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Unread 01-09-2014, 03:44 PM   #1
92JEEPWRANGLERY
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02 Liberty 3.7 Engine Noise

Hello helpful KJ owners!
My daughters Liberty, 02, V6, auto, 4WD, has developed a noise in the engine that sounds like very fast machine gun fire. Not nearly that loud but very fast when idling. Noise seems to go away when revved up but probably covered up by other noise. Engine history...I bought this Jeep in 2012 with blown motor(rods thru the block), completely rebuilt a 05 model engine, changed the crank wheel and right cam wheel. Engine has been in and running great since December 2012 with no issues at all. I drove it to work yesterday and it started making the noise. Sounds like in the valvetrain as rapid as the noise is. I pulled off the right valve cover and found nothing but really sounds like it is from that side. Jeep runs great, no codes, no missing, plenty of power.
I have started it with the valve cover off and all looks good. What is the chance of it being in the timing chains/guides/tensioners? Like maybe one has come loose and is slapping or chain rubbing on it? Any help/suggestions are greatly appreciated.

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Unread 01-09-2014, 07:19 PM   #2
TwoBobsKJ
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I would bet it's the serpentine belt tensioner.

It's located on the lower right side of the engine and when that pulley starts going bad it'll make some weird noises. I really don't think it's the timing chains, guides or tensioners. If one of those went bad there would be a LOT of noise in the engine.

Bob
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Unread 01-09-2014, 07:53 PM   #3
92JEEPWRANGLERY
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Thanks TwoBobs but trust me, I took the belt off first and started it but no difference. That was a lot easier than taking the right valve cover off! Almost easier to pull the motor back out!
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Unread 01-10-2014, 06:32 AM   #4
92JEEPWRANGLERY
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What's the possibility of a broken valve spring?
They all look good but how do you really tell of it's not an obvious break?
I just really want this problem to be on top of this head before I start taking the front off this engine tonight!
Thanks for any and all help.
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Unread 01-14-2014, 06:47 AM   #5
olliehopnoodle
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Check the hla's. Also you can disconnect the spark plug wire and crank the engine. Watch the secondary chain to see if it is slapping. If it is you tensioner is probably bad.
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Unread 01-14-2014, 07:04 PM   #6
92JEEPWRANGLERY
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Update! When I took the front off the engine, I found the Primary Chain Tensioner broken on the side that has the "Leaf spring" that pushes the nylon guide against the chain. The top half of the nylon guide was gone and laying in the front cavity of the engine along with the leaf spring. Great, I have found the noise. The odd part was the tensioner still had a leaf spring on it just like the one that was laying there! I bought a new tensioner which only has 1 leaf spring, installed it, put all the timing chains back on. Put the Jeep back together and started it up and.....wait for it.....same noise was still there!!! I have now torn it back down and I am thinking that the noise is the right(passenger) chain slapping the top guide. If I crank the engine with the plugs out, it will spin fast enough that the chain "Jumps" up and hits the guide and makes a noise. If it was running I'm pretty sure that is the noise. Do I need to replace just the chain? Or chain, guide, and hydraulic tensioner on that side? Long post but thanks for the help
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Unread 01-14-2014, 08:53 PM   #7
TwoBobsKJ
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Well, since you identified the source of the problem (and a strange problem it is - the timing chain system is a lifetime system) I would suggest replacing the guides and the tensioner(s). The chain could be damaged or stretched but the tensioner is designed to account for slight differences in length of the chain.

Since you're going to replace the guide and tensioner anyway - and to do that you have to remove the cam sprocket - you are kinda half pregnant so you might think about replacing the passenger side chain. If you decide to replace the chain you'll have to remove the primary sprocket from the crankshaft and it's chain from the sprocket and idler - which means you'll also have to remove the secondary chain from the driver's side to pull the primary sprocket. Which means you're now you're getting into the "make-sure-all-the-timing-marks-line-up" territory because the entire timing chain system will now have to come apart and be put back together. Can become a very tedious job, but if that secondary chain on the passenger side is ka-flooey then you're gonna have to dive in.

Those are my thoughts - and come from experience gained when I swapped engines from my '03 to an engine from an '07 Dakota. Had to change the cam sprocket and crankshaft timing ring to match my '03 computer so I had the donor engine down to the short block. I know the inside of the 3.7 pretty well now

Bob
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Unread 01-15-2014, 07:10 PM   #8
92JEEPWRANGLERY
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Great thoughts TwoBobs. I have one more question/stupid thing I did. I know the left hyd. tensioner has a plate/shim behind it that has to be installed correctly. When I built this motor a year ago, both the left and right tensioners had a plate/shim behind them. I put both back in even though i dont find mention of the right tensioner having one anywhere. So tonight when i took the right tensioner off to replace it the shim stayed on the block. I used a small screwdriver to flip it off and thats where my problem is. I cannot find it anywhere. I have pulled all the timing components off the front down to the oil pump but no luck. I have stuck magnets down in the oil pan but nothing found. I have no idea unless it went in the pan and floated/sunk down at the sump end. So my question is, does the right side tensioner have a plate/shim behind it originally? No where in the FSM does it say anything about the right side, only the left tensioner. If it is in the oil pan, will it do any harm? You know you cant drop the pan without pulling the engine back out almost. Thoughts? Prayers for the stupid?
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Unread 01-16-2014, 07:02 AM   #9
TwoBobsKJ
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Oh wow...

I HATE when I do things like that! And believe me I've done it more times than I like to remember

Frankly I don't remember a shim on the right side - but if it was there originally it seems it should go back on. Finding the bloody thing though...

Given the size of that shim it is unfortunately just right to fit in the intake of the oil pickup and block it off - and you know what that would mean down the road. Here's a pic showing the opening in the oil pickup:


Anyway you can get a magnetized extension from your local hardware store and fish it around in the sump? Maybe you can get hold of it and pull it back out - or at least satisfy yourself that it's not down in the sump.

Here's to good fortune for you to find that shim and carry on with the installation of the timing chains, etc!

Bob
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Unread 01-16-2014, 10:20 AM   #10
92JEEPWRANGLERY
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I have fished and fished in the pan with a magnet and with just a bent piece of coat hanger but I can't find/feel anything. I'm going by the dealer today to see if I can find a part number for the right side shim. If I can't then that should mean it's not supposed to have one. When I built this motor I had the 02 that was bad and the 05 I built. I had both torn apart so I could get the crank ring etc off of the 02. The 05 was all apart to send to the machine shop. Did I have 2 shims because 2 was off the 02 and one off the 05? So when I built the 05 I thought 1 would go under each side? That's been 13 months ago, no way I remember. If I can't find a part number for that, I'm going to out a decent size magnet on the bottom of the sump so if it is in there maybe it will stay stuck to the pan. Otherwise, it all flys apart and I build a motor again! I will let you know and thank you for the advice.
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Unread 01-17-2014, 07:13 AM   #11
olliehopnoodle
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When you say 'right side' do you mean passenger side? If so, yes it has a plate behind it. I would not reassemble without it. I dropped mine (twice) but was able to get it with a magnet.
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Unread 01-17-2014, 05:22 PM   #12
92JEEPWRANGLERY
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Well, the engine is back together and so far, good to go. No noise at all. I went to the Jeep dealer Friday and the parts dept. tried to look up the plate for either side for a 3.7 from 2002 thru 2011. There is no diagram anywhere that shows that plate for either side. Kinda odd. I then spoke to 3 techs that have built/ worked on 3.7s. All of them said that the left side tensioner(drivers side) has the plate under it but the right(passenger) side does not. They said the left side has it because of the way the engine oils. The left side tensioner gets oil pressure before the right side tensioner does so the oil restrictor/plate is on the left so the right side will build oil pressure at the same time. Makes sense to me. Not being able to find a part number for the plate does not make sense to me! We also checked the FSM and it says to be sure and install the plate on the Left side tensioner. No mention of the right side anywhere. I think I had one off of each engine and that is why I put both back on.
Thanks TwoBob and Olliehopnoodle for the help/advice. Hopefully all will be well and my daughter will have her Jeep back. She misses it very much.
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Unread 01-18-2014, 09:09 AM   #13
olliehopnoodle
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Cool, I am glad you got it working. It's a lot of effort!
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Unread 01-19-2014, 02:14 PM   #14
92JEEPWRANGLERY
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One more post about this and hopefully I'm done!!! Here is a picture of the broken Primary Chain Tensioner. Still no reason for it to snap unless it was put together with 2 springs instaed of 1. But it still took it 13 months to break.
liberty.jpg  
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Unread 01-19-2014, 08:09 PM   #15
olliehopnoodle
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Okay, my bad. I misunderstood what you refered to as the primary tensioner. The leaf spring reference should have clued me in but I thought you were just using the wrong term (my fault).

When I think of tensioner I am thinking of the piece at the bottom of your picture. That is probably properly called the tension adjuster. It does have a plate behind it.


Wow, your tensioner broke good.
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