Mystery Noise - EJ25 Engine Knocking, But Only at Temperature & Under Load

[Numbchux]

Knock knock, your new engine is calling. I bet you have very little oil pressure, as it's all blowing out past your rod bearings. Thicker oil and/or a high volume STi oil pump might buy some time.

If the guide around the crank pulley is too tight, it will rub the text off the back of the belt. Was this clearance set correctly?

 

Mitsuboshi makes belts for most Japanese OEMs. They do not sell them through the major parts stores, so many people don't realize they exist, but if you start watching, you'll see their name, or logo, on most belts (just did one on my Honda Odyssey yesterday, the original belt said Honda on it, but had the Mitsuboshi logo).

 

Gates used to use quality Japanese bearings, but started phasing lower quality ones in probably 10 years ago, becoming increasingly more common. You don't have to search very hard to find wrecked engines due to Gates kits. With a little homework, it's not hard to find quality Japanese components from reputable sellers (NOT Amazon or eBay, lots of counterfeits) for a reasonable price.

Edited July 9, 2022 by Numbchux

[1 Lucky Texan]

I've seen pics online of 'dropped' (shifted) valve guide inspection after dropping the exhaust. I think it is most common on neglected vehicles.

[Numbchux]

1 hour ago, 1 Lucky Texan said:

I've seen pics online of 'dropped' (shifted) valve guide inspection after dropping the exhaust. I think it is most common on neglected vehicles.

We saw many at the dealership. Causes a misfire. Wasn't uncommon to have cars towed in from other shops that had thrown a coil, injector and more at it trying to "diagnose"/repair a misfire, and it was a dropped guide. Never heard one make a noise.

[el_freddo]

@Numbchux- can you describe what a dropped valve guide looks like with inspection from the exhaust port for us? I’ve never encountered this issue and would be guessing as to what to look for. 

Cheers 

Bennie

[jonathan909]

55 minutes ago, el_freddo said:

@Numbchux- can you describe what a dropped valve guide looks like with inspection from the exhaust port for us? I’ve never encountered this issue and would be guessing as to what to look for.

Me too!  I think I can visualize it, but a picture (if anyone happened to have one on file) would be great.  How much do they displace?

[GeneralDisorder]

The guide can be clearly seen from the exhaust port. They typically protrude about 1/4" or so. Any that have moved will be obvious in relation to the others - we typically see them move anywhere from 1/4" to 1/2". At some point if they drop far enough it generally results in a burnt or bent valve (piston strike). They are often oily as well due to the dropped guide causing the stem seal to dislodge.

And yeah - the gates kits are hot garbage. Just did a full kit on a car last week that had a Gates Chinese water pump fail with about 50-60k on it. That's almost worse than Ford 5.0 Coyote water pumps (but not quite). 

GD

Edited July 10, 2022 by GeneralDisorder

[Numbchux]

On 7/10/2022 at 8:55 AM, el_freddo said:

@Numbchux- can you describe what a dropped valve guide looks like with inspection from the exhaust port for us? I’ve never encountered this issue and would be guessing as to what to look for. 

Cheers 

Bennie

quick google search turned up this

Edited July 12, 2022 by Numbchux

[el_freddo]

Awesome and concise video showing the issue @Numbchux 

Thanks for sharing! 

Cheers 

Bennie

[dirty_mech]

So I haven't replied about this for a month because I've been trying to fix it the whole time.  I was waiting to solve the issue so I could come back to you guys with a neat little story to share.  Unfortunately it's been a wild goose chase and now believe the problem isn't an engine issue at all.

So let me share something I previously left out because I didn't think it was relevant.  About 30 miles before this whole mess started, I hit something on the freeway pretty hard.  It was night and I was going 80 and it felt like I hit something about the size of a  4x4" piece lumber laid across the freeway in the dark.  Sent my front end flying up into the air for a second.  Stopped to take a look and didn't see or detect any obvious damage.  Figured I'd have to get my alignment done in the near future just to be safe, but it didn't seem to cause any problems so I just kept going.  By the time that vibration developed later down the road, it didn't even occur to me that hitting an object on the road much earlier could've been related to it.  The issue was behaving so much like an engine problem, even getting better if I parked and let the car cool down.

You guys know I checked the timing belt and found nothing.  Since then, I checked and replaced the spark plugs which hadn't been replaced since August 2020, 30k miles ago.  A couple of them were heavily worn, with a gap of over .060 compared to the maximum 0.43".  I also adjusted the valve clearances, most of which were out.  Between those two major issues I was sure that must be the problem!  The engine certainly ran noticeably better afterwards.  I also did the oil and air filters and checked basic stuff like the battery cables.  All seemed good for a bit.  I was about ready to write back here that I'd fixed it by tuning the engine.

However the problem developed again on the freeway.  That's when I remembered hitting that object on the freeway the night the issue developed.  So I checked my front tires and noticed each tire had only one weight.  Had the tire shop rebalance them and sure enough both were way out.  They rebalanced the tires (dynamically with two weights).  The car began vibrating less overall.  However the vibration during acceleration and heavy engine load is still there, and got worse during extended driving just like before.  So I tried replacing my ignition coil and spark plug wires.  Can't tell if that made any difference to the sound and performance of the engine (maybe a little), but the vibration is still there.  Even checked the cylinders with a boroscope; the ones that had bad spark plugs were a little more carbon encrusted but fairly comparable to the others.

Then I started my car one morning and drove off.  While hitting the gas pretty hard in first gear, I felt a big wobble and vibration as the engine transmissitting power to the wheels.  The same damn type of vibration I feel when I get on the freeway.  This is what made me all but sure it's a powertrain or suspension component issue.  I must have caused some sort of internal component damage when I hit that object going fast on the freeway.  Les Schwab looked under the car and didn't see anything wrong. 

I also just went under the car and didn't see anything wrong either.  Saw a couple of places that might show where I took impact damage from the object on the underbody shell, but there isn't any visible damage or even impact marks anywhere near the suspension or powertrain components.  So I'm about to finally take this tin can to a Subaru mechanic and hopefully they can pinpoint what is going wrong. I've got some guesses but at this point I'm getting tired of guessing.

If you have an idea what could be causing all this, save it for the new thread I'm about to make.  This one is so old and on such a different premise that I think it warrants a fresh start.

 

 

[dirty_mech]

Thanks Numbchux for the heads up about the possibility of this being an oil pressure issue, as well as the guide on how to identify dropped valve guides.  I do track and do all my oil changes with top quality materials and I do use a thicker oil weight.  I can't rule out the possibility of either.  But based on the recent discovery of the same vibration at times in lower gear, I'm starting to bet on a powertrain or suspension issue.  I'll still ask the shop about checking my oil pressure, which sounds like a great idea regardless.

Guide clearance was set correctly to my knowledge; the timing belt came with a guide tool for that purpose, which I reused when I did the water pump. 

[el_freddo]