excessive blow by, + head gasket

I have removed the oil cap on 4 Prii and found excessive air blow by:

• Our 2010 with about 175 k miles on it
• @Pedal Logic ’s 2010 with 79 k miles on it
• @Pedal Logic ’s prius v with 50 k miles on it
• A rental Prius c with 400 miles on it

No coolant loss in any of those.

 

We also checked @SFO ’s 07 with 170 k miles on it and it also had blow by and no coolant loss.

Might just be an Atkinson cycle thing.

 

what about using oil?
what about the amount in the occ?

mine blows pretty strong out of the oil hole, nevertheless, I had only like 2oz in the occ after 5000 miles /

 

Mine uses a quart every 5 k miles.

None of the others sampled did.

Well not sure of the rental c, but since it only had 400 miles on it, I’m thinking it didn’t .

Hope that helps .

 

Remember the Gen2 doesn’t have the egr system.

So that’s an outlier.

 

So there are a few things going on here....

A failed HG will NOT impact "blow-by" in a meaningful way, it will typically present as coolant loss (inter/external), oil and coolant mixing in either of the other, or white exhaust at all times. In rare cases, a HG can fail between two cylinders and the compression readings will be identical on them, but the engine will have low power, potential misfire and generally no coolant loss.

You cannot tell anything about an engine's overall health by removing the oil fill cap with it running. It is more of a statement about the PCV system design than anything else.

The ONLY valid test, to KNOW if the cylinders, HG and valves are serviceable is a leak-down test. The instrument is relatively inexpensive, but it does require some form of air compressor. You do as many as three tests, but generally the first gives the needed results:
1) Cold & dry
2) Hot & dry
3) Wet (squirt oil in cylinders and rotate 720*, then test each in turn)

While the leak-down test is more complex, with the valves needing to be closed and such, it is also THE definitive test of an engine's health or lack thereof.

 

That can't be good.

 

It got HOT!

Did the engine use oil as well?

 

Overheating severe enough to damage a HG is also likely to have taken the spring out of the piston rings, causing compression loss and elevated oil consumption. Hopefully that did not happen.

 

There's a Technical Service Bulletin on the 2010 oil rings. First they do an oil consumption test, and if you "pass" that, they replace the rings, and the pistons, and check all the cranshaft bearing tolerances while they're in there. Has to be under 60K miles, which is usually too early for the failures.

The replacement piston rings indicated in the TSB are the ones that come standard in 2015 Prius. I did some research on the McGeorge Toyota parts department site, regarding the various model years, piston and ring part numbers:

2010~14 piston ring set part number: 13011-37110
2010~13 piston part number: 13101-37120
2014 piston part number: 13101-37240
2015 piston ring set part number: 13011-37260
2015 piston part number: 13101-37240
2016/17 piston ring set part number: 13011-37270
2016/17 piston part number: 13101-37250

It's a little tricky, but if you read through the above, look at the various combinations that were used over the years, I think it says that you can put 2015 piston rings (the ones specd. as replacement rings in the TSB) into a 2010 piston, they're compatible.

Also, @Ragingfit has said he thinks the 4th gen piston rings are also compatible, though there's no paper-trail of parts numbers to confirm that in the TSB's. If they're cheap enough, maybe get a set of both the 2015 and 2016 rings, confirm?

Note also: the tsb instructs to replace the pistons too, which is a bit involved, requiring heating to separate them.

 

Look at the walls, if you can clearly see strong "cross-hatching" on the walls and it is fairly uniform from top to bottom AND there is no apparent damage to the pistons, you can simply re-ring it (pull pistons, clean, install new rings, oil everything and re-install). You could also move to the parts in the TSB, either way, if the cylinders are uniform and undamaged all they need is a LIGHT wiping around with an oiled scotch brite pad or similar (some OEMs say you don't even need to go that far, but I've not tested it).

 

Well that's what I'm thinking, looking at the part numbers I listed. You'll see the changes in rings and pistons don't always happen tandem. In 2014 piston the piston is changed, but it still uses the old rings. Then in 2015 the piston remains the same, but the rings are revised. What this says to me is that they're all interchangeable:



This is from research I did at McGeorge Toyota. I'd enter my vehicle as a 2010, 2011, 2012 and so on, and for each year noted the parts numbers for pistons and rings. Hopefully their database is accurate. Before taking the plunge, maybe do the same exercise on the more official Toyota parts website. I really think they're all going back to the same source though.

And again, @Ragingfit says you can also use the 2016/2017 (4th gen) rings, p/n 13011-37270. Perhaps he'll notice this and comment, what's advantageous, going from 2015 to 2016 rings.