Weird knocking sound on cold start

D M

D M

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Here in tahoe, done snowboarding... went to start her up in 20 degree weather. She started fine, and then had an intermittent knock which had an irregular pattern... upon popping the hood it sounded like it was coming behind/below the york towards the alternator, but nothing sounded like it was coming from under the valve cover. FWIW I use 10w-30 since I rarely see temps below 50F. I let it idle all the way to operating temp and it still was doing it, but after waiting about 30 mins in total and driving away it stopped

For a while I was thinking maybe my PS fluid was frozen and the pump was trying to suction but I dont think my jeep sat long enough to have that issue(plus im sure it would make a way worse noise lol)


Jeep sounds fine now just curious if anyone can relate
 
Nothing here bud, just posting to keep your thread active. Any thing I add would be a pure guess....it does amaze me how hard noises can be to pin down.
 
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AndyG said:
Nothing here bud, just posting to keep your thread active. Any thing I add would be a pure guess....it does amaze me how hard noises can be to pin down.
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Whats most confusing was the fact that it was random and not a pattern
 
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DylanM345 said:
Whats most confusing was the fact that it was random and not a pattern
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Absolutely and makes me wonder if the cold weather was messing with It ...I understand that it should not
 
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I'm going to guess lifters, but it should have been periodic not random. My 92 had a lifter that would stick when cold. It would knock on a cold day until it pumped up completely. I ran a couple of oil changes of high mileage oil and it cleaned it out.

There's no need to let it idle up to operating temp, let it run for a min or two until the oil pressure is up and drive away.
 
Does it sound like this?
https://wranglertjforum.com/threads/help-diagnosing-engine-knock.33602/
A thread of this type comes up from time to time. Almost everybody's Jeep with a 4.0 eventually makes this same sound. No one has been able to figure out exactly what it is, but it doesn't seem to be serious. There are people who have said their 4.0 starting doing this within 50K miles, and some have said their Jeeps have had this same sound for over 100K miles without any other issues.
 
My 2001 Sport bought new didn't start making any lifter noise till it reached around 50,000 miles. Mine will just do a quick 1-2 second start up rattle ONLY when the temperature is in the 50's and below...NEVER during warmer periods. I read an article about hydraulic lifters that stated...when the parts are cold they shrink and as heat is generated they expand. For this reason free play is required to prevent parts from binding when heated. Article went on to say that the 2 biggest reasons for hydraulic lifter noise is poor maintenance regarding oil changes or over revving engine neither of which I am guilty of since I'm the original owner and know it's history.?
 
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Put your hand on the OPDA and see if you can feel the knocking when it makes that noise. Mine is called the camshaft synchronizer, and the upper bushing was worn out and would knock intermittently.
 
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Definitely not the lifters, i had a decent lifter tick before the motor blew and we rebuilt it. @bobthetj03 ill check that when I go to start it today👍
 
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DylanM345 said:
Definitely not the lifters, i had a decent lifter tick before the motor blew and we rebuilt it. @bobthetj03 ill check that when I go to start it today👍
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No, I don't think it is the lifters, either.

There are members in here who have gone through the trouble to replace the timing chain, camshaft, lifters, push rods, rocker arms, fulcrums, and even the oil pump on their Jeeps only to have this peculiar noise remain.
 
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TJRick said:
No, I don't think it is the lifters, either.

There are members in here who have gone through the trouble to replace the timing chain, camshaft, lifters, push rods, rocker arms, fulcrums, and even the oil pump on their Jeeps only to have this peculiar noise remain.
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Hoping its just the cold weather🤞
 
I wonder if your oil filter's anti-drainback valve is leaking and allowing a dry startup. Might want to change it to a filter with a known good quality silicone anti-drainback valve like Fram's Tough Guard.
 
Jerry Bransford said:
I wonder if your oil filter's anti-drainback valve is leaking and allowing a dry startup. Might want to change it to a filter with a known good quality silicone anti-drainback valve like Fram's Tough Guard.
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I don't think that is it, either.

I recently switched to the Fram Tough Guard after using Mopar oil filters for years. There was no change.
 
TJRick said:
I don't think that is it, either.

I recently switched to the Fram Tough Guard after using Mopar oil filters for years. There was no change.
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Ok for you but there's no telling if the OP's unknown brand of oil filter's anti-drainback filter is leaking. Right? And I wouldn't expect a difference between a Mopar or Tough Guard either. Maybe the OP is using an Autozone Duralast or a Wong Suk U.
 
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Jerry Bransford said:
Ok for you but there's no telling if the OP's unknown brand of oil filter's anti-drainback filter is leaking. Right? And I wouldn't expect a difference between a Mopar or Tough Guard either. Maybe the OP is using an Autozone Duralast or a Wong Suk U.
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I always use wix oil filters and change them every 3000 with my conventional high mileage. The noise didnt sound like it was coming from the filter, more torwards the alternator/front of the engine block.
 
DylanM345 said:
I always use wix oil filters and change them every 3000 with my conventional high mileage. The noise didnt sound like it was coming from the filter, more torwards the alternator/front of the engine block.
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I didn't say the filter would have made any noise, it won't, I said the engine could have been making noise if the oil filter's anti-drainback valve leaked and let all the oil drain out of the filter/upper engine which will cause noises during the resulting dry start. It happens. https://www.pgfilters.com/blog/function-anti-drain-back-valve-oil-filter/
 
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Jerry Bransford said:
I didn't say the filter would have made any noise, it won't, I said the engine could have been making noise if the oil filter's anti-drainback valve leaked and let all the oil drain out of the filter/upper engine which will cause noises during the resulting dry start. It happens. https://www.pgfilters.com/blog/function-anti-drain-back-valve-oil-filter/
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How long do you think the knock should go for? Mine was almost at operating temp and still doing it.
 
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