[Aussie50]

Sounds like you have driven the sensor in too far (its a tapered thread) and cracked the cylinder head . I would remove the sensor, clean the crack and affected area 100% with carburetor cleaner and compressed air, and wick some high strength loctite into the crack, even using compressed air to help it in, with a cotton swab inside the hole to soak up excess and prevent it getting down the gallery. coat the threads with a little more loctite, and screw that sensor back in. if its only a short crack it should hold for a long time, but if its a real big one, you make have to patch over the outside too with some instant metal putty or something, either way this is a bodge job, a new cylinder head would be the ideal way to fix it, but you don't want to go there I can imagine

Just keep in mind that even the best adhesives do not like oily surfaces, and getting metal chips inside that oil gallery is bad news, so cutting back and re-tapping the sensor hole is out of the question unless you want to take the head off and strip it down before hand.

 

[Aussie50]

oh, and whatever sealant you use, give it lots of time to cure, more than the tube says to!, or the heat and oil will break it down and push it out again. also make sure its rated for high temps!

 

[Aussie50]

Good stuff!, sounds like your on the ball with it!. the cover plate is a great idea, if it was not in such a nasty spot you could have even drilled and tapped some M4 screw holes and bolted the cover plate on. but that would take some time to get right (proper drill stops etc)

 

[Aussie50]

Can you post a picture of the damage?. the hard part is now you have loctite in part of the crack, so other repair attempts will be even harder since different products do not adhere to one another.

Changing a cylinder head on one of these is a bit fiddly, I have not tried it in the car but I have on a bare engine. you need a good set of tools and a GOOD torque wrench for reinstalling the head bolts.
If you do get a used head, make sure its been surfaced, alloy heads often spring out of shape when removed and do not reseal properly when bolted back down. while your at it I would also get the valve stem seals done, and re-shim the cams, so its essentially a new head then.

Getting the timing belt and intake off are the hardest bits IMO, its tight in there.

you will need a head gasket kit with the head, along with a new timing belt and water pump since you will be in there anyway (unless the current one is fairly new, its cheap insurance)

A few of us here have done cylinder heads and engine rebuilds before, so don't be afraid to start a new thread if you decide to DIY it, we will help.

And if you go all the way with new seals, hoses, gaskets, belts, etc, you will have one happy engine. I imagine it runs just fine now and has good compression?

 

[Aussie50]

if you are really careful, you could cut back the damaged edge with a hacksaw and tap some new threads in further back in the hole, but you will need to make absolutely sure that no swarf goes down that oil passege. stuff a foam earplug or somthing down it first, and use a wood screw to extract it after (like a corkscrew in a wine cork)

 

[Aussie50]

Looks like you have just dropped the oil pressure sensor altogether? a bit of a risk, but it is rare you ever actually have that light come on (punctured sump, neglect)