986 Head Gasket Blown (Rare, but I have Evidence)

[Trudant]

'99 Boxter 2.5L, 62k mi - New to me, I'm now the 4th owner.

Background, I purchased it from a 'relative' of the owner and based on Carfax it had not been driven over 200 miles in 3 years. The grandson in charge of selling the car for the owner spoke of a small coolant leak and overheating, a horn stuck on, and otherwise in seemingly excellent condition. Service done professionally on regular basis and major services every 15k mi.

Got to work. Fixed the horn, replaced water pump, thermostat, changed all fluids, pumped out the bad gas and replaced the fuel filter. Did everything else on the 60k checklist. Surprised there did not appear to be a gasket on the thermostat. Also the water pump and thermostat had a lot of calcium build-up as though someone was replenishing coolant with tap water?! [Terrifying]

So I tested CLR on the calcium from the old water pump and it worked quite well. So I flushed the entire cooling system with CLR to try and remove any deposits from the system with an external rig I put together for 2 hours. Then flushed the entire system again with distilled water. Cleaned radiators and refilled with coolant. No leaks after 24 hours… so far so good.

But after a thorough bleed of the system, the overheating didn't go away. In fact it seemed to get worse. The bleed valve in the trunk was opening at temp on its own and I noticed bubbles in the coolant. After scratching my head for days, I did an exhaust / coolant fluid test which revealed my worst fear - hydrocarbons in the coolant. (Head gasket or worse a crack!)

I left the entire coolant system under pressure (lots of build-up and held until you open the radiator cap or bleed valve.) Then I pulled all the spark plugs and did a compression test.
- US Passenger side (4,5,6) all show 180 psi.
- US Driver Side (1,2,3) show 60 psi, 60 psi, 100 psi.

So I peeked inside with a borescope. I can see fluid in the cylinders and bubbling at the head gasket inside cylinders 1,2,3.

So the question…. Based on this history, would you pull the heads on only the driver side, replace the gasket and give it a go (assuming a visual inspection does not reveal an obvious crack?)

Right now I’m thinking of attempting the ‘replace the gasket in-place’ approach outlined here:
http://986forum.com/forums/performance-technical-chat/78808-blown-head%97how-repair-2.html

….
Looking for advice because I’m not sure what question to ask!

Thanks,
Erik