Oil Catch Can, Eliminate that knock!

It may partly depend on how you delete the EGR. If the ECM can tell the EGR is gone (such as if you electrically unplug the valve, causing P0403), then the ECM says "Schezbzflat! the EGR is gone! I shall super-retard the ignition timing to avoid detonation problems!" and then you probably don't risk the head gasket much (and just end up driving around with super-retarded ignition timing, reduced performance and MPG, and an overheated cat).

On the other hand, if you delete/block the system in such a way that the ECM doesn't know it, then you probably are inviting whatever damage you would expect from an EGR system that had blocked itself.

I wonder how long, in practical terms, you can have it deleted/blocked in a clever way like that before P0401 is reported (and the timing is retarded in reponse).

 

So is the computer really that dependent on dirty air in its initial startup air/fuel mix? If so, an easy way to recreate the startup knock would be to block the EGR and see what it does.

If so, what was Toyota aiming to do by the intake recall?

I'm not convinced the knock, the EGR and the head gasket are related. Or if they are, it's some reverse order. If we can prevent the knock, do we prevent the head gasket from going out? If we have perfectly clean EGR, but have daily knock on startup, will the head gasket be alright? I doubt it. The knock could simply be the tell tale symptom the head gasket has already bit the dust.

Standard order: take a car with a known good head gasket, no oil use, block the EGR and see what happens. If it knocks on startup, we know its probably the EGR.

The reverse order would be: Will a car with clean EGR, newer intake, not burning oil, OCC etc, but a small headgasket leak - will that car knock on startup? Probably.

Dilbone has had 2 headgaskets go on his car in a few years with the EGR being clogged. Lets blame that on the EGR.

My car has 220k, clean EGR, OCC, occasional startup knock, coolant level relatively stable, but burning oodles of oil (1qt every 1,000 miles or so). I can't decide if my startup knock is a minor head gasket, or a major oil burning issue.

 

Mmm no. Zero oil consumption here, and Exhaust Gas Recirculation was the degree of clogging you’d expect, when I did the cleaning (along with intake manifold), around 70k kms.

My take; thoroughly clean intake manifold and Exhaust Gas Recirculation every 50k miles.

 

Ok, so the EGR is gonna clog no matter the oil burning situation. I imagine the oil burning would probably increase the rate of clogging, though as well as messing up the cat (which I suspect happened on my car).

 

And I’m putting my money on the clogged Exhaust Gas Recirculation (and associated passages in the intake) being the main cause of failing head gaskets, due primarily to consequential raised combustion chamber temps. No empirical evidence, purely my opinion, but that’s where I’m placing my money.

When you look at those Exhaust Gas Recirculation passages on the intake, they’re invariably more clogged towards the cylinder one end, and that’s where the head gasket almost always fails first.

 

For comparison, our 2019 Prime at 30k miles and the oil catch can at 9 k mile install:



No oil consumption.

And the engine only runs about 33% of the time based upon the historical EV %.

While the egr system is different, oil blow by is not.

Add a catch can and prevent the spooge from recycling and your engine will last a bit longer.

 

Ok, so lets go the opposite direction - lets open the poorly flowing EGR cooler. If the car wants shitty air, lets give it all the shitty air it can handle.

What if the EGR was just a tube with cooling fins on the outside about 1" in diameter.

The coolant cooled exhaust gas can't be cooled that much, can it?

Kinda outside the realm here but what if we just plumbed the EGR further back in the exhaust stream? It'd get shitty air, but cooler shitty air.

 

So I wonder how long your car would go before it either A) knocks or B) has a head gasket go. Do we have any data on high mileage 4th Gen cars and their head gasket or knocking issues if present?

 

Google thermophoresis. When you cool shitty particulate-laden air the particulates stick to the cold plate like magnets. Colder the cold plate the stronger the thermophoresis.

moto g power ?

 

Ohhhh I get it.

The EGR isn't cooling the exhaust stream into the engine at startup. When exhaust is 250º and EGR is ambient.

It's cooling the exhaust stream into the engine at operating temp. When exhaust is 1000º and EGR coolant is 200º.

Is the EGR really cooling exhaust down to ambient air temps at operating temp? I highly doubt it.

Let says we stuck a big diameter tube in place of the EGR cooler. Same inlet and exit diameter. As we gonna melt the EGR valve and intake?

 

@soldierguy was local out here but ended up selling theirs when it was at 93k miles a couple of years ago.

I'm willing to help collect data.

But it'll take me on my own several more years to determine if the relocation of the takeoff point for the recirculation matters.

But when I do the spark plugs, the egr cooler will be on the list to do.

A bit more complex to do on the Prime / Gen4, but I'll take pics and document the findings.

 

You keep leaving out the fact that "consequential raised combustion chamber temps" is one of your assumptions, not something belonging on the right hand side of "due primarily to" as if your assumptions were being based on it.

Are those "raised combustion chamber temps" "consequential"? They certainly are for the creation of NOx emissions; that's the whole point. Does that make them "consequential" with respect to head gasket limits? What are those temperatures? What are limiting temps for head gaskets? What are limiting temps for head gaskets in cars that don't have EGR and operate above the NOx emission temperature thresholds day in and day out?

I would love to feel less like a broken record, but there are only so many ways to point out the same thing when it doesn't change.

There are some explanations of what EGR does for you that can be found without too much trouble and might interest you. You'd find that in a spark-ignited gasoline engine, there's a lot that "shitty air" can do for you (maybe better to say "intake charge dilution", as "shitty air" sounds like you've jumped to some conclusions already).

Your question about taking it from further down the exhaust is a good one: that's an actual difference between Gen 3 and Gen 4, which coincides with engineers developing another type of EGR, 'catalyzed EGR', where the diluting gas comes from after the cat instead of before. In that type, it is lower in pressure, and chemically different. It might not turn out to be cooler, as the cat does some serious cooking.

 

Exhaust Gas Recirculation gas, having less oxygen, dampens the explosion.

 

I probably should be starting my own thread will all of this, but I finally got the timing chain cover on after replacing the valve stem seals. There weren't in too bad of shape honestly...#4 def had some issues, but it really hadn't been using oil at all. Maybe a half a quart in 5k miles when I did my first oil change on it with 246k on the clock.

I had to pull the cover off twice, once because I thought I forgot to torque the chain guide bolts(turns out I had and didn't remember), after the 2nd installation I realized I had forgotten to encircle the entire water pump passage...so last night was the 3rd installation and I'm good to go with finishing this nightmare.

Next question is are there any special requirements for the initial start up? Turn the heat on high to keep the motor running? Idle for so many minutes before actually driving it?

 

@Ragingfit did some electrical monitoring before actual start up, to verify oil pressure was good. I’m guessing made the car “on”, not “ready” (two pushes of start button without foot on brake) to do this check. Maybe he’ll see this and post details. It is explained in one of the last videos of his engine transplant series. Those videos are linked in thread pinned at top of Prius v mods forum (obscure eh...).

 

So, I've searched and searched for info on initial start up and have seen nothing. I don't have working techstream so there will be no way to monitor anything. In the past I have just started the vehicle allowing it to idle up to operating temp to burp the coolant system before shutting it down. I am hoping the prius doesn't have some special sequence needed at first start up after a head gasket replacement. I should be ready for initial start up this evening at some point...gotta get oil and a new filter once I get finished buttoning up the intake and plenum. I'm leaving the cowl off until I know for sure it looks like I'm in the clear.

 

Ok, well I got everything put back together except the cowl just in case I had to get back in to check something. I powered it up, put the heat on high, and let it run until the motor shut off on its own once the cabin was good and hot...probably 5-6 minutes.

Motor took a minute or 2 to really quiet down and was running a little rough because my makeshift mason jar OCC was leaking around the fittings, once I pushed those down more securely the idle settled in and the motor sounded good.

After putting the cowl back together I took it out for an easy test drive, 10ish miles or so. I wouldn't say it knocked necessarily on the start up but it definitely seemed like there was a hitch in its giddyup, almost like a stumble on the first couple rotations...not the death shake.


Came back from the test drive and re-sealed the OCC fittings with ultra grey over night to tighten those up, this morning seemed like that same stumble at the initial start up but that seems to me the same as what it had been on first start up since I got the 6 months ago. Drove the 33miles to work and all seems well. I will be keeping a close eye on fluids and every initial cold start as nervous as a cat in a dog pound. I hope to at least make it until I can sell this thing without any issues.
My CE light is on but I don't know if that was from before the episodes before the work was done. I really need a code reader since I can't get techstream to work...maybe I do have a legit misfire on start up...not sure why that could be only at start up but I suppose stranger things have happened.

It has these spark plugs in it right now could that be a problem?
Autolite XP Iridium Spark Plug XP5683

Thanks to all who commented and made suggestions to me here in this monster thread. Much appreciated!!!

SM-G981V ?

 

Now that the head gasket has been changed again does your opinion from a few days ago change?

I do think a separate overview thread would be good. Anytime information gets included in an older 100 page thread it is quickly buried.

 

Wondering minds, how did you decide to go with these plugs?

 

Actually I've been looking at 2008 Gen2s with 150k or less miles on them at this point. I'm still not sure if I'm willing to roll the dice on this not blowing up on me again...I could sell this, buy another '08, not be charged the addition Ohio $100 reg for '09 and newer hybrids, and come out ahead pretty well money wise. However, part of the glutton for punishment I am makes me want to keep it just to see how long it will last with a clean EGR cooler...add another data point to the discussion...