2007 3.7L Engine knock, bang, thump

[kuench]

Not sure how to describe it. Cold start today. No problem. Engine starts, revs to about 1500. When the rpms drop to about 1000, I start getting engine noise from the passenger side. Seems like a thump every two seconds. When I turn off the engine and restart, the sound isn't there until the rpms drop to 1000. The sound does not go away when the engine is warm. The sound doesn't increase proportionally upon revving the engine.

Ideas/suggestions ?

https://www.youtube.com/watch?v=NXRrOyIdEJA&feature=youtube_gdata_player

 

[dbjeep]

Sounds a lot like an A/C comp clutch kicking in and out... Just a thought.. look at it as the noise is made to see if it's timed the same... Good luck.

 

[Jo6pak]

Agreed, I also think the AC may be the issue. Or possibly a bearing on one of the serpentine belt pulleys.
Either way, I would get it looked at ASAP, just in case it is something more major that could cause bigger problems.

 

[kuench]

Turned out to that a rocker arm had slipped off.

 

[LibertyTC]

^ oh..great ..how many miles on on your KJ..??

 

[ronjcar]

I also had a rocker arm fly off a few weeks ago due to negative temps and a lash adjuster sticking. Ended up screwing up a lot more than just a rocker arm though.

 

[CactusJacked]

Turned out to that a rocker arm had slipped off.

Keep a watchful eye on the engine. The 3.7's and 4.7's have a tendency for the valve seats to work loose (drop). As the engine sits, a seat could slide down giving the valve a wedgy. Then as you start the engine, the valve, being wedged open, gives slack to the rockerarm, and zing....off flies the arm.

 

[LibertyTC]

I think the company who built the 3.7's heads was named "Built Wrong"

I believe I have found the meaning of....
M O P A R
Many Odd Parts Are Repairable!

:icon_lol:

 

[ltd02]

Turned out to that a rocker arm had slipped off.

Mine's done this twice. #2 exhaust both times. Easy fix but takes some time. Like was mentioned, if it doesn't fall out of the way, like mine did, very bad things happen to important parts. :icon_sad:

 

[kuench]

^ oh..great ..how many miles on on your KJ..??

At the time, a little over 100km. And it happened on a -25°C weekend. I've read a bit and it seems I was one of the "lucky" ones.

 

[LibertyTC]

60,000 miles..hmmm..that's early in life to be having a clank going on.
What did you do to "fix" it?
I take it was on passenger side and only 1 rocker, were you using synthetic oil?

 

[kuench]

Luckily the rocker arm fell down and to the back of the head. I bought a new lash adjuster and install that and then the rocker arm. I was using regular oil at the time but have switched to synthetic.

From various sources, it seems to happen any time, but mostly during start up. Age of the engine has irrelevant as some have never had the issue.

I found an alternative fix which requires installing regular washers under the lash adjusters. It's claimed to cure the issue permanently.

 

[LibertyTC]

Yes I have seen that YouTube video where they were loosing the rocker every few weeks and he used washers. BUT ..I'm not too sure how permanent that my be.
Part of the problem is in the lifter, and how the inside the lifter is a spring that becomes stuck with built up crud (bad oil does not help) best to do the lifter and check the spec on it too.

 

[ltd02]

Like I mentioned in post 9 this happened to me twice and months apart. Same rocker and completely without warning. I just popped it back on but I did get a couple new adjusters since so if it happens again I'll swap a new one in. I have the official rocker removal tool also. Pretty sure mine was a crud issue. I've been treating her better since then and no recent repeats. I thought about the washer but it just seems unnecessary to me.

 

[kuench]

From where and how much for the tool?

I think that the washer would eventually wear out, but it's a much cheaper fix than new adjusters. I've seen videos of adjusters being stripped down and reassembled, but not for Chrysler products.

 

[CactusJacked]

The 3.7 tends to drop valve seats. When the seat drops as the engine is off (valve open), the valve can be held down, tension on the rocker arm is relieved, and the rocker can fly off when the engine is started. I've seen the washer "fix" too, but it's a bandaid, rockers don't fly off just for the hell of it. A stuck lifter or broken valve spring can also be a reason why.

 

[RenKJ]

The 3.7 tends to drop valve seats. When the seat drops as the engine is off (valve open), the valve can be held down, tension on the rocker arm is relieved, and the rocker can fly off when the engine is started. I've seen the washer "fix" too, but it's a bandaid, rockers don't fly off just for the hell of it. A stuck lifter or broken valve spring can also be a reason why.

Would replacing the lash adjusters and valve springs protect from this happening? Im at 147k km, aprox 91k in miles, this thread made me nervous about this, i have a faint tic when the engine starts cold, seems to go away as soon as the oil circulates so i always figured no big deal...

 

[kuench]

I think that keeping your oil fresh and using the block heater when it gets very cold would help avoiding the issue.

 

[RenKJ]

I think that keeping your oil fresh and using the block heater when it gets very cold would help avoiding the issue.

Yes i do that already, forget i mentioned the tic at all, im asking about preventing the valve seats from dropping/losing rocker arms

 

[ltd02]

Yes i do that already, forget i mentioned the tic at all, im asking about preventing the valve seats from dropping/losing rocker arms

Best prevention for dropped valve seats is never let it overheat.