4.0 piston damage after blown head gasket

Jasper79 · Nov 28, 2014

Hey everybody. I'm working on a '96 Ranger XLT with 4.0 OHV that I was going to replace the head gaskets on after experiencing some major white smoke action. Once I got the first head off (passenger side), I noticed some damage to the #3 piston. I'm hoping someone could tell me just how bad this is and if it definitely requires replacement/rebuild. Any feedback would be greatly appreciated.

Angie · Nov 28, 2014

myself, i wouldn't worry about that. white smoke or white steamy looking stuff?

because heavy white smoke could also be transmission oil burning.

downer · Nov 28, 2014

no way i would leave it like that. looks like small chuncks of missing piston. besides the piston damage alone, how do you know the rings aren't shot? i wonder what the lower cylinder wall looks like.

did you see any sign of head damage around that area?

Dune Runner · Nov 28, 2014

Looks like you were on the verge of a complete meltdown.

Angie · Nov 28, 2014

for proper perspective i had to download both pictures to see the full pictures. they really do not look that bad ... complete melt down from a small bits of chips? tear down a complete motor for minimal chip? 96 block almost 20 years and that is all the damage? what are you guys thinking?? a 10 second truck here?? myself i wouldn't worry about this at all. i can show you a piston i have with a roller lifter top imbedded into it and it still ran.... very nosily but still ran before i yanked the motor.... head damage?? ya chunks, still ran though....

Dune Runner · Nov 28, 2014

What!? Those pistons are TOAST!

Rowdy Fitzgerald · Nov 28, 2014

Personally I'd say it's fubar. You've got it appart, pull it and inspect the cylinder wall for damage. If it's good, hone all cylinders and install new bearings, piston rings and that one piston. Then refresh the heads and you're good to go for another 150,000

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drsvox · Nov 28, 2014

I'd be surprised if the walls aren't scored.

Rowdy Fitzgerald · Nov 28, 2014

Yep those chips went somewhere.

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RonD · Nov 28, 2014

That damage is from pre-ignition(pinging/knocking), and that is what blew the head gasket, not the other way around, damage wasn't, couldn't be, caused by blown head gasket.

Google: images piston damaged by pre-ignition

Engine was running lean or without EGR, or it was running rich if you had to scrape off lots of carbon, and the carbon caused hot spots and pre-ignition.
The pinging eats away at the softer metal(piston) and the gasket's ring to seal the cylinder is a very soft metal, so it got eaten away and failed, just guessing.

The damaged piston(s) will fail, but can't say when(crystal ball broken, lol), but you will need to find the reason for the pre-ignition or they will fail sooner than later.

If you don't need the truck running on Monday I would consider pulling engine for rebuild.

Hitchner2009 · Dec 5, 2014

yeah i would not run that the way it is either. it only takes a few minutes to remove the piston depending on where you have the engine located. if its still in the truck its a little more tedious but doable. pull the pan. like someone said. that metal went somewhere and its not where it should be. dont waste your time putting all your hardwork into the job and then slack on repairing a concern like that. because once you put it back together its going to fail probably for low compression or something of the sort. or burn a heck of a lot of oil.

4.0 piston damage after blown head gasket

Jasper79

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Angie

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downer

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