There's plenty of commentary about filter brands in other posts. I have been using Fram and Mobil 1 with start up knock for a few seconds after the Jeep sits for a period of time (Mobil 1 worse than Fram).

I am now on the second OEM Chrysler filter from the local dealer (only 8$). No more knock at all! I have had the Jeep to the dealer twice for this, and ofcourse they can't duplicate it because it never sat long enough. However, two dealers I have been to both went out of their way to say how important it was to use the OEM filter . What would be that different about the Mopar filter that prevents the knock. Could the backflow valve be that much better?

 

Hmmm... I use Mobil 1 filter & I never have a knock at start up.


A knock at start up would have me concerned...

 

On another note.....

Advance Auto Parts always carries OEM Mopar filters in stock. You can pick them up there instead of taking a special trip to the dealer.

 

I have only used the oem filter since new and have had no issues, I don't think it is even any more expensive than the aftermarkets. I dont see any point of spending a lot of money on filters just to throw them away every 5000 km.

 

Kflash
I bought the jeep new in 09 and let it sit many times and never had the knock. I did the first oil change myself and used a fram oil filter (the orange one) and had to travel so I parked the jeep at the airport and four days later when I came in and started it, sure enough it knocked at stratup.

So I will be testing your theory Kflash and will install the Mopar filter and see what happens.

Also from other experiences I noticed that heavier oil like 10-40 or 20-50 leave a thicker coating behind on the cylinder wall which tends to last longer and cause less of that knock at startup. However as we all know these oils are not recommended by our manual as we must use 5-20.

For those of you who say that you never heard the knock, do you leave you Jeep for a couple of days without starting it and not get the knock? because if you drive it daily you will never get it.

John
09 X Unlimited 4x4

 

All I can say is that I had the knock for a second at start up with other filters and don't with the Mopar version (x2 changes). Has to be something to it...

 

I'm trying a Napa Gold I've heard they are good. Also I run Mobile 1 5W-20W my jeep and it does sit around alot since I have a company truck to drive, I hope this gets rid of it. We will soon find out. Said on the box that it had a anti drain back valve in it. Oem filters are hard for me to get!!!

 

I would guess that the oem filter has a check valve that keeps all of the oil from running back into the pan. By doing this the pump doesn't have to refill the oil galleys before any pressure (refill=knock). I have been using Motorcraft filter that most autoparts stores carry and it's working great so far I believe it is a s400. I'll check to be sure.

 

Hey John
When you get start-up knock, what is the outside temperature?
I only ask as I also get the same thing. What I have discovered (in my case anyways) is the start-up knock is there or worse the colder it is outside. When I leave it in my garage I never get start-up knock, but when it's at my work place, parked outside, it's nearly always there. I was out of town for 5 days and again didn't hear a thing as it was a warmer day.

I did manage to get the dealership to replicate it, but they seem to think it was lifter noise, but they were not prepared to do anything about it.

Does this match anyone Else's case?

 

I would be surprised if any but the cheapest of filters did not have an anti-drainback valve. Some are better than others, of course.

The suggestion (in this thread) that only certain brand filters prevent the dreaded start-up knock doesn't hold up. For a few reasons.

1) No "proof" that the start-up knock complained of is the same noise many posters are hearing. (it could be but it could also be A/C compressor, power-steering, etc.) (I don't know, either) In other words, there may be different problems being described as the same one.

2) There is no agreement that filters draining back or not causes or cures the noise.

3) There is no agreement that one brand filter fixes the problem or causes it. Individual testing results contradict across the board.

for example see:
https://www.jk-forum.com/forums/show...ht=start+knock

IF (big IF) the problem described by many is, in fact, the same problem of filters draining and therefore causing dry starts, then the conclusion can only be that some filters work for some people some of the time.

Wish I had an answer for it....