Long story, I will try to keep it short. 1998 4runner supercharger + WMI @ 290k.
I did valve cover gaskets 600 miles ago and I obsessed about them but couldn't find a leak. 110 miles into a road trip the EGT started creeping up and ECT was rising (200) so I pulled off the highway asap.
Oil was leaking out onto the ds crossover, idle was pretty rough and there was a knocking noise that almost sounded like an exhaust leak. When I tried starting the car it sounded like there was no compression in a cylinder. I had the car towed to a shop, rented a car and continued on our way.
The shop eventually called and told me the VCGs were leaking. I told them I thought more was wrong, asked if they could check compression and got dismissed. I was told work was done, no more oil leak, no overheating and the cooling system help pressure. I drove out to pick up and when starting it sounded the same along with rough idle and an odd exhaust tone. I got upset, talked to the tech and he re-pressurized the cooling system, made sure no more oil was leaking and sent me on my way.
I drove home carefully, car was warm and gas mileage was worse than usual.
Took it apart today and found low compression in cylinder 1 (90psi dry/ 130 psi wet), leakdown was 65%, the plug was melted and most of the cylinder is scored.
What do I do with the engine? is it salvageable?
What do I do with the non local shop that missed the root problem?
Also, what the hell happened here???
Thamks,
Matthew

 

I have a 5vz swap 1995 4 runner and need help wiring the auto trans to the 5vz harness that I also auto

 

On the leakdown test, where was the air coming out? Although the dry/wet difference is very, very strongly suggesting rings/coming out the crankcase ventilation system.

Can you get a picture of the top of the piston?

How hard were you driving it at the time it did this. In boost? I'm just tossing a wild guess out there, but I'd be suspecting a bad injector stopped flowing enough, that cylinder went lean, combustion temps spiked, detonation happened, and the piston was damaged. With a cylinder blowing a lot of compression into the crankcase, that found some exit other than the PCV system and blew some oil out.
Of course, it's salvageable, if the piston was damaged it would be basically a bare block rebuild. Bore the cylinders out to the next oversize, new pistons, new bearings and seals while you're at it. The real question would be if that's an economically wise thing to do. 5VZ's are not hard to find, a low mile junkyard motor might be cheaper and possible even better - factory built motors have a little 'magic' that rebuilt motors don't always have.
Ehh, they didn't cause the problem, they just didn't feel like messing with it any more than they did. I wouldn't go back there, if that's what you're asking.

 

The top of the piston looked ok, clean and undamaged. I'll see if I can find a pic.
When it happened I had the family and we were loaded down. I was on the highway cruising, possibly under boost but nothing crazy.
I was pretty certain my leak was exiting in the crank case, The valves looked ok in the camera.
I Don't know what would make more sense, I could probably pull the engine. What would labor cost vs a shiny new rebuilt 5vz?
I guess my problem with the shop is if they told me that I needed a rebuild (or whatever) I would have discussed that with them or had the car towed home. I would not have paid their ridiculous price for valve cover gaskets knowing it would have to be done again. They missed the root cause and would not listen when I asked them to check a few other things for me.

 

Too much boost and not enough meth or fuel maybe, running lean will melt things, maybe a weak injector, meth not atomizing properly and not evenly distributed through cylinders, could be a number of things, are you using pure meth and deionized/distilled water 50:50, do you have a boost controller to tell the meth pump when to turn on with a LED in cab indicating the pump is powering up. I assume you have a wideband aswell to monitor fuel ratio as EGT's are a little to late to let you know there is a problem.

 

I have been running the 7th injector and 50/50 meth/h20 with a snow progressive kit for close to 150k miles. I do have a wideband and have never really seen a lean condition under boost. If anything I am running rich under boost.
I wasn't pushing it when this happened so I'm guessing maybe it was the injector? I didn't see anything on the wide and but I can't watch it 100%.EGT was out of normal range for cruising on the highway but not anywhere near critical.

 

A bad injector (unless it's so bad it stops flowing completely, lol) will ruin a piston pretty damn quickly. Although I don't really see too much in the way of detonation pockmarks on that piston crown. Maybe a little in the shiniest part of the pic (upper left corner). It's possible it might have just been enough to break the top compression ring, but you didn't keep going until it really chewed the piston up.

And on the leakdown test, where was the air coming out? I'm assuming it's coming out of the crankcase, just making sure.

 

And on the leakdown test, where was the air coming out? I'm assuming it's coming out of the crankcase, just making sure.[/QUOTE]
I nead to recheck leakdown. It definitely wasn't exhaust, intake or cooling system. I assumed crank case but I would like to listen to double check. I also want to get a full shot of that piston.

 

Often when a piston is scoured that clean, it is a sign of coolant entry into that cylinder.
You say you're using meth/water injection.
It would be interesting to see if the other cylinders are scoured clean as this one is.
Perhaps the water injection has been a tad excessive??

 

All my pistons are clean, has been that way since wmi. I don't think it is excessive, I use the smallest nozzle available. I think this is typical of this type of setup?