99 SUS cold start knocking sound debate

[spooln30]

Ok guys I have a friend that just bought a 99 SUS 2.5 and I replaced the valve cover gaskets last week and the next morning he called me and said that the car made a knocking sound on a cold start for approximately 1-3 seconds or untill it built oil pressure. Now he just bought the car from a dealer auction and that day was the first time it made this noise. In the first week he had it it didn't make this noise. He is adamant that is has a rod bearing that is bad and the noise goes away after a couple seconds because of the engine building oil pressure. I disagree 100% and told him that if the rod bearing was bad or loose enough to create a noise that it would be its loudest at start up then only quite down when the oil pressure builds but never fully disappear and would get somewhat louder when you rev the engine, this engine does not make any noise what so ever after the first 1-3 seconds of cold starting. I have been a auto mechanic for 15 years so Ive heard plenty of rod knocks in those years. I did a search and found a bunch of info mostly on NASICO and the common answer is that it's normal and could be promoted by the use of a non- Subaru oil filter and running the wrong weight synthetic oil. Here's another issue, he gave me the car so I could hear the noise and in the 4 days I've had the car it hasn't once made the knocking noise. I haven't had a chance to remove the t-belt covers and inspect the tensioner, which could also possibly make a noise. I did drain the oil and didn't notice any metal in the oil so I suggested that he just change the oil and get a Subaru oil filter. I'm sure it's not piston slap but I've yet to hear the noise. Have or do any of you guys have this same noise at cold start ups or have you heard of such a problem to be common?

Thanks for any help.

Btw I own a 99 LGT and run Subaru filters and mines never made any noises like described nor does his son's 98 LGT.

[spooln30]

???

[spooln30]

Nobody has had this issue?

[johnegg]

use better oil.

check the level.

check valve adjustment.

 

the tensioner makes noise going on and off the throttle.

 

if you don't hear it there is something different in how you park it and how he parks it. hill?

or it isn't really there.

[subieadam]

Yes you need to use the proper subaru oil in these engines because the fluid properties are designed for the types of metals inside the engine. Also most likely you have bearing issues. The rod bearings were a poor design on these engines and do not allow a proper oil supply to the rods between the crank and that will give you that sorta dry knock sound. There are companies that make aftermarket bearings that are better as far as letting the oil lubricate. Supposedly the new bearings that subaru offers for these ej25 engines and whatnot are better but they will eventually do the same thing so aftermarket is the best way to go in this case. You are not alone BTW, pretty much all subarus in this year range will start to knock, even 02 and up wrxs... and its all because of the rod bearings. Using the proper subaru oil would prolong the issue but it will happen eventually.

[spooln30]

It's weird because this is the first 2.5na legacy I've heard of making this noise out of the 3 me and my friend and his son owns and the multiple other ones I've worked on being an auto mechanic. I've never heard the noise just going on my friends diagnoses but talking to him today its only done it twice in a week supposedly. Just from what I've read it seemed to be a common issue but more so on turbo engines. Sounds like it needs an Accusump.