Air bubbles in 2012 toyota prius coolant system

If the water pump is spinning at a speed slightly lower than what it should be, it will not trigger a trouble code. I have read many threads in this forum where the car is overheating from a water pump that is going bad without triggering a trouble code.

 

The air bubbles are not making it heat up. The water pump is not spinning fast enough, so the flow of water through the engine is not sufficient to cool it, and the coolant is boiling inside the engine water passages and forces "air" pockets back to the plastic reservoir. If you have the time, drain the coolant out of the car and remove the water pump, and check for resistance of spinning the impeller.

 

Personally, I would only buy an OEM water pump from a Toyota dealership. I have read too many problems with aftermarket water pumps going bad quickly, even the Aisin WPT-190 pumps purchased on Amazon.

 

I am pointing to it with that spring-like thing you see, that enters picture near top at left side.

circled in red now:

 

Because you are using more throttle going up a hill or mountain, you are creating more heat in the engine, which needs to be cooled down by the cooling system which is not able to do it because the water pump is not spinning fast enough.

 

How long have you owned the car? Have you replaced the head gasket or engine?

To your knowledge, has stop leak ever been used in the engine cooling system?

 

Hmm, Brian is suggesting the 'bubbles' are from boiling. From what I read, 50/50 glycol coolant boils around 220 ℉ if the cap is left off, but that point should be closer to 250 ℉ with the cap on and the system pressurized. Curious.

As for the pump target and actual speed readings over OBD, I would avoid reading too much into a difference if it is just a slight one. For example, this post seems to suggest that the actual RPM shown by Techstream can be lower by about 25 RPM than what the pump's actual tachometer is saying, and that also might not exactly match what the ECM is thinking for a target RPM. (The target RPM is only communicated to the pump by varying a pulse train's duty cycle within a certain range.)

So I think I'd be inclined to shrug off any target/actual difference that wasn't more than, I don't know, a hundred or couple hundred RPM.

 

@Stevenschu74#?20 I noticed (I could easily have messed it) one of Chaps questions.
When do you see the bubbles?

Don't know how else to put it. like how often do you see them? "all the time" doesn't really tell us much.

If you can be more specific about when you're checking coolant, what the coolant temp is, when you see bubbles and if you've ever checked coolant levels and not seen any bubbles.

edit: sorry Chap, I wouldn't have posted if I'd seen yours (#56 above)

 

@Stevenschu74#?20 Take a look at this thread:
https://priuschat.com/index.php?threads/245878/

 

@Stevenschu74#?20
Can you please give an update on your car? Did you fix the overheating problem?