Valve cover gasket replacement
 

Did my search in the forums but wasn't able to get a second opinion to confirm this but has anyone personally replaced the valve cover gasket while the engine is in the car themselves? Is this even possible? I am trying to imagine the work involved and I think the removal of the cover is possible but wasn't too sure on removal of the old/existing Three Bond sealant if it can be done with the limited space.

Also, when placing the new Three Bond sealant is it applied directly on the cylinder head sub assembly (not sure if this is the correct name but basically it is where the valve cover will be fastened down to)? And the valve cover gasket will be pre-installed under the valve cover prior to securing it down to the engine?

I've put off the valve cover replacement (as I also needed to replace the spark plug gaskets) since I am still unsure if the replacement is possible with the engine still in the car.

I would say not possible. Even if it is since you have to be clean and precise with the sealant to get a good job you will probably end up with a larger leak then you started with.

Why do you think you need to replace the spark plug gaskets?

It would be less work to just pull the engine than to try to do it in place.

some oil on the spark plugs when I replaced them.

I figured but was hoping to avoid pulling the engine if possible.

It sucks, but it is super easy compared to most any other engine I have ever pulled. The bell housing sits so far forward of the firewall access is no problem. The engine harness is one big plug. 2 motor mount nuts is all that is holding the engine in place once the bell housing is loose, just need to pay attention to the ground straps on the bottom of the head on each side. A lot of people forget about these and break them.

Chiming in. My driver-side valve cover is leaking. Yay! Can't win with these cars. I came from a 2014 FRS which had a leaking timing cover, valve cover, and cam plate. At least it is only a valve cover leak on my BRZ!

IMO, unless it's really leaking and causing a running issue, you don't really need to replace the valve cover gaskets. My WRX has been leaking for years with 155k and I haven't replaced them. It's only if you're getting a ton of oil on the spark plug wire/coilpacks that you should. Many times the gasket will leak outside a bit, but it's just not worth the time/effort/cost to do it. I would clean up the exterior if you can - I hate oil on everything.

You should be able to replace them while the engine is in the car if it's like any other Subaru boxer engine. It's just not fun and very tight. I wouldn't pull the engine just to replace the gasket though.

Yup, I just wipe it up every so often. Not a big deal.