2007 Prius B12 piston soak.

TLDR: Just did piston soak with B12. Did not turn by hand. Haven't driven much yet, but feels really smooth. Oil is clean, since everything else and draining the little bit that stays on the sump.



Purchased with 123k. Now has 194k. I used synthetic oil with 10k OCI, which helped to somewhat clean out a motor that was mistreated at a buy/here pay/here lot for a couple of years. (had to remove the gps tracker to get the obdii reader to work.)

Burned about 1 qt every 3 to 5 tankfuls. (900 to 1500 miles. we refill at 300 miles, after running out of gas once with 3 bars)

Started getting an intermittent P0420, and knew a piston soak would be good, but long covid kept me from having the energy. Kept driving as it was and the P0420 came back quicker and quicker, as expected.

To prepare, I bought a big jug of cataclean, a pint of auto-rx plus, 12 qts of Valvoline synthetic blend (all they had in stock at the Walmart) in a "wine box". I actually ended up liking the wine box a lot, as I found I could fill an empty 5 qt oil jug with the amount I wanted, making a single, easy pour into the crankcase.

I changed the very dark engine oil (8k on synthetic) using my pnuematic extractor for the first time. It got most of the oil out of the prius through the dipstick. I liked only needing a very small pan underneath to drop the oil filter and drain the little bit left in the oil sump. There was always a little bit left there when changing oil, and my oil would get darker almost immediately. So I tried holding a paper shop towel up to the oil drain to wick out the nasty stuff that was still left. A lot of thick stuff dripped out. I was planning to run this for just a tank or two, to flush stuff out. Then do the piston soak.

This oil change actually stayed pretty clean looking, but was easy to see on the dip-stick.

I put cataclean in a 1/4 tank of gas and ran that. It ran smoother, with no rough start/stops of the ice. Of course had no effect on the P0420.

After running a couple of tanks of gas, I started the piston soak. Cleaned pcv valve, and it rattled nicely before and after cleaning.

Then poured b12 into cylinders. The piston was near tdc, as it filled over the spark plug threads quickly. I could hear it tinkling down in the others. I kept adding a little to each cylinder over the next few hours until the 15 oz can was empty. I would replace the spark plugs after each fill (except the far left one, just a paper towel in the plug well) to keep the good stuff from evaporating out. I decided to leave it overnight.

Mid morning, I checked to see if / how much b12 was left in each cylinder by putting a q-tip down into each cylinder ( electrical taped on end of 12 awg wire) The q-tips all came back wet, with tea colored liquid. I did not turn the engine by hand, as I did not want to jack it up and pull the front wheel.

I extracted the liquid with my pnuematic extractor as best I could, and then put a towel over the empty spark plug holes and allowed the car to try to start a couple of times.

I had done a pretty good job of getting all the liquid out of all pistons except for the piston on the right. There was a nice brown spot on the towel from that one. Of course, by doing this, the filter got b12 oil circulated in it, so it would need to be changed too.

All carbon I encountered at this point was very soft and came off easily (spark plugs and bits that came up on tube of extractor).

I drained the oil, which looked pretty good in the extractor tube except for black splotches of loose carbon, black pepper medium size flakes.

The oil that drained with the filter was thin and pretty black, but not dirty or sludgy, if you know what I mean.

Draining the little bit of thin stuff left in the sump was easy and quick.

Filled with Valvoline synthetic blend and a bottle of Auto-rx and new Toyota filter. I liked that the gasket was pre-lubed.

Treated full gas tank with Cataclean.

No smoke on startup, just the smell of B12 chemtool. The car was blocked in, and it was cool out, so I left the car on with the climate in auto, to run the ice to warm up the car. Seemed to run pretty smooth. Then drove down and up a big hill. Acceleration was nice, and couriously, the SOC meter stayed green even after getting up the hill (200 or 300 foot rise, some of it at 25% grade). That has never happened before on that hill. Might have been the charging while warming the car in addition to the down hill charging, plus the SOC meter bars are not that precise, IMHO.

Went on a short drive today, and with the heater/blower on, it was not easy to know when the ice was running. The oil is clean enough that it is hard to see on the dipstick.

I plan on running with the Cataclean until I don't have anymore left (3 qt jug, should treat 90 qts of fuel, so 3 to 4 tankfuls, since I always fill at 300 miles.

I plan on changing this oil at 3000 miles, then one more Valvoline synthetic blend with a maintenance dose of Auto-rx, and then 3000 miles on that. Afterwards, will go on synthetic with Auto-rx maintenance and change every 5000 miles.

If the cataclean does not let me get inspected, I will change out the cat. Hoping I don't have to do that.

All in all, if running this smoothly is not just because of the cataclean, it is worth it just for that. If I live to regret not turning the motor by hand, it is easy enough to just do it again sometime.

 

Thanks,

I am going to keep trying, but since I waited so long I am probably best described as cautiously pessimistic.

 

Thanks for the pricing info. I am still hoping the cleaning works. I am just really swamped, having been too tired to do much for a couple of years. If I have to swap them, I will.

 

Thank you for the feedback. I made good use of some threads here, and at Bob is the Oil Guy, and reddit. Seemed best to start another one rather than reply to those, as their conversations kind of wandered.

A couple of things that I wish I would have done:

1. Squirting a little oil in the cylinders before closing it back up

2. I usually prefill the oil filter a little while lubing the gasket, before spinning it on, but skipped that since the filter gasket was pre-lubed. I won't do that again.

I have gone about 300 miles now.

No obvious oil use and still looks really clean. P420 is popping up more slowly than it was, but is still popping back up reliably.

The pneumatic extractor works well for me in this 2007 prius, ( can put the tube in and just to get almost all oil out ), but that was not the case on our 1997 tercel.

Even on the Prius, it does take a while.

 

I had never read any discussions about the pros and cons of pre-filling oil filters.

I had always pre-filled, to the extent allowed by the filter mounting angle.

The other thing I did like about the toyota filters was that in addition to having a lubricated gasket, the filters were covered to prevent dirt or debris from getting into the filter.

I had never considered the possibility of getting dirt on the wrong side of the filter element while filling it with clean fluid. I am pretty careful about things like that.

I can see how the additional handling could cause an issue while trying to avoid a different one, but after hearing the engine while it was waiting for oil to make it to the cylinders, I will continue to carefully pre-fill the filter.

 

Have not driven it asmuch as previously. Only at about 2500 miles, with a slight loss of oil and the oil is still clean on the dipstick.
Catalytic converter is back to throwing P0420 as quickly as it did before piston soak.

Piston soak seems to have been a good idea, and I wish I had done it before the cats got contaminated.

Might try to clean them. I woukd be more likely to get a replacement cat right away, but fear my fate would be more like the negative reviews.

Doug