We have now done 3k+ miles since the new cooler/EGR valve and intake cleaning. New updated spark plugs and PVC valve as well. No oil use at all ... car now past 216k. i was suing some previous to the fix. We were getting the EGR code and 2/3 miss prior to the fix. Car has never used any coolant.
I'm surprised about the oil .. checked it a few times. It's kind of scary that a car with so many miles can have oil so clean that you have to check it a few times to be sure where it is on the stick. It still right up around the full mark. It was using well over a quart in 10k. I mentioned in another thread that the slight engine flutter (for lack of a better term) as you pull away from a stop has also not come back -- noticeable under very light power around 10mph. I have to believe this was unequal EGR gas going to the cylinders because of the almost totally blocked intake.
i find it amazing that permanent damage wasn't done. i guess if you escape without the blown head gasket,you're good.
I'm trying to understand the mechanics of a blown HG due to the clogged pipes? My only thought is the partially clogged cooler allows for hotter gas that overheats the heads? Maybe the partially blocked intake will cause missing -- but i don't see that causing a head gasket to fail? I'm thinking the particle clogged cooler adds to the oil use as well .... I think that's why it started to drop after increasing. I'm thinking as the cooler became more clogged it allowed less and less air ... less air is less heat = less oil use.
It all adds up to catastrophic engine failure if the signs are ignored. People like me buy the ones that have been the most neglected, not realizing the fuse has been lit on the bomb(figuratively speaking). Then when it blows, we either buy less worn out engines, or Frankenstein together the love child of a Gen 4 block and a rebuilt Gen 3 head.
Anything burns hotter and faster with more oxygen. EGR is just a way to remove the oxygen from the fire in your engine and at the same time increase the thermodynamic engine efficiency. When comparing 0% EGR from 20% EGR on a different engine the result was 20% higher peak cylinder pressures and 150*C (270*F) higher cylinder temperatures. My educated guess is that an EGR blockage results in a hotter engine that burns oil more easily. Higher pressures may unseal the engine leading to oil burning as well.
Maybe a malfunctioning PCV valve is a factor too, in increasing oil consumption: if the crankcase isn't venting properly, when pistons come down air/oil mist is forcing up past the rings into the combustion chamber?
WOW...you mean if we do preventative maintenance "beyond" that spelled out in the owners manual...our vehicles work better?
Same fluids, same filters, same smog equipment, same shocks, same bearings, same isolators, same everything...we just have the hybrid stuff too. So change your DOT 3, WS, oil and everything else per industry standards,..not MINIMUM mfg recommended or not even mentioned.
It would be interesting to know the temp of the air coming from the EGR valve -- the air being injected through the intake ports would have to be hotter (even with a working cooler) vs the outside air. The cooling effect in the CYL would only come from the lower combustion temps due to lower O2 levels. The coolant is 200 F .. so it's can't lower it to ambient temps. Would this hotter gas from a non working cooler really add much ? or is the hotter combustion temps when the system is fully plugged causing the head gasket problems? In my case I was getting #2 misfire (not all the time) ...my mechanic said that was the only port that was partially open when we removed the intake. My thought was this was allowing a slight change in intake air to that one cylinder -- throwing off the engine. It's really hard to tell as my system was so clogged .. I don;t see how much (if any) air was getting through the cooler. I was getting the EGR circuit code .. I was not going to play around with cleaning the valve ,, and the cooler was too clogged to clean in a timely manner ... so that got replaced with a new part as well. With a few k of miles now -- it's clear the cooler and valve were the problems. The replacement OE plugs had about 60k + on them .. and did not look perfect (as they did when I replaced the OE set) ... so I'm thinking maybe the higher oil use and possibly high Cylinder temps(?) effected them to some degree. When I found out that the plug had been changed to a hotter plug -- for $40 bucks I ordered up a set from Toyota. I had a lot of oil sitting in that intake TB area -- we also did the PVC valve as its so easy to replace with the intake off.
Think of it this way: how thick is the metallic head gasket and how much temperature imbalance would it require to distort it. The gasket is thin and temperature variance can have effect on the metals properties. Since metals change with temperature, even a small imbalance could have effects.
IMO it would be more engine specific vs just saying "thin head gaskets". For various reason some engines are prone to head gasket problems. Typically they have a weak link someplace in the design that corresponds to a particular area that also overheats when things go wrong.
At the highest. Around here at least, monitoring with ScanGauge (hey: wouldn't it be nice if the Prius had a coolant gauge...), I'd see a range of temps, maybe averaging around 150~160F? I think it's not so much "hotter gas" as a lack of cooling gas with reduced oxygen. It'll take an oil catch can install to prevent that coming back.
