Question to expand general mechanical engine knowledge. A head removal job can address.. ?

[JT20]

This is designed to be a general engine question, not so much about my specific car. It is about engines in general, though I do have a Subaru EJ25 in case anyone was wondering. (EJ251 as per stamp in my car engine bay, it is not an EJ253 or a turbo.) So with that, let me ask so that I may learn.. of anyone were to brand this somehow a "dumb question."

Alright. So. That out of the way.. If the heads were to come off an engine, in my engine most likely because of eventually the Head Gaskets are supposed to fail, perhaps de-laminate perhaps just fail (they are doing fine at the moment as is the engine.) What other things can be addressed or fixed with the heads off?

Specifically.. Can piston seals and valve guides be addressed with the change of a head, or does the block have to be taken out of the car?

Quirky to Subarus, I have heard it said that removal of a Subaru engine is not a big deal. Also that everything requires taking the engine out, since it is low, wide, and flat.

My engine runs fine, this just so I can learn . ?

 

[KGMtech]

Well it would be a good time to replace the timing components, waterpump, and inspect the valve seals. Having said that, the valve seals are the only thing made easier by having the heads off.

 

[JT20]

Well it would be a good time to replace the timing components, waterpump, and inspect the valve seals. Having said that, the valve seals are the only thing made easier by having the heads off.

Is it true that valve guides can cause a rattling noise at start-up? I know you mentioned valve seals. Does my engine even have valve guides?

As to that particular thing, this noise has been driving me absolutely bonkers but I'm also noticing some other things that make me believe 1 out of the 4 cylinders seems to be ever ever so slightly sub-par, which is prompting me to think and ask this.

Still a general engine question, though.

 

[ABN_CBT_ENGR]

As to that particular thing, this noise has been driving me absolutely bonkers

I suggest you get a cheap mechanics stethoscope ($5) from HF and probe your engine to specifically locate and isolate this "noise"

Then do a assembly drawing recon to see what mechanical component(s) may be the most likely suspects before you just go "looking".

 

[JT20]

I suggest you get a cheap mechanics stethoscope ($5) from HF and probe your engine to specifically locate and isolate this "noise"

Then do a assembly drawing recon to see what mechanical component(s) may be the most likely suspects before you just go "looking".

I have an 18" long screwdriver would that work too? However the handle is that blue rubber from AutoZone, methinks you need something that isn't muffled on the end?

As to ascertaining the noise.

 

[ABN_CBT_ENGR]

I have an 18" long screwdriver would that work too? However the handle is that blue rubber from AutoZone, methinks you need something that isn't muffled on the end?

As to ascertaining the noise.

I used a precision balanced "John Smith" screwdriver for years before I used my first stethoscope ( my original one was an actual medical one my Doctor gave me).

The screwdriver certainly can and does work to a degree but the stethoscope is greatly superior in diagnosing and pinpointing a noise.

 

[andyd]

Find a Suburu enthusiast forum and ask them what they use for a service manual. Also ask about the noise and power questions. Please post a followup.

 

[Number_35]

I used a precision balanced "John Smith" screwdriver for years before I used my first stethoscope ( my original one was an actual medical one my Doctor gave me).

The screwdriver certainly can and does work to a degree but the stethoscope is greatly superior in diagnosing and pinpointing a noise.

Check out Eric O's homemade auto stethoscope on YouTube. I think the post is titled "Checking Out A Noisy Idler Pulley".

I've used a long screwdriver in the past, but bought a mechanic's stethoscope quite a few years ago. I think it's a Lisle tool, and it wasn't expensive.

But anyway, Eric O cut an empty plastic jug, round in cross-section, and slipped the narrow mouth over a long screwdriver handle. The open cone serves as a speaker/amplifier. Safer too, as it keeps your ear away from the end of the screwdriver handle.

As far as what else to do when a head is off, I've always taken the head to a machine shop where the valves are ground, the valve guides are inspected and replaced if necessary, and the valve stem seals are replaced.

 

[JT20]

Find a Suburu enthusiast forum and ask them what they use for a service manual. Also ask about the noise and power questions. Please post a followup.

One said "Just sounds like normal valve train clatter on startup" however I found that dismissive...

Or a tensioner fail?

 

[mk378]

They have hydraulic lifters. It is normal to have some slack in the valvetrain at startup causing a rattle for a few seconds until the lifters refill with oil. It won't hurt anything.

If it's on the same side as the oil filler you can take the oil cap off and listen if it is louder from inside. This can differentiate internal engine noise versus external parts like pulleys.

 

[wpod]

Compare your engine to others .

 

[JT20]

They have hydraulic lifters. It is normal to have some slack in the valvetrain at startup causing a rattle for a few seconds until the lifters refill with oil. It won't hurt anything.

If it's on the same side as the oil filler you can take the oil cap off and listen if it is louder from inside. This can differentiate internal engine noise versus external parts like pulleys.

Honestly, if it's normal then I'm happy and relieved. It never used to "rattle on start up" for a second or less, now the past few weeks It has. Thought something was broken OR a piston was flopping around. Seems like it's just hydraulic lifters.

Now for the quest for a really thin motor oil, seen a few videos about hydraulic lifters coming back from the dead.

 

[andyd]

Did the startup noise begin after an oil filter change?

 

[JT20]

Did the startup noise begin after an oil filter change?

Not exactly sure, ?

 

[HangFire]

What other things can be addressed or fixed with the heads off?

Specifically.. Can piston seals and valve guides be addressed with the change of a head, or does the block have to be taken out of the car?

Not sure what "piston seals" are, maybe piston rings. That's the main thing you cannot address with the heads off. Cylinder bore wear as well.

With the heads off, your heads should go to a trusted machine shop where they will:

• hot tank/clean it
• surface it flat ("Shave the heads")
• remove all the valves, replace all the bad ones
• remove and test all the springs, replace all the bad ones
• grind the valve seats
• replace the valve seals

This is also called an "upper engine rebuild". If you have uneven or high wear in the lower end, doing all this will quickly make it worse. If you have an otherwise sound engine, and are replacing a bad headgasket anyway, it is very worthwhile.

A wet/dry and leakdown test will help determine your lower end wear, along with a careful examination once the heads are off.

 

[meep]

I’ve owned a couple of subarus and my brother had 3. I know the 2.5 had some head gasket issues a while, but outside of that, the heads themselves are pretty stout, as well as the rest of the motors. Unless there is a head gasket problem, I wouldn’t go looking for reasons to pull them off. Those engines can go a long, long time, and often do. Mine developed piston slap which was audible every morning, but I drove it hard (it was the 2.2, smaller engine) just to keep up with DC beltway traffic and it handled it with no fuss.... it was a solid motor, despite a quirk or two.

m

 

[SSerian]

One said "Just sounds like normal valve train clatter on startup" however I found that dismissive...

Or a tensioner fail?

My 2016 STi with the 2.5 turbo filled with Redline 5w40 and only 31k miles rattles at startup.