What does rod knock sound like?

Philbar71 · 01-05-2012, 08:45 PM

My 2.4 has a odd knock when the engine is cold, at idle (around 800rpm). I only hear this noise from somewhere in the bottom end. Def not near the lifters or valve train.When the engine is fully warm i do not hear the noise at idle (550 rpm). However, when im driving and and the engine is under load and at about 4000-5000rpm i hear a very quick and faintnt ticking/knocking. What could be these noises? This noise eventually goes away and cant hear it again until the engine cools down.

JLw7123 · 01-05-2012, 08:52 PM

piston slap?

comanche · 01-05-2012, 08:56 PM

Generally sounds like a clatter coming from the guts/lower end of the engine.
But usually when a rod bearing goes, the noise is a pretty loud clatter that won't go away but gets slightly better when the engine is revved.

With a 2.4L it's inevitable if the engine hasn't been taken care of...

Philbar71 · 01-05-2012, 10:18 PM

Its well taken care of. Oil changes at regular intervals with synthetic oil.

I suppose it could be piston slap, however i didnt know that 2.4 was known for piaton slap.

Philbar71 · 01-12-2012, 08:56 AM

Bump.

Any ideas as to what this noise could be? Its getting louder when its cold but goes away when the engine is warm.

rocketfast321 · 01-12-2012, 10:29 AM

kind of hard to say, i know my 2.4 makes some weird sounds when its cold, but i don't worry about it.

Philbar71 · 01-12-2012, 01:36 PM

Could it even be piston slap? I swear all of the noise is from the bottom end.

comanche · 01-12-2012, 03:11 PM

What I do when I have a noise with a 2.4L is carefully pull the oil drain plug and put my finger in its place while I check the plug for shavings.

Most of the time I have found that a lower end noise in a 2.4L is caused by bad bearings. These aren't the best engines (understatement)

Philbar71 · 01-12-2012, 03:48 PM

Well I have a magnetic oil drain plug so I see a good amount of metal shavings on the plug.

But waht does it mean if the noise goes away once the engine is warm? Rod knocks dont do that do they?

sleepyalero · 01-12-2012, 04:38 PM

its most likely just piston slap. i wouldnt worry about it, mines noisy too when cold.

comanche · 01-12-2012, 06:11 PM

Rod knocks still have a very distinct clatter once the engine warms up, though revving at the right rpms can almost make you think it is getting better.

I guess the best thing you can do is post upload a sound file.

Philbar71 · 01-12-2012, 07:28 PM

Hmmmm well I had the car up on ramps tonight and the noise was all on the bottom end is somewhere underneath, near the drivers side. Right at the no. 3 piston it seems... But this noise gets quieter as the engine warms up and when its fully warm its nearly gone.

I'll try to get a video of it soon.

a.graham52 · 01-12-2012, 08:39 PM

u might want to put some thought into what ur doing. ur putting secret cams into an engine with a potential lower end problem....

Philbar71 · 01-12-2012, 08:57 PM

Yeah Ive though about it. But the noise just started to get worse today as it was about 30 degrees for the first time in months when I started it up. So it could be the extreme cold and just be something simple as piston slap.

Its extremely hard to tell where exactly the noise is coming from. With my head underneath the oil pan I hear it the loudest on the drivers side. Like either no. 3 or 4. But near the passenger side it sounds the same almost, just not as loud.

It almost sounds like something is shaking loose and taping on something. I listened to 2.4 rod knock vids on Youtube and it sounds nowhere near as loud or as bad as that.

The oil was just changed and I drove it around pretty hard and got back and put it on ramps and the noise is either completely gone or so quiet I cant hear it over the rest of the engine noises when its warm.

Are the pistons aluminum in the 2.4? I would imagine so right? So it could be piston slap. The only engine I have heard with a audible piston slap was my dads 5.7L LS1 in his Camaro. That sounded like a diesel until it was fully warm.

Philbar71 · 01-21-2012, 11:28 AM

Well, its got to be piston slap. We had a day or two of warm weather where it was near 70 and i didnt hear any knock when cold. When warmed up its quiet as well.

But as soon as the temp drops below 60 it knocks when the engine is cold -_-

xXManwhoreXx · 01-21-2012, 01:34 PM

Its piston slap guarenteed. I dont know much about the 2.4s but im guessing cast pistons? They dont heat expand as fast as the cylinder walls so it give em room to bounce around until they tighten up