Prius overheating after water pump replacement

If he has Toyota Techstream, it has a Data List function under Engine and ECT, where he can see both "Elec Water Pump Target Spd" (how fast the ECM wants the pump to run) and "Elec Water Pump Spd" (how fast the pump is in fact running), and both values are shown in RPM.

Techstream also allows you to pick a couple values and graph them while driving around, so it would be pretty easy to do that.

Various other professional-grade scan tools ought to be able to show the same PIDs.

That would take some improvisational skill—I don't think the repair manual offers any ready-made procedures for it—but it's mostly a tedious matter of buckling down to disconnect various hoses to isolate different parts of the coolant path and apply some repeatable water pressure to see what happens.

An absolute or severe blockage might be unmistakable, but some less-severe restriction might only show up on comparison to some other, known-working Prius.

There was a recent thread showing the basic game plan except that the cooling system for the inverter and transaxle was concerned, instead of the one for the engine. In that case, a wayward bolt was found inside one of the hoses, blocking it. (I am hoping that particular explanation stays a rare one.)

 

So is it a plumbing issue or a controls (electronics) issue?

 

That's the present open question, with a few available ways of getting at it.

 

It seems obvious the car knows there is an overheating issue. It could be as simple as a fuse or bad connector. I would try to figure out why the fans are not running. If they run in ac mode they are obvious good. So they have some king of relay or wiring issue. I would certainly run the ac continuously as a temporary workaround of the fan issue.

The free or slight fee upgraded "Car Scanner" app with a $30 bluetooth scanner will give you basic data.

This is a screen I use.


Finally, I would spend $150 for a dealer diagnosis rather than further risking the engine.

 

Is that screen showing 62.5% control duty for the (engine) water pump, and 3375 RPM for the inverter pump?

There should be a separate PID for RPM of the engine water pump. Both pumps are variable speed in Gen 3, with essentially the same control scheme, but controlled independently.

The engine water pump RPM is a PID of the ECM, while the inverter pump RPM is a PID of the power management control ECU.

Edit: come to think of it, I think the screen is showing both the duty control output and the RPM for the same pump, the inverter pump, and it would be clearer if the control duty label said it was for the inverter pump.

The reason I think so is that the power management control ECU exposes a PID for its control output to the inverter pump, in units of percent duty cycle.

The ECM exposes a PID for its control output to the engine water pump, but that one is labeled Elec Water Pump Target Spd, and it is given as a target RPM.

 

There are about 400 Prius data points provided by Car Scanner. The labeling of three user configurable "dashboards" can be edited. The list of points available in this app includes these water pump options:

 

When the car is hot, does the heater put out very hot air from the vents? That would tell you if there is any coolant circulating from the ICE through the heater core.

Car Scanner gives decent data on a Gen3. You might want to check out the ThinkCar ThinkDiag OBD2 device and app or the XTool Anyscan. Both are pricier than Car Scanner. On a Gen2 I found ThinkDiag is very close to the functionality of Toyota Techstream. Anyscan isn't quite as complete but has codes, data, and bidirectional controls on all systems.

Either one would let you command the water pump on, watch pump RPM data, etc.

Posted via the PriusChat mobile app.

 

Gen3s always have oil in the intake manifold, primarily from a bad pcv design. The only option for reduction of oil and condensate in the intake manifold is an oil catch can. Unlikely to be a cause of overheating.

Overheating due to a loss of coolant through the head gasket is common as are clogged passages when someone tries to fix the hg with sealant. Or they have a bad water pump often caused by incompatible coolant or they installed counterfeit "oem" water pumps which fail quickly.

 

If three different mechanics diagnosed a head gasket on a gen3, I would tend to believe them, especially if one or more of them verified water pump operation and used an in cylinder borescope to confirm the head gasket issue.

Unfortunately the combustion gas check is not always accurate on common gen3 head gasket failures. Especially in the early stages where small leakage into the cylinder only happens after the engine cools and the coolant system maintains pressure. But an occasional severe cold start rattle that some like to blame on the egr is a good indicator. At first the coolant quickly stops seeping as the cylinders start firing. As a failing hg gets worse the traditional combustion gas analyzer may work but those engines are usually blowing white smoke out of the tailpipe and losing coolant fast where its obvious and not just when cold. A borescope inspection as shown below is more definitive in early stages.

Sometimes a quick fix sealer has been used which temporarily seals the hg leak but clogs up other lines or passages.

Again, a dealer diagnosis would be money well spent. Otherwise ask your three mechanics HOW they determined it was the head gasket and report back.

Bonus Tips:
In the wiring diagram below an experienced tech can easily verify the water pump for 12v power and ground. However the two lines highlighted by the red pointers are a form of pulse width modulation that controls the water pump's speed. These lines are normally inspected with an oscilloscope or advanced graphing meter. Most simply verify movement in the reservoir but if its not there the tech has to move to working from the repair instructions. Similar diagrams exist for the radiator fans.

 

I don't like the recurring abs lights but they could be false or they could be the common brake booster failure. Brake booster is not going to cause overheating.

Simple test for the fans. Just leave the ac on which should keep the fans on continuously. A normal cooling system can easily handle the engine and ac even in 105f weather without ever overheating.

When that fails and it still overheats, spend the next $150 at the dealer and know what the problems really is/are. Then consider options to fix it.

Yes, it is possible to blow fuses or have a bad ecu. But its not going to run for hours with blown fuses. If you see reservoir movement (verified?) most, if not all, of the water pump electrical is decent.

It is possible (probable) to get two faulty aftermarket water pumps. We know only OEM water pumps are reliable and even some Amazon or Ebay "oem" pumps are counterfeit. It is possible to install the thermostat wrong.

 

@rjparker Makes a good point. By OEM do you mean the pump with the Toyota logo ground off? Or one from a legit online or local Toyota dealer?