2010 knocking after sitting

Changing the EGR may do it

 

The mechanic will have to go outside of the manual, as the egr cooler and intake manifold are most likely plugged.

How much oil does your Prius consume?
Has the egr circuit been cleaned?
Is the engine coolant level stable?

Good luck and keep us posted .

 

My bet is they just did the egr valve and did nothing else.

You could pull the egr pipe and see the condition, but the intake manifold and egr cooler will be severely plugged.

When you attempt this service, look for an independent mechanic as the dealer will not take this job on. Might want to look for a spare egr cooler as the one that gets pulled will be coked up and will take time to clean.

Good luck and keep us posted .

 

As Raytheeagle sugguested, please do yourself a favor by cleaning the egr cooler/pipe/intake manifold to save the head gasket, and do it ASAP. I hope the knocking has not damage the head gasket yet.

Best of luck!

 

The EGR cooler is the gold mine.

 

Probably the head gasket has started to leak

That is why when sitting for more time it knocks. Probably some fluid leaking in one cylinder a bit. Check missing coolant

Could be also an injector leaking

 

Do compression check. Most likely head gasket.

 

This got me looking through the repair manual. Found the compression test instruction, and be forewarned: it does use Techstream. Not sure if there's a work-around for that.

But also, casting fore and aft a few pages found various other inspection procedures, so "printed" a compilation of all. The compression test is in there:

 

To see am injector leek you have to remove or and test it

However I still think it's the head gasket

 

The workaround I did when I was diagnosing mine was this. Remove all coils and plugs. Install tester in cylinder. Put car in Ready mode and push down accelerator. The resulting spin up of engine will satisfy the requirements of test. I had 190 psi across the cylinders after my bent valve got replaced.

 

What about disconnecting the injector leads, avoid a gas wash? Or would that prevent the car going into Ready?

 

No longer then it takes to get a reading, I didn’t worry about it. But that’s a great idea.

 

When the car is hot, the deposits on the intake are softer. But as the car cools, these deposits harden, and it’s more difficult for the engine to pull in the fuel/air. There are some fairly small inlets in the intake manifold which can partially or fully clog with deposits.

This is why I would begin by cleaning out the EGR pipe and the intake manifold. You need to use new gaskets when you do these tasks! These are fairly simple tasks. The EGR and EGR cooler are more difficult. While you have the intake manifold off, it’s very easy to replace the PCV valve, so do that at the same time.

By way of explanation: Fuel and air enter your engine through the intake manifold. But in addition, pressure which builds inside the engine is vented into the intake manifold, so that it can be burned instead of vented to the atmosphere. That’s what the PCV valve does, but it can also let oil enter the engine, which can cause deposits and other problems. In addition, some of your engine’s exhaust gases are routed back into the engine to be burned, and that’s what the EGR valve does. So a problem with the PCV or the EGR, and time itself, will gradually clog the intake manifold.

 

I agree with most everything, but when I went through these chores, albeit with only a bit over 70K kms, I didn't change any gaskets. They all looked very good, still very pliant. But yeah, maybe better to be safe, who knows.

 

Round 1 I had new gaskets, round 2 I went with what was there.

Round 3, might just keep everything the same too.

 

To each their own, but OP has 246k miles on his Prius, I would assume the intake manifold gasket will need to be replaced once opened up for cleaning.

 

I’d have a spare set around just in case.

The elastomeric material that is used for the gasket does not take a set very easily, probably even over 246k miles i’d bet.

But life does favor the prepared .