2011 Prius Head Gasket Failure

@mjoo did a flow experiment with his. IIRC, pouring a measured amount of water through one end, timing how long it took to get through. That'd be a good before-and-after test for everyone doing a cleaning, I think. Doubly so if they post the results here, and the miles they were at.

Water flow differences maybe don't equate to air flow, but it's at least a benchmark we can do.

 

Water flow (I used a garden hose) IMHO would better approximate the restriction of exhaust gas recirculation at typical engine operating speed. I.e. at 2500 RPM, the EGR circuit flows 1.9 x 2500 x 0.20 L/m = 950 L/m or approximately 16 liters of air per second. This is through a 1-2" diameter pipe.

After completing several oxi-clean soaks until the cooler was spotless I was surprised by the large drop in restriction. This was compared to just drilling out the fins with a copper wire and using carb cleaner.

 

Not only that, but oil clogging up the cooler is going to reduce its cooling ability.

 

Because the weather was nice over the weekend and I'm at around 143,000 right now, I was looking for a way to judge how worried I should be about the EGR system at this point.

I noticed that Techstream has an "EGR valve step" active test, where you can tell it to open the EGR valve in tiny steps numbered 0 to 110. At idle, I found that just setting mine to step 14 or 15 was enough to very noticeably roughen the idle, and 17 (out of 110) would just about kill the engine.

So at least I'm confident my EGR passages aren't completely blocked. I'm curious what the corresponding results are for people who have just completed a spotless Oxi-cleaning.

 

Since I am around 12000 miles post cleaning/engine install, i will check mine out tomorrow and post the result. Maybe that will provide an insight that can help the cause.

 

At 145k miles mine was completely clogged. I sprayed brake cleaner into one end and nothing came out the other. Granted, I bought it with that many miles and the original owner was in Arizona where it gets much warmer. I know nothing of how it was previously driven and from what I've read here, I believe that pushing the engine with aggressive driving or a lead foot contributes more to the carbon build up.

It's fairly quick and easy to remove the EGR pipe. I would check that out and observe the amount of carbon build up there. If it's thick then your EGR cooler has a ton more.

 

Thats very easy way to test if its completely blocked. Nice to know!

 

I'm sceptical, think EGR clogging is as inevitable as death and taxes. Not a fan of Italian tune up lol.

 

My version of Techstreeam will not run the EGR test. Fatal error. So looks like someone else will have to do it.

 

Maybe? Definitely !!

 

Which versions of Techstream have the EGR valve step test?

 

Well, 10.10.018 does for sure.

I was connected over a Tactrix Openport 2.0 dongle. I also have a Mini VCI dongle, but it messes up more often talking to my Gen 3.

 

The cooler is too cool for that to happen in it.

 

Would pushing the engine at higher RPMs not release more of the carbon and oil mix that builds up in the EGR?

 

It may, but deposits are going to build up over time no matter what.

 

The EGR cooler is a backwater. A tiny valve regulates flow; I don't think it matters what rpm or load conditions are happening.

 

Until contradicted by someone more knowledgeable, I assume there will be a higher proportion of carbon gunk in the exhaust when we push the engine toward max torque, therefore richer fuel-air ratio. Right?

 

generally, in fuel injected cars with oxygen sensor, the fuel-air ratio is kept constant, except for fuel enrichment at WOT. however, i was told it doesn't apply in prius, where redline and max power are reduced.