BulldogMJP

Ill be cooking that sprocket at 200 for twenty mins. Yummy.

BulldogMJP

Took two weeks to get the chain set up here in Canada. Its -18 today so I used the cold temps to my advantage .I heated the sprocket in the oven @ 350 for twenty mins. With the crank shaft being so cold the heated sprocket slid right on. Result!
Will tackle the rest of it tomorrow.

spartan99

Can't the timing be checked to indicate whether the chain is worn out?

Replacing the chain is a big job that I'd avoid if it wasn't necessary. A nice new chain is never a bad thing of course though!!!

Sahara Lee

Check YouTube. Lots of 3.8L (and 3.3L) repair videos. Not much difference between Jeep and Town & Country engine.

Just be careful you have the right parts...
https://www.youtube.com/watch?v=5YOS_OzK5XI

BulldogMJP

Ok.Its all back together. Runs nice and quiet now. It sounded so so bad before. It was a deep hollow knock . I had three mechanics tell me the sound was main bearings and that I needed a new motor. Also when ordering parts I had two dealers tell me they have never needed to do a timing chain yet on a jk and that is why no one stocks the parts. They told me I was wasting my time. Hope this thread helps others. Im sure as the early jk's get up in milage there will be more chains starting to stretch.

webejeepin

Good to hear it all worked out well.

Haha nice way to use old man winter to your advantage eh.

Thanks for info!

spartan99

Nice job. Timing chains aren't easy.

I am developing that sound as well. Isn't there a way to check the timing?

ronjenx

You can check valve timing, but there is a 12° tolerance (6° each way), so it is only an indirect way to check chain stretch.
There is a direct procedure to check chain wear/stretch, but it requires chain cover removal.

spartan99

Thanks.

I have to admit that I am skeptical that swapping out the chain fixed the problem. No offense at all to the OP. My skepticism could merely reflect my lack of understanding how a timing chain results in knock. Here is how I understand the situation:

Knock results from detonation; pre-ignition in the combustion chamber due to a problem with timing or excessive heat in a combustion chamber due to low octain fuel or carbon/ debris build up.

My understanding is that these engines have a knock sensor, which advance or retard ignition timing if a pre-ignition problem from age related timing changes. And knock comes from pre-ignition, so shouldn't the sensor adjust for a slack in a timing chain and eliminate it, unless the pre-ignition came from something for which it couldn't compensate, such as low octane fuel or carbon build up?

Is it possible that by doing the chain, you inadvertently cleaned whatever was the source of the pre-ignition? Did you do any other types of maintenance at the same time, or recently, that effects the intake and or the cleanliness of the combustion chambers? Did you get the injectors cleaned? Flush the motor to remove carbon build up in the valves? Etc?

Again I am simply trying to understand the situation because my 08 has developed a similar sound and naturally I want to get rid of it. Like I said before, a new chain is never a bad thing and it's s big job so hats off to you.

Baddkarmaracing

When he was talking about a knock it was a different kind of knock than you are thinking of, your thinking spark knock while the op is talking about a knock from something hitting something else, in his case the chain hitting the timing cover