Engine Knocking- 2005 XT Limted

I have a 2005 Outback XT Limited. It has 117,000 miles on it. I've owned it for a little over 2 years. During that time, I've kept up with the maintenance. It has had new plugs/coils/timing belt with all new idlers/tensioner/all new belts/all new hoses/one valve cover gasket, cleaned throttle body, oil changes for engine/diffs/transmission fluid changed twice.

 

A few months ago, I cranked the car and thought I heard a slight knocking sound on startup. This was soon confirmed on the next startup, and over the next 3 months, this problem got worse and worse. I have run Rotella T6 Synthetic in the car since I bought it, with a Subaru oil filter. It now knocks pretty loud until it gets oil pressure (about 1-1.5 seconds from the time it starts running when cold) and then the noise gets quieter, but doesn't go away, for another 3-5 seconds. It's silent on hot startup interestingly enough, just very noisy on cold starts!

 

Any ideas? How should I proceed? I'm guessing I need an new engine, or rebuild this one.

I'd be curious to know as well, same exact situation.

 

Logs show very low load and low rpm knock events, but WOT pulls are totally clear.

 

IAM is dropping relatively quickly though.

 

Wondering how much time I have to save for a shortblock.

Knock, as in pre-ignition, or just the sound, "knock"? Can you isolate it? Are you saying you know you have low oil pressure until it goes away?

 

A knocking sound can also be a failed tensioner, not uncommon, even with a new tensioner in there. You should be able to isolate the location to see if it's valves or from under the timing cover.

mine did it before and after timing belt change, so I don't think its tensioner. sounds like rod knock, but just at startup.

Agreed, yours almost certainly no the tensioner if it was replaced. Are you sure it's not just the knock sensor? I'm not sure how rod knock could be related to 'knock' events. Seems unlikely they are.

It may be the sensor, have chased down just about everything I can think of that could be causing a false knock.

so after a bunch of digging/reading/fiddling I think the knock sensor was responding to variable voltage. cleaned up the battery terminals and ground connections and everything seems much better. knock events only show up at on off throttle now.

 

so the knock I was seeing in the logs wasn't related to the start-up knocking sound.

Are you still having this startup knock/slap? --curious bc mine exhibits a knock/slap noise when at idle and more so when cold. But can't rule out the occurrences during warm idle. 128k (06lgt)

I almost always get a noticeable knock for about 1 second at cold start, and sometimes I can detect a bit of what I assume is piston slap few seconds after on really cold mornings. Definitely goes away very quickly. I've had the symptom for quite a while and it hasn't gotten worse. Think it is just the tolerances growing between crank shaft and rods.

 

If you are getting it all the time, or even warm at idle, I'd look into it more deeply.

What oil do you use?

Have you leak tested your intake system lately?

Seems frequent. Didn't do it this am from what I noticed. Sometimes paranoid. Sometimes tuned into the noises and sometimes not. Thinking cold piston slap til warm enough. Mobil 1 5-30. No I haven't leak checked it. Paranoid bc money at the moment doesn't allow for me to put out on a rebuild etc. Also don't recall any I these noises when I had my mustangs. Or I didn't pay attn if they existed. Hasn't seemed to be worse but has been going on for awhile. Notice it within say first 3-5mins of car running, like I jump in start up and cruise to some stop lights and notice it at the red lights.

Haven't noticed anything in the oil

 

Also paranoid bc have had the car for 4 years---longer than I keep cars so far..and it's treated me well, possibly better than my mustangs and I haven't had issues with it. Easy

On the car for the most part aside from the 20% of the time in its life with me that I've ran it hard.

might try using rotella t6 5w40 with the next oil change.

 

also, do you do a lot of short trips?

I find that towards the end of the OCI i get a bit more knocking, I think from fuel dilution.

No I drive mainly 1-1.5 hours and 50miles to work and the same home.

Has anyone figured out the Startup knock issue? If I lightly hit the ignition so the engine turns over but doesn't start up a few time then turn it over there is no knock. Almost as if I am priming the the engine with oil.

I'd go with a 10w-30 or 10w-40 this time of year, but I think I'd be planning for a new short block.

 

EJ257 are about $1800 new shipped, get a gasket set for your year car and have the heads rebuild and get ARP head studs.

 

 

If you want to keep the car, do the SB before something bad happens.

 

See my click here link.

Jesus, I just had the turbo replaced, oil cooler gasket replaced, timing belt, powersteering pump, rear end, front half shafts, wtf else... I don't even really push this car.