knocking when cold

[buddylee21]

new to these cars. i have a 99 eclipse auto non turbo. 2.0 420a motor. the problem is a hva a bad knocking sound upon start up when engine is cold. as soon as it warms up it becomes more of a intermitten knock. if you rev it up the knock goes away or if you put it in gear it goes away. have checked upper and lower end of the motor every thing seems to be fine. oil has no metal in it. tried pulling the wires off each cylinder didnt stop the knock..im ata loss. any help would be awesome

 

[boost97gst]

Piston slap will happen to cold engines, then as they warm and metal expands it stops. Thats not normally a "knock" sound though. Rod/crank knock would be present throughout the temp cycle so i think you're safe there but cant say for sure.
Sure it isnt loud lifter tap? Symptoms fit it pretty well but i would think you would be able to identify that quickly.
Get a mechanics stethescope.



**edit** You may notice excessive bluish smoke on start up as well while youre hearing this "knock". If it is indeed slap.

 

[LOWBOOST91]

its most likely piston slap, neons have the same "problem". (almost the same engine)

 

[Jreg]

Yeah piston slap will make that noise when the engine is cold. Another possibility is a sludgy valve lifter. Not terribly likely though. The 420a engines are usually pretty quiet even with low oil pressure. I've run mine down to the oil light before and never heard any internal noises. Make sure your oil is clean too.

 

[zachwilliams02]

Easiest way to check it is just pull the oil pan. If your car is like any other dsm in the world than your oil pan leaks so its time to re rtv it anyways. When you pull the pan shine a flashlight on the cylinder walls. Look for shiny spots on the front or back of the cylinder walls. That is where it will be slapping. Plus you get a new oil change so that could help you if you run sea foam or marvel mystery oil before you pull the pan. So you are finding your knock, fixing leaks, and cleaning your internals all at once. Work smart not hard

 

[buddylee21]

after it warms up sounds like a rattle every so often. when a load is placed on the motor via revving it up or put in gear the knock/rattle goes away. pulled the pan and looks normal. oil has no miles on it. all the lifter appear to be ok none are stuckfrom what ive seen turning the motor over by hand..

 

[boost97gst]

You sound like you have an A/T, correct? Perhaps the noise is coming from the tranny? IDK, just throwing an idea out. You need that steth so you can hear exactly where its loudest when its happening. It will help

 

[420a Monster]

I have nearly the same problem. I'm new to these cars so I don't know how or what to do, this is my first dsm. When I first start up my 420a, it has the usual cold engine knock sound and gets quieter as it warms up. When the engine is warm and I drive it, there is no noise, but when I put it in park or neutral, it knocks and the noise seems to be more loud on the bottom end. I'm not sure what it is. I changed the oil and there was not any metal shavings either. Not sure what to do. I don't want to go out and buy things and it not solve the problem, any suggestions? Any help would be great.

 

[95talongirl]

Piston slap will happen to cold engines, then as they warm and metal expands it stops. Thats not normally a "knock" sound though. Rod/crank knock would be present throughout the temp cycle so i think you're safe there but cant say for sure.
Sure it isnt loud lifter tap? Symptoms fit it pretty well but i would think you would be able to identify that quickly.
Get a mechanics stethescope.



**edit** You may notice excessive bluish smoke on start up as well while youre hearing this "knock". If it is indeed slap.

Beat me to it. Pretty common issue with the Chrysler engine. Had many a Neon with the piston slap, and it never really hurt anything. But yeah, it would do away once the car warmed up. So if its still there, I would investigate further.

 

[420a Monster]

Is there any way to upload a video so you can hear what I'm talking about?