Water Pump

I'm really feeling that way too. If yours hasn't continued to malfunction further that helps ease me slightly. I did start driving the car again but w/o AC which I learned isn't great either. So my next step is still clean battery fan and proceed to monitor the engine cooling fan. I don't think I feel that much better about running ac. Is there an ohms test I can do to check the engine fans quality?

I'll likely replace it if a non oem fan is ok. Then continue to monitor to see if that changed it. It's a really big deal to not spend double which is $70 more for comfort of oem to preserve my car with a part I may not need? I'm really glad this site and all of you are here to assist with this process. Thanks.

 

Ohms test I don't know. Brush-commutated motors are pretty electrically sloppy, hard to say what one'll show on an ohmmeter standing still.

Often what you'll find specified as a fan or other motor test is the running current. That should settle down to a more meaningful measurement, once the fan has spun up.

Annnnd, yup, that's what they put in the manual:



They're assuming you have a Hall-effect DC current clamp you can clamp around the wire.

If you don't have one of those, given the expected current range, you might get away with using your 20 amp or better ordinary ammeter in series, but you might want a way to bring the voltage up slowly, because if you just connect 12 V all at once, the fan's initial current draw will be much more than 4.7 to 8.7 A.

 

Hi pius community.

I have found very intereting and informative information to troubleshoot here, however I'm still stuck with my water pump problem and therefore I want to ask for some advice from all the experts out there including main prius pump expert ChapmanF

I'm trying to troubleshoot my prius water pump. I am not getting any trouble codes however the pump is behaving erratically according to the techstream tests I did. When the coolant temperature is low the electric water pump target speed stays at 2400 rpm which i believe is normal when the coolant is low. However the electric water pump speed fluctuates between 2800 rpm and 2900 rpm. But once the coolant temperature gets around 180 F or higher the electric pump target speed starts to fluctuate between 2400 rpm and 2425 rpm and the electric water pump speed at 2950 rpm starts having big drop outs to 0 rpm. As the coolant temperature continues to rise the electric water pump speed fluctuations to 0 rpm become more and more frequent and then around 195F the target speed starts fluctuating between 3675 rpm and 0 rpm. I'm attaching pictures of the techstream graphs as the temperature increases. Once the temperature gets to about 205 F the electic fan comes on and the temperature goes briefly down to 200 F then come back up to 210 then down again, but techstream is showing at that point that the pump speed is mostly at 0 RPM

I am not sure how to determine if my water pump is the problem or the wiring to the ECU or if the ECU is the culprit. Also not completely sure on how to test the wiring continuity from the fuse box cover showed in ChapmanF post #36 of this thread to the pump connector and or to the ECU and the values that I should expect. Do I only need continuity or a certain number of resistance?

Any insight would be appreciated.

 

Can you please provide some information on the car?
What is the year and mileage?
Is the engine water pump the original, or was it replaced with something else?

My guess is that your water pump is the problem and needs to be replaced.
What does not make sense to me in the 195F picture is the water pump target speed going down to zero. The target speed should never go down to zero when the coolant temperature is 195F.

 

It is a 2011 Prius with 138K miles on it. Before I did the techstream test (I didn't have it at the moment) I replaced the water pump since my coolant reservoir was overflowing and getting down. The new pump is aftermarket one, and might be the problem. So I already ordered a AISIN new pump which should be here this week and will change and test again. If I get the same results then I can assume it is either the wiring or the ECU, but wondering what is the procedure to narrow it down.

 

@ChapmanF , Take a look at post # 103.

 

Is it absolutely certain there is no check-engine light and no water pump codes?

In the 2010 repair manual, the stated "fail-safe operation" when a P261B code is detected is for the ECM to repeatedly target 0% for 30 seconds and 85% for 5 seconds (maybe as an attempt to unstick a sticking impeller). The fail-safe operation for P261C or P261D is simply to clamp the target at 0%. (Which seems to me like an odd choice for a water pump fail-safe behavior, but anyway.)

So it seems as if the ECM is doing something at least a little bit like what it is programmed to do when there is a water pump trouble code. But reportedly there is no code, which is odd.

The other thing the ECM does when it thinks there is a water pump code is shut the engine immediately off if the coolant temperature hits 221 ℉ (105 ℃). The posted graphs don't go that far, but if running the engine up to that temperature caused it to stop, that would also suggest that the ECM has noticed a water pump issue. Under normal circumstances, that coolant temperature does not shut the engine off.

 

My take, from what I’ve read here about failures and when they occur, it’d be prudent to replace every 100k miles.

 

The new pump arrives tomorrow, so I will do Techstream Test again after changing it and update the results here.