Hello everyone,

I need someone's help because when I start my jeep wrangler 3.8L in the morning it makes a lot of noise. The starter motor sounds since I have not done any maintenance on it but another sound also sounds, at first I thought it was the lifters and I took it to a mechanic who changed the distribution kit and lifters but the sound remains the same. I forgot to mention that as the engine warms up the noise decreases. I will leave a video where the noise is appreciated -->
Also add that it does not have any check engine code. If anyone knows what it could be, please comment.

Thank you very much in advance,

Diego.

 

Welcome to JKF.. checked you profile you have a 2011 so that would be a 3.8L.. How many miles on your ride? I only have 3.6L so I can't compare.

 

Thanks , It has approx 90100 miles.

 

OK, 90K Did this start happening recently? Does it speed up with the engine rpm? Can it be isolated to 1 cylinder (removal of individual spark plug wire to determine which if only 1 cylinder is generating the noise)?

 

The noise started a few months ago. It has no problems with RPM and speed. Try to see if disconnecting the coil cables the noise disappears, I should try it when the motor is completely cold since it only sounds when cold.

Could it be an oil pressure problem? Since when turning on, after a few minutes the sound goes away, but it does not show me oil pump errors.

 

Check your exhaust manifold on the driver side for cracks (underneath the heat shield).

 

I'll check it out, thanks!

 

Also check if the bolts on the exhaust manifold flanges leading to the cats are loose. If they are, it will take plenty of penetrating oil or replacement to get them tight again -- the square nut holders on the top side spin pretty easy. It's a 2-bolt flange and replacing or tightening just 1 of the 2 is all that's necessary.

Edit: Sometimes you can just push each cat up and down to see there is play in the flange joint.

 

Sounds like exhaust to me.
I had issues with brand new manifolds getting loose on me where they meet with the exhaust system.
The bolts kept backing out,
I retorque and 100 miles later the sound returned!

And it did the same thing, sounded fine when hot, but loud when cold.
Get it fixed sooner than later since it will mess with the AFR readings, my gas mileage went to shit while it was leaking.

New manifolds are threaded, so I just added a nut on the top of the bolts to keep them from backing out again.

Here are the ones I used on my 3.8.

Right
Amazon.com: Dorman 674-914 Passenger Side Exhaust Manifold Kit - Includes Required Gaskets and Hardware Compatible with Select Jeep Models : Automotive

Left
Amazon.com: Dorman 674-915 Driver Side Exhaust Manifold Kit - Includes Required Gaskets and Hardware Compatible with Select Jeep Models : Automotive
These also come with the good mls gaskets.

New Bolts
Amazon.com: Dorman 03413B Exhaust Manifold Hardware Kit Compatible with Select Models : Automotive

Before install I coated them with silver header paint to keep them looking pretty longer.
and I also smoothed out any sharp casting edges, I hate working on stuff with sharp edges.
A favor for future me.

I don't know what the thread pitch is, but I would recommend grabbing a set of nuts to make sure they don't come loose on you.

 

It was hard for me to remove the heat shield, but I was finally able to and this is evident, a crack in the exhaust manifold. could this be the problem?