Bank 2 Valvetrain Noise

[MrSir]

After replacing the sound deadening for the B2 side injectors, the sound persists.

This is what I believe to be the “sewing machine” sound when warm, which is addressed by Subaru’s TSB 02-151-14R. It involves the replacement of multiple valvetrain components “to reduce a tapping sound (sometimes described as “a sewing machine type” sound) which may be heard coming from the left-hand (B2) side of the engine when the engine is warm.”; copy/paste directly from the TSB.

I have worked on a handful of 2014+ 86s, and haven’t heard this sound in them. I’ve heard it in 13s, but to a greater degree usually.

Looking for the noise with a stethoscope didn’t turn up anything exciting, as most of the sound is drowned out by the HPFP.

Should add that I recorded this after a 185* warm start, with IATs of about 100*. The sound also disappears after blipping the throttle to about 5 grand, which I have a hunch is due to cooler oil being dumped into the B2 head.

[Ultramaroon]

That sounds nasty. I hear a bunch of not-ok valvetrain shit on top of the normal stuff.

[MrSir]

Originally Posted by Ultramaroon

That sounds nasty. I hear a bunch of not-ok valvetrain shit on top of the normal stuff.

It’s kinda harsh sounding for sure. Kinda strange how it basically disappears as soon as stuff gets flowing again. Mechanical gauge shows normal oil pressure (for an FA20), and while I don’t have enough UOAs to say it’s getting worse, it’s certainly not going to explode. So it could just be an NVH issue? Not sure....

A lot of the noise you hear is the trans too though. It has a prolite flywheel. Lol

[Ultramaroon]

Originally Posted by MrSir

A lot of the noise you hear is the trans too though. It has a prolite flywheel. Lol

Can't make a coffee grinder sound like a flute. There's at least one very chatty lifter in there for sure.

[MrSir]

Originally Posted by Ultramaroon

Can't make a coffee grinder sound like a flute. There's at least one very chatty lifter in there for sure.

120%. We’ll see how long this one lasts anyway. Lol I’ve heard a handful of high-ish mileage 13s make a similar sound, so I’m not gonna throw a fit. Especially considering the sound is specific to warm starts, and goes away pretty much as soon as you leave the parking lot. Still, awareness is always nice.

Subaru is a pay to play car.

[MrSir]

Further documentation:

The sound only occurs after a hot start, and usually only after it’s sat long enough to suffer heat soak. This video is after 40 minutes of very hard driving. Lots of pulls to redline, CT spikes of about 213*, IAT spikes upwards of 140*.

This leads me to believe that it’s strictly an NVH issue. Especially because the revision includes new valve clearances for the B2 head.

If it dies, it dies. I’ll replace the engine in 6 beers time. Lol

[mrg666]

You can try Seafoam. It can ease up the valve train. One 16 oz. bottle. 4 oz. goes to oil, 12 oz. goes to full fuel tank. Replace oil after half tank fuel used. Carbon and sludge build up can increase the valvetrain noise.

[Ultramaroon]

Sounds perfect in that clip!


Maybe valve lash is just a touch on the loose side and snugs up as the valve stem expands. I understand that, on this engine, it's preferred to err on the loose side because lash decreases on break-in.

[MrSir]

Originally Posted by mrg666

You can try Seafoam. It can ease up the valve train. One 16 oz. bottle. 4 oz. goes to oil, 12 oz. goes to full fuel tank. Replace oil after half tank fuel used. Carbon and sludge build up can increase the valvetrain noise.

I have used sea foam on many many cars with limited success. My preferred method is a walnut blast for intake ports, and very frequent oil changes with brands of oil that have a specific detergent package depending on my end goal. Plus, my engine is super clean. At least from what I could see when I dropped the pan to check for stray sealant in the pickup tube. I perform maintenance like it’s some kind of fucked up expensive religion. Lol

In this case, it’s literally a design fault on Subaru’s part. The 14+ engines have revised valvetrain geometry to reduce the SOUND. According to any information I can dig up, on top of observations I’ve made when working on these cars, it’s strictly an NVH issue. 2013 FA20s just kinda sound like single jingle KAs, and that’s okay I guess. Lol

[MrSir]

Originally Posted by Ultramaroon

Sounds perfect in that clip!


Maybe valve lash is just a touch on the loose side and snugs up as the valve stem expands. I understand that, on this engine, it's preferred to err on the loose side because lash decreases on break-in.

Valve lash is specified at .0039”-.0059” on the intake side, and .0078”-.0094” on the exhaust side. It’s on the tight end of normal as far as factory lash is concerned for aluminum heads and steel alloy VT components, at least in my experience. Could be wrong, but again that’s just what I’ve seen.

I think the issue is mostly due to the angle at which the rocker acts upon the valve. That, and because the valvetrain component’s CoTE is less than the head, I believe valve lash actually increases with heat. Which would explain why it only happens after heat soak.

[mrg666]

Originally Posted by MrSir

I have used sea foam on many many cars with limited success. My preferred method is a walnut blast for intake ports, and very frequent oil changes with brands of oil that have a specific detergent package depending on my end goal. Plus, my engine is super clean. At least from what I could see when I dropped the pan to check for stray sealant in the pickup tube. I perform maintenance like it’s some kind of fucked up expensive religion. Lol

In this case, it’s literally a design fault on Subaru’s part. The 14+ engines have revised valvetrain geometry to reduce the SOUND. According to any information I can dig up, on top of observations I’ve made when working on these cars, it’s strictly an NVH issue. 2013 FA20s just kinda sound like single jingle KAs, and that’s okay I guess. Lol

It helped my 2014 FR-S. But that is your call of course.

[MrSir]

Originally Posted by mrg666

It helped my 2014 FR-S. But that is your call of course.

I could imagine it quiets down the injectors and hpfp really well. But The intake ports and internals on my motor are too clean to make any difference. I drive up and down a mountain every day, so it spends a lot of time running port injection at low load which keeps the ports clean, and then a lot of time at high RPMs getting really hot, baking all the sludge out. Lol

[Ultramaroon]

Originally Posted by MrSir

because the valvetrain component’s CoTE is less than the head, I believe valve lash actually increases with heat. Which would explain why it only happens after heat soak.

Brilliant. I questioned that very thing as I typed. Totally agree.

[MrSir]

Originally Posted by Ultramaroon

Brilliant. I questioned that very thing as I typed. Totally agree.

It was a serious mindfuck for me when I accidentally found that out. I was like 16 messing with a Honda, set valvelash on a cold engine, and rechecked valvelash on a warm engine. Chasing an intermittent long cold crank was fun. Lol