Topside "Rattle/Knock" in 3.7L?

[TwoBobsKJ]

So this has been tackled before in some fashion but I haven't seen a thread on this particular sound in the 3.7L engine. I'm just shy of 123,000 miles.

There are times when I hear a distinct 'rattle' or higher pitched 'knock' that is perfectly timed with engine speed - but especially when quickly pressing the throttle - that is loud enough to hear from inside the Jeep. It's not a 'knock' like a rod would make down toward the crank and it seems to come from the top front of the engine - doesn't seem to be coming from the valve train on either side. When I pop the hood and blip the throttle I can distinctly hear it on the top of the engine - like I said more of a rattle sound than knock but it's internal.

Doesn't matter if the engine is hot or cold - though it happens more frequently when the engine is hot versus when it's cold. And it only happens when it's under load - a quick blip of the throttle or when accelerating, not at idle. And it's not there all the time; it'll be there for a few minutes then disappear and will randomly appear again a few minutes or a few days later. But it is happening more frequently recently.

Could it be related to the timing chains? Is the chain starved for oil due to blockage? Should I be ready for the engine to grenade on me? (I doubt it but what the heck, right?) Is it piston slap (don't know exactly what that means...)?

Like I said, I've seen lots of threads about the 3.7 'ticking' but not this type of sound from the topside.

Thoughts?

Bob

 

[ThunderbirdJunkie]

Timing chains/tensionsers, wonky balance shaft sprocket?

 

[TwoBobsKJ]

So is the balance shaft sprocket repairable?

Bob

 

[ThunderbirdJunkie]

ITBJRC yes, it has a keyway and a shoulder bolt.

 

[sota]

mine's WAY newer than yours and it likes to rattle sometimes, especially when the computer and I disagree about power output during takeoff. I get the impression that the engine's design is somehow prone to it. Either that or my 40k mile engine is going to essplode at some point.

 

[STW]

I have 150k miles and it rattles a little. I haven't listened as closely but ... When in doubt, a little marvel mystery oil couldn't hurt...

S

 

[Skudy]

Jeep 3.7 rattle

Just been looking at this thread regarding the "Jeep knock"on the 3.7 V6 engine/gearbox and thought I would add my thoughts.I have the dreaded knock(or rattle)on my 2002 3.7 KJ.I first noticed it app 2,000 miles ago,when lifting my foot off the gas pedal.It sounds distinctly like a big end rattle and b eing a mechanic for 35 years I was pretty sure this was the problem.

Well,since that time I have attempted to pin this noise down and between myself and 3 other mechanics we are about to admit defeat.The really weird thing is the noise has not got worse and in fact seems to have lessened.I drive the car daily and apart from the infrequent rattle now and again I can't fault the car.At this point I should point out that the car has been converted to LPG since new and this has been checked out and deemed to be in perfect working order.I would repeat that this noise is always noticable on the over run (deceleration) and is totally absent when under load.

The list of suspected items varies greatly,depending on who looks at it and includes little ends(gudgeon pins),valve lifter,flex plate,torque convertor,etc,but no one is sure.A recent development has been that the rattle is more pronounced when the stick shift is in the 2 position and when put back into drive will stop,which points to the gearbox,but this noise definitely seems to be emanating from the engine.All oils,etc are ok and the motor doesn't smoke or use oil.I have actually taken it on a 450 mile round trip recently and it performed faultlessly.

Any suggestions would be most welcome,because it is becoming somewhat of an obsession with me.:freak3::flamingdevil:

 

[TwoBobsKJ]

UPDATE:

So the "rattle" on the top side of the engine is becoming more frequent - sometimes at cold startup but most frequently when the engine is fully warmed up.

I can make it go away by revving the engine several times up to 2500 - 3000 RPM's; seems like the increased oil flow from higher speeds temporarily stops the rattle/knock.

Are there oil galleys in the front top of the engine that get clogged? Is it coincidental that revving the engine makes the rattle disappear?

I'm OCD about my vehicles and so getting concerned the engine will let go any time, especially if it's a valvetrain issue. For those who've had a #2 valve go bad did you have the rattle/knock beforehand?

Bob

 

[Mickeychop]

Updates?

Anyone find a solution or a possible source of the rattle / engine knock yet?

 

[tommudd]

Sort of.........................TwoBobs just replaced the engine, problem solved :icon_lol:

 

[Mickeychop]

Bad news.... Thank you for the heads up. At least I know what to suspect...

 

[TwoBobsKJ]

Bad news.... Thank you for the heads up. At least I know what to suspect...

This is what I ended up doing...

Bob

 

[trailbound]

Our 05 has 175,000 miles on the 3.7 auto trans. Its been my wife's daily driver since new and we go 5,000 miles between oil changes with conventional oil.

Its just started to tick at cold start up for the first 5-10 seconds and the noise seems to be coming from the front right top end of the engine. Noise is dependent on engine speed and I'm not sure what to think of it yet.

 

[trailbound]

Its not dependent on outside temperature. It did it this summer at 90 degrees and today at -10 degrees. Just at start up after its been sitting awhile.

 

[02blue]

I have a pretty bad tick since I fried my headgasket last year. HOAT doesn't mix well with oil. I'll be doing the headgaskets soon and changing the heads (160K) but I'd recommend a quart of Marvel Mystery oil with the next oil change. Quieted mine down really well. Mine does it regardless of outside temp but worse in winter. I usually don't like adding those things as I change the oil on a 5k interval too but the MMO really seemed to help me.