Subaru H4 piston soak possible?

[PhilloBeddow]

2014 Subaru legacy FB25 6MT, 95000 miles, owned since new.

Short block replaced under warranty at 50000 miles because of excessive oil consumption. Spark plugs replaced at same time just because. Iridiums.

Oil consumption is … ok I guess but still there. My annual mileage about halved when I retired to about 6-7k / year and I’m on the severe OCI schedule as I do a lot of in-town driving.

Currently close to the end of my first 0W-20 VRP OCI and oil consumption seems somewhat reduced but hard to quantify. I’ll be staying with VRP for the next few OCIs. I’m aware 5W-30 will probably reduce oil consumption but I want a baseline for comparison, hence Subaru recommended 0W-20 for the first few OCIs.

Gas is usually Costco Top Tier and the 2014 legacy is port injected (MY2018 was when the Legacy went GDI I believe) so I don’t anticipate valve carbon build up being a problem.

That’s the background. Here’s my question -

Is a piston soak feasible for a flat 4 engine ? Notwithstanding the difficulty of getting to the spark plugs how would you soak the rings evenly?

The only way I can think to do that is to lay an old mattress down and flip the car on its side. I don’t want to do that because my wife will want the extra garage space and then I’ll have to park like that all the time.

Would adding Berrymans B-12 to the gas tank help if I’m already using Top Tier?

I want to minimize the oil consumption as best I can going forwards but I think I might already be past the point of diminishing returns and I don’t want to be an idiot about it.

What say you all?

 

[PhilloBeddow]

that's 10W weather

Well yeah, the oil might be spec’s for 5F but I’m not.

It’s snowing right now and more to come so I’m staying home.

 

[PhilloBeddow]

You can add the chemical and use a leakdown tester to force the fluid into the rings. Kia uses this approach for their piston soaks in this TSB:

https://static.nhtsa.gov/odi/tsbs/2022/MC-10206642-0001.pdf

Haven’t seen that before, thanks for the link. Might have been useful for my sons 2019 Optima but that’s over 100k miles now so no warranty left, and that’s for another thread.

Going further off topic -

It’s interesting that Kia pressurize the cylinder to force the chemicals into the nooks and crannies. That’s probably beyond what most DIYers have available, so dealer only?

Also interesting that they reference a Valvoline product as a cross reference to the Kia chemical #. I googled it and it took me to Valvolines Pro site and the first thing I saw there was an ad for Restore and Protect.

And round and round we go…

Thanks again

Phil

 

[The Critic]

It’s interesting that Kia pressurize the cylinder to force the chemicals into the nooks and crannies. That’s probably beyond what most DIYers have available, so dealer only?

Conceptually, a leakdown tester could work.

https://www.amazon.com/OTC-5609-Cyl...cphy=9031992&hvtargid=pla-2281435182658&psc=1

 

[IndyIan]

Thanks for the suggestions. That’s pretty well aligned with what I’m thinking. Already using the Fram Ultra.

This week isn’t the time to switch from 0W to a 5W though it’s going to be cold

View attachment 257445

5F is about my lower limit for starting my tractor with 15W40 conventional in it... Any 5W30 will be fine at 5F, and especially a synthetic one.
I run 0W30 or 5W30 syn year round in our 2018 outback. It sees quite a few -10F starts and I think the coldest as been -20F, with no odd noises or delay in the oil light going off.

 

[KrisZ]

Here is an idea, remove the intake manifold, which is at the top and fill from the intake valves. You would probably only be able to do one cylinder at a time since the engine would need to be rotated by hand to open the valves.
Also, jack up the side being soaked, that should help with the gravity doing its thing.

 

[Overfill]

@mt23 do you have on hand that updated part# for the large PCV valve?

The larger PCV valve would help reduce the vapor/mist velocity, and help liquids drop out some. Reducing oil mist getting to the intake and pistons will help reduce consumption and ring fouling. I personally added a catch can too, and constantly caught oil.

 

[PhilloBeddow]

Conceptually, a leakdown tester could work.

https://www.amazon.com/OTC-5609-Cyl...cphy=9031992&hvtargid=pla-2281435182658&psc=1

Ok, I think I got it now. Not familiar with that type of tester, so thanks for that.

If I’m reading this right, you position the piston at BDC on the combustion stroke so the valves are closed and monitor the pressure in the cylinder?

The slower the pressure decays the better the chamber is sealed, which gives a measure of how much the piston rings are sealing?

But in our example we’re using the air pressure to force ring cleaning solvent into the ring grooves.

 

[D60]

Ok, I think I got it now. Not familiar with that type of tester, so thanks for that.

If I’m reading this right, you position the piston at BDC on the combustion stroke so the valves are closed and monitor the pressure in the cylinder?

The slower the pressure decays the better the chamber is sealed, which gives a measure of how much the piston rings are sealing?

But in our example we’re using the air pressure to force ring cleaning solvent into the ring grooves.

The H4s will absolutely spin when you pressurize a cylinder (I also figured that out from the thread I linked above) so be sure you have a breaker bar on the crank.

I used a long piece of aluminum TIG filler to stick in the plug hole and visually monitor piston travel. It's flexible so you can bend it to fit and it's of course soft so won't hurt anything. Your LWS would likely sell you one cheap or swing by a fab shop with a 6 pack

 

[ARCOgraphite]

2014 Subaru legacy FB25 6MT, 95000 miles, owned since new.

Short block replaced under warranty at 50000 miles because of excessive oil consumption. Spark plugs replaced at same time just because. Iridiums.

Oil consumption is … ok I guess but still there. My annual mileage about halved when I retired to about 6-7k / year and I’m on the severe OCI schedule as I do a lot of in-town driving.

Currently close to the end of my first 0W-20 VRP OCI and oil consumption seems somewhat reduced but hard to quantify. I’ll be staying with VRP for the next few OCIs. I’m aware 5W-30 will probably reduce oil consumption but I want a baseline for comparison, hence Subaru recommended 0W-20 for the first few OCIs.

Gas is usually Costco Top Tier and the 2014 legacy is port injected (MY2018 was when the Legacy went GDI I believe) so I don’t anticipate valve carbon build up being a problem.

That’s the background. Here’s my question -

Is a piston soak feasible for a flat 4 engine ? Notwithstanding the difficulty of getting to the spark plugs how would you soak the rings evenly?

The only way I can think to do that is to lay an old mattress down and flip the car on its side. I don’t want to do that because my wife will want the extra garage space and then I’ll have to park like that all the time.

Would adding Berrymans B-12 to the gas tank help if I’m already using Top Tier?

I want to minimize the oil consumption as best I can going forwards but I think I might already be past the point of diminishing returns and I don’t want to be an idiot about it.

What say you all?

Just run the top tier fuel, no FI cleaners whatso ever and stick with VR&P. No solvents in the holes!

I have Never removed what enend up to be a non-functioning or sludged PCV from a Subaru. They are hard to get to, and the factory hose clamp is an absolute BEAR - at least on the EJ253.

Give it time and run it somewhat hard now and then with highish rpm off-throttle coast downs in lower "gears" on the Interstate to get a good vacuum in the cylinders. Think NASCAR backpedalin' heading into that big oval corner one.

We have owned over eight or nine subarus I think over the years. Lost count. - Arco

 

[PhilloBeddow]

The H4s will absolutely spin when you pressurize a cylinder (I also figured that out from the thread I linked above) so be sure you have a breaker bar on the crank.

I used a long piece of aluminum TIG filler to stick in the plug hole and visually monitor piston travel. It's flexible so you can bend it to fit and it's of course soft so won't hurt anything. Your LWS would likely sell you one cheap or swing by a fab shop with a 6 pack

Understood and agree. Thats why I said to position the piston at BCD but didn't get into the weeds of locking the crankshaft in position in case it isn't at end of stroke. That could hurt if you don't . . .

Thanks for the tip on the TIG too!

 

[PhilloBeddow]

Just run the top tier fuel, no FI cleaners whatso ever and stick with VR&P. No solvents in the holes!

I have Never removed what enend up to be a non-functioning or sludged PCV from a Subaru. They are hard to get to, and the factory hose clamp is an absolute BEAR - at least on the EJ253.

Give it time and run it somewhat hard now and then with highish rpm off-throttle coast downs in lower "gears" on the Interstate to get a good vacuum in the cylinders. Think NASCAR backpedalin' heading into that big oval corner one.

We have owned over eight or nine subarus I think over the years. Lost count. - Arco

Thats the plan so far - I think I've got the low-hanging fruit taken care of, I'm asking BITOG if there's anything else to try that's not too involved. There's been some good suggestions but I think that'll take me to where it's 80% effort for 20% improvement.

Subaru USA don't offer the 6MT in the Legacy anymore so I'm planning on keeping it as long as possible. I see a 6MT Crosstrek in your SIG - how do you like it? I'm on my 4th Subaru but I'm not against a fifth.

 

[Ranger83]

This isn't mine but I need a one and done approach.

I think the pressure pot will clean injectors (kinda the point, and I realize not really the target here) and rings but not so much valves -- at least not intake valves. Still, seems a more elegant solution.

The Seafoam would more so do valves and rings since it goes through the intake.

I've previously rigged an FB to run on my pot, so if I can remember how I did it I think I'll try again, but with proper "hot" cleaner:
Post in thread 'Subaru FB25 - misfires and O2 sensor?' https://bobistheoilguy.com/forums/threads/subaru-fb25-misfires-and-o2-sensor.378857/post-6779783

Our 98 Outback had a hesitation at 169,000 miles that was said to be due to deposits. From advice on Ultimatesubaru, fed a half a can or can (don’t remember) of Seafoam into the induction tract via a vacuum hose.

The amount of smoke was unbelievable: but it worked!

 

[CarlB]

I soaked one by lifting one side, then used a sparkplug air fitting adapter+hose that was pointed vertically. This allowed me to pour in B12 until the cylinder was full enough for the berryman's to come out the top of the hose. Then I would top off as it found its way past the rings.

 

[mt23]

@mt23 do you have on hand that updated part# for the large PCV valve?

The larger PCV valve would help reduce the vapor/mist velocity, and help liquids drop out some. Reducing oil mist getting to the intake and pistons will help reduce consumption and ring fouling. I personally added a catch can too, and constantly caught oil.

Larger PCV valve part number 11810AA200. Requires larger hose and modification to existing hose from smaller pcv valve. This greatly helped my 2018 Forester FB25 6mt highway oil consumption which spikes after 3,000 miles of age on the smaller pcv valve, and 10,000 miles on the larger pcv valve. Larger valve is also 1/3rd the price. I intend to add air oil separator as mine still has quite a bit of oil in the pcv hose.

OP could try a piston soak at just after TDC for the cylinder using a hollowed out compression hose or regular hose attached to a hollowed out spark plug? I've wanted to try this.

I have also been recently using B12 as a flush in the oil as directed on B12 website. 1.5-2.0 ounces B12 per quart of oil in cold engine oil immediately before change. This has helped my engine and others.

 

[mt23]

I have also just started using B12 in the gas tank every 3rd tank as recommended on back of bottle. Curious if this will help, just like OP.

 

[ARCOgraphite]

Thats the plan so far - I think I've got the low-hanging fruit taken care of, I'm asking BITOG if there's anything else to try that's not too involved. There's been some good suggestions but I think that'll take me to where it's 80% effort for 20% improvement.

Subaru USA don't offer the 6MT in the Legacy anymore so I'm planning on keeping it as long as possible. I see a 6MT Crosstrek in your SIG - how do you like it? I'm on my 4th Subaru but I'm not against a fifth.

Wifes car. She is doing more highway driving again - that thing is geared for "trail slugging" spins at 3500 on the highway in 6th. Busy and Noisy. And the new engine all seem to develop a mechanical knock which doesn't inspire confidence.

I like the older, lighter more tossable Impreza wagon from the mid 90's with the 2.2 and solid cam. Those days are gone.

 

[D60]

Wifes car. She is doing more highway driving again - that thing is geared for "trail slugging" spins at 3500 on the highway in 6th. Busy and Noisy. And the new engine all seem to develop a mechanical knock which doesn't inspire confidence.

I like the older, lighter more tossable Impreza wagon from the mid 90's with the 2.2 and solid cam. Those days are gone.

The early '80s had that two-speed t-case. You just need that

In high school on the highway climb to the ski area my buddy used to clutch it, throw it into low range and release the clutch to make the squirrels work. I've never researched it but it must have only been a ~20-30% reduction, not 2:1 or more like trucks

 

[ARCOgraphite]

The early '80s had that two-speed t-case. You just need that

In high school on the highway climb to the ski area my buddy used to clutch it, throw it into low range and release the clutch to make the squirrels work. I've never researched it but it must have only been a ~20-30% reduction, not 2:1 or more like trucks

Those old Subaru didn't have much power. Sort of a front engine Vasserboxer from Japan. But quite loveable little puppies. Regs and then Toyota interest is beating the "Subaru charm" out of them these days and I don't like it one bit.