Need experienced eyeballs re: cracked 1.6 head (?)...

[sparkoid]

Hello all, been lurking here for years, finally got registered.

I have a 1.6 na Caddy, ~80K miles, daily driver on a LONG 160 mi commute.  Never got over 34 mpg, and power has been low(er) than normal.  Couple weeks ago, pressure in the cooling system pushed a hose off my new radiator, bottom one of course.  Did the glove-over-the-coolant-cap thing, glove inflates at running rpm's, but not at idle.  Compression on test on a cold engine got low numbers in 3 and 4 (~360), lower numbers in 1 and 2 (~340).

Suspected the head gasket, so I popped the head for a look.  Found stuff "growing" in cyl 4 (a little bit on the valve seats too), but no obvious divots anywhere on the gasket.

So I put the head back on and did what I should have done earlier, the listen part of a leakdown test.  Don't have a LD tester, but I used my compression tester fittings to push compressed air into the cylinder(s).  Heard air rushing out of exhaust port on 4, absolutely no residual release.  Cyl 1 pressurizes and (somewhat) slowly releases air after I remove supply air.

Seems a little early in the engine's life for this stuff, but I'm now resigned to a rebuild; my question here: has anyone seen this kind of "growth" on a piston crown (I suspect it's crystallized coolant)?  If there is no gasket issue, is this a symptom of a cracked head, or a cracked block?  Any way I can differentiate?  Thanks for any sage advice you can offer...

[libbydiesel]

Weird camera angle.  340-360 is fine.  Lower than ideal, but not really a problem.  Maybe a case of too thick of a head gasket or a compression tester adapter that doesn't have the schrader valve right at the tip.  Regardless, with compression results there, it should start up easily and run fine even down into the single digits °F.  How was the cam oriented when you did your cylinder pressurizing?  Did you have a valve open?  Looks like #4 had coolant leaking into it.  You can get the head pressure tested to see if it's cracked enough to leak.  Close inspection of that cylinder would be in order also or if you do decide to rebuild it all, then have it magnafluxed.   

[sparkoid]

My Chinese compression tester has schrader valve in fitting that attaches to the injector plug.  Putting a little oil in the cyl put the numbers in the 500's, warm engine, so I'm thinking rings are tired along with whatever is going on upstairs.  Did the compression test about a month ago, coolant issue may be more recent than that(?).

Put cyl'1 1 and 4 at TDC when pressurized, cam lobes off both valves.