2011 Prius startup noise

Engine coolant level stable? How many miles? Ever cleaned the EGR?

 

The car can be more prone to do this, if you did a cold start, and quickly shut down, then it sits, say overnight. Why nobody's sure.

 

Was the tube as far as you went? With 180K, I'd think the EGR valve, cooler, and the intake manifold EGR passageways, will all be moderately coked up.

The head gaskets seem to be going, with monotonous regularity, between cylinders 1 and 2.

 

It may be closing the barn door after the horses have bolted, but always a good idea to do an EGR cleaning. Still, I would definitely consider a leak-down test, to see what's happening with the head gasket. Maybe also a block tester, which checks for exhaust gas in coolant. Anyway, regarding EGR:

I found draining two quarts of coolant (from the radiator drain), into a clean container, I was able to subsequently remove the cooler without spilling a drop: the level of coolant is below the EGR system. There's just a few tablespoons of coolant at the lower back corner of the cooler: lift it out without tipping, and pour it into the previous coolant collected. After everything's back together, pour the coolant into the reservoir. It'll be a little high, but in my experience was back to normal with a day or two driving. I also left the coolant vent open while adding coolant (only possible 2010/11 model years), and squeezed hoses a bit.

I found Oxi-Clean soaks slow but effective for completely cleaning the cooler, and also ran a thin wire through to aid with circulation. I've not tried it, but @Raytheeagle swears by pressure washer for this.

You can also use Oxi on the intake manifold, something that's really part of the EGR circuit, and should be cleaned as well. While you're doing the intake manifold, clean the throttle body too. There's no need to disconnect it's coolant hoses: just unbolt and lift off the throttle body, lift it up and out of the way.

The EGR valve is mostly aluminum, so I would not use Oxi on it, just carb or brake cleaner. It's relatively easy to clean. I tried but wasn't able to break loose the screws on the black cap. Maybe for the best: it's relatively easy to clean; I was able to gently pry up the valve and clean around anyway.

You for sure want to remove the wipers and cowl, and it's good to have the car up slightly on ramps or safety stands, and the undercover removed.

Some boiler plate info:

The simplest way to see where you're at, is to check the degree of carbon build up in the EGR pipe, a stainless steel connecting pipe between the EGR valve and intake manifold. Watch @NutzAboutBolts video #16 here:

Nutz About Bolts Prius Maintenance Videos | PriusChat

Two or three other videos linked there too, for the full cleaning of the intake manifold, full EGR clean, and Oil Catch Can install.

Good thread:

EGR & Intake Manifold Clean Results | PriusChat

Another:

Oil Catch Can, Eliminate that knock! | PriusChat

Some tools worth having:

E8 Torx socket (mandatory)
E6 Torx socket (optional, but good to have, to remove the throttle body studs from intake manifold)
3/8" ratchet wrench, regular and long handle, flex head, you can never have enough
1/4" ratchet wrench, or 3/8" to 1/4" reducer
Ratchet extensions: you can never have enough
Long needle nose piers, straight and bent tip
Ratcheting 12mm box wrench (optional, but makes disconnection of the EGR cooler from exhaust easier)
Torque wrench (3/8" and 1/4" both good to have)
Floor jack and safety stands (or ramps): basically some method to raise front, if you need to take underpanel off, which you may need to, both for access and to recover dropped items.

See the attachments for all the relevant torque values, more info.

 

Go for the pressure washer .

With a pressure washer, you are in and out in 10-15 minutes .

The setup and disassembly are the longest bits of the job.

And you get the cooler spotless in the process.

 

oh boy

 

some have found it more cost effective to put in a low mile engine

 

Leak-down test first, see what's leaking into what, if anything?

Boroscope check of the cylinders for coolant is something else you could do.

It's common for there to be oil below the throttle body. There'll be a pool if you don't have an oil catch can, say at least 1/8". With and OCC it'll be "oily", nothing more. I suspect some oil spits out of the intake ports