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surreal0769 05-24-2014 04:25 PM

2001 4.7l Jeep Grand Cherokee Rebuild
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Hi there, this is my first post to the forum. I bought a 2001 4.7l Power Tech limited GC and have taken the heads etc off the top of the engine and plan to take out the harmonic bal with timing cover to reset my spring tensioners. My question at this point is related to a pocked piston i noticed on the number 8 cylinder i believe, standing in front of the Jeep its the far left piston toward the back. I know this is not ideal but what are the chances this could last me the life of the Jeep or is this really bad? I would just rebuild the whole engine but I am on borrowed time and money where I am and have to leave. I plan to travel 1500 miles back to Colorado once I put everything back together. Just to give you some background the engine ran but had really loud ticking sounds. I pulled valve covers and saw nearly every rocker thrown and must have been over a half inch or more of sludge in some places and spark plugs were down to the nub where you almost couldnt see the metal that arcs. I havent looked underneath to see the piston bearings or crankshaft status but when cranking by hand all is quiet. So assuming all else is well has anyone had experience with this type of piston issue in regards to if its still structurally strong or not? **Last picture is not the correct side where the damaged piston is but just for reference purposes.

jnicewan 05-24-2014 11:51 PM

Man that sludge is BAD, these engines are already known for oiling issues on the top end. Anybody who treats engines like that needs to be kicked square in the balls. That is not from letting oil changes slip a thousand miles or so, that's from going well beyond oil life. As far as the piston from what I see it looks like what happens to a piston from excessive pre-ignition or detonation. I've seen that before on pistons but not usually grouped in a small area like that, probably from a hot spot, it could have been from debris but doesn't really look like that either. Other than the concern of why that one piston looks like that, the damage doesn't look too bad.

Anyway I think your biggest worry is the sludge at this point. What I would worry about the most is how much sludge is in the bottom end of the engine. Plus by removing the heads and timing cover, how much of that crud are you going to knock loose and fall down into the bottom end. If enough of that sludge is in the pan or pieces falling down there to stop up the oil pump pick up screen you will have bad problems. Also since that sludge is cooked oil, how much of that crap is cooked into the piston rings, oil passages etc.

Jeep_Fanatic 05-26-2014 06:49 AM

that jeep just scares me, sludge is a huge issue since it can chew bearings out and block the pump.

like the post above, get the sludge cleared first. and I would suggest a engine rebuild as well as new pistons while u already got it apart.

surreal0769 05-27-2014 12:27 PM

Thanks for the advice. Yeah, the person I bought it from said that they got it from a dealer and the dealer said this couple drove it in that way and traded it in for a new Jeep. It looks to me like the spark plugs were never changed for the life of the motor and if that wasn't done who knows about the oil. The curious thing is that the Jeep itself is in near mint condition. The air filter looked new and the air housing throttle body looked great. I've decided to definitely replace the pistons and I have new heads that I paid $100 bucks for from a 2000 Dodge Durango that had bottom end problems. Good to know about the bearings possibly having issues, I'll check those on the bottom end. I would have done this by now but don't have jack stands but I'll see in the next 2 days if I can get it done by jacking it up and putting blocks underneath. If the bearings are ok, then i figure about $300 bucks for new pistons and a gasket kit for the timing and head, etc. I am hoping the oil pump itself is ok. From what I can see going through the block the oil channels don't look plugged and when I drained the oil all looked good. I'll post an update later and the ultimate resolution. Thanks!

surreal0769 05-27-2014 12:46 PM

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Looks like the photos didn't upload so I'm re-posting the used heads I got and a pic of the actual jeep.

surreal0769 05-27-2014 09:47 PM

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I took the oil pan off and looks like I have a bad bearing on #8 and just checked #1 bearing is relatively ok. I'm wishing there was a way to tell if the crankshaft bearings are ok or not without removing it. There is a way you can pull the transmission and unbolt the bottom motor mounts from what I've heard so you can remove the crank without taking out the engine. I'm thinking of doing this and while I'm at it the person I bought the Jeep from gave me a rebuilt trans so I'll pop that in too.

jeepdaddy2000 05-28-2014 05:20 AM

You're this far, why short sheet yourself by trying to do an in frame? Pull the engine and methodically go through it. If there is no wear in the cylinder walls, then you can get away with a hone and rings. Same goes for the cams. Replace the crank and bearings, check the rods, tank the block and related parts to clear the sludge, and reassemble with new gaskets. You will have a solid rig that won't spit out parts on your next vacation.

surreal0769 05-28-2014 05:17 PM

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Well I noticed this today. Looks like the crankshaft counterweight is scored maybe near the thrust washer? I saw this before on a youtube video here . If you look at the end of the video he shows the same thing on his seized engine. Mine still rotates but wondering if anyone knows how bad this new issue is? If I get the money to pull the engine I'm definitely going that route.

surreal0769 05-29-2014 03:40 PM

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Machine shop said this could be the thrust washer and crank grinding against engine which is what I kind of suspected. In examining this I noticed something weird in between two cylinders toward the back of the engine. Thinking its a crack but not sure. Asking the machine shop about this one as well but I suppose it could be part of the way they cast the engine. Also noticed it looks pretty burned around the 8 cylinder as well. Any feedback on this is welcome. I should have just named this thread rebuild 4.7 but I didn't think I'd have this many bottom end issues too!

surreal0769 05-29-2014 04:22 PM

Machine shop thinks this is a casting mark so looks like I'm still good to go forward.

surreal0769 05-30-2014 08:45 PM

First quote for an engine hoist was $75 bucks for 4 hours so this is why I didn't really want to do this but after calling around a bit I found one for $30. for 4 hours or $40. bucks a day and $15 dollars a day for the engine stand. I will be pulling the engine around the 10th when I get my meager pay check. I'll pull the harmonic balancer and girdle or bedplate at that time and check the rest of the engine out. Was quoted $80 bucks for an engine bath from a machine shop and $100. bucks to resurface and clean both of my heads that I got. I suppose if I just asked if they really needed it they would say yes even if they didn't to get the money, unless you know the people or they have an ethic. That said I've never dealt with a machine shop before so I don't know how they are. A new reconditioned crankshaft kit is $233.99 at autozone with a $50. core. If my thrust washer bearing surface on the crank is ok I'll just re-use it. I should probably have the machine shop check that out too though. I want to do everything exactly the way it should be done but I have 30 days left to fix this, get it one the road and have gas money for 1500 miles of travel, food is a luxury. At some point I'll have to say I'm putting it together "as is" no matter what I should do next and I better have the ability to do so. Might seem silly getting an engine bath if it costs me the whole project from being completed on time. I have a feeling I'll make it through. Where there's a will there's a way""!

jnicewan 05-30-2014 11:12 PM

Cleaning the engine is very important at this point, spending extra dollars on stuff sucks but as dirty as your engine was, its obvious that some of the engine damage could have been the result of the sludge. You could probably clean most of the sludge but their cleaner will clean all the hard to reach areas, oil passages etc. Its hard to cut corners on things like this but if you don't make it right you might have to do it all again. Go over you budget real well because there are a lot of things to consider that are easy to overlook (fluids, filters, belts, hoses, spark plugs, gaskets, timing chain tensioners etc...)

I've removed a 4.7 engine in a WJ before and they are tight, you are ahead by having the intake and heads off, it will be close on the front so you might want to remove the accessories, w/p, and radiator. Even the bell housing bolts are a tight fit especially when doing it on the ground.

surreal0769 06-01-2014 04:35 PM

Thanks for the advice. I'll go that route most likely. I'm going to get my engine rebuild kit from Ebay here: . Comes with the pistons, timing, gasket stuff, and new head bolts for $595.. I'll get most of my specialty tools from this rental place I found that's going to save me from having to buy tools like a piston ring compressor. Hopefully they have a Jeep harmonic balance pulley or maybe a regular 3 jaw puller. Still don't know if the crank will be ok but it occurs to me that sludge could build up inside of that also.

jnicewan 06-01-2014 11:31 PM

I dont know about stores around you but most of the bigger name auto parts stores do tool rental too. The difference is you rent the tool and when you bring it back you get all your money back. Basically the price they charge you is what the tool costs only they give the money back if you bring it back, keep it if you want. I'm not sure if they would have the bigger tools but things like pullers, installers, ring compressors etc should be there.

jeepdaddy2000 06-03-2014 06:35 AM


harmonic balance pulley or maybe a regular 3 jaw puller
Please do not use a 3 jawed puller on the harmonic balancer. It uses a rubber dampener and you will damage it.

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