This may be in my near future, 90K on 08 JK. Do you have a list of everything you replaced? I have put 2 water pumps in mine so far due to leaking... thinking next one will have to be a Mopar OEM rather than rebuilt/manufactured. What timing chain sprocket do you recommend? Very nice write up by the way!

 

I purchased all parts from rockauto
Timing chain kit: MOPAR 68001402AA (Standard Replacement)
Crankshaft seal: TIMKEN 3638
Oilpan gasket: FEL-PRO OS30622R
Waterpump: MOPAR 4666044BB

 

Mopar sells a gasket kit for the chain replacement process that has everything you need. Probably can get it from Rock Auto as well. It is part #68029544AC.

Because the factory chain wore out so quickly I was tempted to try a Melling kit but couldn't find out anything about it. Might be worse, who knows.

Good luck!

 

Thanks to this I was successfully able to replace a friend's timing cover gasket. No more leaks!

A few tips I have

- Blow out all the holes behind the timing cover to get all the dirt, oil, and coolant out. I had to buy a new TC gasket because when I put everything back together the first time, a bunch of oil came out of one of the holes and got all over the gasket before I could tighten everything down.

- Not required but my 15mm TC bolts were really crusty so I cleaned them on a wire wheel and put some thread sealant on them.

- Remember you're removing the UPPER oil pan. I was in a rush and didn't notice that you were supposed to remove the upper oil pan (the frame) and leave the lower pan attached. I ended up cracking the upper part trying to pry the TC off and having to weld it back.(+2 days)

- The service manual says not to use any type of sealant on the TC gasket but I found it nearly impossible to line up without some RTV. I think the gaskets they were using originally when the service manual was written were different than the ones they are using today so I wouldn't worry about that.

- Put grease on inside of the new crank seal. I didn't do this at first and the lip didn't go in right. Luckily I had another one from my second TC gasket set.

- Here are a few torque specs that might help some

Oil pan - 105 in. lbs.

Timing Cover - Small bolts 20 ft. lbs. Big bolts 40 ft. lbs.

Tensioner - 30 ft. lbs

Pulley - 45 ft. lbs

Water Pump - 105 in. lbs.

Harmonic Balancer - 40 ft lbs.

 

Mine has had mild timing chain rattle between 700-800 rpm since day 1 (almost 130K now). It's quiet at other RPM's, so this is probably an RPM range where the chain slack gets unstable for some reason. Usually it's most noticeable on a warm start as the high idle speed is decreasing. From listening with the belt off I'm 98% sure it's the timing chain. Recently listened to a couple other 3.8 Jeeps and hear similar.

I'm close to deciding to replace the chain. But if a little chain rattle between 700 & 800 RPM is inevitable, that would put it a lot lower on my priority list.

So my question is: Did this rattle go away after the chain replacement, and did you have this rattle in the RPM band I'm referring too early on before it became worse?

 

Yes, after 5k miles since the replacement it's noise free. The bigger concern with these cheezy chain & gear sets is the sloughed off metal that you'll find inside the engine. The inside of my JK's timing cover was coated with it, like a grey film, as was the lifter area when I removed the intake manifolds to deal with the leaking lower intake seal. Filter will get it except during cold startup bypass which is when bearing, etc. damage is going to occur. The amount of slack I found on mine was what I would call extreme for the low miles (60k+) when I discovered it.

What sucks is the only way you can really tell the condition of the chain & gear set is to remove the oil pan at a minimum. Better is to pull the front cover, and at that point regardless you might as well swap out the chain & gears. BS design, combined with crap components.

 

Thanks -- An inspection port in the front cover would have made it easy. On the old engines with distributors I'd just rotate the crank back and forth while watching the rotor for movement.

 

Finished changing out the chain, and just in time for a 2K mile trip with some Jeep friends. Here's a few thoughts before I forget...

I figured out a way to test the slack in the timing chain before disassembly, here's a link to the write-up. The cam sensor gap was set by simply retracting the sensor approximately .03 from where it touched the cam sprocket. Turned out that the chain in mine wasn't outside the limits, but the specs are pretty loose. It's silent now, all of the time. Idle is smoother, low RPM torque seems a bit better too.

The OEM chain only flexes one way, around the sprockets -- It doesn't flex backwards, the links bind to prevent that. The Cloyes replacement chain flexes both ways. Don't know what advantages there might be in either design.

To make it easier to line up the flats on the oil pump, the pump was filled with the thick Lucas oil and positioned with the flats vertical to match the crank. The Lucas makes the pump stay in place, and it should self-prime faster as well.

Used Permatex Hi Tack on the timing cover side of the gasket only. This holds the gasket in place on the cover, the other side being bare so it slides easily on the engine block for lining up the bolt holes.

This is what I do on any initial engine start when the oil system has been apart -- Generically it's remove fuel, spark, pull plugs, and crank with starter. For the 3.8L JK, remove the fuse for the fuel pump, the spark plugs, and electrical connector on the coil pack. After adding engine oil, fill the oil filter half way and install it. Crank the engine with the starter to prime the oil pump, and pressurize the whole oil system. Probably best to do this for several 30 second runs even if an oil pressure gauge is showing normal pressure to bleed out the air.

The special tools (mentioned earlier in this thread), or an equivalent, are absolutely necessary.

 

Worked on this project the last two days and followed all the steps, but once I went to turn on the jeep, the oil light wouldn’t go away, was idling very rough and then engine shut off on itself. Not sure what I did wrong but now I’m at a loss for how to fix it.

 

Reference this from my post above yours:
Hopefully it didn't wipe a bearing -- it sounds like the oil pump didn't prime or the flats on the pump weren't lined up with the crank. Doubtful the latter could happen without noticing the cover didn't go on properly.

Ways to prime the pump include temporarily overfilling the oil pan and/or cranking with the oil filter removed with lots of rags to catch the oil. There is a fuse to pull to prevent an engine start while cranking.