Knocking sound on start up

T

tkostelni

New Member
Joined
Mar 5, 2020
Messages
8
Location
Virginia
When I start my 03 Rubicon when the engine is cold, it has a knocking sound that goes away once the engine is up to operating temp. I’m not sure where it’s coming from but it doesn’t sound great but goes away when the engine gets up to temp. Its more pronounced when it’s cold outside and I start it, and less so when outside temps are more mild. I attached a video of what it sounds like, sorry for the wind noise and mediocre video quality.
 
Is it a stuck lifter? Mine occasionally makes 5-10 angry tapping sounds when it starts up. I think it is more likely if it has not been started in a while.
 
The video won’t play on my iPad. I’m curious because I have an ‘angry’ tapping from my 05 Rubicon too, that also goes away when warmed up.
 
I can't play the video either, but that can be a symptom of piston slap. If there's excessive clearance between the piston & cylinder wall it will make noise until everything expands once you get to operating temperature.
 
It could be piston slap. I had a 2000 gmc with a 5.3 that did it for 30 seconds and then it would go away. Dealer said it was ok and dont worry about it. I got an attorney from lemon law attorneys and sued gm. They let me keep my truck and gave me 12k. It was three years old with 35k on the odometer. Went to the dealer the next day and they gave me a new one even up. I was a happy camper.😄
 
qslim said:
I can't play the video either, but that can be a symptom of piston slap. If there's excessive clearance between the piston & cylinder wall it will make noise until everything expands once you get to operating temperature.
Click to expand...
Thank you for your guess, I just uploaded the video again, hopefully it works this time.
 
Flush your engine oil with "motor flush" twice in a row at 100 mile interval.
Then use a 5w-30 oil. I did mine that way before I spend money for the fix but it went away. I add this CRC snake oil just to feel good :)
1584314203720.png
1584314427968.png
1584314378807.png
 
Last edited:
Could be chain slap. Stretched chains can slap around the rubber insulator guide making all that ruckus.

On your next cold start. Listen closely in the front of the engine where the crankshaft's located.
 
tkostelni said:
When I start my 03 Rubicon when the engine is cold, it has a knocking sound that goes away once the engine is up to operating temp. I’m not sure where it’s coming from but it doesn’t sound great but goes away when the engine gets up to temp. Its more pronounced when it’s cold outside and I start it, and less so when outside temps are more mild. I attached a video of what it sounds like, sorry for the wind noise and mediocre video quality.
Click to expand...
Mine 2012 and do same , all jeeps makes this sounds after thousands milage (180000miles) mine
 
  • Like
Reactions: TJRick
It's the lifters. Very common noise on the 4.0. Some people have had success with Marvel. Honestly, I ignore it. My Cherokee with 250k has made that noise for most of its life.
 
It doesn't sound that bad to me. I do hear at least 2 things going on. One is the 'diesel type' sound that I believe is the torque converter (mine makes the exact same sound, and seems pretty clear under the Jeep it's coming from torque converter) and the second is a lighter, higher pitched ticking that sounds like valve noise. Mine also sounds just like that on good days.
 
My 04 TJR with 74000 miles had some momentary problem with a rattle when first starting when new to me. I changed oil and installed a Mopar filter and problem stopped. Might have something to do with the check valve in your present filter. Depending on your climate the oil weight you are using could make a difference.
 
Top Bottom
Back