Still P0401 after cleaning egr !! should we drive it?

So that's 104F...wonder what the temp of the EGR valve might have been at that point. And what the melting point of the plastic disc is... And whether Toyota engineers ever expected Aussies to do hillclimb races...

 

I think it's probably not necessary, unless you think you cleaned the springs off so thoroughly with such harsh solvents or something that there is now nothing protecting them from corrosion, in which case lightly smearing with your favorite grease or lightly spraying with WD40 or pretty much anything like that might bring peace of mind on that score.

 

Some high heat resistant grease on the threads is a good idea, maybe on the spring so it can
slide smoothly. WD40 probably wouldn't last long after the first time the valve opens.

 

All the stuff being talked about for grease or spray is in the actuator portion of the valve, not where exhaust is flowing over it, and the springs don't need lube because they aren't sliding on anything ... just possibly a coating of anything for corrosion resistance and only if the OP was worried about having very harshly cleaned them in the first place. Even a cooked coating of WD40 would still probably suffice for that.

And yes, it's good to avoid too much grease. The OEM didn't put a whole lot in there. Some of it did end up pushed off of the threads and piled up in places it did no good. I just scooped it back up from there and put it back on the threads.

Whatever they had used for grease, it was white, and didn't seem cooked at all, after however long.

Sounds like a successful repair.

 

You just need to coat it, not pack it like a wheel bearing.
Sounds like what you used will work. After a few thousand miles you can pull the top off and look at it.

 

Anybody notice the recent thread over in the c forum showing how that EGR valve even has the cooler juice routed through it, maybe keeping it cooler?

 

Just speculating: coolant would flow from valve to cooler? Or vice versa? Does it matter, lol?

 

good question; obviously it works perfect for dozens of other car models /

 

Interesting question. A related question: would head gasket failure occur if the four manifold ports clogged at the exact same rate (or if they never clogged but the EGR cooler itself clogged completely or the EGR valve failed and the car was driven 10s of thousands of miles)? Because if so, then the low-oxygen EGR gas may be necessary and blanking would likely make matters worse. If not, then maybe the ECU is smart enough to compensate for the presumed-even-across-all-cylinders lack of EGR gas (but can't tell there's uneven gas due to one clogged intake manifold port).

Either way, I'm just going to clean the system and keep it as Toyota's engineers intended, even though they obviously made some mistakes.

 

This is a good question. It seems that EGR cleaning is touted online as a preventative to head gasget failure. I am not really sure what the connection is, if there is any at all.

It seems to me that EGR cleaning is the best way to keep your EGR from clogging and thats about it. Its a worthwhile endeavour in my mind, but I never understood it to be anything more than that.

I should really say that I have 0 knowledge about even the basics of what causes a headgasget failure, other than somehow the gasget gets degraded and coolant and oil start to move through the gasget into the wrong systems causing big problems.

 

Right. I'm basing the EGR-headgasket failure connection off of what people on PriusChat say, which is that headgasket failure tends to be associated with cylinder 1, and intake manifold EGR port clogging is typically worst for cylinder 1.

People elsewhere say it's a thermal cycling thing...aluminum head and block acting differently than steel bolts and a gasket that couldn't make up the difference over the thousands/millions of on/off cycles that occur over 100-200k miles. Of course, that would imply that failures would be less common on primarily-highway-driven cars, which I don't think is the experience at least on PriusChat.

Possibly it's a little of both...or neither...as many point out, there are hundreds of thousands of Prius owners that never post on PriusChat, etc.