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HELP! Piston hitting spark plug?!

S

svtcont98

CEG'er
Joined
Jan 19, 2010
Messages
101
Location
Syracuse, NY
I did a compression test on bank 1 yesterday because of the car's lean condition, bad smell, and power loss. cylinders one and two came back 185-190psi, cylinder 3 reported 80psi. : (

When i put the spark plugs back in, i heard a new knocking noise and shut the car off. i pulled the spark plug on cylinder 3 and it was crushed. i don't think the other's are damaged and haven't checked the others, but they must be okay because the car starts fine and idles okay. i put a new spark plug in and it ate that one too!

the plugs were torqued to spec and they were fine (albeit white from being lean) before i reinstalled. What is happening?!
 
You could have a rod that has spun a bearing and will break soon, or you have too long of a reaching spark plug. Try a different plug that does not extend into the cylinder as much. If it tags it then something is very wrong inside the motor.
 
the car had a ping before i did gaskets from the LIM up and then it went away, only to come back when the water pump went. could a headgasket failure cause a rod bearing to go bad immediately after i removed the plug for a compression test? it didn't have the sound before so i assume i messed something up but i don't know what could go wrong. i used the same plug before buying a new set. to try to alleviate my problem
 
Your headgasket isn't thick enough. Causes piston to travel closer to spark plugs..... but only one? :confused:
 
Maybe it's possible the upper threads are damaged/non-existent and the spark plug is sitting too far down into the cylinder?
 
blu_fuz said:
Oh, thought he said that his headgasket was bad.
Click to expand...

Hi blufuz, sorry i wasn't clear before. when my waterpump went i replaced that along with the LIM, UIM, EGR, and IAC gaskets. the car ran okay for a while but started having hesitation issues and after a month threw the P0174 code for bank one along with the P1131 code that has been on and off since i got the car. (Never bothered with the 02 sensor because it never affected the car's performance as it was sporadic. The headgasket was NOT changed and i'm assuming it's bad because of the smell when my car gets up to temp and the low compression in bank one cylinder three.
 
You may be right on the brink of total engine destruction. Pull the plug and see if still knocking when plug out and engine running, if so it's gone bubba. Head gasket fail can easily knock out rod bearing with one good crank with leftover water in cylinder to make hydrolock. Rod bends slightly and bearing goes like lightning after.

Once piston top hits head or high temp from failed gasket overheats it, piston top will start failing at lands and the pieces start breaking up everything else including plug ends.

Or non standard plug in place to hit, is it the correct plug for engine? If so, motor is history. If not for God's sake get the right plug.

'Maybe it's possible the upper threads are damaged/non-existent and the spark plug is sitting too far down into the cylinder?'

No. All plugs have a stop, either flat butt end or taper seat, only incorrect plug can go in too far. Even no threads at all will still limit by the stop area.
 
There is no way the piston is hitting the spark plug. The piston would hit the bottom of the cylinder head long before it would hit the spark plug, unless it is the incorrect spark plug. Even if the top threads were damaged or even gone, the plug would still stop at the desired location. Either way, what ever ruined the spark plugs is probably tearing up your cylinder head, valves, cylinder walls, or piston. If it is the piston hitting the spark plug, make sure you didn't damage the piston.
 
I pulled the spark plug and tried to clear the cylinder by cranking with the spark plug hole and lots of carbon and gunk came out and it has stopped breaking spark plugs. however, the cylinder is reading 80-90 psi compared to the other two cylinders at 185-190 psi a piece. Thanks for all the replies.
 
That low cylinder reading is telling you something..............
 
I bought my 98 svt with the same problem. The left bank #3 piston was busted all to pieces and the rod was bent. but I think someone put a longer plug in it. I bought it from a dealer who said a girl was trying it out and it made a loud noise and died locking up the engine. The one thing I didn"t understand was how did it run that far with a longer plug. I bought a 99 cougar with 69000 mi. and put all my upper engine parts on it and it runs real strong. I couldn't be happier. I got a nice svt for a total of $700. Anyway good luck.
 
Smokinjoe said:
It doesn't have to be. Other than the engine, what is the condition of the car? Is it worth putting a 3L into?
Click to expand...

No sir, the body is in rough shape as is the interior. there's a bunch of new parts however. I've determined the knock is coming from one of the camshafts, and slightly overfilling the oil seemed to quiet it down temporarily. is it possible i have gunked up oil passageways that are making it run dry?
 
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