Can a water pump go bad with no check engine light?

That was exactly the question when we first learned of that code. The manual says right out that code does not light up the MIL.

The over-revolution probably means the impeller has split and now can spin too fast because it isn't moving much water.

 

... or if the first year of Gen 3 had the P148F code ...

 

Per the link above, it first showed up in the 2011 repair manual.

 

If the impeller is broken, it's not turning or turning but not moving the coolant.
But the magnetic part "is" turning, if it's broken from the plastic impellor.

 

Can separate where it's bonded together, like this:




Then the pump motor tends to spin too fast (because it's not really moving much water, so it is not working as hard). In a 2011 or later you can see the P148F code, but in 2010 nobody had thought they would need a code for "pump runs too fast".

 

Usually if you command the pump on with tech or the software you can actually hear the pump struggling to try and run because the impeller plastic has frayed and is rubbing the housing or the impeller is spinning and not turning with the rest of the assembly etc You can actually hear this It makes the sound of a struggling electric motor that's having trouble making a complete rotation so you get all that funny noise then when you unbolt it and remove the black liner piece between the pump body and the engine then you see the impeller and what's really happening A lot of nothing.

 

When our water pump failed we had no CEL. The red over temp warning light turned on and I quickly parked it until it cooled off. Then, I added some distilled water and nursed it home without the light returning. 10k miles later the head gasket failed at cylinder #2 at only 125k miles.

 

It might be over speeding for a quick second, but 10/10 times we pull one with this code they are completely or almost completely seized up.

 

Well done. Thanks for coming back to report what you found on the water pump. Hopefully, you changed it in time before damage was done to the head gasket. Only milage and time will tell.

 

You think that's bad oh my God I should have posted mine up but it's so hard to do I don't bother All that white you see on there You're pumped with the little rusty crack in it and mine that white was all peeled off the impeller like lifting up like as in peeling off of an orange The pump impeller would not move in its bore. Dropped in another impeller from another pump working fine of course the car was blown up so it didn't really matter

 

I would install a scangauge so that I could monitor the ECT. Lots of people think no dummy light, no CEL everything is fine. Especially those who don't pay attention to their instrument cluster.

Just my 2-cents..

 

Wouldn’t it though. Most every car we’ve had in past had one.

 

Ditto; the Prius is the only cars I've ever owned without a temperature gauge in the cluster.

There's been many arguments here about the over temperature lamp flashing on for only and second and no CEL; so everything must be fine. Or I took it to my mechanic and he/she couldn't find anything and there wasn't any CEL or codes stored. Can't argue with that, other than the mechanic gave it a 5 minute look and moved on; time is money. Whereas an in-depth look could've revealed that the engine was running hot all the time, just not hot enough to trip the ECT. This would make it a major contributor to the blown head gaskets in the gen3. In time, we may find out that the gen4 has a similar issue because it monitors ECT in the same fashion; unless those e-water pumps has gotten a lot better between those two generations.

You can lead a horse to water, but you can't make them drink the Kool-Aid.

YMMV

 

All my hybrids have coolant temps displayed. The Rav4 has a normal dash gauge while the Prius has had an $35 monitor for years.

There is value in understanding normal temperature variations can be more than 40f after warmup.

The add-on monitor is configured with a much lower alarm limit than 248f which is important since temps rise quickly with a problem. I had the secondary 210f alarm once and it was when the reservoir cap was loose.

Original pumps but frequent cooling drain and fills.