Water pump or Head Gasket

If the EGR system has not been previously cleaned, very likely the head gasket. Leak-down test is definitive for determining if it's leaking and how.

The water pump replacement is worthwhile; they seem to prone to failure somewhere between 100K~200K, but I'd check the head gasket first.

 

$1,300. for a water pump? any other mechs in the area?

 

This engine does not put coolant in the oil, it burns it. No white smoke or loss of power at first because it normally seals up after a few minutes. An occasional severe rattle in the morning that sounds like a broken rod is the early sign. Later the coolant level drops enough to overheat, a bad sign for an aluminum engine. At this stage a borescope inspection of the cylinders tells the story with a steam cleaned piston.

No, it is not worth $1300 for the water pump parts cannon. Most average mechanics have not seen how a Gen3 head gasket fails and the symptoms it presents. A dealer has seen it, perhaps every week. Some shops do three a week. In California there is one shop that does it mobile and is now selling franchises. California, Florida and Texas have independent hybrid shops specializing in head gaskets and hybrid batteries.

What if you could get a head gasket for $1550 or $2,000? Many do. What if you really need an engine? With this car, a known flawed engine with many many head gasket problems, an engine is what you probably need. I would say 98% because of history and the dealer diagnosis. What if you can get another engine for $3,500 (used) or $5,000 rebuilt? Many do.

 

Water pump really easy repair.
Under $300 if you do it yourself.
The car will run very rough for ten seconds after sitting... If the head gasket is bad.
Most of the time if you are low on water it's the head gasket.
Expect more very expensive things to happen
Very unreliable once past 200,000
Brake system will go out $3000
Traction battery $1600 if u do it yourself
Gen 3 really not a car you can count on gets good mpg but u loose all the gas saving with super high repair costs.

 

Hi @Tim Jones. Could you give me some detail on the $3000 repair on the brake system?

To the OP, @sterlingtech, what's the year and which sub-model?
Also, what is the coolant level and when was anything last done to it?
Do you have the specific code stored by the ecu?

[EDIT] I see it now. 2013 Prius Three. I failed to look in the right place for this.
No telling what it is now, but I would have to agree with RJ. Sooner or later, this engine is going to fail (IMO).
For me, our car has 130k miles on it, and because I can do the work myself, I am putting a rebuilt engine in mine for $4500 including new water pump and various other parts. It was much less expensive than trying to replace the car.
I got my engine from Hybrid Pitstop in California. It has updated pistons and rings, and a Fel-Pro head gasket.
If you're unable to complete the work yourself, I would highly recommend finding someone to either rebuild it, or install a rebuilt engine. I would not go with a "used" motor. You'd just be paying for an engine with the same issues down the road.