2002 2.5 Engine noise in new engine

[AaronsScoobyru]

I just replaced the engine in my 2002 2.5 Outback, got through 1,000 mile break-in, changed oil and I am about half way to the first 3,000 mile until I change the oil again.

When I start the car and let it warm up a little and accelerate I hear a ticking/knocking noise, which sounds like the lifters, but when it warms completely the noise stops. The sound is not there when I simply manipulate the throttle under the hood and only seems to be present when the car is under a load during acceleration.

I took the car into the shop where they serviced the heads, during the swap, and they checked the valve clearances and said the side I checked and adjusted was a little off, going by what Chilton's specs where, not knowing the clearances were posted on the bottom of the hood, so they reset them.

The engine is still making the noise, but it baffles me as to why it stops once the engine is at optimum temperature, because it seems like if it were lifter or bearing related it would get worse as the oil thinned out as it heats up.

At this point the only thing I can figure is that I put a Pure Power billet aluminum oil filter on the new engine that pumps 19 gal per minute, and that maybe this was somehow pumping too powerful a stream, causing the oil not to properly get up top when the oil is cool and thick, if that makes any kind of sense.

If anyone has any kind of insight into this, or if this ticking is normal with some 2,500 miles on new engine, any help would be greatly appreciated.

Thanks!

[grossgary]

Was the timing tensioner replaced? The new styles aren't that robust and prone to issues. It doesn't sound like it to me but if the tapping is coming from the front drivers side of the engine right behind hte timing cover then it's likely the tensioner. They loose hydraulic pressure and cause issues under load, with the cover pulled you can physically see the tensioner sort of flopping around and it can be very loud - sounds like rod knock sometimes.

My guess is piston slap though. Piston slap is common with EJ25's and the symptoms are identical to what you said - a ticking/tapping that goes away when warm.

Fortunately it is benign, just leave the windows up and turn the radio up.

There is a piston redesign to fix that issue.....not sure which generation (96-99 or 2000-2004 EJ25's as they have different pistons). I would have assumed a rebuilt would include the latest and greatest pistons, but luckily it at least doesn't matter besides it being an annoyance.

Subaru will hit it with a stethoscope and can replace the one offending piston. And they did it for EJ25's under warranty.

Being a rebuilt engine I'm unsure, if you posted this description on an OEM Subaru engine I would call it piston slap and you're done...

[susiemk]

Sorta makes sense that lifter noise or even piston slap will decrease once the car warms up as the clearances decrease as the engine gets warm/hot (remember heat expands things) - so where there was enough space / clearance to make loud noise between the rocker arm adjuster & valve when the engine is cold there is a smaller space / less noise on the same part when the engine is warm.

[AaronsScoobyru]

I did change out the timing idlers and tensioner, but I don't know if that would stop after the engine warms up, but the lifters and piston slap expansion does make sense.

The engine is a factory reman, and apparently from Japan, because it had a weird number associated with it, so they may have not updated the pistons, but it did come with a 3 year warranty. I'm not sure if that covers piston slap though.

If it is indeed an piston slap will it eventually go away?

Thanks for the info guys!

[grossgary]

Probably is piston slap, very common in Ej25's.

Piston slap will never go away.

Subaru I believe warrantied them in new cars and had updated pistons to alleviate it. Not sure that warranty would apply to engines or not...just call, they're very familiar with piston slap just as I am and I'm not even a Subaru trained mechanic.