10K oil changes are BAD! ??

Unplugging it might be safer method---not that I recommend disabling EGR.

 

Could it be that as the EGR progressively gets plugged (from excess oil control ring wear, blowby, etc) the carbon does not foul all EGR ports at the same rate? We've seen enough evidence that EGR intake manifold ports 1&2 are typically more fouled with carbon deposits. Because of this, cylinders 1& 2 are most likely to be starved of EGR gas, causing overheating, knock and eventually gasket failure. Meanwhile cylinders 3&4 are getting an oversupply of the combustion cooling EGR gas. The knocking is only sensed on one or two cylinders, and the EGR valve test doesn't throw a code because "enough" exhaust gas is being passed - it's just not getting equally distributed across all 4 cylinders as the intake manifold gets plugged.

 

In my case port 3 showed the start signs of clogging, other ports were clean at 90.000 miles. Also not even a drop of oil under the throttle body.

 

Most of the Pruii cleaning anecdotes and photos i've seen indicate more significant carbon buildup in manifold egr channels leading to cylinders 1 or 2. But I think the knock and subsequent head gasket failure theory holds if the EGR cooler and valve have enough carbon-laden exhaust gas flowing to pass the periodic EGR system test, yet one or more cylinders isn't receiving its share of EGR gases. The test logic seems to assume the gas is being equally distributed to all cylinders when in fact they are not, leading to unequal combustion temperatures across cylinders and high stresses in those that are knocking.

A better failure mode would be if all four EGR channels got plugged at the same rate because the EGR flow test would fail, throw a code, and the ECM could adjust the timing to avoid pre-detonation. For these reasons, I think it could be wise to perform the relatively easy mainenance chore of removing and cleaning the intake manifold/EGR channels at a greater frequency (say every 50K miles) vs the PIA EGR cooler itself ... even if the EGR cooler is clean enough to pass the periodic flow test, the engine isn't healthy if one of the cylinders has a partially blocked EGR manifold channel and is running hotter than the rest.

 

It’s 91 octane for ours, always has, always will. (Willing to blend in 100 if needed). Nope, don’t want any knock…

 

And this alone will keep the chronic head gasket failure from happening? Is that the idea?
Or do you still do the intake/EGR cooler cleaning?

 

We have a number of cars in our family and some are closing in on 200,000 miles....5,000 mile oil changes on them all and none are burning oil or have lost a head gasket. We have a couple with those V-6 2GRFE engines that are notorious to develop oil leaks but, so far, no issues at all.
The proof is in the pudding! But if folks are okay just doing 10,000 oil changes, that's their choice....hopefully it works out!!

 

I'm all there with you. I halve the coolant change recommended by Toyota, too.

Clean is always better than dirty. The oil operates the variable valve timing. Any dirt or variation of viscosity and/or pressure can cause erratic function.

 

Why? I have replaced the coolant in inverter together with engine coolant, but just to do it all at once and to optimize the coolant quantity. But I really do not see any added value in this. Both coolant were in great condition at 90.000 miles.

 

There has been speculation that deteriorated coolant has degraded the rubber elastomeric compound in the head gasket and contributing its failure. This opinion is from "The Car Care Nut" in one of his YouTube videos.

 

Good policy, one I follow (5000 miles OR 6 months, whichever comes first) but I don't think that'll save a third gen from head gasket failure. My money's on regular EGR cleaning for that, say at least every 50K miles.

 

I’m afraid our 10 year old v has 33.5k mi. I may be dead before I reach the point where it is recommended, but I’ll not clean it for a data point here…

 

I think cleaning the EGR cooler every 50K miles is onerous and excessive - about every 100K miles should be sufficient. But cleaning the intake manifold, the intake EGR channels and EGR valve every 50K is relatively easy and ensures each cylinder can receive its equal share of combustion cooling EGR gases. See post #204 for my rationale.

And yes, totally agree that a 5K mile OCI + oil catch can is the best preventative maintenance for the oil burning chain of events.

 

Yep Toyota coolant is not expensive and the reason we change it out at 50,000 miles or every 5-years, whatever comes first. (Dirty coolant can lead to issues with the head gasket and water pumps.)

 

Thank you for sharing your location. Looks like elevation 7000 ft? (Do you think this has anything to do with it)? Shrugs…

 

Gosh, I don't really know. Our standard gas is 85 octane and works just fine. Sometimes, when cars come up here from lower elevations, vehicles can run rough (the computer can have a hard time figuring it out) so just disconnecting the negative battery cable for a few minutes makes it reset the settings and then it'll run fine.

 

With our 2010 we piled on the miles "modestly quickly" in the early years, but now we're proceeding at "dead slow", pretty much in the same boat now, have 96K kms, just cleaned the full EGR for second time, and am a little too embarassed to post before pics of the cooler...

Anyway, everything's nice and shiny.

Part of my motivation was to stay limber on the EGR exercise. It really helped having the lower EGR cooler lower nut (and stud) removed, plus my usual bag-o-tricks, say for spilling next to no coolant, and so on.

 

I admire your work ethic, Mendel, and have greatly benefited from your findings with only 46K miles on our '12 v thus far.
Please post 'before' pics!

 

Likewise, my 2012 has only 28k miles on it.

 

That's exactly a suspicion of mine, as I've written in past posts. The EGR monitor test has to rely on just the single MAP sensor in the manifold, so necessarily it is just a test of the overall flow.

To make up the right overall flow, when some of the manifold passages are more clogged, involves delivering too much EGR through the others. So, in addition to too little EGR in some cylinders (and a risk of detonation), there's also too much going to others (and a risk of misfiring).

Between detonation and misfiring, you'd rather have misfiring (at least if you're a head gasket), but misfiring, if bad enough, can also sound awful, bang up the transmission input damper, and melt the catalytic converter innards.

Every so often we do get a report of a Prius with an engine that runs rough, only in the mid-load regions where EGR is used. If that's the pattern—engine runs nicely except at the exact times the EGR valve opens to let some EGR through—then those manifold passages are prime suspects.

I also second your suggestion that inspecting/cleaning the manifold is effort well spent. It is a much easier job than the whole upstream EGR ream-out, and it harbors the most convincing potential culprits, which the car's regular overall EGR flow test cannot check on.

Clogging locations upstream of that point, as well as the mashed ski-jump valve failure, are all in the purview of the regular overall flow test, so you can see those effects in the flow test results any time you want to look, or eventually in a P0401 code if the test result gets low enough (it has to get really low).