Good points. Like you said, I suppose if it fails in the future, then rebuild the bottom end with new pistons and everything 🤷‍♂️ I do like the peace of mind knowing that I wouldn’t have to get in there again for a good while if done right this time though. I guess it’ll depend on how the cost of everything will add up. If I need to replace the head, I may leave it alone and send it

 

@Stormrider84 ahh i had meant these but seems camera angle related. But yes those bronze looking rusty marks are interesting, matches the head shape but it's highly odd.

My hunch, headgasket or oil cooler has been leaking for a bit, leaving coolant sitting on the pistons creating the tiny amount of surface rust. The rest of the piston is more exposed to carbon which leaves that weird outline of the head. Being Canadian it certainly looks like surface rust which is all to common up here, usually not inside your engine tho lol....

 

Oh gotcha haha. Yeah I have no idea. It sucks not knowing anything about the history of the engine or how it was running. I don’t know what caused it to overheat in the first place, how far they drove it with the blown gasket, etc.
While it’s sitting while I wait for parts and to get the head back, I’m thinking about pouring some Seafoam into the cylinders to soak the pistons overnight to break up some of that carbon (the owner left a brand new can of it in the car so why not?)

 

@Stormrider84 Yes! Seafoam, degreaser and a green scrub pad. Hurts the fingers but >>>

 

Damn that looks really good! What kind of scrub pad exactly? Should I also take out all the valves and clean them all up really well since the head is already out?

 

As pictured below. Do not use anything more abrasive, as much as sandpaper would help, DO NOT!. I wouldn't use anything more then a degreaser or seafoam as parts of this will ultimately end up in your oil. WD-40 degreaser worked well for me, still takes a ton of manual scrubbing!

Valves you can take out, or scrub the bottom / piston side. Really up to you, can also replace the valve seals at this point to if you want to with a full gasket set.

 

Good to know! Yeah I wasn’t intending on using sandpaper, I figured it could cause damage. I’ll do the Seafoam soak and scrub with degreaser and see how the pistons look, I’d think they’ll look pretty nice. Am I able to remove the pistons to clean them without changing/damaging the rings? Just pull the pistons out the top, scrub them clean, and pop them back in with the new rod bearings?

 

@Stormrider84 Yes I believe it's possible to remove the pistons without damaging the rings. How I'm unsure as I have not went this far with the W11 and don't want to give bad advice. It's apparently possible while the block is in the car!

 

I wouldn't worry about the carbon. Any you remove is just going to reaccumulate after you start running it. To some degree it also acts like free thermal barrier coating, too

I WOULD worry about using Scotch-Brite pads on internal engine parts. The grit they can leave behind is no joke.

 

It's all a give and take. And we all have different considerations when weighing out our options, so I'm not trying to tell you what you "should" do.

But if you replace one piston, then my mind goes to the 3 that you leave alone. And I would be leery of removing a piston without rehoning cylinders. Now if I'm rehoning one cylinder, what about the rest? So that escalates so quickly for me, the next thing I know I'm looking at how much more would it be to just rebuild. Same with replacing bearings. Even if you did all the rod bearings, my mind goes next to the cam bearings..

And for risk/reward, if you just resemble and send it, what happens with a catastrophic failure? The piston burns a hole in it? That's not gonna do any additional damage.

All that said, it's easy for me to gamble with your engine. Just like it's easy for me to spend your money. Lol