1997 3.4L 5VZ-FE, 280k miles

I've been getting coolant leaking into cyl 6. Compression seems fine (numbers below). The head gasket seems fine – a leakdown test from TDC didn't give me any bubbles in the radiator. So I thought maybe it's not the HG, maybe it's the lower intake manifold gasket. But both have been replaced within the last 30k, HG by previous owner, intake gasket by me.

I'm wondering if my head is cracked between the intake valves. On both heads, I have something that looks like a crack running between the valves in every cylinder (picture below). But it's only cylinder 6 that has been giving me trouble. It's been like this since I've owned it, but the coolant leak in cyl 6 has slowly gotten a little worse. I've driven it for about 2 years and 15k miles before I've gotten much smoke in the exhaust or rough starts (but now I certainly have them). Is this head cracked?




189 — 189

150 — 181 (when I added a little oil, went to 160. Leak down test I heard air out of the dipstick tube)

185 — 189