06 Solstice, 2.4L Ecotec LE5 (GM inline 4). Again.

I had an overheating issue recently, where the temp went from ~200 to ~290ish very rapidly. I shut the car down and had it towed home. A few days later, when doing a compression test, steam came out of the spark plug holes.

The obvious answer here is a blown head gasket. So, I proceeded to tear the thing down, and found:

The head gasket looks fine. (Note that this is an MLS gasket.) No cracks in the cylinder walls or the head.

The piston tops look a little rough, though:

Block and head studs

I personally rebuilt this engine about 10k miles ago. Aftermarket turbo, always on 93 octane and Mobil 1. Which may be a huge waste of money but, after one has rebuilt one's own engine, the extra $300/yr seems trivial.

I'm taking the head over to the local machine shop to be inspected, pressure tested & potentially resurfaced. I'd rather have them check it out and find that it's fine than put the car back together and learn that it is not fine.

The only weird thing I found is that the RH head stud (ARP) between the number 1 and number 2 cylinders was loose. But, those aren't really supposed to be super-tight, anyway. After the compression test, though, I could see coolant seeping into the number 2 cylinder when looking down through the spark plug hole.

Also, during the compression test, I found cylinder 2 to be low (around 120PSI vs the spec 150psi).

So, The Question

What looks and acts like a blown head gasket, resulting in coolant in the cylinder, when the head gasket is fine?

Based on the color and condition of the piston tops, is there anything else I should be looking at before I put this thing back together? (I find it odd that they're so clean on the intake side (top in the picture)

  • How do you know the head gasket is fine? Given, an MLS head gasket should do a fine job, but how do you know for sure? I take it the head bolt holes are open? Was any sealant put on the studs during assembly? If not, this could be the source of your leak. I don't know why one cylinder would be low, but the machinist should be able to give you an idea with whether you have a bad valve seal or not. May 5, 2017 at 22:13
  • @Pᴀᴜʟsᴛᴇʀ2 visual inspection only, don't really have another way to test it. No sealant on the studs as ARP didn't recommend it. Maybe I should just weld the head on.
    – 3Dave
    May 5, 2017 at 23:06
  • Regardless of what ARP states, if you have a wet hole, you need to put sealant on it. Maybe not Loctite, but at least sealant to ensure you don't have coolant coming up around the threads and into ... well, quite possibly the cylinder. May 5, 2017 at 23:19
  • @Pᴀᴜʟsᴛᴇʀ2 also, when I put some oil in #2, the compression went up to 160psi. So, probably bad rings on that one. Which makes no sense given the age of this build. Time to put that LS1 to use.
    – 3Dave
    May 6, 2017 at 0:52
  • 2
    @CharlieRB head was warped. I had it resurfaced, also had some bad valve guides which they replaced. Hoping to put it back together tomorrow if the weather cooperates. (This is one of those times I wish the garage wasn't full of useless stuff. )
    – 3Dave
    May 12, 2017 at 14:53

1 Answer 1


To answer the question - moot at this point for you I'm sure, but this is a Question and Answer site after all - What looks and acts like a blown head gasket, resulting in coolant in the cylinder, when the head gasket is fine:

  • cracked head
  • warped head
  • improperly torqued ore loose head bolts (torque them down in a pattern)
  • missing parts (o-rings, dowel pins, etc) after engine reassembly.
  • Old gasket material not fully removed
  • the head gasket really is blown you just can't see it
  • Thanks for the response, and getting this off the ‘unanswered questions` list. The gasket was, in fact blown - the rubber coating was trashed in a few places, though the gasket substrate was fine. New OEM MLS head gasket works great (after having the head resurfaced). Cheers, and thanks for contributing.
    – 3Dave
    Mar 2, 2018 at 21:05
  • 1
    @3Dave you're welcome! I'm taking my head apart right now because coolant is leaking into my oil, yet my compression numbers are all good. That's how I stumbled across your question. In my situation, I suspect there's either a small leak between a coolant passage and oil passage, or gasket is barely holding compression while performing the compression test but when the engine is running and warmed up then it leaks out under the higher pressure of combustion. I'm hoping its the later because the engine is also running too hot after being on the road for a while Jun 15, 2018 at 20:28

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