HELP!.... Spark plug Porcelain broke off

Not much help can be provided at this point. Just drive the car and as long as it runs, don't worry about it. Worst case, you'll have to replace the engine - but you are a long way from having to take that action.

 

As Patrick said the worse case is a new engine, but that is most unlikely.
The fact that the engine runs smoothly is a big plus. Valve damage is the most likely thing to happen when something is dropped in a cylinder, but this is immediately followed by a continuous misfire at low engine speeds.
A regular check on your oil consumption will tell if there is bore damage, but this is less likely. The CAT will not be damaged or blocked by a small piece of porcelain. If you are worried by this the CAT could be removed and the piece (s) shaken out, but not worth the effort in my opinion.

John (Britprius)

 

Yes valve damage is the most common result in this scenario as the object has to pass through a small gap when the valve is open. This is a very short time period and as the valve shuts it can trap the object under it stopping the valve from closing. The valve is then hit by the rising piston bending it so that it can never close properly again causing compression loss and a misfire.
If the bore is scored oil is passed up the score mark and burnt in the cylinder. Obviously this causes a higher rate of oil consumption.

John (Britprius)

 

If you are really worried about it, a mechanic can remove the spark plug and look inside the cylinder with a bore scope, but as others have stated any potential damage was likely done once the engine was started. At this point, just keep your fingers crossed.

 

"lol not very rewarding for doing your own maintenance."
If you DIY, you need to perform the work correctly and use appropriate tools. In this particular case you need a spark plug socket with the rubber insert to protect the porcelain tail. Did you use such a socket?

Or, you need to figure out that the tail was broken before you fully remove the plug from the hole, so that you could improve your chances of vacuuming up the porcelain bits before they enter the combustion chamber.

What was the odometer reading when you replaced the spark plugs? Some owners like to defer this work beyond the 120K mile schedule. That just makes it harder to replace the plugs if the threads get seized.

 

i think your fine. disregard any 'sounds' you hear, as your imagination will be working overtiime.

 

tom,

its always the cheapest part that causes the most damage or costs the most to replace...

 

"Idk how it broke..."
Usually, this will happen if the socket is tipped at an angle, to put pressure on the porcelain tail. If the spark plug remains coaxial with the socket then the tail will not have any stress placed upon it.

Anyway, it sounds like your engine is probably OK. Check oil consumption over time and if that remains normal and you don't hear any other noises, you should be good.

 

I appreciate this could be a difficult question to answer. Is the tapping noise at half engine speed or engine speed. Half engine speed would point to valve noise. At engine speed would point to piston, or little end noise.
Listening through the handle of a long screw driver used like a stethoscope "if you do not have access to stethoscope" will often pin point such noises.

John (Britprius)

 

If there was something in the cylinder and there was a rattle sound, you already know a foreign object was in your cylinder trying to escape.

As was already said, that foreign object likely ejected itself through the only way possible, past a valve. The valves only open a fraction of an inch and many times a second. This isn't much of a passage or opportunity for the foreign object to escape. It is very likely a piece was jamming a valve (likely an exhaust, but possibly an intake) open until combustion forces pushed it into the exhaust or intake tract.

While it is stuck in that opening, it is possible that the valve bent since it's just a coin on a stick and is designed to hit square and if it is pushed off of square it can bend the stem. It can also put a divot in the valve or valve seat, but this is a piece of porcelain we're talking about-- it will be pulverized and ejected, but it can still do damage.

a leakdown test on that cylinder will tell the technician if there is an abnormal amount of leakage in that cylinder which would indicate poor sealing. A good technician will be able to ascertain if it is the rings or possibly the intake or exhaust valve that is not sealing correctly, if anything at all.

Likely, if anything, you would have a slight leak due to some damage to the valve and seat mating surface which is lowering your peak combustion pressure in that cylinder and combustion gasses are leaking out either through an intake or exhaust valve. Ask the shop if they performed a leakdown test on that cylinder and compared it to the other cylinders and if there was any significant variance.

IF there is a bent valve or damaged seat, the ONLY fix requires removing the head and performing a valve job and possibly replacing a seat and / or valve.

Drive it. If there's damage done, it's already done. It will get progressively worse if it's damaged. If it is damaged, the worst case scenario is you'll need to replace the motor. But more than likely, it'll blow a head gasket or completely burn a valve which will prevent you from being able to drive the car LONG before it completely destroys the motor.

 

In other words, there's a greater chance that if you decide to have the head removed to inspect for damage you're just spending your money unnecessarily. Some people need that peace-of-mind, though.

 

I will assume that you are correct and that your engine is producing a new noise. So what?

If you don't notice any power train driveability or engine oil consumption issues and your fuel economy is normal, then why worry?

Or, are you determined to spend a four-digit amount to replace the engine just because there is more noise now than in the past?

 

To learn from the OP's mistake, would this be the correct procedure to completely remove the broken spark plug pieces? Assuming non-overhead valves, which is the case for Gen2 Prius?

1) remove the valve cover (or whatever it is called that contains the spark plug threads)
2) remove the broken spark plug porcelain pieces from cylinder
3) NEW valve cover gasket (guessing not a good idea to reuse old gasket?)
4) reattach valve cover
5) replace spark plug this last spark plug (as the other three were installed and torqued correctly)