2007 Prius Piston Soak

[oggb]

UPDATE

Alright, I think I’m ready to declare this a success for my ‘07 Prius as well.
It’s been 500 miles since the soak. Oil consumption is drastically reduced so far. Previous owner states consumption was as bad as 1 qt. per 500 miles in some cases.

With fresh GTX HM 10w-40 after the soak, oil level is down maybe 1/16” in 500 miles.

Before you call 10w-40 “cheating” to reduce consumption, I tried SuperTech 10w-40 before the soak, and 1/2 qt. was gone in 850 miles.

The oil is still very light colored and “new” looking at 500 miles, whereas the oil turned really dark amber to black in just a few miles previously. I know you can’t tell much by how oil “looks” to the naked eye, but this all lines up and makes sense to me, at least.

I’ll try to post an update in the future as well. So far, I’d completely recommend a piston soak if you have a Prius with a drinking problem.

I guess the acid test will be getting back to a 5w-30 synthetic for the cold MT winters.

Glad to hear it's working!

Oil weight never made a difference in mine before the piston soak. 15w-40, 10w-40, 10w-30, synthetic, blend, dino. Didn't matter, drank 'em all at the same speed. That's why after just 500-1000 miles of driving I knew I'd fixed the problem.

It's such a simple procedure on the Prius it's almost like why not at least try it?

Did yours smoke like crazy when you first started it?

 

[Cheenist]

Glad to hear it's working!

Oil weight never made a difference in mine before the piston soak. 15w-40, 10w-40, 10w-30, synthetic, blend, dino. Didn't matter, drank 'em all at the same speed. That's why after just 500-1000 miles of driving I knew I'd fixed the problem.

It's such a simple procedure on the Prius it's almost like why not at least try it?

Did yours smoke like crazy when you first started it?

I had my wife filming and everything for the first start after the soak, but the smoke show was really disappointing. A few puffs is all I got. I slurped all the liquid I could get through the spark plug holes with a brake bleeder vac pump, then I did a couple start cycles with no plugs to blow more B12 out. I guess I was a little nervous about hydro lock.

Maybe the lack of smoke was due to very little B12 left in the cylinders?

 

[oggb]

Yeah, maybe. I just blew mine out with the air hose real quick and threw the plugs back in. Tops of the pistons were really wet. Mine put out a decent little cloud of smoke for ~10 seconds then stopped.

I doubt the smoke means much in this case. A lot of the crud from the oil control rings would've ended up in the oil pan.

 

[nthach]

I’m doing the soak in mine right now - in two hours, cylinders 1, 2 and 4 are dry, cylinder 3 is holding liquid still.

As of an hour ago, I sprayed down a few seconds worth of Valvtect Marine Motor Decarb - it’s the same composition and smell as the old ACDelco X66/Motorcraft Carburetor Tune-Up Cleaner into 1/2/4 and more B-12 Chemtool down 3. I’ll let it soak overnight, and then I’ll turn the engine over by hand and focus my effort on #3.

 

[nthach]

So I checked on the car this afternoon after last nights chemical addition. Cylinder 3 which was full of B-12 Chemtool leaked down overnight. I heard it drip down when I turned the engine over with all the spark plugs installed loosely last night. The rest of the cylinders drained their dosage of Valvtect quickly.

I added in another shot of Valvtect to the rest, and a repeat dose of B-12 to #3. I’ll blow the cylinders dry of liquid, add a little motor oil to lube the rings and let ‘er rip tonight.

 

[nthach]

I buttoned the car back up tonight after another 4 hours of soaking. I blew the cylinders with compressed air to get the solvents out to avoid hydro lock. I also saw a fair bit of carbon blow out. The spark plugs had 80K on them, no need to change them.

In went a frankenbrew of 1 quart Valvoline Premium Blue Restore and 2.5 quarts of Formula Shell 5W-30(I accidentally grabbed a 10W-30, but the VPBR is also a 10W-30, but thick). Started the car up - it stumbled for 15-30 seconds and then idled normal. No smoke show or twisted rods. The car seems to run better but that could be a placebo. The oil is turning color already. I’ll run this fill for no more than 1K.

I have a quart of the Chevron-made BMW/GM Top Engine and Fuel Injector cleaner on the way - part two of this experiment is to soak piston #3 with that stuff. The rest of the cylinders were dry in hours. I’ll gas up and dump in 1/2 bottle of Red Line SI-1 tomorrow. This car has been fueled with Top Tier or Costco gas for as long as it’s been in the family. I’m assuming the carbon buildup on the pistons was pooled oil that got oxidized and burned, like a cast iron pan - not the normal coating of carbon on a well-tuned engine.

 

[meep]

@JRed , it sounds like the cleaning was totally the right path. Consider keeping a long term dose of seafoam in the crankcase, such as a half can or less? Ive done this with several high mileage vehicles, including our current Lexus, resulting in less oil consumption or less noise..... over a long period, not overnight. I’m surprised by how coked up these things become nowadays, and a little seafoam has helped. Now... I’m assuming the prius engine is not inherently demanding on oil, as my engines arent, and I generally don’t romp on them much. The Lexus probably is more high strung but we loaf about 96% of the time. Anyway, since the soak did help, a long term, gentle cleaner may get a little deeper if anything was missed. Nice work!

 

[oggb]

I heard it drip down when I turned the engine over with all the spark plugs installed loosely last night.

That was actually something I don't think I mentioned here. I would fill the cylinders with B12, thread the spark plugs in, and gently turn the engine by the crank bolt. 1 and 4 on mine drained quickly, 2 and 3 were better. I also did as you did and blew everything out

I’m assuming the carbon buildup on the pistons was pooled oil that got oxidized and burned, like a cast iron pan - not the normal coating of carbon on a well-tuned engine.

Yeah, I think it's just the result of the car burning a lot of oil over time. Figure mine burned at least 25 gallons of oil in 100k miles.

I’m assuming the prius engine is not inherently demanding on oil, as my engines arent

It really isn't. The problem is that as with other Toyota engines that are famous oil burners the small holes behind the oil control rings are too small/too few and end up getting clogged. That's why Toyota's fix when they finally decided to fix this problem with the Prius in ~2015 was redesigned rings and pistons.

 

[nthach]

70 miles since Tuesday night - car seems to run smoother and the slapping/rattle which I assume is the timing chain or piston slap is gone.

I still plan to soak the #3 piston with the BMW TEC and dump that frankenbrew before 300-500 miles rolls along.

 

[meep]

@JRed , very interesting. The 3.5 v6 in the 2014 GS we have came home with a whole lot more piston slap than I heard on the test drive (like, none.... I heard none on the test drive). On cold winter days it thumps hard, until it warms up and its fine. Though the engine seems spotless, I splashed some seafoam in the crankcase and have been dosing the fuel with MMO. I wasn’t expecting anything, but it’s been 3 months now and the noise is reduced by maybe a third to half.

could this be related to clogging of the oil control rings? It came used with 73k on it, in good shape but undermaintained, with the cheapest tires possible.

 

[oggb]

@meep I think the 3.5 is a pretty famous piston slapper isn't it? Never really heard of oil control rings exacerbating piston slap. I hate that sound though. My grandparents had a Buick that had awful piston slap and it was hard to believe a properly functioning engine could sound like that.

 

[meep]

@JRed - yes, it is... and I had no idea. Ive never seen that in a toyota product before and didn’t know to watch for it. Still a great vehicle to live with. The slap basically holds me back so I don’t hear it when it’s cold. as you said, “hate“ is a good word for the sound!

 

[nthach]

So I soaked the #3 cylinder with BMW’s relabel of ACDelco’s X66P this week. I added Schaeffer’s 131 Neutra to the oil and drive around the neighborhood. Did an oil change, this time with Vavoline MaxLife full synthetic and OE Toyota filter. Let’s see if my oil consumption problem is done.

 

[nthach]

With 1200 miles on the clock since soaking the pistons, I have to say this is a success. My oil level is still at the F mark. It would have dropped about a 1/4 way down by now.

I expect to do some yearly maintenance every 2nd OCI, either a quick soak or running BG EPR/Liqui Moly engine flush. I’m sticking to HM synthetic oils for now. but from my test of Valvoline Premium Blue Restore, I saw no MPG hit. And that’s a thick 10W-30. I’m thinking of using a Euro-spec oil or Rotella T6 Multi Vehicle if I can find it.

 

[oggb]

I have to say this is a success

Glad to hear! Mine is still burning so little oil I don't need to add any between oil changes.

from my test of Valvoline Premium Blue Restore, I saw no MPG hit. And that’s a thick 10W-30

I've run Rotella 15w-40 and T6 5w-40 before and saw no difference in MPG. The 15w-40 did drop MPG a little as temps cooled off in the fall.

 

[snoobler]

Bump.

Wanted to mention the friend that has the '07 did the treatment with B-9 and a 24 hour soak. His oil burn went from >1 qt/400 mile to < 1/4 qt per 500 mile. This is with mostly highway driving - little start/stop of the engine since they're rural. He would top the oil off every two days of driving. Now he does it about once every two weeks.

 

[nthach]

I’m 1300 miles into this OCI cycle. Shell Rotella T6 Multi-Vehicle(dual CK-4/SN rating but not Ford approved for the PSDs) and a Fram EG. I’m down about 3mm on the dipstick from the F mark.