'99 LTZ 3.8 Bent Spark Plug Electrode

[Corndog Man]

It's been a long time since I posted here. I finally made some time to see what is going on with the 3.8. I got it running a while back with fresh plugs. I had coolant in the oil so I am also sure the intake gaskets are gone with 125 K miles. Maybe head gaskets? When running I had a code display for a number 6 misfire. I pulled all the plugs and will do a compression check but Number 6 was dead because of the electrode. I did hear ticking so either I have dropped a valve in that cylinder or worse. I did see a lot of steam coming from the exhaust.

I think at this point I may pull the intake but I think it may be a good idea to pull the heads. Any idea? Could the coolant in the cylinder cause a hydraulic and bend the electrode?

Thanks,

Corndog

[Corndog Man]

I pulled all the plugs, placed the compression tester in #6. Cranking over 8 or so times resulted in 220lbs on #6. I didn't check any more as coolant seemed to be blowing out of cylinders 2,4 and 6 and maybe 3. Wow.

Without digging any further, is this the dreaded intake gasket failure or worse?

Thanks!

Corndog...

[Doug Rodrigues]

If you have coolant in the oil, you have no choice but to pull the head. The gasket is probably leaking, or worse, maybe a cracked cylinder wall? I've sleeved a lot of those in the past on various engines, usually the ones which were badly overheated. If you badly overheated your engine in the past, then anything is possible. If you're lucky, the problem will only be the head or head gasket. Inspect it very closely as you don't want to be putting the engine back together without knowing exactly what caused the problem. If the head and head gasket looks okay, then turn the engine over by hand to move each piston to the bottom of the cylinder being inspected and look for a crack. If you have a cracked cylinder, then the engine has to be disassembled and that particular cylinder sleeved at an automotive machine shop. If you're really lucky, maybe it'll just be an intake gasket, but what would have caused a bent spark plug electrode? Something solid had to have gone through the cylinder? What? I wish you the best of luck. Let us know what you find.

[maxwedge]

More likely the upper intake manifiold has the usual crack at the egr passge allowing coolant into the cyliders, pull it off and look behind the throttle body, very common.

[jeffcoslacker]

Hydrostatic cylinder pressure won't bend an electrode.

Getting tapped by a piston with a loose wrist pin will....

[Corndog Man]

Originally Posted by jeffcoslacker

Hydrostatic cylinder pressure won't bend an electrode.

Getting tapped by a piston with a loose wrist pin will....

Thanks Jeff!

I have removed the intake. I am going to put another plug in it and crank it over. I will pin it over but don't think it will bend a plug just turning the starter. If it doesn't I may pull the head and see if there are marks on that piston top.

When it was running, number 6 was missing and it seemed like a knock to me. The compression was good in all of the cylinders. I did remove the plugs and a lot of coolant blew from the plug holes.

Corndog.