I have a 2001 Dakota 4.7L. After tearing it down I found #1 piston with this damage on the top. Of course now I need to have the machine shop fix the cylinder wall and head. Is there a common cause of this type of damage on one piston? I've not seen this before. In general the rest of the pistons and everything look in decent shape. I attached another pic showing the side view and the skirt on a "good" piston. The coating is worn off mostly. I figure there is some reason for this coating, and do you think it is an issue which would require replacing the piston? If I don't need to step up to 8x$45/piston I would prefer not to. Too far in to back up now though. Thanks.

 

Did the ring break? What does the cylinder wall look like? If it's more than a honing will fix it will have to be bored out.

 

Could be caused by detonation - maybe a bad injector or an intake manifold leak.

 

Yeah, I figure the shop will want to bore the cylinder or something. Let them advise, but I can't hone it out. Part of the top ring is missing due to the missing part of the piston. The rest are fused to the piston.

I was wondering about detonation, but hadn't considered the injector, so will look at that. Good idea. I suspect any leak will be resolved when putting it back together.

Thanks.

 

Could be just bad luck during factory build it had a crack in it or out of round a half a hair installer dropped that piston. It just happened


What made you pull the engine out running poor?

 

Well, the engine has 295K on it, there was a pretty serious tick in one #1 cylinder (later bad piston), thought it might be valve adjusters. Pulled the valve cover and found the timing chain loose. One thing lead to another, couldn't get the oil pan off, figured I'd change the oil pump since I'm there, so pulled the engien since I had 95% of the work done to get it out.

Since I got the engine out, might as well finish the job and change bearings and rings. Good thing I did after all. #8 piston has some dings also because the ground on the spark plug broke off, (crappy Autolite plugs, live and learn). Now I plan to replace 2 damaged pistons, but wondering about the coating on the skirt on the rest of them. Like to just replaced the whole bunch, but the $ is stacking up.

Maybe should have put her out of her misery, as she had a long life, but I love it, and I'm honestly too cheep to go out and buy another. I'd rather fix it since I'm the original owner.

 

At this point I say get Reman and slam it in make it easy on yourself. A thread was up a year back where he installed a reman 3.7 he had no problems from the company he got it from look it up for the company.

 

I'm not familiar with the 4.7's but it looks like an antifriction coating on the skirt. look at sealed power pistons, They come with it. Most other you have to apply it.

 

The friction coating is very common with most engines for around 10 to 15 years now.

I just learned this myself I was surprised

I looked for that thread on the reman 3.7 but cant find it I think it was jasper the engine remen company.

 

Like many newer engines your 4.7 has almost no piston skirt. There is more piston above the pin than below it. To keep the piston stable the cylinder wall to piston clearance is held to less than .001 inch. To do that an anti-friction coating is used to prevent scuffing. When wear makes the clearance bigger, the piston rocks in the bore, and I think that the top ring groove failed because of piston slap.
To make 300k miles is a testament to Dodge and your maintenance. But the pistons are done - all of them. Maximum taper for that engine is .002 inch, and after honing you'll be past that for sure, and the piston ring grooves are probably worn out too.
Put a set of oversize pistons in it, or get an exchange engine. Most modern engines can't be "re-ringed" like in the old days.