Bryan Tift

Hey guys. So two weeks ago I bought a 2001 Jeep Cherokee Anniversary Edition (Sport VIN #). Everything checked out when I bought the car, but now, not so much. I have a noise coming from the bottom of my engine. I don't have much experience with these engines or engines in general and I can't figure it out. I found online that the flexplate bolts could be loose or the flexplate could be cracked, but I inspected both and the bolts were tight and I didn't see any cracks on the plate. Here is a video of the noise: https://drive.google.com/open?id=1OD...0CpwUUIGj8-aOt
When driving around 10-20 mph or 900-1300 rpm it sounds like a frickin diesel engine. Anything from 1400-1900 rpm sounds just like a knock and 2000+ rpm I don't hear it at all.

So I pulled the plugs and did a compression test. Here is a pic of the spark plugs, just in case anyone is wondering: https://drive.google.com/open?id=16M...pW4ZqLczOWX5b3

Whenever I post numbers from a compression test I always get someone asking my method used, so here it is: I bought a nicely reviewed $60 compression test kit on Amazon. I first removed the heater hoses and coil rail, then I took out each spark plug. I unplugged the fuel pump relay and disconnected my injectors. I tightened my tester into cylinder 1 tightly by hand. I had my sister hold the throttle plate open while I cranked the engine over 5 times. I did this for each cylinder. I then repeated the whole test but with about a tablespoon of oil in each one of the cylinders. Here are my results:

Dry: 100, 90, 58, 84, 109, 152
Wet: 111, 105, 76, 126, 137, 199

No bueno. Except for cylinder 6, for some reason it's perfect (almost too perfect!) I figure this means I just have wear on the rings. Would this be an accurate observation? The jeep actually runs really solid still. It has a bit of a rough idle but accelerates quickly and does the highway just fine. Never had any trouble starting it except for my fuel check valve going bad which makes me prime the damn thing 4 times before I can start it.

Anyways, I'm stumped at this point. I took it to firestone to have the noise checked out. They did an inspection and told me they checked out everything that could be making noise other than the engine, which left them with the conclusion that it was internal damage to the engine that was causing the noise. Great. I already knew that. But they told me they couldn't investigate on the engine any further, so I just thanked them and drove home. In the notes though, the listed these two things:

"Recommend engine shop for further inspection. Vehicle has internal engine noise. Pistons knocking"
and written on the inspection sheet by the technician,
"internal engine noise, wrist pint/piston skirt noise"

So they think the noise is my piston skirt. I guess before I write too much more I should just be asking: what next?

I use the car as my daily driver to and from school every day (meaning it gets about 50 miles a day on it). The noise has been happening for about 300 miles now. I am going to drop the oil pan Tuesday and see if I can find any pieces of the piston in it/check out the pistons from the bottom. Is there anything I should be looking for? Also any tips on removing the oil pan? First time doing this on any car ever...

I figure that if the piston skirt is broken but the cylinder bore is still in good condition I can just replace that piston (and maybe do all the bearings and main bearing while I'm down there). If the piston skirt is broken and it's pretty large chunks/the wall is bad, I think I might pull the engine and rebuild it and get it rebored. And lastly if I don't find any piston skirt pieces, what should I do then??

Should I mention I'm on the budget of a 17 year old making $9.50/h? Thanks for any help guys!

GreaseMonkey17

Bryan Tift

Thanks. I've been spending hours researching this stuff on these forums. I love the support these cars and engines have even 20 years later.

Anyways, I'm going to continue driving it and I'll check out the valve cover on Tuesday before I remove the oil pan. What exactly should I be looking for? Lifters that aren't opening/closing all of the way? Oh and should I grab a new gasket for the valve cover if I'm going to be taking it off? I've heard you have to replace those each time you remove the valve cover...

GreaseMonkey17

Turbo X_J

Transmission has to be removed to inspect, the cracks are found around the crankshaft flange.

Cherojakee

If it’s a bottom end noise at idle but goes away with higher rpm, I’d say it’s likely a flex plate knock. The low compression could be a number of things. Blown head gasket, piston rings, valves. I would start with the top end and get that fixed. Pull the cylinder head and get it inspected by a machine shop. With head off, you can pull the pistons from the top. Drop the oil pan and disconnect the rods. You have to ream the ridges at the top of the cylinder bore to get the pistons out. You can rent the reamer from parts store. With the oil pan off you can get a better look at the flex plate and make sure the bolts are tighten down to the right specs.

Bryan Tift

The noise is always there at idle, but quiet. It's much louder when a load is on the engine, such as driving down the street in the neighborhood (so between 1000-2000 rpms). It almost sounds like a diesel when in that rpm range. But beyond 2000 rpm I can't hear anything really.

I'll start by removing the valve cover on Tuesday, and if that checks out then the oil pan. That should rule out valves and piston skirts. I'll move on to removing the head/pistons if I haven't found my culprit by then. I'm trying to do this as cheap as I possibly can so I don't want to just start pulling things off and sending them off to shops yet.

As for the flexplate cover with the three bolts... I actually cannot get that off. One of the bolts looks to be on backward and I cannot take the bolt off due to it hitting the exhaust pipes... I would love to get a closer look at the flex plate but as said above it sounds like the best way to inspect it is to remove the transmission which I don't have the knowledge or transmission jack to do.

Thanks for all the replies so far guys.

Cherojakee

Good strategy. Yeah I meant inspect everything, then move to the next step if you haven’t found the problem. The inspection cover for the flex plate is in a tight spot. You need to get a wrench on there. The bolt you can’t get off, you don’t need to remove, the inspection cover is slotted there. Loosen that bolt and remove the other two and you should be able to slide the cover off. I would still consider the flex plate the likely source of your knock. A rod knock would get louder with higher rpms. As far as sounding like a deisel, a lot of them do.

dzywicki

That does not sound like a broken piston skirt. I had that happen to me on my '99. It sounds a heck of a lot worse that that. I do, however, have a similar noise to yours on my '99. It started after I replaces the pistons due to a cracked skirt. It makes noise at idle and up to about 2k RPM like yours. After that it disappears. I ran it with the serpentine belt removed just to make sure it wasn't an accessory. It wasn't. Oil pressure is great 40-50 at hot idle and otherwise it drives great. My motor has 240k miles on it now. I have been driving it with the ticking noise for 3 years and 10k miles. At this mileage, if something goes wrong, it will be time for a rebuild.
I would say check everything you can externally:
1. Remove the valve cover and check all the rocker arms to make sure they are tight
2. Remove the serpentine belt and run the engine to make sure it's not an accessory
3. You can check the flex plate bolts for tightness from underneath after you remove the inspection cover.
4. If you really want to make sure it's not a cracked piston skirt (highly unlikely). You can drop the oil pan and then fish around in the deep end for any chunks of metal.

I see you mentioned you were going to remove the oil pan. Do some reading, but my tip is to get the front on jack stands, lower the front axle, remove all the oil pan bolts. To get the oil pan out, put a jack under the axle and jack it up. this will move the axle forward and give you room to get the pan out. Otherwise, there just isn't enough room. When replacing the pan, you may need to take off the oil pump first. When replacing, put the oil pump in the pan, then lift it into place. then drop the pan down enough to get a socket in place to secure the oil pump. I also use floss to hold the oil pan gasket in place when replacing the pan. Tie it to the pan to hold it in place and then you are good to go.

With those compression numbers, you may want to look into a leak down tester. Those are really low and inconsistent. A leak down tester will also check your valves. With a 2001, you may also be looking at a cracked head, but I'll let others with 2000 or 2001 chime in on that. I have a '98 and '99 and have not had to deal with that before.

Bryan Tift

Thank you for all of the feedback. I haven't gotten time to start digging into my engine yet but I did record a video of the diesel sound I am hearing:

https://drive.google.com/open?id=1_P...hxp8ln8mLkBy_2

I noticed too that the noise wasn't so pronounced at idle near the end of the video. Anyways, the noise is bugging me. I'm going to remove the valve cover Tuesday afternoon and check it out and then I'll get back to you guys.

Bryan Tift

I took the valve cover off and ran the engine. Everything seems to be running perfectly fine. Nothing is sticking, it's all moving fast. I also grabbed the push rods and they aren't loose and are straight. Here is a picture of what they look like:


And here is a video of them running: https://drive.google.com/open?id=14E...UfGbQTKKbCgJJS

I also looked closely around the head from above and the sides and I can't see any crack. I've heard you can sometimes see them from under the valve cover. I don't know if that's entirely true, but I did check.

Thanks

Cherojakee

The head usually cracks between the 3 and 4 cylinder. While that is good to check for, it is not likely the cause of the low compression. You may want to look into a leakdown test to see where you are losing compression. For the lower end knock, have you inspected the flex plate yet?

Bryan Tift

Interesting. I have inspected the flex plate. All bolts were tight (I attempted to tighten them anyways) and I didn't see any cracks on the plate. It was a chore though, since the only way I could figure out how to move the flex plate was to rotate the engine. I've heard other people have an easier time moving their flex plate, but I doubt that has anything to do with it.

What should be the next thing I check out? I'm thinking of dropping the oil pan this weekend if I have enough money after changing out the back brakes (they're basically gone). If I drop the oil pan, I've heard I can get a better look at the flex plate. And according to a member above, removing the transmission is the only way to know for sure. My question is though, would the knocking sound the flex plate be making also make the diesel sound when the engine is under load?

I may not have enough money to invest in a leak down tester right now. My primary goal is to fix the knocking noise. I actually remember something that happened that I had forgot about until last night. About a week ago I had started my jeep and revved it up a few times. On one of the revs, I heard a loud CLANK in the engine. Could be something not relevant, but yeah.

Anyways, thanks for the help so far. I'm hoping to figure this out quite soon before anything else goes wrong.

GreaseMonkey17

Bryan Tift

Okay. I just purchased a cheap ($20) borescope with good reviews on Amazon. What should I be looking for in the cylinder?

I'll probably take this weekend to use the borescope and drop the oil pan/cut open oil filter. I won't buy a gasket or anything unless the engine is determined saveable.

I'll update once I get the borescope and check the cylinders (should be this Saturday/Sunday). Thanks