2013 Prius Knock and losing coolant but oil looks fine

What you get in your catch can. Is going to have residual moisture in it The little drips that are coming in cylinder 1 2 3 whatever it is That's causing the rattle as it quenches the fire It's like you got a fire extinguisher built into one of your cylinders Not really ideal when you need the fire to power your engine or make the power your engine needs to make the fire is what it's all about now you're quenching that with drips of coolant coming to your head gasket what you're going to catch in your catch can is that vapor moisture and oil which is what you see I think in the second picture what's in the oil pan will not look like what's in the catch can as you're seeing when you pull your stick It's not like the old days where you have a massive flood coming through the head gasket dropping on top of the piston going past the rings and dropping into the pan and getting stirred up to the coffee light mixture You're used to viewing a long time ago.

 

What’s the miles?

I’d ask about EGR and intake manifold cleaning too, but that might be considered “leading the witness”.

 

Just because coolant isn't mixing in your engine oil, does not eliminate the possibility of a blown head gasket.

If you can borrow a camera (bore-scope) from your local auto parts store, compare the top of cylinders 1&4 to 2&3. The piston tops should all be pitch black with carbon. Any piston top that looks like it's been steam cleaned, has coolant leaking into it. Blown head gasket.

Good Luck....

 

Those pressures are not good, probably because of procedure needed with Techstream. 157-199 psi or more is the min-max. Regardless a borescope inspection is preferred.

From Manual:

Warm up engine.
(a) Put the engine in inspection (Maintenance) mode.*
(b) Warm up and stop the engine.
(c) Remove the 4 spark plugs

Inspect the cylinder compression pressure.

(1) Insert a compression gauge into the spark plug hole.
(2) Connect the Techstream to the DLC3.
(3) Turn the power switch on (IG).
(4) Turn the Techstream on.
(5) Enter the following menus: Powertrain / Hybrid Control / Active Test / Compression Test / ON.
(6) Fully depress the acceleration pedal.
(7) Depress and hold the brake pedal, and turn the power switch on (READY).

NOTICE:
The measurement must be done as quickly as possible.
 Noise may emit from the transmission. However, this is not a malfunction.
 Always use a fully charged battery to obtain an engine speed of 200 rpm or more.

Standard compression pressure:
1373 kPa (14.0 kgf/cm2 , 199 psi) or more
Minimum pressure:
1079 kPa (11.0 kgf/cm2 , 157 psi)
Pressure difference between each cylinder:
98 kPa (1.0 kgf/cm2 , 14.2 psi) or less

————————————————
* Inspection (Maintenance) Mode Using Techstream:

Activating maintenance mode (Using the Techstream)

Connect the Techstream to the DLC3.
Turn the power switch on (IG).
Turn the Techstream on.

Enter following menus: Powertrain / Hybrid Control / Utility / Inspection Mode - 2WD

Check that "MAINTENANCE MODE" is displayed on the multi-information display

Start the engine by turning the power switch on (READY) while depressing the brake pedal.

The idle speed in maintenance mode is approximately 1000 rpm with park (P) selected. The engine speed increases to 1500 rpm when the accelerator pedal is depressed midway with park (P) selected. When the accelerator pedal is depressed more than midway, or when the accelerator pedal is fully depressed, the engine

Do Not Drive in Maintenance Mode!

 

Borescope Video

Car Care Nut HG Borescope at 10:57, watch at least through 14:00

Note cheap borescope with one camera are not able to see the head gasket

 

Try leak down test?

 

The 200 psi readings are at 850 rpm. 150 psi is typical at 250 rpm. Consistent pressures are key at any rpm.

Compression is not your problem.