now for the really bad news. This lesson was learned on the aluminum block Vega engines back in the 70s. When coolant gets in the bore, under high ignition temperatures, it forms a hard abrasive crystal which eats bores quickly. Your low compression is likely due to bore damage, rather than air escaping via a crack in the head or block. A crack that big would likely be visible to the naked eye without the aid of zyglo.
 

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Discussion Starter · #18 ·
I do plan on dropping in new pistons now that its coming apart, but that wouldn't really affect the underlying issue: coolant in the crank.
The shop surfaced the head and pressure checked the head (off the block) for leaks (aka no cracks in the head) so the only source for error left is the block. Going to pull that next week and see if I can't chase this leak down.

Addertooth: would Zyglo pick up a crack that pressure checking it wouldn't?
 

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Zyglo allows you to see things only God knows. It is amazing stuff. Back when I worked at a machinist (very long ago) it was a staple. You can't effectively MagnaFlux non-ferrous aluminum parts. Cylinder pressure during combustion usually exceeds any value shops perform pressure tests at.
 
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