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Knocking noise after fresh oil change...

C

CommanderXJ

NAXJA Forum User
Location
Arizona
You know one weird thing that I never quite understood about my Jeep is how it tends to knock after a fresh oil change or when it's cold.

The motor is a 4.0 and it's a 96' with 116k miles. I have been using Castrol GTX 10w30 except for the last oil change I put in 10w40. I switched back to 10w30 and also switched brands to Shell Rotella with a PureOne Puralator oil filter to match with it.

I noticed that on cold starts, there's a loud knocking sound. It goes away if I rev it up a little bit and it honestly sounds like it's coming from underneath the car. I was thinking that it could be a cracked flexplate (though I don't know how this could happen consider the car was driven by an old lady before me) but what leads me to rethink my thoughts is that after about 2000-2500 miles after the oil change, the cold start knocking noises diminishes.

The noise also diminishes when its warm.

I am very confused as to what could be causing this.
 
interesting....

most vehicles usually knock a little bit right after an oil change...coughfordcough

i have no idea why it would take 2500 miles for the knock to stop though. maybe someone else will chime in.
 
Its worn main bearings. Don't worry about it, every 4.2 and 4.0 jeep ive ever had done that. The first one i changed the oil like 3 times in a row to different weights with no change. Eventually the noise went away. Ive noticed every one ive had since then does it too, so I just don't pay it any attention as it will go away. I do recommend running a oil additive like lucas though. I use a bottle of lucas oil stabilizer with every oil change. It really raises pressure and protects it at cold starts. It also keeps the oil from thinning so much at high temps like slow crawling when wheeling.
 
I'm thinking it has something to do with the oil filter. Maybe a combination of a bad anti-drainback valve and it going into bypass around the 2500 mile mark. Have you always used the same brand? Try a different filter next time. I've had good luck with the Mobil1 and Napa gold filters.

Anyone know if the Purolator PureOne is a "good" filter.
 
I'm glad i saw this. I did an oil change Monday, and had a slight knock at idle immediately after. I changed the oil again yesterday to 10-30 with a quart of MMO and the knock is almost gone at idle. Above idle i hear nothing. Scared the heck out of me at first.
 
gw204 said:
I've had good luck with the Mobil1 and Napa gold filters.

Anyone know if the Purolator PureOne is a "good" filter.
Click to expand...

Somewhere around here, there's a link to a comparison of filters- their construction, who makes which brands, filter capacity, medium type, etc. Interesting reading. I believe there was something about the Purolator in there as well as Mobil, K&N, Fram, and Wix.


edit- here it is
http://minimopar.knizefamily.net/oilfilters/
 
Pure One filters have a very dense media. They restrict oil flow somewhat. I've had a couple of vehicles that hated them. Knocking on start up and the oil pressure gauge would spike. Stick with Wix or Napa gold and mopar filters.
 
I have had the car since 109k miles so I have changed the oil three times so far. The first time I put in Castrol GTX 10w30 with a Bosch Oil filter. Second time I switched weights to a 10w40 (don't think my car likes this weight too much) with a Mopar oil filter and the third time I switched over to Rotella 10w30 weight with a puralator pure one filter. I have read the purolators were excellent filters, and the price difference between the three filters were all within the same range so I just picked one up.

I don't think the choice of oil filter has anything to do with the noise. I am thinking of running a qt of atf fluid towards my next oil change to see if that helps with anything. Do you guys think it's worth doing this, and if so how shall I do it?
 
I usually add a quart of ATF right before the oil change. this time i added it, let the engine idle for about 30 minutes, then changed the oil like normal. It definitely helped, because i drained the oil 24 hours later to switch from 20-50 to 10-30, and the day old oil was as black as 5000 mile oil. I was shocked. I am going to change the oil again in a week to see if it's as bad.
 
If you are going to do the ATF, then add it just before the next change, and let the engine idle, do not put a load on it.

However, Shell Rotella or any other diesel motor oil will clean the engine out. Give it time to do its job.

Any oil filter with a nitrile rubber anti-drain back valve is problematic. Make sure the filters you use have the silicone valve.
 
joe_peters said:
If you are going to do the ATF, then add it just before the next change, and let the engine idle, do not put a load on it.

However, Shell Rotella or any other diesel motor oil will clean the engine out. Give it time to do its job.

Any oil filter with a nitrile rubber anti-drain back valve is problematic. Make sure the filters you use have the silicone valve.
Click to expand...


Yah I checked the box on the puralator filter and it's silicone valve. That's one of the reasons why I bought it.

EDIT: Does anyone have any experience on Shell Rotella T synthetic blend? I was at wally world and noticed they had several 1 gallon jugs at the 10w30 weight. I had to special order the conventional order online through some farm store because I couldn't find the 10w30 conventional in the stores.

I am thinking I might switch to that on the next go around, but so far the jeep likes the rotella. Very smooth.
 
Could be filter. I had a bad pure1. Sent it and they admitted it was bad but would not send a replacement. For a few bucks try any other filter first.
 
As mentioned, change your filter. I've seen filters cause pressure issues and knock issues at startup. Its $6 and half a quart of oil. Personally I use mopar filters, walmart round here sells em, I pick em up when I buy my oil.
 
It's not the oil filter. I don't know how many times I need to say this.

I have used three different oil filters (including mopar filters) since I got the car and the knocking noise has always been there right after a fresh oil change.

And it's not like the oil filter I got was a fram or some cheapo store brand, it's a purolator pure one filter which is nearly 6 bucks and according to some breakdown tests is infact one of the top leading oil filters out there.
 
Long shot - might try pre-filling the filter with oil, then installing it. Gets some of the air out so less has to be forced thru oil system.
Cold start- oil pressure should climb right up to normal in about 2 - 3 seconds of startup if all is well.
 
orange said:
Long shot - might try pre-filling the filter with oil, then installing it. Gets some of the air out so less has to be forced thru oil system.
Cold start- oil pressure should climb right up to normal in about 2 - 3 seconds of startup if all is well.
Click to expand...

On cold starts the oil pressure takes a while to read to where it should be. For instance, after I turn it on in the morning the oil pressure reads 80 psi at idle. I drive the car normally for maybe 20-30 min and the oil pressure slowly starts dropping down to around 40psi at idle and then 60-70 under load.


Is this a symptom?
 
I'm sure someone will advise you, but the oil pressure should rise pretty quick unless you just done a change. But I have the same issue with that sound after a fresh oil change when on a cold idle. I chased everywhere to track it down with no joy. After a few thousand miles, the cold start tap/knock/rattle dissappears. Mine started doing this with 35,000 on the clock so I'd be suprised if it was bearings.
 
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